DOD 250 Mods...

[TheChris]

I recently got an old Yellow DOD 250 since it was one of my first effects back in
the day. It's pretty tricked out - 3D3P switch making it true bypass and a nice
bright LED.

However, when I used it - I thought it was pretty shrill. I was able to tame it
by knocking down the treble on my amp - but - would really like to knock the
treble off at the pedal.

Looking for mods on the net... didn't see any that dealt with a 'tone pot' mod. I
realize it's a simple circuit. Should I just put a passive (guitar type) of tone
pot in there, or is there something cooler.

Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.

Any insight would be appreciated.

Thanks.

[LULU]

Post by TheChris
I recently got an old Yellow DOD 250 since it was one of my first effects back in
the day.  It's pretty tricked out - 3D3P switch making it true bypass and a nice
bright LED.
However, when I used it - I thought it was pretty shrill.  I was able to tame it
by knocking down the treble on my amp - but - would really like to knock the
treble off at the pedal.
Looking for mods on the net... didn't see any that dealt with a 'tone pot' mod. I
realize it's a simple circuit. Should I just put a passive (guitar type) of tone
pot in there, or is there something cooler.
Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.
Any insight would be appreciated.
Thanks.

============================

Maybe take a few photos of your pedal and then contact these guys.
They can deal with almost any type of pedal problem or mod
preference. Perhaps they can suggest a "solution" for your pedal's
shrillness.

Good Luck,
Lulu : )

DOD OD-250 Mods -
http://www.analogman.com/dodmod.htm

============================

[TheChris]

Post by LULU
Maybe take a few photos of your pedal and then contact these guys.
They can deal with almost any type of pedal problem or mod
preference. Perhaps they can suggest a "solution" for your pedal's
shrillness.
Good Luck,
Lulu : )
DOD OD-250 Mods -
http://www.analogman.com/dodmod.htm

Yeah, they're pretty prominent here. Their mods for this pedal mainly deal with
knocking it back to 'vintage specs' - which is a non-issue since the pedal is from
1982...

I guess I don't like top end as much as most people. I have Celestions in my
Fender Amps, and on my Marshalls, the tone is set to Zero...

One day I just had 3 overdrives hooked up (Old Rat, DOD 250, Boss SD-1) and the
DOD was the only one without a tone knob that let me dial out some of that
harshness.

Thanks for the link.

[LULU]

Post by TheChris

Post by LULU
Maybe take a few photos of your pedal and then contact these guys.
They can deal with almost any type of pedal problem or mod
preference.  Perhaps they can suggest a "solution" for your pedal's
shrillness.
Good Luck,
Lulu : )
DOD OD-250 Mods -
http://www.analogman.com/dodmod.htm

Yeah, they're pretty prominent here. Their mods for this pedal mainly deal with
knocking it back to 'vintage specs' - which is a non-issue since the pedal is from
1982...
I guess I don't like top end as much as most people.  I have Celestions in my
Fender Amps, and on my Marshalls, the tone is set to Zero...
One day I just had 3 overdrives hooked up (Old Rat, DOD 250, Boss SD-1) and the
DOD was the only one without a tone knob that let me dial out some of that
harshness.
Thanks for the link.

===============================

The 250 reminds me somewhat of the MXR distortion plus soundwise.
Both use diodes to ground to clip the signal. Try adjusting your amp
so it is at a point where it is slightly overdriving and setting the
DOD at a lower level. When you kick in the 250, the amp's tubes
should smooth the harshness out of the pedal's signal.

Good Luck,
Lulu : )

===============================

[TheChris]

Post by LULU
The 250 reminds me somewhat of the MXR distortion plus soundwise.
Both use diodes to ground to clip the signal. Try adjusting your amp
so it is at a point where it is slightly overdriving and setting the
DOD at a lower level. When you kick in the 250, the amp's tubes
should smooth the harshness out of the pedal's signal.

They're almost identical circuits. I've seen where you can put both pedals in one
enclosure with just one or two switches.

As I said... I don't want to make amp adjustments to compensate for a pedal that
was designed a long time ago. All my other OD's/Distortions have tone stacks - for
good reason - they're necessary. I'd just like to modernize this one by rolling
off the top end

I found a site that explains how to put a Big Muff tone stack in with one pot..

http://www.beavisaudio.com/techpages/BigMuffToneControl/

[LULU]

Post by TheChris

Post by LULU
The 250 reminds me somewhat of the MXR distortion plus soundwise.
Both use diodes to ground to clip the signal.  Try adjusting your amp
so it is at a point where it is slightly overdriving and setting the
DOD at a lower level.  When you kick in the 250, the amp's tubes
should smooth the harshness out of the pedal's signal.

They're almost identical circuits. I've seen where you can put both pedals in one
enclosure with just one or two switches.
As I said... I don't want to make amp adjustments to compensate for a pedal that
was designed a long time ago. All my other OD's/Distortions have tone stacks - for
good reason - they're necessary. I'd just like to modernize this one by rolling
off the top end
I found a site that explains how to put a Big Muff tone stack in with one pot..
http://www.beavisaudio.com/techpages/BigMuffToneControl/

===============================

Thanks for the link Chris. Nice clear diagrams of a simple circuit.

Lulu : )

===============================

[Flasherly]

Post by TheChris
I recently got an old Yellow DOD 250 since it was one of my first effects back in
the day. It's pretty tricked out - 3D3P switch making it true bypass and a nice
bright LED.
However, when I used it - I thought it was pretty shrill. I was able to tame it
by knocking down the treble on my amp - but - would really like to knock the
treble off at the pedal.
Looking for mods on the net... didn't see any that dealt with a 'tone pot' mod. I
realize it's a simple circuit. Should I just put a passive (guitar type) of tone
pot in there, or is there something cooler.
Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.
Any insight would be appreciated.
Thanks.

When pushed, the amp's power EL84 valves, some of the treble/presence
seem to me to blend better with mids - between the guitar's tone pot -
although that's with a mix of both pre/post gain at both sides of
adjustable mid/high frequencies in between the actual bass/mid/hi
final set points. That makes 7 knobs total in a modeler on an ultra-
linear selection (Bassman 59, so I've as well something of lows,
besides the highs, to figure). I do it through a USB connection into
the effects, though, with a working picture of the parameters, on a PC
screen, via a dedicated program that came with the modeler. If it's
going to grind, it'll be the gain knobs -- but with that kind of
setup, single coil & Fender oriented, tends nicely to a cleaner side
of the grind. Didn't bother with a LED when I wired in a 3Pole
2Throw, which can be annoying, depending, when both amp & Fx are set
and sound similar.

[TheChris]

Post by Flasherly

Post by TheChris
I recently got an old Yellow DOD 250 since it was one of my first
effects back in the day. It's pretty tricked out - 3D3P switch
making it true bypass and a nice bright LED.
However, when I used it - I thought it was pretty shrill. I was
able to tame it by knocking down the treble on my amp - but - would
really like to knock the treble off at the pedal.
Looking for mods on the net... didn't see any that dealt with a
'tone pot' mod. I realize it's a simple circuit. Should I just put a
passive (guitar type) of tone pot in there, or is there something
cooler.
Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.
Any insight would be appreciated.
Thanks.

When pushed, the amp's power EL84 valves, some of the treble/presence
seem to me to blend better with mids - between the guitar's tone pot
- although that's with a mix of both pre/post gain at both sides of
adjustable mid/high frequencies in between the actual bass/mid/hi
final set points. That makes 7 knobs total in a modeler on an ultra-
linear selection (Bassman 59, so I've as well something of lows,
besides the highs, to figure). I do it through a USB connection into
the effects, though, with a working picture of the parameters, on a
PC screen, via a dedicated program that came with the modeler. If
it's going to grind, it'll be the gain knobs -- but with that kind of
setup, single coil & Fender oriented, tends nicely to a cleaner side
of the grind. Didn't bother with a LED when I wired in a 3Pole
2Throw, which can be annoying, depending, when both amp & Fx are set
and sound similar.

I'm not following you at all. I didn't mention what amp I'm using it
with. Let's say I line up 5 distortion pedals. All the ones that have
a tone pot are set very lot (I don't like bright sounds). The DOD -
that doesn't have a tone pot - is too bright to me - it adds brightness
to it. ANY amp - SS - Tube. The amp is not a factor - just the fact
that the EQ curve changes significantly coming OUT of that pedal.

[Flasherly]

Post by TheChris

Post by Flasherly

Post by TheChris
I recently got an old Yellow DOD 250 since it was one of my first
effects back in the day. It's pretty tricked out - 3D3P switch
making it true bypass and a nice bright LED.
However, when I used it - I thought it was pretty shrill. I was
able to tame it by knocking down the treble on my amp - but - would
really like to knock the treble off at the pedal.
Looking for mods on the net... didn't see any that dealt with a
'tone pot' mod. I realize it's a simple circuit. Should I just put a
passive (guitar type) of tone pot in there, or is there something
cooler.
Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.
Any insight would be appreciated.
Thanks.

When pushed, the amp's power EL84 valves, some of the treble/presence
seem to me to blend better with mids - between the guitar's tone pot
- although that's with a mix of both pre/post gain at both sides of
adjustable mid/high frequencies in between the actual bass/mid/hi
final set points. That makes 7 knobs total in a modeler on an ultra-
linear selection (Bassman 59, so I've as well something of lows,
besides the highs, to figure). I do it through a USB connection into
the effects, though, with a working picture of the parameters, on a
PC screen, via a dedicated program that came with the modeler. If
it's going to grind, it'll be the gain knobs -- but with that kind of
setup, single coil & Fender oriented, tends nicely to a cleaner side
of the grind. Didn't bother with a LED when I wired in a 3Pole
2Throw, which can be annoying, depending, when both amp & Fx are set
and sound similar.

I'm not following you at all. I didn't mention what amp I'm using it
with. Let's say I line up 5 distortion pedals. All the ones that have
a tone pot are set very lot (I don't like bright sounds). The DOD -
that doesn't have a tone pot - is too bright to me - it adds brightness
to it. ANY amp - SS - Tube. The amp is not a factor - just the fact
that the EQ curve changes significantly coming OUT of that pedal.

I see. I suppose I could say the same thing. Any amp (model) is
going to be bright as well to me (being the nature of my guitar and
amp). In a roundabout way, as that's what I have and have to deal
with - an excess, almost, of brightness. Taking a directer approach
to the pedals doesn't occur in any actual sense - even with those
pedal Fx I mentioned in 7 pods in so many sweep-band parameters,
there's, besides, a BOSS 7 band I'm using in the chain. Guess I'm
saying I've learned to live with it, with of course adaptation by way
of suggestion for pushing the power stage tubes as a means of taking
off some strident high/trebles. Rolling off the highs of course...
Eliminating it all just hadn't occurred to me, not even remotely. Heh
- even the closest in dual humbucker guitar I do have, (through the
body neck and on a thin/light construction side of a Paul), plays
almost exclusively, though lower than the single coils and over a mid-
range, with my gear. Punchy lows, crisp, pronounced and growling
while overdriven - I might know the sound, perhaps a step lower, but
not much more insofar as setting up an amp for it. That humbucker
guitar is kind of neat, but I want to do a little work on it first.
Could conceivably be doing more what you are then.

[l***@hotmail.com]

Post by TheChris
I recently got an old Yellow DOD 250 since it was one of my first effects back in
the day. It's pretty tricked out - 3D3P switch making it true bypass and a nice
bright LED.
However, when I used it - I thought it was pretty shrill. I was able to tame it
by knocking down the treble on my amp - but - would really like to knock the
treble off at the pedal.
Looking for mods on the net... didn't see any that dealt with a 'tone pot' mod. I
realize it's a simple circuit. Should I just put a passive (guitar type) of tone
pot in there, or is there something cooler.
Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.
Any insight would be appreciated.

The 250's made in recent years are very difficult to modify to the gray or early yellow circuit. The opamp has different pinouts. You cannot simply install the correct chip.

I tossed the stock board in the trash, and rebuilt to the gray cicuit on perf board. I also added true bypass and LED.

Post by TheChris
Thanks.

[TheChris]

Post by l***@hotmail.com
The 250's made in recent years are very difficult to modify to the gray or early

yellow circuit. The opamp has different pinouts. You cannot simply install the
correct chip.

Post by l***@hotmail.com
I tossed the stock board in the trash, and rebuilt to the gray cicuit on perf

board. I also added true bypass and LED.
This isn't a new one... and... back to my original question... Would I be able to
add a passive tone pot - like adding a tone pot to a guitar? Perhaps prior to the
circuit?

[l***@hotmail.com]

Post by l***@hotmail.com

Post by l***@hotmail.com
The 250's made in recent years are very difficult to modify to the gray or early

yellow circuit. The opamp has different pinouts. You cannot simply install the
correct chip.

Post by l***@hotmail.com
I tossed the stock board in the trash, and rebuilt to the gray cicuit on perf

board. I also added true bypass and LED.
This isn't a new one... and... back to my original question... Would I be able to
add a passive tone pot - like adding a tone pot to a guitar? Perhaps prior to the
circuit?

If you add a simple high cut pot, do it after the distortion, at the output (but not right a the jack, you don't want to defeat true bypass!). But there may be a better answer. And I won't know what schematic to look at unless you tell me what chip is in it. It also sounds like it might be modified.

Sometimes a "shrillness" is better solved by negative feedback in the chip.

I don't know your level of technical knowledge. I'm far above the average player, far below an MSEE (electrical engineer).

Opamps are complicated inside, but simple in operation. There is a + and - input. You tie the output back to the negative input, and that acts to cancel out some of the signal (reduces the gain). If you place a capacitor that only passes the higher frequencies, only those higher frequecies are canceled out, and you reshape the entire frequency response. So one cheap part and no pot and drilling could be the best answer. It rolls off the high end (before the clipping), and the value of the cap determines where it rolls off.

But if it's fine clean and harsh distorted, there's a second capacitor by the diodes that could be the answer.

Or a combination of the above.

Or it you're the type of player that finds a setting and leaves it alone, a simple capacitor and maybe resistor at near the output will do it.

A tone control allows you to vary things, but requires fitting a pot. Don't forget, your going to have board mounted pots in that thing. Finding room in a small case isn't always easy.

*I* would be tweaking the above spots by ear, not trying to fit an additional pot.

[TheChris]

Post by l***@hotmail.com
If you add a simple high cut pot, do it after the distortion, at the output

(but not right a the jack, you don't want to defeat true bypass!). But there
may be a better answer. And I won't know what schematic to look at unless you
tell me what chip is in it. It also sounds like it might be modified.

Post by l***@hotmail.com
Sometimes a "shrillness" is better solved by negative feedback in the chip.
I don't know your level of technical knowledge. I'm far above the average

player, far below an MSEE (electrical engineer).

Post by l***@hotmail.com
Opamps are complicated inside, but simple in operation. There is a + and -

input. You tie the output back to the negative input, and that acts to cancel
out some of the signal (reduces the gain). If you place a capacitor that only
passes the higher frequencies, only those higher frequecies are canceled out,
and you reshape the entire frequency response. So one cheap part and no pot and
drilling could be the best answer. It rolls off the high end (before the
clipping), and the value of the cap determines where it rolls off.

Post by l***@hotmail.com
But if it's fine clean and harsh distorted, there's a second capacitor by the

diodes that could be the answer.

Post by l***@hotmail.com
Or a combination of the above.
Or it you're the type of player that finds a setting and leaves it alone, a

simple capacitor and maybe resistor at near the output will do it.

Post by l***@hotmail.com
A tone control allows you to vary things, but requires fitting a pot. Don't

forget, your going to have board mounted pots in that thing. Finding room in a
small case isn't always easy.

Post by l***@hotmail.com
*I* would be tweaking the above spots by ear, not trying to fit an additional pot.

I didn't even think of the true bypass part of it! Thanks for reminding me.
With Electronics - I can solder and know basic circuit logic. I wire guitars,
and some easy pedal stuff. Nothing involving a Frequency Analyzer - just a
meter. I have two degrees in 'Computer Science' - that's about it :)

The chip is a 351N. I found a page that showed how to add a BIG Muff tone stack
(passive) with resistors and caps soldered right to the pot. I *might* try that
one. Honestly, what I *should* do is use the model included in my Line6 DM4,
and just turn down the tone knob :) But,I'd like to see what I can do with this
pedal.

Thanks for this. I will save this post for when I get to it!

[l***@hotmail.com]

Post by l***@hotmail.com

Post by l***@hotmail.com
If you add a simple high cut pot, do it after the distortion, at the output

(but not right a the jack, you don't want to defeat true bypass!). But there
may be a better answer. And I won't know what schematic to look at unless you
tell me what chip is in it. It also sounds like it might be modified.

Post by l***@hotmail.com
Sometimes a "shrillness" is better solved by negative feedback in the chip.
I don't know your level of technical knowledge. I'm far above the average

player, far below an MSEE (electrical engineer).

Post by l***@hotmail.com
Opamps are complicated inside, but simple in operation. There is a + and -

input. You tie the output back to the negative input, and that acts to cancel
out some of the signal (reduces the gain). If you place a capacitor that only
passes the higher frequencies, only those higher frequecies are canceled out,
and you reshape the entire frequency response. So one cheap part and no pot and
drilling could be the best answer. It rolls off the high end (before the
clipping), and the value of the cap determines where it rolls off.

Post by l***@hotmail.com
But if it's fine clean and harsh distorted, there's a second capacitor by the

diodes that could be the answer.

Post by l***@hotmail.com
Or a combination of the above.
Or it you're the type of player that finds a setting and leaves it alone, a

simple capacitor and maybe resistor at near the output will do it.

Post by l***@hotmail.com
A tone control allows you to vary things, but requires fitting a pot. Don't

forget, your going to have board mounted pots in that thing. Finding room in a
small case isn't always easy.

Post by l***@hotmail.com
*I* would be tweaking the above spots by ear, not trying to fit an additional

pot.
I didn't even think of the true bypass part of it! Thanks for reminding me.
With Electronics - I can solder and know basic circuit logic. I wire guitars,
and some easy pedal stuff. Nothing involving a Frequency Analyzer - just a
meter. I have two degrees in 'Computer Science' - that's about it :)
The chip is a 351N.

Then it's a "good one."

I found a page that showed how to add a BIG Muff tone stack

Post by l***@hotmail.com
(passive) with resistors and caps soldered right to the pot. I *might* try that
one. Honestly, what I *should* do is use the model included in my Line6 DM4,
and just turn down the tone knob :) But,I'd like to see what I can do with this
pedal.
Thanks for this. I will save this post for when I get to it!

Look at the post by RS. He is ALWAYS worth reading. He's been very helpful when I run out of my knowledge base.

You won't have an external pot, but you can fine tune the trim pot and be good to go.

[l***@hotmail.com]

Post by l***@hotmail.com

Post by l***@hotmail.com

Post by l***@hotmail.com
If you add a simple high cut pot, do it after the distortion, at the output

(but not right a the jack, you don't want to defeat true bypass!). But there
may be a better answer. And I won't know what schematic to look at unless you
tell me what chip is in it. It also sounds like it might be modified.

Post by l***@hotmail.com
Sometimes a "shrillness" is better solved by negative feedback in the chip.
I don't know your level of technical knowledge. I'm far above the average

player, far below an MSEE (electrical engineer).

Post by l***@hotmail.com
Opamps are complicated inside, but simple in operation. There is a + and -

input. You tie the output back to the negative input, and that acts to cancel
out some of the signal (reduces the gain). If you place a capacitor that only
passes the higher frequencies, only those higher frequecies are canceled out,
and you reshape the entire frequency response. So one cheap part and no pot and
drilling could be the best answer. It rolls off the high end (before the
clipping), and the value of the cap determines where it rolls off.

Post by l***@hotmail.com
But if it's fine clean and harsh distorted, there's a second capacitor by the

diodes that could be the answer.

Post by l***@hotmail.com
Or a combination of the above.
Or it you're the type of player that finds a setting and leaves it alone, a

simple capacitor and maybe resistor at near the output will do it.

Post by l***@hotmail.com
A tone control allows you to vary things, but requires fitting a pot. Don't

forget, your going to have board mounted pots in that thing. Finding room in a
small case isn't always easy.

Post by l***@hotmail.com
*I* would be tweaking the above spots by ear, not trying to fit an additional

pot.
I didn't even think of the true bypass part of it! Thanks for reminding me.
With Electronics - I can solder and know basic circuit logic. I wire guitars,
and some easy pedal stuff. Nothing involving a Frequency Analyzer - just a
meter. I have two degrees in 'Computer Science' - that's about it :)
The chip is a 351N.

Then it's a "good one."
I found a page that showed how to add a BIG Muff tone stack

Post by l***@hotmail.com
(passive) with resistors and caps soldered right to the pot. I *might* try that
one. Honestly, what I *should* do is use the model included in my Line6 DM4,
and just turn down the tone knob :) But,I'd like to see what I can do with this
pedal.
Thanks for this. I will save this post for when I get to it!

Look at the post by RS. He is ALWAYS worth reading. He's been very helpful when I run out of my knowledge base.
You won't have an external pot, but you can fine tune the trim pot and be good to go.

I should also note that my 250 sees use in front of my Marshall that is unusually dark sounding for a Marshall (speaker choice has much to do with that). So what sounds "shrill" on a bright amp sounds "cruchy" on a dark amp!

The 250's that sound great in front of an already pushed tube amp that's on the verge of distortion? ...sound like sh!t in front of a clean amp. These are early BOOST pedals to get more gain. It even says preamp on the pedal. They are great in the right application. But horrible in other situations.

My use depends on gain level of the amp. But here's the typical setup:

Marshall JMP 2204 with a true mix of preamp and power tube distortion, attenuated down by a Hot Plate. Kick the 250 for a slightly edgier, gainier tone. Truly FLAVORING the amp, instead of amplifying the pedal tone.

[RS]

Post by l***@hotmail.com
Look at the post by RS. He is ALWAYS worth reading. He's been very helpful when I run out of my knowledge base.

Thanks for the kind comment! I was lucky to grow up around two
engineers who worked in the music industry, so I learned electronics
and music in parallel. They don't teach the specialized stuff in
universities, so why not try to pass the knowledge on. I enjoy it.
Definitely easier to make a living doing engineering. :-)

Your posts, including this thread, are on target. You have good
intuition--that's important. If you're interested, there's a nice
collection of vintage audio and tube engineering books online:

http://www.tubebooks.org/technical_books_online.htm

I inherited many of those in original paper form, but it's great to
have the pdfs. Make sure you get the Radiotron books if you don't have
them already. The 4th edition is much more complete, but the 3rd is
useful as a kind of condensed quick-start. There are other very good
ones... check Reich and Crowhurst.

Post by l***@hotmail.com
I should also note that my 250 sees use in front of my Marshall
that is unusually dark sounding for a Marshall (speaker choice has
much to do with that).

I like darker, more mid-rangey speakers in general. Which speakers are
you using?

Post by l***@hotmail.com
So what sounds "shrill" on a bright amp
sounds "cruchy" on a dark amp!

There's a lot of chemistry going on. Occasionally you see an FX pedal
that sounds pretty bad in general, but comes to life with a certain
amp. Surprisingly hard to predict that sometimes.

[RS]

Post by l***@hotmail.com
The 250's made in recent years are very difficult to modify to the
gray or early yellow circuit. The opamp has different pinouts. You
cannot simply install the correct chip.

Hi LS, The older 250's used an LF351n, which was a single JFET-input
opamp. I think the newest reissues use a dual opamp, like a 4558 which
does indeed have a different pinout since it's a dual. But there's an
LF353, which is basically a dual version of the LF351. Same pinout as
the 4558. That should work in the newer pedals.

http://www.datasheetcatalog.org/datasheet/on_semiconductor/LF347-D.PDF

[Tony Done]

Post by TheChris
I recently got an old Yellow DOD 250 since it was one of my first effects back in
the day. It's pretty tricked out - 3D3P switch making it true bypass and a nice
bright LED.
However, when I used it - I thought it was pretty shrill. I was able to tame it
by knocking down the treble on my amp - but - would really like to knock the
treble off at the pedal.
Looking for mods on the net... didn't see any that dealt with a 'tone pot' mod. I
realize it's a simple circuit. Should I just put a passive (guitar type) of tone
pot in there, or is there something cooler.
Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.
Any insight would be appreciated.
Thanks.

If you can get the desired effect rolling off the treble of the guitar,
then it should be possible to install a simple treble-to-earth tone
control in the stomp box. If you put it immediately after the input, it
would be the same as having it in the guitar. You could do it without
changing any of the current set up, just solder it in between the switch
output and earth. I did something similar with a Baggs M1 active
soundhole pickup. I just stuck a tone control (a small on-off-on-toggle
with two different caps in the on positions) between the hot and ground
on the lead socket. It works fine.

[%]

Post by Tony Done

Post by TheChris
I recently got an old Yellow DOD 250 since it was one of my first
effects back in the day. It's pretty tricked out - 3D3P switch
making it true bypass and a nice bright LED.
However, when I used it - I thought it was pretty shrill. I was
able to tame it by knocking down the treble on my amp - but - would
really like to knock the treble off at the pedal.
Looking for mods on the net... didn't see any that dealt with a
'tone pot' mod. I realize it's a simple circuit. Should I just put a
passive (guitar type) of tone pot in there, or is there something
cooler.
Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.
Any insight would be appreciated.
Thanks.

If you can get the desired effect rolling off the treble of the
guitar, then it should be possible to install a simple
treble-to-earth tone control in the stomp box. If you put it
immediately after the input, it would be the same as having it in the
guitar. You could do it without changing any of the current set up,
just solder it in between the switch output and earth. I did
something similar with a Baggs M1 active soundhole pickup. I just
stuck a tone control (a small on-off-on-toggle with two different
caps in the on positions) between the hot and ground on the lead
socket. It works fine.

yea but it looks stupid

[Tony Done]

Post by %

Post by Tony Done

Post by TheChris
I recently got an old Yellow DOD 250 since it was one of my first
effects back in the day. It's pretty tricked out - 3D3P switch
making it true bypass and a nice bright LED.
However, when I used it - I thought it was pretty shrill. I was
able to tame it by knocking down the treble on my amp - but - would
really like to knock the treble off at the pedal.
Looking for mods on the net... didn't see any that dealt with a
'tone pot' mod. I realize it's a simple circuit. Should I just put a
passive (guitar type) of tone pot in there, or is there something
cooler.
Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.
Any insight would be appreciated.
Thanks.

If you can get the desired effect rolling off the treble of the
guitar, then it should be possible to install a simple
treble-to-earth tone control in the stomp box. If you put it
immediately after the input, it would be the same as having it in the
guitar. You could do it without changing any of the current set up,
just solder it in between the switch output and earth. I did
something similar with a Baggs M1 active soundhole pickup. I just
stuck a tone control (a small on-off-on-toggle with two different
caps in the on positions) between the hot and ground on the lead
socket. It works fine.

yea but it looks stupid

Look closely at this pic.

http://www.flickr.com/photos/done_family/6879852336/in/photostream

Does the setup on the L-00 look stupid to you?

[%]

Post by Tony Done

Post by %

Post by Tony Done

Post by TheChris
I recently got an old Yellow DOD 250 since it was one of my first
effects back in the day. It's pretty tricked out - 3D3P switch
making it true bypass and a nice bright LED.
However, when I used it - I thought it was pretty shrill. I was
able to tame it by knocking down the treble on my amp - but - would
really like to knock the treble off at the pedal.
Looking for mods on the net... didn't see any that dealt with a
'tone pot' mod. I realize it's a simple circuit. Should I just put
a passive (guitar type) of tone pot in there, or is there something
cooler.
Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.
Any insight would be appreciated.
Thanks.

If you can get the desired effect rolling off the treble of the
guitar, then it should be possible to install a simple
treble-to-earth tone control in the stomp box. If you put it
immediately after the input, it would be the same as having it in
the guitar. You could do it without changing any of the current set
up, just solder it in between the switch output and earth. I did
something similar with a Baggs M1 active soundhole pickup. I just
stuck a tone control (a small on-off-on-toggle with two different
caps in the on positions) between the hot and ground on the lead
socket. It works fine.

yea but it looks stupid

Look closely at this pic.

no

[TheChris]

Post by Tony Done
If you can get the desired effect rolling off the treble of the guitar,
then it should be possible to install a simple treble-to-earth tone
control in the stomp box. If you put it immediately after the input, it
would be the same as having it in the guitar. You could do it without
changing any of the current set up, just solder it in between the switch
output and earth. I did something similar with a Baggs M1 active
soundhole pickup. I just stuck a tone control (a small on-off-on-toggle
with two different caps in the on positions) between the hot and ground
on the lead socket. It works fine.

Okay - thanks for that - that's what I was thinking. The problem with 'rolling it
off at the guitar' is that most of my guitars DON'T have tone pots. I disengaged
them because I'm really not a tone pot guy :)

Thanks again. I think I'll test out the theory with clips first.

[Tony Done]

Post by TheChris

Post by Tony Done
If you can get the desired effect rolling off the treble of the guitar,
then it should be possible to install a simple treble-to-earth tone
control in the stomp box. If you put it immediately after the input, it
would be the same as having it in the guitar. You could do it without
changing any of the current set up, just solder it in between the switch
output and earth. I did something similar with a Baggs M1 active
soundhole pickup. I just stuck a tone control (a small on-off-on-toggle
with two different caps in the on positions) between the hot and ground
on the lead socket. It works fine.

Okay - thanks for that - that's what I was thinking. The problem with 'rolling it
off at the guitar' is that most of my guitars DON'T have tone pots. I disengaged
them because I'm really not a tone pot guy :)

<g, sigh> You don't know what you're missing. I've recently discovered
that I get good tones with moderate OD by rolling off the treble from
the guitar, and using the OD harmonics to create the high transients.
Gives a thick earthy sound that doesn't sound too cluttered with my
fingerpicking style

Post by TheChris
Thanks again. I think I'll test out the theory with clips first.

Good idea, I hadn't thought of that.

[TheChris]

Post by Tony Done
<g, sigh> You don't know what you're missing. I've recently discovered
that I get good tones with moderate OD by rolling off the treble from
the guitar, and using the OD harmonics to create the high transients.
Gives a thick earthy sound that doesn't sound too cluttered with my
fingerpicking style

I'm a hard rock player. I barely even use neck pickups. So, the subtleties of tone
controls are lost on me. In the old days, I'd hit one by mistake, and then spend
20 minutes on stage boosting trebles on amps and pedals until I figured it out.
Then I read how many of my favorite players just disconnected them. Made all the
sense in the world.

My point is - If I line up a bunch of overdrives, I don't want one to require
extremely different amp/guitar settings. I want a baseline.

I've read many forums where people say the same thing - it's a shrill overdrive.
So, it ain't just me. On any other one, you could just turn a knob
counter-clockwise. That's what I'm looking for.

[l***@hotmail.com]

Post by TheChris
I recently got an old Yellow DOD 250 since it was one of my first effects back in
the day. It's pretty tricked out - 3D3P switch making it true bypass and a nice
bright LED.
However, when I used it - I thought it was pretty shrill. I was able to tame it
by knocking down the treble on my amp - but - would really like to knock the
treble off at the pedal.
Looking for mods on the net... didn't see any that dealt with a 'tone pot' mod. I
realize it's a simple circuit. Should I just put a passive (guitar type) of tone
pot in there, or is there something cooler.

I posted about problems converted the more recent 250's to the original circuit.

But maybe you could verify a couple of things:

What chip is in it?

Does it sound too shrill when clean, or just when it's clipping?

That would give me something to go on.

Post by TheChris
Trust me, I looked..... just saw a bunch of Yellow/Grey mods, etc.
Any insight would be appreciated.
Thanks.

[TheChris]

Post by l***@hotmail.com
I posted about problems converted the more recent 250's to the original circuit.
What chip is in it?
Does it sound too shrill when clean, or just when it's clipping?
That would give me something to go on.

Looks like the chip is a 351N? There's a top number too - 117?

As for your other question - I think as I add gain, it just gets more shrill. I
haven't tried your test of listening to it clean - and by that - I'm assuming the
gain all the way down.

[boardjunkie1]

Post by TheChris

Post by l***@hotmail.com
I posted about problems converted the more recent 250's to the original circuit.
What chip is in it?
Does it sound too shrill when clean, or just when it's clipping?
That would give me something to go on.

Looks like the chip is a 351N? There's a top number too - 117?
As for your other question - I think as I add gain, it just gets more shrill.  I
haven't tried your test of listening to it clean - and by that - I'm assuming the
gain all the way down.

Identify the output lead (effect output) on the switch. Add a .01u cap
and a 10k trimpot. Set the trimpot where it sounds best, put the cover
back on. If its still too bright or lets thru too much high mids, try
a .1u.

[RS]

On Tue, 5 Mar 2013 16:30:32 +0000 (UTC), TheChris

Post by TheChris

Post by l***@hotmail.com
I posted about problems converted the more recent 250's to the original circuit.
What chip is in it?
Does it sound too shrill when clean, or just when it's clipping?
That would give me something to go on.

Looks like the chip is a 351N? There's a top number too - 117?

How've you been, Chris!

The chip would be an LF351n. Originally from National Semi, but others
have also made it. The 117 is probably just a batch number. The LF351
is a JFET-input opamp. The pinouts are pretty standard for a single
opamp chip: 2,3 and 6 for inputs and output (resp). Just like the old
741 family. No big reason to swap it, but if you do, use a socket so
you can try various opamps. Still, that won't result in the dramatic
tone change that you're looking for.

You've already got some good suggestions in this thread, and you could
indeed just treat this as moving a guitar tone control into the box.
IOW, put the rolloff cap right at the input.

I personally prefer to have rolloff circuits -after- an overdrive
element (the diodes) so it rolls off high harmonics generated by the
OD itself. I presume your circuit is similar to these:

Loading Image...
Loading Image...

If so, here is my recommendation:
(I'm going to assume that the pot is directly soldered to the board)

Use a resistor before the unit's output volume pot to isolate the
diodes from the rolloff. Do that by unsoldering the 'top' terminal of
the output pot (diagrammed as '3' on both charts above) and pulling it
away from the circuit board. You may want to use 'solder wick' which
will draw up the solder and allow you to use long-nose pliers to pull
the pot terminal free. That's the trickiest part. Careful not to flex
the pot terminal too much. You don't want to crack the mounting on the
pot.

Now solder a 33K resistor between the now-empty solder pad on the
circuit board, and the same pot terminal. The point of this is to add
series resistance to isolate the diodes and allow more predictable
rolloff. Wattage rating of the resistor is not critical.

Then you simply wire a cap across the two 'outside' terminals of the
volume pot. The value of the cap will determine the frequency at which
the rolloff starts. If you're looking for slight rolloff of extreme
highs, you could shoot for 4Khz or so, but I'm guessing you want to
cut down highs more. I'll guess at a cap value around .003, which will
roll off at about 1600hz. That will still leave high mids which
should cut through without sounding harsh.

If you want to add a tone pot, then you'll have more options. You
could increase the value of the cap. But it sounds like you're a
minimalist. :-) Let me know if you want to add the tone pot.

You can use other resistor values in that general range. I picked 33K
as a standard value that's in range. If you already have a resistor
between 15k and 39k, I'll rework the cap values. Let me know.

Also, I don't think you'd want to use the tone stack from a Big Muff
Pi. The control that I remember does have a treble cut at one end, but
there's treble boost at the other. No point in that, right?

Post by TheChris
As for your other question - I think as I add gain, it just gets more shrill.

See my comments above about post-diode rolloff. Other posters'
suggestions for putting a cap on the input or around the opamp are
electronically valid and will work fine. The main advantage in my
suggestion above is in rolling off harmonics generated in the pedal's
OD circuit.

[TheChris]

Post by RS
On Tue, 5 Mar 2013 16:30:32 +0000 (UTC), TheChris

Post by TheChris

Post by l***@hotmail.com
I posted about problems converted the more recent 250's to the original circuit.
What chip is in it?
Does it sound too shrill when clean, or just when it's clipping?
That would give me something to go on.

Looks like the chip is a 351N? There's a top number too - 117?

How've you been, Chris!
The chip would be an LF351n. Originally from National Semi, but others
have also made it. The 117 is probably just a batch number. The LF351
is a JFET-input opamp. The pinouts are pretty standard for a single
opamp chip: 2,3 and 6 for inputs and output (resp). Just like the old
741 family. No big reason to swap it, but if you do, use a socket so
you can try various opamps. Still, that won't result in the dramatic
tone change that you're looking for.
You've already got some good suggestions in this thread, and you could
indeed just treat this as moving a guitar tone control into the box.
IOW, put the rolloff cap right at the input.
I personally prefer to have rolloff circuits -after- an overdrive
element (the diodes) so it rolls off high harmonics generated by the
http://home.comcast.net/~snmavronis/1982dod250schematic.jpg
http://gaussmarkov.net/layouts/dod250/dod250-schem.png
(I'm going to assume that the pot is directly soldered to the board)
Use a resistor before the unit's output volume pot to isolate the
diodes from the rolloff. Do that by unsoldering the 'top' terminal of
the output pot (diagrammed as '3' on both charts above) and pulling it
away from the circuit board. You may want to use 'solder wick' which
will draw up the solder and allow you to use long-nose pliers to pull
the pot terminal free. That's the trickiest part. Careful not to flex
the pot terminal too much. You don't want to crack the mounting on the
pot.
Now solder a 33K resistor between the now-empty solder pad on the
circuit board, and the same pot terminal. The point of this is to add
series resistance to isolate the diodes and allow more predictable
rolloff. Wattage rating of the resistor is not critical.
Then you simply wire a cap across the two 'outside' terminals of the
volume pot. The value of the cap will determine the frequency at which
the rolloff starts. If you're looking for slight rolloff of extreme
highs, you could shoot for 4Khz or so, but I'm guessing you want to
cut down highs more. I'll guess at a cap value around .003, which will
roll off at about 1600hz. That will still leave high mids which
should cut through without sounding harsh.
If you want to add a tone pot, then you'll have more options. You
could increase the value of the cap. But it sounds like you're a
minimalist. :-) Let me know if you want to add the tone pot.
You can use other resistor values in that general range. I picked 33K
as a standard value that's in range. If you already have a resistor
between 15k and 39k, I'll rework the cap values. Let me know.
Also, I don't think you'd want to use the tone stack from a Big Muff
Pi. The control that I remember does have a treble cut at one end, but
there's treble boost at the other. No point in that, right?

Post by TheChris
As for your other question - I think as I add gain, it just gets more shrill.

See my comments above about post-diode rolloff. Other posters'
suggestions for putting a cap on the input or around the opamp are
electronically valid and will work fine. The main advantage in my
suggestion above is in rolling off harmonics generated in the pedal's
OD circuit.

Thanks for all this!! I will investigate thoroughly! :)

[Tony Done]

Post by RS
See my comments above about post-diode rolloff. Other posters'
suggestions for putting a cap on the input or around the opamp are
electronically valid and will work fine. The main advantage in my
suggestion above is in rolling off harmonics generated in the pedal's
OD circuit.

There's an interesting contrast here. Chris (I assume) wants to roll off
the OD harmonics as per your suggestion, because his guitar has a lot of
top end. I've found the other route works better with the OD I'm using -
a Sansamp Character - roll off the guitar's top end and use the OD
harmonics. A good example of there being more than one way to skin the
tonal cat.

[TheChris]

Post by Tony Done
There's an interesting contrast here. Chris (I assume) wants to roll off
the OD harmonics as per your suggestion, because his guitar has a lot of
top end. I've found the other route works better with the OD I'm using -
a Sansamp Character - roll off the guitar's top end and use the OD
harmonics. A good example of there being more than one way to skin the
tonal cat.

My guitar has no more top end than any other guitar with Duncan Distortions. The
DOD sound is brittle. As I said, if I line up 5 overdrives - that one is very
shrill - with the others, I can turn down the tone knob - the 250 doesn't have
one.

I don't have tone knobs on my guitar - and I don't want to make changes on
amps/etc that are clearly a problem with this pedal.

Just want to add a tone knob. I posted a link I think I'll follow.

[Tony Done]

Post by TheChris

Post by Tony Done
There's an interesting contrast here. Chris (I assume) wants to roll off
the OD harmonics as per your suggestion, because his guitar has a lot of
top end. I've found the other route works better with the OD I'm using -
a Sansamp Character - roll off the guitar's top end and use the OD
harmonics. A good example of there being more than one way to skin the
tonal cat.

My guitar has no more top end than any other guitar with Duncan Distortions. The
DOD sound is brittle.

That's what I'm saying, you don't take off any of the top end at the
guitar, so so you end up with a combination of the high end from the
guitar, OD and amp. Turns out to be too much of a good thing with the
DOD. I've found I get a good result, with at least the Sansamp OD, by
eliminating most of the high end from the guitar and using the OD
harmonics. Doing that wouldn't work in your case, because taking out the
guitar high end would affect all the other stuff in your amplification
chain, and you clearly don't want that. Putting a guitar-style tone
control inside the DOD would though, because it would be out of the
circuit when the effect is bypassed.

[TheChris]

Post by Tony Done
That's what I'm saying, you don't take off any of the top end at the
guitar, so so you end up with a combination of the high end from the
guitar, OD and amp. Turns out to be too much of a good thing with the
DOD. I've found I get a good result, with at least the Sansamp OD, by
eliminating most of the high end from the guitar and using the OD
harmonics. Doing that wouldn't work in your case, because taking out the
guitar high end would affect all the other stuff in your amplification
chain, and you clearly don't want that. Putting a guitar-style tone
control inside the DOD would though, because it would be out of the
circuit when the effect is bypassed.

Correct - and that's something I didn't even think of - I need the circuit OUT of
the bypassed signal...

Or, I should just sell them all, and use my DM-4 :) Selling all those vintage
pedals would pay for it many times over :)

[RS]

On Wed, 6 Mar 2013 14:47:50 +0000 (UTC), TheChris

Post by TheChris
My guitar has no more top end than any other guitar with Duncan Distortions. The
DOD sound is brittle.

Hi again, Chris.

Any chance that you could A/B your pedal with another DOD 250 or with
an MXR Distortion+? (Almost the same circuit). Perhaps your circuit
has been modified for more treble?

Post by TheChris
I don't have tone knobs on my guitar - and I don't want to make changes on
amps/etc that are clearly a problem with this pedal.
Just want to add a tone knob. I posted a link I think I'll follow.

Are you referring to the Big Muff Pi tone control? I had already
commented about that. One 'side' does roll off high end, but the
other is a treble boost, which you may not need. :-) You'd probably
be using less than half of the control's rotation.

When incorporating additional circuitry, you also have to consider
something called 'impedance scaling.' The non-tech explanation is
that you can lose signal if it's not scaled properly. In this case,
presuming that you'd just place the Muff circuit after the volume
control, you would get some interaction. Probably 3db to 6db,
depending on setting of the volume and tone controls (rough estimate).
You could try it to see if that's objectionable.

[TheChris]

Post by RS
Any chance that you could A/B your pedal with another DOD 250 or with
an MXR Distortion+? (Almost the same circuit). Perhaps your circuit
has been modified for more treble?

Funny you should mention a Distortion +... I realize they are extremely similar
circuits... IMO, the D+ suffers from the same harshness.

I can safely say - from owning these pedals since 1985 - they're brittle...

I don't think this one has been modded. It would be easy to see... I was in there
a lot when I put the LED and the 3D3P switch in...

[RS]

On Wed, 6 Mar 2013 23:30:16 +0000 (UTC), TheChris

Post by TheChris

Post by RS
Any chance that you could A/B your pedal with another DOD 250 or with
an MXR Distortion+? (Almost the same circuit). Perhaps your circuit
has been modified for more treble?

Funny you should mention a Distortion +... I realize they are extremely similar
circuits... IMO, the D+ suffers from the same harshness.
I can safely say - from owning these pedals since 1985 - they're brittle...
I don't think this one has been modded. It would be easy to see... I was in there
a lot when I put the LED and the 3D3P switch in...

Ah, I knew that it had true bypass and the LED. I didn't realize that
you had installed those. Given that, and your similar comment about
the D+, it's safe to say that the DOD is just too bright. :-)

There are many pedals, especially from that era, that don't have any
high end rolloff. The rolloff is usually a good idea, and many newer
pedals do use a rolloff circuit.

I often incorporate post-rolloff when designing tube overdrive
circuits. It does smooth out harsh high end.

[TheChris]

Post by RS
When incorporating additional circuitry, you also have to consider
something called 'impedance scaling.' The non-tech explanation is
that you can lose signal if it's not scaled properly. In this case,
presuming that you'd just place the Muff circuit after the volume
control, you would get some interaction. Probably 3db to 6db,
depending on setting of the volume and tone controls (rough estimate).
You could try it to see if that's objectionable.

I know I'm going to lose something with regards to output. But, I think the DOD
has SO much output, that I'll just be required to turn that Output knob a
mili-inch :)

[RS]

On Wed, 6 Mar 2013 23:31:32 +0000 (UTC), TheChris

Post by TheChris

Post by RS
When incorporating additional circuitry, you also have to consider
something called 'impedance scaling.' The non-tech explanation is
that you can lose signal if it's not scaled properly. In this case,
presuming that you'd just place the Muff circuit after the volume
control, you would get some interaction. Probably 3db to 6db,
depending on setting of the volume and tone controls (rough estimate).
You could try it to see if that's objectionable.

I know I'm going to lose something with regards to output. But, I think the DOD
has SO much output, that I'll just be required to turn that Output knob a
mili-inch :)

In this case you're right, Chris, there's gain to spare. But control
operation can also be inconsistent. Changing one control can affect
the other due to impedance change. Scaling helps to minimize that.

The general idea is that you're starting off with a low source
impedance. The next stage in the circuit is a bit higher, the next
higher still. This minimizes interaction between stages.

An example: Look at the bass path in the Fender tone stack. The
'slope' resistor is 100K. Next is the bass control, 250K. Then the
volume control, 1 Meg. (For the technically inclined: ref Kirchoff
loops)

Ideally, you'd want to do something similar, and that's why I
suggested 33K to bridge the 10k source and 100k volume pot in your
circuit. But ultimately it's all in how well it works for you.* This
circuit is right around the edge of where the interaction might be
annoying to some, but maybe it's easiest to just try it and see.

Incidentally, one of the differences between your circuit and the
Distortion+ is that the D+ volume control is 10k, compared to 100k in
the DOD. If your control were 10k, I would have suggested putting the
tone control after it rather than before.

I don't think you'll be happy with the treble-boost aspect of the Muff
circuit though, so let me know if you want to try another circuit. I
think a treble-cut-only circuit would make better use of control
rotation range, with fewer components and less wiring hassle.

* BTW, there are circuits like the Fuzz Face that are horrible from a
design point of view, but when you hear Jimi or Eric Johnson use them,
they're perfect.

[RS]

Post by RS
I don't think you'll be happy with the treble-boost aspect of the Muff
circuit though, so let me know if you want to try another circuit. I
think a treble-cut-only circuit would make better use of control
rotation range, with fewer components and less wiring hassle.

Chris, If you haven't lost interest in this, I can send you a circuit
that will do what you want with only a pot and a small cap. I've
looked at the layout and it seems like the pot would be a tight
squeeze, but if you can fit it, you'll have a pretty versatile
circuit.

[TheChris]

Post by RS

Post by RS
I don't think you'll be happy with the treble-boost aspect of the Muff
circuit though, so let me know if you want to try another circuit. I
think a treble-cut-only circuit would make better use of control
rotation range, with fewer components and less wiring hassle.

Chris, If you haven't lost interest in this, I can send you a circuit
that will do what you want with only a pot and a small cap. I've
looked at the layout and it seems like the pot would be a tight
squeeze, but if you can fit it, you'll have a pretty versatile
circuit.

I'm down for it... Time is tight though... I'm leaving for Afghanistan on
Thursday.... I'm going to be using my Guild Thunderbird tonight with my SD-1..
And I might bring my DS-1 out just in case!

[RS]

On Fri, 8 Mar 2013 22:01:48 +0000 (UTC), TheChris

Post by TheChris

Post by RS

Post by RS
I don't think you'll be happy with the treble-boost aspect of the Muff
circuit though, so let me know if you want to try another circuit. I
think a treble-cut-only circuit would make better use of control
rotation range, with fewer components and less wiring hassle.

Chris, If you haven't lost interest in this, I can send you a circuit
that will do what you want with only a pot and a small cap. I've
looked at the layout and it seems like the pot would be a tight
squeeze, but if you can fit it, you'll have a pretty versatile
circuit.

I'm down for it... Time is tight though... I'm leaving for Afghanistan on
Thursday.... I'm going to be using my Guild Thunderbird tonight with my SD-1..
And I might bring my DS-1 out just in case!

I like the SD1. DS1 not as much but it's OK. Odd how just a few
component changes can make a difference in some pedals--filtering and
response can completely change the personality.

OK then, we'll try to turn it around fast.

Verbal description:

Break the connection between the current volume pot wiper and the
switch. Insert a 250k tone pot -in series- with the signal at that
point (diagram and comments on pot taper below).

Add a .001 cap between the 'switch' side of that connection and
ground.

Diagram: View this with a non-proportional font (like Courier), else
it will look like a jumble. Most text editors have that option.


------
|
/
100k / 250K tone
Vol /<----///////
/ ^
/ |
| +--------> to switch
| |
--- ---
- --- .001
|
|
---
-

This is a bit different from normal tone circuits. Usually there's a
fixed series resistor and a cap to ground that determines a fixed
corner frequency (-3db 'knee' in the response curve). The frequency
where the rolloff starts never changes. OK for some apps.

The idea behind using the pot in series is that it varies the
frequency where the rolloff starts, so you can maintain as much of the
mids as you want. I find that important to keeping some incisive bite
to the sound while still rolling off the harsh edges of overdriven
signals. I've scaled this to work -after- your volume control so you
won't have to lift anything from the PC board.

Pot taper: Since this is operating a bit differently from a normal
db-only tone control, use a linear pot instead of log so the taper
works more smoothly. When you're looking at the pot from the front,
you'd use the center terminal and the terminal at the left. The
terminal at the right is unconnected.

Or alternately you could use a log taper pot and wire it opposite. The
perceived rotational taper will actually be smoother, but treble will
increase as you turn the pot counterclockwise.

You could get the best of both by using an anti-log taper, but those
are tough to find. So try the linear 250k first.

If you can't find 250k, use a 500k with a 470p cap (or anything in
that range). I favor 250k so you're not putting as much resistance in
series with your signal, but this won't matter much, as you're only
affecting the OD'd signal anyway.

This is the general idea that I use for post-overdrive circuits in
tube amps. With values above, you be able to vary the rolloff knee
from around 6400Hz down to 640Hz. That should cover the range that
you're looking for.

Get back with any questions or if you can't find components.

So...Afghanistan?

[RS]

On Fri, 8 Mar 2013 22:01:48 +0000 (UTC), TheChris

Post by TheChris

Post by RS

Post by RS
I don't think you'll be happy with the treble-boost aspect of the Muff
circuit though, so let me know if you want to try another circuit. I
think a treble-cut-only circuit would make better use of control
rotation range, with fewer components and less wiring hassle.

Chris, If you haven't lost interest in this, I can send you a circuit
that will do what you want with only a pot and a small cap. I've
looked at the layout and it seems like the pot would be a tight
squeeze, but if you can fit it, you'll have a pretty versatile
circuit.

I'm down for it... Time is tight though... I'm leaving for Afghanistan on
Thursday....

Chris, Just checking in to make sure you got my last reply and were
able to find parts. Let me know how everything is going.

Also, if any tech-minded ag'ers want a quick explanation of the theory
behind the circuit that I posted, speak up.

[The_Chris]

Post by RS
Chris, Just checking in to make sure you got my last reply and were
able to find parts. Let me know how everything is going.
Also, if any tech-minded ag'ers want a quick explanation of the theory
behind the circuit that I posted, speak up.

I think I'm going to try this tomorrow... On a side note, I ordered one of the Monte Allum mods for my DS-1. I had a modded one a while back, and REALLY liked it. Don't remember why I sold it. But, somebody gave me another older DS-1, so, I'm ahead of the game :)

[RS]

On Mon, 4 Nov 2013 20:01:46 -0800 (PST), The_Chris

Post by The_Chris

Post by RS
Chris, Just checking in to make sure you got my last reply and were
able to find parts. Let me know how everything is going.
Also, if any tech-minded ag'ers want a quick explanation of the theory
behind the circuit that I posted, speak up.

I think I'm going to try this tomorrow... On a side note, I ordered
one of the Monte Allum mods for my DS-1. I had a modded one a while
back, and REALLY liked it. Don't remember why I sold it. But,
somebody gave me another older DS-1, so, I'm ahead of the game :)

Wow...that was from back in ...March? I was wondering what happened.
I think you said you were leaving for parts unknown a couple days
after.

Chris, I had just recommended a similar circuit to Tony, who was doing
something very different--piezo preamp. The time constants will be
different, but maybe you two can compare notes.

I'll have to look up the old post for this to refresh my memory on
exact component values, but I think you should have a good starting
point. Let me know how it goes.

[The_Chris]

Post by RS
On Mon, 4 Nov 2013 20:01:46 -0800 (PST), The_Chris

Post by The_Chris

Post by RS
Chris, Just checking in to make sure you got my last reply and were
able to find parts. Let me know how everything is going.
Also, if any tech-minded ag'ers want a quick explanation of the theory
behind the circuit that I posted, speak up.

I think I'm going to try this tomorrow... On a side note, I ordered
one of the Monte Allum mods for my DS-1. I had a modded one a while
back, and REALLY liked it. Don't remember why I sold it. But,
somebody gave me another older DS-1, so, I'm ahead of the game :)

Wow...that was from back in ...March? I was wondering what happened.
I think you said you were leaving for parts unknown a couple days
after.
Chris, I had just recommended a similar circuit to Tony, who was doing
something very different--piezo preamp. The time constants will be
different, but maybe you two can compare notes.
I'll have to look up the old post for this to refresh my memory on
exact component values, but I think you should have a good starting
point. Let me know how it goes.

You sent me something... I just printed it out.... Might hit Radio Shack
tomorrow...

Yeah, I only get home every 3 months :(

[RS]

On Tue, 5 Nov 2013 21:15:47 +0000 (UTC), "The_Chris"

Post by The_Chris

Post by RS
On Mon, 4 Nov 2013 20:01:46 -0800 (PST), The_Chris

Post by The_Chris

Post by RS
Chris, Just checking in to make sure you got my last reply and were
able to find parts. Let me know how everything is going.
Also, if any tech-minded ag'ers want a quick explanation of the theory
behind the circuit that I posted, speak up.

I think I'm going to try this tomorrow... On a side note, I ordered
one of the Monte Allum mods for my DS-1. I had a modded one a while
back, and REALLY liked it. Don't remember why I sold it. But,
somebody gave me another older DS-1, so, I'm ahead of the game :)

Wow...that was from back in ...March? I was wondering what happened.
I think you said you were leaving for parts unknown a couple days
after.
Chris, I had just recommended a similar circuit to Tony, who was doing
something very different--piezo preamp. The time constants will be
different, but maybe you two can compare notes.
I'll have to look up the old post for this to refresh my memory on
exact component values, but I think you should have a good starting
point. Let me know how it goes.

You sent me something... I just printed it out.... Might hit Radio Shack
tomorrow...

I think I found the original exchange, and I sent my post back up
again, just in case.

Post by The_Chris
Yeah, I only get home every 3 months :(

Where are you? Military?

I'll try to monitor ag over the next couple days. Let me know if you
have any trouble with that, and I'll retrace where we left it before.

[The_Chris]

Post by RS
On Tue, 5 Nov 2013 21:15:47 +0000 (UTC), "The_Chris"

Post by The_Chris

Post by RS
On Mon, 4 Nov 2013 20:01:46 -0800 (PST), The_Chris

Post by The_Chris

Post by RS
Chris, Just checking in to make sure you got my last reply and were
able to find parts. Let me know how everything is going.
Also, if any tech-minded ag'ers want a quick explanation of the theory
behind the circuit that I posted, speak up.

I think I'm going to try this tomorrow... On a side note, I ordered
one of the Monte Allum mods for my DS-1. I had a modded one a while
back, and REALLY liked it. Don't remember why I sold it. But,
somebody gave me another older DS-1, so, I'm ahead of the game :)

Wow...that was from back in ...March? I was wondering what happened.
I think you said you were leaving for parts unknown a couple days
after.
Chris, I had just recommended a similar circuit to Tony, who was doing
something very different--piezo preamp. The time constants will be
different, but maybe you two can compare notes.
I'll have to look up the old post for this to refresh my memory on
exact component values, but I think you should have a good starting
point. Let me know how it goes.

You sent me something... I just printed it out.... Might hit Radio Shack
tomorrow...

I think I found the original exchange, and I sent my post back up
again, just in case.

Post by The_Chris
Yeah, I only get home every 3 months :(

Where are you? Military?
I'll try to monitor ag over the next couple days. Let me know if you
have any trouble with that, and I'll retrace where we left it before.

Used my energies doing a Monte Allums mod to my DS-1... Even though this
is the second one I've owned, this is the first one I did myself.

I am very underwhelmed by it.... I keep wondering what I did wrong, but
I followed the directions, and it had me check after each component
swap. The sound went south after the first change (the OPAMP)... So,
I've been focused on that. I could swear this mod sounded better. Now
it sounds like the upper strings are over saturated - almost like what a
fuzz pedal sounds like - and I don't like that.....

The DOD awaits...

[RS]

Just thought I'd refresh this in case it has scrolled off your news

Post by RS
On Tue, 5 Mar 2013 16:30:32 +0000 (UTC), TheChris

Post by TheChris

Post by l***@hotmail.com
I posted about problems converted the more recent 250's to the original circuit.
What chip is in it?
Does it sound too shrill when clean, or just when it's clipping?
That would give me something to go on.

Looks like the chip is a 351N? There's a top number too - 117?

How've you been, Chris!
The chip would be an LF351n. Originally from National Semi, but others
have also made it. The 117 is probably just a batch number. The LF351
is a JFET-input opamp. The pinouts are pretty standard for a single
opamp chip: 2,3 and 6 for inputs and output (resp). Just like the old
741 family. No big reason to swap it, but if you do, use a socket so
you can try various opamps. Still, that won't result in the dramatic
tone change that you're looking for.
You've already got some good suggestions in this thread, and you could
indeed just treat this as moving a guitar tone control into the box.
IOW, put the rolloff cap right at the input.
I personally prefer to have rolloff circuits -after- an overdrive
element (the diodes) so it rolls off high harmonics generated by the
http://home.comcast.net/~snmavronis/1982dod250schematic.jpg
http://gaussmarkov.net/layouts/dod250/dod250-schem.png
(I'm going to assume that the pot is directly soldered to the board)
Use a resistor before the unit's output volume pot to isolate the
diodes from the rolloff. Do that by unsoldering the 'top' terminal of
the output pot (diagrammed as '3' on both charts above) and pulling it
away from the circuit board. You may want to use 'solder wick' which
will draw up the solder and allow you to use long-nose pliers to pull
the pot terminal free. That's the trickiest part. Careful not to flex
the pot terminal too much. You don't want to crack the mounting on the
pot.
Now solder a 33K resistor between the now-empty solder pad on the
circuit board, and the same pot terminal. The point of this is to add
series resistance to isolate the diodes and allow more predictable
rolloff. Wattage rating of the resistor is not critical.
Then you simply wire a cap across the two 'outside' terminals of the
volume pot. The value of the cap will determine the frequency at which
the rolloff starts. If you're looking for slight rolloff of extreme
highs, you could shoot for 4Khz or so, but I'm guessing you want to
cut down highs more. I'll guess at a cap value around .003, which will
roll off at about 1600hz. That will still leave high mids which
should cut through without sounding harsh.
If you want to add a tone pot, then you'll have more options. You
could increase the value of the cap. But it sounds like you're a
minimalist. :-) Let me know if you want to add the tone pot.
You can use other resistor values in that general range. I picked 33K
as a standard value that's in range. If you already have a resistor
between 15k and 39k, I'll rework the cap values. Let me know.
Also, I don't think you'd want to use the tone stack from a Big Muff
Pi. The control that I remember does have a treble cut at one end, but
there's treble boost at the other. No point in that, right?

Post by TheChris
As for your other question - I think as I add gain, it just gets more shrill.

See my comments above about post-diode rolloff. Other posters'
suggestions for putting a cap on the input or around the opamp are
electronically valid and will work fine. The main advantage in my
suggestion above is in rolling off harmonics generated in the pedal's
OD circuit.