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I never had a Boss DS-1 and I always built distortion pedals I liked more. But want to try the DS-1 and get fun with all the mods.
There are so much schematics and versions that I need to choice the right for me.
I found different versions adapted in different way, with some different values especially and different IC.
Old DS-1 used a single op-amp (TA7136P). Later the IC was replaced by a dual op-amp, but with some changes in the gain stages. Anyway, the two version sound very similar.

I want to build on veroboard the version with buffers and the dual op-amp without the switching system.
Tagboard has a bufferless (but even without the first stage) version with a rare M5223P and a complete version where suggest JRC4558, TL072 or similar.
Sabrotone has a bufferless version with Keeley switches and values change. There's a NJM3404AL on it (I think it should be 3404AD, because the format).
Dirtbox Layout has a single op-amp version, (LM741, TL061...).
The Aion version (Comet) can be built with the original single op-amp or with a JRC4558.
Tonepad schematic has something new. Original single op-amp and dual op-amp like a TL072, but for the dual op-amp version some value in the first stage change. (???)

Meanwhile, I modified the layout of Dirtbox with a single op-amp swapping it to adjust it for a dual. But maybe I could use directly the verified tagboard layout. Do you think a JRC3404AD I could buy worth? it's more expansive than other dual op-amp.

What do you suggest about all this?

Thanks!

To be honest a second hand DS-1 is impossible to beat DIY ... the typical stompbox quality is the best part of so many BOSS pedals....
It is one of those pedals I modded to hell and back so many times ....
Just as the best Tube Screamer is modding a cheap SD-1 .....

Someone gave me a newish DS1.  Horrible sounding pedal! And I'm a Boss fan. Interested to hear what mods you like. 

Quote from: blackieNYC on October 16, 2022, 07:16:26 PM
Someone gave me a newish DS1.  Horrible sounding pedal! And I'm a Boss fan. Interested to hear what mods you like.

There's dozens of Youtube videos that want to tell you how the pedal's great but you're using it wrong?!? And then there's probably dozens more telling you how *this* mod is the one that turns it into the killer tone pedal you always dreamt of! ;)

I studied it a bit recently, as it happens. It's an odd design, and it got odder after the single-to-dual amp change, since one of the amps basically does nothing. It's there just to make the replacement easy. A lot of the buffering is just because of Boss's FET switching, and without that, there's really no need for it. From a noise point of view, probably better off without it. The crucial parts are the pre-op-amp boost stage, which tweaks the tone and provides the first clipping, since it is likely to hit the rails (+35dB max boost). Then comes the op-amp gain stage (clips again, now up to 60dB gain) and then the diodes (clips again, chops the level) and the tone control and volume. You could go directly out from there. The last bit is just another FET switch and another buffer.

Input buffer is required. Don't leave it out.

Quote from: Steben on October 16, 2022, 01:45:18 PM
To be honest a second hand DS-1 is impossible to beat DIY ... the typical stompbox quality is the best part of so many BOSS pedals....
It is one of those pedals I modded to hell and back so many times ....
Just as the best Tube Screamer is modding a cheap SD-1 .....

You're right. But As you can understand I want to build, not to buy pedals. ;D It's just for fun, to build it starting from zero, include how many pots and switches I wanted, if I wanted, etc.

Quote from: blackieNYC on October 16, 2022, 07:16:26 PM
Someone gave me a newish DS1.  Horrible sounding pedal! And I'm a Boss fan. Interested to hear what mods you like. 

In the DIY pedal forums you can find any kind of mod you want. Mods to reduce the scoop mid, clipping texture, gain amount, volume loss, op-amp, boost, true bypass, fuzziness, low end, fizziness... Wampler mods, JHS mod, Keeley mod, customized mod, fuzz/synth/oscillation mod...
The pedal is what it is, but I like to try all the possible mod when I try a new circuit.

Quote from: ElectricDruid on October 16, 2022, 08:16:14 PM
I studied it a bit recently, as it happens. It's an odd design, and it got odder after the single-to-dual amp change, since one of the amps basically does nothing. It's there just to make the replacement easy. A lot of the buffering is just because of Boss's FET switching, and without that, there's really no need for it. From a noise point of view, probably better off without it. The crucial parts are the pre-op-amp boost stage, which tweaks the tone and provides the first clipping, since it is likely to hit the rails (+35dB max boost). Then comes the op-amp gain stage (clips again, now up to 60dB gain) and then the diodes (clips again, chops the level) and the tone control and volume. You could go directly out from there. The last bit is just another FET switch and another buffer.

Quote from: m4268588 on October 16, 2022, 11:11:33 PM
Input buffer is required. Don't leave it out.

Indeed, I can't see what the buffer op-amp stage does, too. But it always be ok, afterall.

Maybe I could build this:
https://dirtboxlayouts.blogspot.com/2019/06/boss-ds-1-distortion-pre-1994.html
What is a good quality single op-amp? Burr Brown? I have a lot of dual op-amp alternative, but not much single op-amp.

Or this:
https://tagboardeffects.blogspot.com/2014/10/boss-ds-1-distortion.html
I have a lot of dual op-amp alternative.
https://reverb.com/news/swapping-boss-ds-1-op-amps-hear-20-variations-in-action
It seems that the op-amp make a lot of difference!

Well, thinking to the DS-1 buffers, I thought the output buffer was more important than the input buffer, for the impedance. (For Example the las version of the OCD has added an output stage to improve the signal in chain with other pedal after it.) Instead, I thought if I don't include the input buffer there's anyway a booster stage, that works kind of like that.

I wanted to built the whole schematic of the DS-1, excluding the fet switching.

We need some schematics:

(https://i.postimg.cc/0MfRV8FQ/771c13a12b30ac47733ce1a21fdb27eb-guitar-pedals-electric-guitars.jpg) (https://postimg.cc/0MfRV8FQ)

(https://i.postimg.cc/R3wNVH6D/Boss-DS-1-Schematic2.png) (https://postimg.cc/R3wNVH6D)

Quote from: m4268588 on October 16, 2022, 11:11:33 PM
Input buffer is required. Don't leave it out.

The Q1 buffer has a higher impedance than the Q2 gain stage, so yeah, there's that.

Or you could get really weird and try it with a discrete op amp.   

https://vero-p2p.blogspot.com/2021/10/boss-modded-ds-1-diode-compression-opamp.html

Quote from: ElectricDruid on October 17, 2022, 05:39:59 AM

Quote from: m4268588 on October 16, 2022, 11:11:33 PM
Input buffer is required. Don't leave it out.

The Q1 buffer has a higher impedance than the Q2 gain stage, so yeah, there's that.

By making R10 470k and IC1A with gain of that of Q2 stage, he can delete both Q1 & Q2 stages.. :icon_wink:
(with extra bonus IN-OUT been in phase..)

Quote from: antonis on October 17, 2022, 07:11:13 AM

Quote from: ElectricDruid on October 17, 2022, 05:39:59 AM

Quote from: m4268588 on October 16, 2022, 11:11:33 PM
Input buffer is required. Don't leave it out.

The Q1 buffer has a higher impedance than the Q2 gain stage, so yeah, there's that.

By making R10 470k and IC1A with gain of that of Q2 stage, he can delete both Q1 & Q2 stages.. :icon_wink:
(with extra bonus IN-OUT been in phase..)

Channel 1 of ds2 is pretty much that. I did not notice that much difference in tone indeed.....

Quote from: antonis on October 17, 2022, 07:11:13 AM
By making R10 470k and IC1A with gain of that of Q2 stage, he can delete both Q1 & Q2 stages.. :icon_wink:
(with extra bonus IN-OUT been in phase..)

I had this thought too. There's some tone shaping around Q2 which is important, but it's possible to copy that too. I had a go in LTspice and got the frequency responses identical through the different stages:
(https://i.postimg.cc/Jt1Pjs0N/Boss-DS-1.png) (https://postimg.cc/Jt1Pjs0N)

It seemed to me there was quite a lot of simplifications could be done to the circuit, especially given that there's a "spare" op-amp in the original circuit waiting to be used.
The potential problem with this (if there is one - I haven't tried it to listen to, and I don't have a DS-1 to compare it to either) is that the Q2 will clip pretty heavily, so if the op-amp distortion has a different character, you'll end up changing the tone of the pedal. It might be *better*, who knows?!? But it won't be a DS-1 exactly any more...

<edit>Steben is fast! Ok, so it might work quite nicely, if the DS-2 doesn't sound so different.

Thanks to everybody for your answers. I didn't know if I had to start this thread because the topic could be a bit "old". :D

Quote from: andy-h-h on October 17, 2022, 06:23:00 AM
Or you could get really weird and try it with a discrete op amp.   
https://vero-p2p.blogspot.com/2021/10/boss-modded-ds-1-diode-compression-opamp.html

Quote from: antonis on October 17, 2022, 07:11:13 AM

Quote from: ElectricDruid on October 17, 2022, 05:39:59 AM

Quote from: m4268588 on October 16, 2022, 11:11:33 PM
Input buffer is required. Don't leave it out.

The Q1 buffer has a higher impedance than the Q2 gain stage, so yeah, there's that.

By making R10 470k and IC1A with gain of that of Q2 stage, he can delete both Q1 & Q2 stages.. :icon_wink:
(with extra bonus IN-OUT been in phase..)

Thanks, but I prefer to build something more close to the original pedal.

DS-1 and DS-2 are made in very different way, though. I  drawn a veroboard layout of the DS-2, but I never wanted to verify it. Maybe I'll post in the forum.

Right now the tagboard layout is winning. I'm woriking on the design to make it more "moddable".
Then, my impression si that nice op-amp for clean boost or buffer are not so good in distortion pedal. I'm not sure if I had to buy more expansive IC (not absurdly expensive) and to find I like TL072 or JRC4558.

Quote from: Elijah-Baley on October 17, 2022, 10:57:14 AM
Thanks to everybody for your answers. I didn't know if I had to start this thread because the topic could be a bit "old". :D

Quote from: andy-h-h on October 17, 2022, 06:23:00 AM
Or you could get really weird and try it with a discrete op amp.   
https://vero-p2p.blogspot.com/2021/10/boss-modded-ds-1-diode-compression-opamp.html

Quote from: antonis on October 17, 2022, 07:11:13 AM

Quote from: ElectricDruid on October 17, 2022, 05:39:59 AM

Quote from: m4268588 on October 16, 2022, 11:11:33 PM
Input buffer is required. Don't leave it out.

The Q1 buffer has a higher impedance than the Q2 gain stage, so yeah, there's that.

By making R10 470k and IC1A with gain of that of Q2 stage, he can delete both Q1 & Q2 stages.. :icon_wink:
(with extra bonus IN-OUT been in phase..)

Thanks, but I prefer to build something more close to the original pedal.

DS-1 and DS-2 are made in very different way, though. I  drawn a veroboard layout of the DS-2, but I never wanted to verify it. Maybe I'll post in the forum.

Right now the tagboard layout is winning. I'm woriking on the design to make it more "moddable".
Then, my impression si that nice op-amp for clean boost or buffer are not so good in distortion pedal. I'm not sure if I had to buy more expansive IC (not absurdly expensive) and to find I like TL072 or JRC4558.

DS-2 does have a BJT stage in front as well.... Frankly the slight differences between DS1 and DS2 in distortion 1 mode are slightly in favour of the DS2.
That's taste ;).

Quote from: Elijah-Baley on October 17, 2022, 10:57:14 AM
Thanks, but I prefer to build something more close to the original pedal.

Fair enough. You know what us lot are like - give us a schematic and we can't leave well alone ;)

Quote from: ElectricDruid on October 17, 2022, 02:21:29 PM

Quote from: Elijah-Baley on October 17, 2022, 10:57:14 AM
Thanks, but I prefer to build something more close to the original pedal.

Fair enough. You know what us lot are like - give us a schematic and we can't leave well alone ;)

My favourite mod is lowering gain (def Q2) followed by having higher clipping treshold (LED's) - perhaps tinkering with complex clipping and also more mids in the tone control.
So yeah .... pretty much what you say.

Quote from: ElectricDruid on October 17, 2022, 02:21:29 PM
Fair enough. You know what us lot are like - give us a schematic and we can't leave well alone ;)

I'll post soon a schematic with my comments about the mod of a lot of parts. ;)

Quote from: Steben on October 17, 2022, 02:38:46 PM

Quote from: ElectricDruid on October 17, 2022, 02:21:29 PM

Quote from: Elijah-Baley on October 17, 2022, 10:57:14 AM
Thanks, but I prefer to build something more close to the original pedal.

Fair enough. You know what us lot are like - give us a schematic and we can't leave well alone ;)

My favourite mod is lowering gain (def Q2) followed by having higher clipping treshold (LED's) - perhaps tinkering with complex clipping and also more mids in the tone control.
So yeah .... pretty much what you say.

To make sounds "better" this pedal the mods you mentioned are a must: less boost, more dynamic clipping (and more volume), more low end, more mids and smoother high.
I'm not sure if I'll build a simple modified DS-1, but I like to hear the difference between the original one and the mods. Maybe some mod will be fixed, but for other mods I'll use switches.

One thing is sure. Dual op-amp version.
Not because that, but I was thinking about the op-amp buffer stage. What if I turn it into a boost stage? Is it too much for this circuit? ;D

Quote from: Elijah-Baley on October 18, 2022, 04:16:36 AM
I'm not sure if I'll build a simple modified DS-1, but I like to hear the difference between the original one and the mods.

https://www.premierguitar.com/diy/pedal-projects/boss-ds-1-mods (https://www.premierguitar.com/diy/pedal-projects/boss-ds-1-mods)
https://www.csguitars.co.uk/ds1-mod (https://www.csguitars.co.uk/ds1-mod)
https://www.instructables.com/Modify-Your-Boss-DS-1/ (https://www.instructables.com/Modify-Your-Boss-DS-1/)
and of course: https://www.diystompboxes.com/DIYFiles/up/Build_Your_Own_DS-1_Distortion.pdf (https://www.diystompboxes.com/DIYFiles/up/Build_Your_Own_DS-1_Distortion.pdf)

Quote from: Elijah-Baley on October 18, 2022, 04:16:36 AM
One thing is sure. Dual op-amp version.
Not because that, but I was thinking about the op-amp buffer stage. What if I turn it into a boost stage? Is it too much for this circuit?

I'd say, yes, it probably *is* too much for this circuit. That Q2 gain stage has +35dB, so there's already a lot of boosting going on ahead of the op-amp.
But yeah, why not? Turn the DS-1 into a high gain monster pedal! Alternatively, if you modded the Q2 stage for less gain, you could add a bit in front.

Quote from: Elijah-Baley on October 18, 2022, 04:16:36 AM
Not because that, but I was thinking about the op-amp buffer stage. What if I turn it into a boost stage? Is it too much for this circuit? ;D

Below is what said above..

Quote from: antonis on October 17, 2022, 07:11:13 AM
By making R10 470k and IC1A with gain of that of Q2 stage, he can delete both Q1 & Q2 stages.. :icon_wink:
(with extra bonus IN-OUT been in phase..)

Quote from: antonis on October 18, 2022, 07:58:32 AM
https://www.premierguitar.com/diy/pedal-projects/boss-ds-1-mods (https://www.premierguitar.com/diy/pedal-projects/boss-ds-1-mods)
https://www.csguitars.co.uk/ds1-mod (https://www.csguitars.co.uk/ds1-mod)
https://www.instructables.com/Modify-Your-Boss-DS-1/ (https://www.instructables.com/Modify-Your-Boss-DS-1/)
and of course: https://www.diystompboxes.com/DIYFiles/up/Build_Your_Own_DS-1_Distortion.pdf (https://www.diystompboxes.com/DIYFiles/up/Build_Your_Own_DS-1_Distortion.pdf)

Thank you antonis. I think I knew all of them. ;D I'm collecting pages and note about all the possible mods by whoever.
I'll report soon not every single mod or package of mod, but a sort of instructions about all the mod of the critical parts. :)

Quote from: ElectricDruid on October 18, 2022, 08:29:18 AM

Quote from: Elijah-Baley on October 18, 2022, 04:16:36 AM
One thing is sure. Dual op-amp version.
Not because that, but I was thinking about the op-amp buffer stage. What if I turn it into a boost stage? Is it too much for this circuit?

I'd say, yes, it probably *is* too much for this circuit. That Q2 gain stage has +35dB, so there's already a lot of boosting going on ahead of the op-amp.
But yeah, why not? Turn the DS-1 into a high gain monster pedal! Alternatively, if you modded the Q2 stage for less gain, you could add a bit in front.

Yes, I noticed that a sort of "fat mod" by Muzique.com is to increase the 1k, this pairs the bass and the treble response of the boost stage, but cut a lot of boost, too. If you mean this I could try to cut the boost of the Q2 stage, and to turn the buffer op-amp stage into a boost.
It was this what you meant, right?

Quote from: Elijah-Baley on October 19, 2022, 04:17:55 AM
Yes, I noticed that a sort of "fat mod" by Muzique.com is to increase the 1k, this pairs the bass and the treble response of the boost stage, but cut a lot of boost, too. If you mean this I could try to cut the boost of the Q2 stage, and to turn the buffer op-amp stage into a boost.
It was this what you meant, right?

Yes, exactly. Tame the Q2 stage a bit, then try a op-amp boost in front of it.

I drawn this for my personal use, so maybe some parts could be seem cryptic, and I have to explain at least those areas. I'll report what the software emulator does.

(https://i.postimg.cc/fJ1t280m/Boss-DS-1-Complete-schematic.jpg) (https://postimg.cc/fJ1t280m)

1. This parts is generally left out to cut the fet switching. Bypassing it I got a little bass boost.
(From Aion Comet Project:
«With the FET switching in the original, there are two capacitors in series here, 470n and 47n. A series
calculation puts the "consolidated" value for this at 42n. However, since 42n is a pretty rare value for a
capacitor, the more common 47n can be used instead and won't be noticeably different.»)

2. One mod is add the Big Muff clipping.

3. Some mod are called Synth/Fuzz/Oscillation (now called SFO) and three start from there.

4. This is a buffer, originally, but it could be a boost. (R41, R42, C24, C25 are ipothetical.) This mod is never been documented.

5. Connecting this spots it shuld sound like a fuzz.

6. It's one of the connection of the SFO.

7. It's one of the connection of the SFO.

8. In rare schematic R40 1k resistor is missing. My emulator doesn't prove it but that resistor could give a bit of mid boost.

9. One mod add that cap.

10. It's one of the connection of the SFO.

Later I'll write some possible mods.

The Q2 gain stage of DS-1 has quite some gain. Is that intentional? It almost looks like it clips right there.
Someone has asked me to make his DS-1 sound less harsh. I wonder if lowering that gain would help.

Quote from: Lino22 on October 20, 2022, 11:35:18 AM
The Q2 gain stage of DS-1 has quite some gain. Is that intentional? It almost looks like it clips right there.
Someone has asked me to make his DS-1 sound less harsh. I wonder if lowering that gain would help.

there are two harsh-es: too much treble and too much gain.
The Q2 stage has a bit of a low cut effect. Classic AMZ mod lowers the gain while tempering the high boost at once. SO yes, this might help.
Or you could change the freq response of the tone control circuit if the gain character suits you anyway.

Hello.
Here's the schematic, with some correction, though the old one contain some other thing I described in my post that you can read.

(https://i.postimg.cc/Z93R0vhq/Total-Boss-DS-1.jpg) (https://postimg.cc/Z93R0vhq)

I added some other synth/fuzz/oscillation option, one of these is the tremolo effect.
I added (I don't know if somebody really tried it) the soft clipping diodes in the gain stage.

The following descriptions are based on what someone else tried, experimented or just what my emulator software said, and those have to considered tried one by one, and the response if adopted some together could influence themselves, of course. I am no still building this pedal, so I can't give you my personal opinion, anyway there are ton of opinion. Phrase between « » are taken from someone else in some forums.
I indicated the number of the part, what happens if you change it, and the range of the value.
I avoided to speak about all the package of mods.

R2: 470k - Increase it for an higher impedance.
R6: 100k - It adjusts the bias of the boost stage and increasing it seems we get slightly more treble. (150k).
R7: 470k - «Increasing the value increases gain, while decreasing it will give you a little less gain overall but will tighten up the DS-1's low-end.» In my emulator lower value cut bass, higher value boost bass and cut treble. (180k-1M).
R9: 22R - It determines the amount of the gain of the boost stage. Bigger resistor decrease the treble boost. (10R-1k).
R11: 100k - «It controls the gain in combination with the distortion knob, R13 and C8.» I found just one that change it with a 220k, my emulator doesn't show any change in the amount of gain.
R13: 4.7k - Smaller resistor to push the gain in the high frequency. Bigger resister to decrease the gain an get lower frequency (510R-10k).
R14: 2.2k - Smaller value for more treble, bigger value cut bass, but very big value cut treble and gain, too. (1.5k-10k).
R15: 2,5k - Bigger value cut treble, smaller value increase it.
R16: 6.8k - Smaller value decrease treble and increase mi, low-mid. (1k-4.7k)
R17: 6.8k - Bigger value for flat eq more volume. Take it out for maximum effect. SMaller value increase the mid scoop. (3.3k 8.2k-33k).
R21: 10k/100k. The value is often 10k, but some schematic shown 100k. I think it doesn't change so much.
R39*: 47k - Someone decrease this resistor, but in my emulator doesn't make almost difference even if you jumper it. In theory it should let pass more gain and maybe more treble.
R40*: 1k - It seems has some effect in the midrange. «This resistor is labeled as R40 and will force the op-amp to work into class-A reducing distortion».
R43: It's the pull down resistor, necessary when the pedal is true bypass. It could influence the impedance. (1M-2.2M)

C1: 47nF - Bigger cap increases the low end, but hardly perceptible. (100nF).
C3: 47nF - Bigger cap increases the low end, smaller cap decrease it. (15nF-100nF).
C4: 250pF - Bigger cap to smooth the high end, smaller cap let pass more treble. (100pF, 220pF, 1nF).
C5: 68nF - Bigger cap increase bass (but it can't increase so much), smaller cap decrease it. (22nF, 100nF, 220nF 470nF, 1uF, 10uF).
C7: 100pF - Bigger cap to smooth the treble. Generically it's increased, in one case it's been removed. (220pF-470pF)
C8: 470nF - 1uF. Bigger cap pushes the gain in lower frequency. (One schematic show a 47nF, maybe a mistake, it seems too much small). (1uF-2.2uF).
C9: 470nF - Bigger cap increases the low end. But the increasing is minimal. (1uF).
C10: 10nF - Bigger cap cut treble, smaller let pass more treble. (1nF-56nF).
C11: 22nF - Bigger cap for a flat eq, smaller cap for (even) more mid scoop. (10nF-56nF).
C12: 100nF - Small cap for mid boost. Someone removes it for more treble, but my emulator says it seems mess up the tone control. (15nF-56n).
C13: 47nF - Bigger cap to increase the low end. But it seems the change is invisible. (100nF-1uF)
C25 47pF - Adding it in parallel with the diode D4 and D5 to tame a treble. But in the emulator it's almost not visible. My opinion is that cap is very small.

D4 & D5: 1N4148 - Replace both or one with two or more diodes to change texture, gain and volume. There are all the combiantion you want. Old Boss DS-1 pedal used diodes that measured about 1.0v as voltage forward. In the newer the 1N4148 diodes are not so close to that voltage forward. (All diodes!).
D8*: 1N4148. «The diode D8 is placed to protect the op-amp input».

Distortion pot 100k Linear - Higher resistance for more gain, maybe it give just more fuzziness. (250k).

Transistors: I think I'll use 2N3904 for the buffers and a 2N5088 for the booster.

IC: TL072, JRC4558, OPA2134, MC1458, LM358, NE5532, LM833, TL2262, LM385N...

*R39, R40 and D8 has been added in the circuit after the single op-amp was replaced by the dual op-amp. Maybe this parts was necessary for the DS-1 stock dual op-amp M5223AL, but maybe unnecessary with other models. Not sure about it.
«If you were to replace the amp with a more common bi-polar amp such as the TL072, you should probably remove R40.
Oh and R39? I think power-up/down could cause a damaging negative voltage on the amp input. D8 limits that, but R39 then keeps the discharge current from C5 low. Where it is, R39 won't affect the tone at all.»

The soft clippers won't do much on their own since the input of the opamp will be far over any small signal <<< diode treshold.
This means the diodes will conduct early on and the opamp will mainly have a signal out almost like "unity gain above diode treshold". This means you get the hard clipping without all the gain in front. So unless the boost stage has very low gain it won't feel as soft clipped but rather as though you "take away some gain" from the hard clipping.
Soft feedback clipping is a finicky thing. It needs careful design to shape your tone.
A soft clipper with a low input (think guitar), high gain and very treshold (think a couple of volts) will sound rather hard clipping.
A soft clipper with a high input (think booster out), low gain and very low treshold (think one silicon diode) will sound rather dull and muffled and almost like added noise and chances are the opamp will clip rather than the diodes add tone.
The Timmy was a good example of doubling the treshold compared to a Tube Screamer for example, making it sound a tad "tighter".

Quote from: Elijah-Baley on October 26, 2022, 10:20:39 AM
R21: 10k/100k. The value is often 10k, but some schematic shown 100k. I think it doesn't change so much.

It strongly depends on R23 value (serving for load)..
T3 Emitter is biased at about 3.7V and can't go lower than 1.75V due to R21/R23 voltage dividing effect (50% for particular values)..

High value Emitter resistor (for voltage follower, like T3) contributes positively for current consumption but negatively both for load drive capability and output impedance (0.026/I_C^Q)

P.S.
Make R23 10k, set Level pot FCW and observe the "extra" negative clipping via Tina-TI oscilloscope.. :icon_wink:

Quote from: Steben on October 26, 2022, 11:55:19 AM
The soft clippers won't do much on their own since the input of the opamp will be far over any small signal <<< diode treshold.
This means the diodes will conduct early on and the opamp will mainly have a signal out almost like "unity gain above diode treshold". This means you get the hard clipping without all the gain in front. So unless the boost stage has very low gain it won't feel as soft clipped but rather as though you "take away some gain" from the hard clipping.
Soft feedback clipping is a finicky thing. It needs careful design to shape your tone.
A soft clipper with a low input (think guitar), high gain and very treshold (think a couple of volts) will sound rather hard clipping.
A soft clipper with a high input (think booster out), low gain and very low treshold (think one silicon diode) will sound rather dull and muffled and almost like added noise and chances are the opamp will clip rather than the diodes add tone.
The Timmy was a good example of doubling the treshold compared to a Tube Screamer for example, making it sound a tad "tighter".

The soft clipping it's an idea I found that come form the Boss HM-2, but has you said, that could cut signal more useful for the hard clipping.
I think it's a bit the same thing for the muff clipping, it isn't? That idea come from the Aion project (Comet).

Quote from: antonis on October 26, 2022, 01:20:12 PM

Quote from: Elijah-Baley on October 26, 2022, 10:20:39 AM
R21: 10k/100k. The value is often 10k, but some schematic shown 100k. I think it doesn't change so much.

It strongly depends on R23 value (serving for load)..
T3 Emitter is biased at about 3.7V and can't go lower than 1.75V due to R21/R23 voltage dividing effect (50% for particular values)..

High value Emitter resistor (for voltage follower, like T3) contributes positively for current consumption but negatively both for load drive capability and output impedance (0.026/I_C^Q)

P.S.
Make R23 10k, set Level pot FCW and observe the "extra" negative clipping via Tina-TI oscilloscope.. :icon_wink:

I think I don't care it too much and I'll use a 100k as R23, but I'll try some experiment with Tina-TI oscilloscope.

Quote from: Elijah-Baley on October 28, 2022, 04:23:20 AM
I think I don't care it too much and I'll use a 100k as R23

The "problem" isn't R23 value but R21 one..

As far as you really don't care, I can't see any (obvious or hidden) reason for anyone else to deal with it.. :icon_wink:
(walk in peace with an output buffer of 37μA working current, hence an output impedance of 675R..)

This is probably erroneous.
(https://i.postimg.cc/34XtdB54/ds1pg2.jpg) (https://postimg.cc/34XtdB54)
I couldn't find gut shot with R21 is 100k.

Quote from: antonis on October 28, 2022, 02:43:54 PM

Quote from: Elijah-Baley on October 28, 2022, 04:23:20 AM
I think I don't care it too much and I'll use a 100k as R23

The "problem" isn't R23 value but R21 one..

As far as you really don't care, I can't see any (obvious or hidden) reason for anyone else to deal with it.. :icon_wink:
(walk in peace with an output buffer of 37μA working current, hence an output impedance of 675R..)

Is that was sarcastic? :D
I didn't say we can't discuss about it, just I think I'm going to trust with the original Boss schematic because I saw this is not a thing that other guys used to change in this circuit. I just find some discrepancy in the schematics with R21: 100k/10k. More precisely, in the schematic with the single op-amp R21 is 100k, in the dual op-amp R21 is 10k.
Probably I'll use 10k, in my schematic there's a mistake: R21 should be a 10k.

Quote from: Elijah-Baley on October 29, 2022, 04:15:01 AM
Is that was sarcastic? :D

Definately not..!!  :icon_wink:

I was just trying to explain you the reason for output buffer Emitter resistor to be of low value..
(like below..)

(https://i.imgur.com/YUK6mAC.png)

Thanks, antonis. :)

I have in my archive that schematic, too, but I thought that 1k to the emitter in the last stage was a mistake (or is it a mod?).
Maybe it's bit hard to hear the effect of the output impedance in the pedal because I assume it depends from the amp, or other pedal after it, or something else. So I don't know if I'll test that resistor. The veroboard layout I'm drawing has already a lot of socket pins: I want to try a lot of parts! ;D

Quote from: Elijah-Baley on October 30, 2022, 05:17:07 AM
I have in my archive that schematic, too, but I thought that 1k to the emitter in the last stage was a mistake (or is it a mod?).

Can't say for sure but a 10k Emitter resistor should be upwards marginally OK.. :icon_wink:
(same value resistor is implemented to Q1 input buffer which drives Q2 CE amp ridiculously low input impedance..)

P.S.
After all, IN-OUT buffers should (or not..??) let "main" circuit character be unaltered..

The input impedance declared of the original DS-1 is not so high, but still fine: "just" 470k 'cause R2. Indications I read around say: "R2: 470k - Increase it for an higher impedance".
In the true bypass schematic the thing could be a bit difference, we need (probably) a pull down resistor 1M-2.2M (R43 in my schematic) that should pair with R2 and change the impedance. And I'm thinking about it right now, maybe this lowers the 470k impedance. To adjust the impedance around the original Boss I should use as R2 an 1M ressistor (or 820k), if the pull down resistor is 1M.

Considering I will not build this pedal soon, we could go deep in some discussion. Indeed, now I'm wondering what determines the input impedance in the DS-1 schematic, not in the original, but in the true bypass version, my schematic above. I'm calculating R2 and R43 in parallel, but does R1 1k make some difference? To calculate the input impedance is important the transistor? (by the way, a trick to raise up the impedance could be to replace the BJT transistor with a jfet).

Quote from: Elijah-Baley on October 31, 2022, 05:15:57 AM
Indications I read around say: "R2: 470k - Increase it for an higher impedance".

But why?  :icon_cool:

Quote from: Elijah-Baley on October 31, 2022, 05:15:57 AM
Considering I will not build this pedal soon, we could go deep in some discussion. Indeed, now I'm wondering what determines the input impedance in the DS-1 schematic, not in the original, but in the true bypass version, my schematic above. I'm calculating R2 and R43 in parallel, but does R1 1k make some difference? To calculate the input impedance is important the transistor?

Actually, it's important the transistor DC current gain at particular working condition.. :icon_wink:

T1 input impedance is considered the equivalent resistance of R43 // { R1 + X_C1 + [ R2 // ( β*re + (β+1)*R3) // β*rc ], where re = 26mV / Collector current and rc = Early voltage / Collector current..

By neglecting series low values and shunt high values, we simplify it to R43//R2//R3*β..
For a minimun h_FE of 55 for 2N3904 at 370μA quiescent current, we get about 200k input impedance.. :icon_wink:
By making R2 1M, total input impedance is raised only 30% (from 200K to 260K) while voltage drop across it, due to Base current, is overdoubled resulting into even lower Emitter voltage hence lower next stage driving capability for signal negative waveform..
(R3 forms a voltage divider with T2 input impedance precluding T1 Emitter from going all the way down to zero volts..) :icon_wink:

As for input HPF corner frequency, it's set by 1 / 2π*C1*(R3 + R2//R3*β)

It's quite random but I remember modding a DS-1 once by
- taming Q2's gain and filtering as AMZ mod suggests
- raising the opamp stage's gain
- modding the freq response of the opamp stage
- swpped for clipping LED's

This resulted in a cleaner low gain setting and more marshall-esque distortion.
The Q2 mod makes the stage more linear with a slight hint of even order harmonics while the actual hard clipping is done after that. Stock, the Q2 stage adds (on the edge of fuzz) clipping as well which makes the DS-1 an aggressive beast but less "amp like".

On another I swapped the stage for a jFET stage by omitting the feedback 470k R and changed some R values. Can't recall it sounded better than the BJT solution.

Quote from: Elijah-Baley on October 30, 2022, 05:17:07 AM
Thanks, antonis. :)

I have in my archive that schematic, too, but I thought that 1k to the emitter in the last stage was a mistake (or is it a mod?).
Maybe it's bit hard to hear the effect of the output impedance in the pedal because I assume it depends from the amp, or other pedal after it, or something else. So I don't know if I'll test that resistor. The veroboard layout I'm drawing has already a lot of socket pins: I want to try a lot of parts! ;D

Don't worry too much, but if the emitter resistor is large, it will clip when the load impedance(=Rl) is small.
0.22*R21/(4.5-0.6) = R21‖Rl
(Assume 440mv P-P)

Thank you, but I'm kind of lost. ;D

Antonis, please, can you translate in number this formula? R43//R2//R3*β..
200k impedance seems lower than I thought, and I can't understand why.

Quote from: Elijah-Baley on October 31, 2022, 02:29:04 PM
Thank you, but I'm kind of lost. ;D

Antonis, please, can you translate in number this formula? R43//R2//R3*β..
200k impedance seems lower than I thought, and I can't understand why.

// means parallel. You know parallel impedance?
the 200k is when the hFE (= β)  is around 55 as Antonis said.
Each transistor's gain is different, so the input impedance is as well. So it could be 400k for example.
One of the reasons opamps came to live was the reliable and predictable performance and properties.

Quote from: Elijah-Baley on October 31, 2022, 02:29:04 PM
Antonis, please, can you translate in number this formula? R43//R2//R3*β..
200k impedance seems lower than I thought, and I can't understand why.

What Steben said above.. :icon_wink:

(https://i.imgur.com/NqIdCml.jpg)

(https://i.imgur.com/f2zfdcM.png)

edit: Wrong h_FE estimation..
(thought Q1 was 2N3904..)

Could be 250 ish as minimum.... So Zin (base) is about 2.5Mohms.

(https://i.postimg.cc/QH99KdFj/2-N5088-data.jpg) (https://postimg.cc/QH99KdFj)

The result is dominated by the 470k however, Zin circuit will always be << 470k.

R43//R2//R3*β = 1M // 470k // 2M5 = 1/(1/1M + 1/470k + 1/2M5) = 282k.
So we have a Zin which becomes less than 50% higher although the component (transistor) seems to have 5 times higher current gain than 2N3904.

This explains why one always has to change the dominant element, which means here the lowest impedance = R2.
Changing it to 1M will give Zin circuit of 417k. Which means doubling the component value gives 50% change in result.

I do find the input impedance chapter sometimes overrated. It can be an issue if placed straight after the guitar especially with humbuckers and high value pots.
282k input impedance for a high gain device however is more than ok if it is placed after circuits with a low output impedance anyway. Think of all circuits with buffers (Boss and Ibanez pedals).

Do not forget that high impedance parts are usually found in tube amps. Zin of tubes are galactic. In those amps the signals are huge compared to our 9V circuits. Any noise coming from high impedance resistors is in comparison to the signal low and tube amps have their own sources of noise and hum and whatever.
In 9V circuits the signals are much lower, yet the noise coming from resistors not.
It is generally speaking always preferable to use the lowest R value possible without losing too much signal. Behind buffers and opamps this can go muuuuuuch lower than 100dreds of k.

I presume that at DS-1 initial release times, 2 BJTs should be much cheaper than a dual op-amp.. :icon_wink:

Quote from: antonis on November 01, 2022, 07:53:25 AM
I presume that at DS-1 initial release times, 2 BJTs should be much cheaper than a dual op-amp.. :icon_wink:

yes.
Yet the boost stage can't be but deliberate. It is not the most beautiful way of overdrive yet I imagine in those times fuzz and simple distortion was mainstream. The non true bypass was still alive. The wah hardly ten years old? So we see a sturdy box, buffered and with excellent electronic switching giving one hell of a distortion. Couldn't loose.

what antonis said below.

Quote from: antonis on October 31, 2022, 04:26:22 PM

(https://i.imgur.com/NqIdCml.jpg)

is there Collector resistance in that dia that I can't see?

Quote from: duck_arse on November 01, 2022, 09:50:16 AM
what antonis said below.

Quote from: antonis on October 31, 2022, 04:26:22 PM
(https://i.imgur.com/NqIdCml.jpg)

is there Collector resistance in that dia that I can't see?

It surely is there.. :icon_wink:
If you notice my expression, I said "resistance" (physical quantity) and not "resistor" (real world item)..

A BJT Collector can be considered as a non-ideal current source (either g_m*Vbe or β*Ib)..
Any non-ideal current source has a high value internal resistance which is considered in parallel with the source (just like a voltage source is considered with its internal resistance in series..)

That resistance measures (V_A+V_CE) / I_C, where V_A is the Early voltage of particular device (usually between 50 and 150 Volts)

Just look at dashed framed model below:
(https://i.imgur.com/0LyfrDk.png)

Quote from: antonis on November 01, 2022, 11:05:30 AM

Quote from: duck_arse on November 01, 2022, 09:50:16 AM
is there Collector resistance in that dia that I can't see?

It surely is there.. :icon_wink:
If you notice my expression, I said "resistance" (physical quantity) and not "resistor" (real world item)..

I did, indeed, notice your use of resistance, which is why I corrected my werding before posting to read that I can't see. coffees all round.

oh, and a rockcake each.
(https://i.imgur.com/X8zQy1c.jpg)

Quote from: duck_arse on November 02, 2022, 09:44:34 AM
coffees all round.

Not enough here, yet.. :icon_wink:
(spilled all over the keyboard..) :icon_evil:

Quote from: duck_arse on November 01, 2022, 09:50:16 AM
is there Collector resistance in that dia that I can't see?

On clean modern (post 1963) Silicon, the collector impedance is thousands of times higher than anything else. Megaohms. At least for resistance-coupled work.

That's for sure, Paul but whereas its high value can easily omitted for applications like the above buffer, there are cases (e.g. CE amp current source) where it should be taken into account..

This Dirt Sky One not learning from his Dirt Vader which supposed to be stayin alive
maybe due to the influence of Oddy One Knob Be to use the buffer

TA7504M which I think is the 741 family from Toshiba has a slew rate of around 0.5 V/us
for this I have feeling that for hard clipping is better using low slew rate like Dirty RAT does LM308 0.3 V/us
make not so square

for  TA7136AP I dont know what slew rate value is, but one think I notice it has greater THD compare to 741
perhaps Q2 is to push harmonic

compare with this table for your preference

741       0.5 V/us      THD=0.06%
TA7504M   0.5 V/us
TA7136AP  VNI=0.8uV rms THD=0.1%
BA728N    0.7 V/us
M5223AL   0.6 V/us
NJM2904L  0.5 V/us     
NJM3404   1.2 V/us
JRC4580   5.0 V/us SMD  Noooooooooooooo........

The slew rate itself is not all you should be considering.
If like in the RAT you are driving the op amp into clipping then its behaviour as the output level approaches the supply rails is probably more important as regards the resultant sound.
Some op amps clip gracefully when the output approaches the supply rails whilst others exhibit unwanted characteristics like 'foldback' or phase inversion of the waveform.
You probably need to get a scope and test the various op amps rather than rely on specifications on datasheets.

Quote from: FSFX on December 26, 2022, 10:01:01 AM
Some op amps clip gracefully when the output approaches the supply rails whilst others exhibit unwanted characteristics like 'foldback' or phase inversion of the waveform.

Do I smell a circuitous TL072 admonition..?? :icon_wink:

I tell you, the original MIJ DS-1 was a real goto pedal. You could do R. Fripp cello-style lines with ease as well as hammer-on only legato or pick any possible harmonics. The ones they made after are just like any other ton-of-gain + clipping box that just seems to choke your playing unless the amp is loud enough for natural feedback assistance.

Anyway, I never noticed the original had that BJT preamp stage.  I'm suspecting it is probably of high importance and a 741 might do for the opamp. I think it's no wonder the mods hoping to backdate the dual opamp versions don't really work.

Quote from: antonis on December 27, 2022, 05:12:19 AM

Quote from: FSFX on December 26, 2022, 10:01:01 AM
Some op amps clip gracefully when the output approaches the supply rails whilst others exhibit unwanted characteristics like 'foldback' or phase inversion of the waveform.

Do I smell a circuitous TL072 admonition..?? :icon_wink:

or a positive wink to some rail to rail opamps that seem to be made for clipping.
What about the TLC2262? Afaik the sansamp uses them and not the TL0xx series, which is seen in some kits/clones....

Noooooooooooooo........

I though no fat not good, the Low Fat 351 and Tender Loin 081 which 13V/us
would be bad but some folks like also

in case of DOD Preamp 250
4558 1V/us mod to 1458 0.5V/us only 0.5 different ???
this probably my thinking could be about slew rate

the most dangling for RAT which OP07 same slew rate with 308

https://www.electrosmash.com/boss-ds1-analysis (https://www.electrosmash.com/boss-ds1-analysis)

M5223AL (3K pull up resistor) and NJM2904L (Rp<Rl//Rf pull down resistor)
are noisy probably because crossover distortion
which replace with better chip 4580

is it bias of original ?
feeling like Tube Screamer JRC4558
or Original Colonel Sanders KFC
or People resist to change ???
people are awesome

in case Roland Jet Phaser the distortion part is using LM324
well if we change LM324 with TL074 would it be better?
or it will loosing it signature

my preference will choose 741 family instead 324 family

the odd of OCD with TL082, people like it or because of that mosfet clipping

The klon TL072 is weird to using more voltage to make slewrate to max 13V/us ???
would not chip with slewrate 13V/us at 9V enough if it is slewrate

Thinking about my klon is like RAT(LM308) 0.3V/us + BULL(LM318) 50V/us,
just using 9V supply.

(https://www.electrosmash.com/images/tech/ds1/boss-ds1-transistor-booster-waveform.png)

Q2 form asymmetric clipping, unlike Range Master which change Peak Voltage
or like pair Led + Diode, it seem it make change duty cycle.
another trick to make asymmetric

Range Master + MXR D+ or DOD 250
Q2 + DOD 250



(https://i.postimg.cc/QF4D6pfn/ds1.png) (https://postimg.cc/QF4D6pfn)

cant find NJM3404 but I think would be better find old chip like TA7136 pre amplifier
many like Sanyo, Panasonic, NEC

Hello guys.
Finally I started (months ago) to build this circuit, and in these last days I began some tests.

I had a weird problem, I could hear at low gain setting a sort of a bad op-amp clipping. I solved thanks to suggestion linked at me:
https://www.diystompboxes.com/smfforum/index.php?topic=131466.0 I moved the D8 diode.

Just for start, I didn't like the taper of the distortion pot, I got almost all the change in the last quarter and in the last 10%. So, after a pair ot test, I guess I'll use a 15k resistor between the lug 2 and 3 getting some more balanced distortion setting. I could use a rev log pot, but I want to limit adjusting this linear pot.

Now, I'm testing all the mods.

There's one mode I don't know how do it. The Trem Mod.


Just this clue: "These mods are based on the JHS Synth bend and the Devi Ever (E13) Tremolo bend".

It seems to come from the Devi Ever forum, but I really can't find anything about it: not a schematic, not a detailed description or the original image from the forum.
Do someone have got the image how do this mod, please?