My Favorite Boost Pedal

[James Freeman]

My favorite boost for everything, tube amps, solid state amps, modelers, plugins, you name it, is the SD-1 with clipping diodes removed and series output resistor bypassed for additional +3dB at maximum volume.
The modified SD-1 has the perfect amount of bass and treble rolloff but without the ugly sounding (imo) soft-clipping diodes in the opamp feedback loop of the stock SD-1.

If there's a pedal worth having more than one of, it's the SD-1.
The GT-OD is set to the ZW-44 side which measures and sounds exactly like the SD-1 but has true bypass and can take 12v for even higher output.

 

[hunga]

 

[JiveTurkey]

GT-OD is underrated imo

 

[metropolis_4]

Of all the drive pedals I’ve used over all these years, the SD-1 is probably the one I’ve used the most.

I remember back when you could pick up used ones for $20 and mod the junk out of them! And I remember the first time I discovered them thinking “wait, this sounds way better than a TS and it costs half as much?”

 

[Orvillain]

I'm a BIG fan of the Wampler Tumnus Deluxe and SD-1. More so than the TS808.

 

[Piing]

Of all the drive pedals I’ve used over all these years, the SD-1 is probably the one I’ve used the most.

I remember back when you could pick up used ones for $20 and mod the junk out of them! And I remember the first time I discovered them thinking “wait, this sounds way better than a TS and it costs half as much?”

Is $40 a good deal? There is one at FB Marketplace for that price in my neighborhood.

I am wondering if it is the old model with discrete components in an old PCB, for easy mods.

There is a cheaper one, for $42. But it is a modern version made in Malaysia I'm afraid it my have SMD components.

 

[dronerstone]

My favorite boost for everything, tube amps, solid state amps, modelers, plugins, you name it, is the SD-1 with clipping diodes removed and series output resistor bypassed for additional +3dB at maximum volume.
The modified SD-1 has the perfect amount of bass and treble rolloff but without the ugly sounding (imo) soft-clipping diodes in the opamp feedback loop of the stock SD-1.

If there's a pedal worth having more than one of, it's the SD-1.
The GT-OD is set to the ZW-44 side which measures and sounds exactly like the SD-1 but has true bypass and can take 12v for even higher output.

View attachment 60003

Does the SD-1 still have its significant low cut with the mod you described? If so, that sounds very handy.

 

[James Freeman]

Does the SD-1 still have its significant low cut with the mod you described? If so, that sounds very handy.

Yes, the same exact mid-boost frequency response but without the bad (imo) diode clipping buzz in the background.
It does clip when the opamp is hitting the 9v rail voltage and sounds way more natural when pushing an amp.

An on/off sample:

 

[MirrorProfiles]

Tried so many times with the SD-1 and I just can’t get on with it. It’s almost too thick/blocky with how the harmonics stack up and feels wrong to me.

OD808 or OD9 here (which I believe are both closer to a TS-9). The gain feels clearer and less congested, and it weaves into amp gain much nicer.

Love a klon too.

 

[James Freeman]

Tried so many times with the SD-1 and I just can’t get on with it. It’s almost too thick/blocky with how the harmonics stack up and feels wrong to me.

This is exactly why I removed the diodes.
What's left is a louder boost with the perfect amount of low and high cut for boosting gainy amps, almost sounds like an external 12ax7 gain stage.

Below you can see and hear that the modified SD-1 is much louder and clipping the opamp rails, while the stock SD-1 has the ugly soft clipping distortion on top of the clean sound and is much quieter at maximum volume, both with Drive at 1 (8:00) and Tone at 5 (12:00).

Bypass


Stock SD-1


Diodes Removed

 

[MirrorProfiles]

This is exactly why I removed the diodes.
What's left is a louder boost with the perfect amount of low and high cut for boosting gainy amps, almost sounds like an external 12ax7 gain stage.

Below you can see and hear that the modified SD-1 is much louder and clipping the opamp rails, while the stock SD-1 has the ugly soft clipping distortion on top of the clean sound and is much quieter at maximum volume, both with Drive at 1 (8:00) and Tone at 5 (12:00).

View attachment 60081

Bypass


Stock SD-1


Diodes Removed

night and day difference there between stock and modified, despite how simple the mod is

 

[FuzzyAce]

I did the 'remove clipping diodes' mod to my DS-1 (I don't own an SD-1). Much more usable with tons of output. It's still not my preferred boost, haha, but now it at least gets consideration.

 

[Orvillain]

Huh.... I have the Waza SD-1, which I'm guessing is all surface mount and the diode removal can't be done. Maybe I need to pick up an old SD-1 so I can try this.

 

[Piing]

OMG! @FractalAudio!! How can we unsolder these diodes!

 

[James Freeman]

OMG! @FractalAudio!! How can we unsolder these diodes!

View attachment 60086

4x Blue LEDs on each side.

But yes, removing the diodes is an existing request on the forum.

 

[dronerstone]

Yes, the same exact mid-boost frequency response but without the bad (imo) diode clipping buzz in the background.
It does clip when the opamp is hitting the 9v rail voltage and sounds way more natural when pushing an amp.

An on/off sample:

That's awesome! Did you just remove the diodes and resistor, or did you solder in a jumper?

 

[James Freeman]

That's awesome! Did you just remove the diodes and resistor, or did you solder in a jumper?

Remove diodes completely (leave open), bypass R10 resistor.
I've done this to an SMD version, the components on the PCB are labeled exactly as they did in the old 80s schematic.

Through Hole

SMD

Huh.... I have the Waza SD-1, which I'm guessing is all surface mount and the diode removal can't be done. Maybe I need to pick up an old SD-1 so I can try this.

It can be done.
Buy a new SD-1 it's 60$ and worth the result.

 

[dronerstone]

Remove diodes completely (leave open), bypass R10 resistor.
I've done this to an SMD version, the components on the PCB are labeled exactly as they did in the old 80s schematic.


View attachment 60094

Through Hole
View attachment 60096

SMD
View attachment 60095



It can be done.
Buy a new SD-1 it's 60$ and worth the result.

Thanks much, that's very helpful!

I have one from 1995 laying around mostly unused. Did the ACA>PSA mod when I bought it for 20€ a few years ago, but nothing further, and I still have a pack of insulated drop-in jumpers somewhere in a drawer...

 

[Chocol8]

Huh.... I have the Waza SD-1, which I'm guessing is all surface mount and the diode removal can't be done. Maybe I need to pick up an old SD-1 so I can try this.

It's not bad to remove them, it's putting them back that's a lot harder with SMD!