ZVex super duper tone

[DaSt]

Hi,

I made a super duper using that vero :
http://tagboardeffects.blogspot.fr/2012/01/zvex-super-duper-2-in-1.html

Is there any way to make its tone more "medium-bass" like the Super Hard On ? I first thought the filter cap was the key but its the same in both effects.

Thanks :)

[negativefx]

The Super Duper is just two SHOs plus a master control on one of them.  They should be pretty damn close to the same.  I've owned a real SHO and a SD2i1 and they sound the same to me.  Maybe make a daugtherboard with a small med-bass eq boost either before or after.

[induction]

The filter cap is the 100uF from 9V to ground. It's purpose is to stabilize the power and prevent oscillation and hum. It has nothing to do with frequency response.

I suspect you meant to say that the input and/or output caps have a strong influence on the frequency response, which is true, but those caps function as components of high-pass filters, so you can't adjust them to decrease treble without decreasing bass even more. The stock values give a full-range boost, without preferential treatment to any frequency range that matters.

The design of the SHO (and thus the Super Duper) gives a very high input impedance. This means it maintains more treble from your guitar signal than most other pedals and amps. Putting two of these in a row causes more clipping, which by its nature increases the high frequencies in the signal. But, as negativefx said, if you use just the first stage in the Super Duper, you are in fact just using a SHO, so they should sound the same. If they don't, there's something wrong with your build.

Assuming your build is fine and you just want to tame the highs a little, one thing you could try is to decrease those 10M resistors (make them, say, 1M each and then experiment from there). That will reduce the input impedance and drop the highs a bit. Or you could put a small cap from the gate of one or both mosfets to ground (start with 100p, and increase it for less treble, or decrease it for more). Or you could just turn down the tone knob on your guitar, or add an eq stage or external eq pedal.

Edit: I just realized that I don't know what you mean by making it 'more "medium-bass"'. Do you want to increase bass or decrease it? Or something else?

[DaSt]

Hi,

Thanks for both your answers. I made several SHOs and SDs and they all have the same tone difference i described. Even when using only the first stage of the SD.

The goal would be to increase bass on the SD.

Anyway i'll look into that resistor and cap experimentation and will let you know.

[negativefx]

Are you using a bass, or looking for a bass focused eq boost on a guitar?

If bass guitar, increasing the filter cap values will allow the sub-guitar signal through and as a result, a more bass heavy output.  Changing filter caps to higher values allows lower frequencies to make their way in to and out of the circuit.  I believe this is a high pass filter but I could be mistaken.  

If guitar, you'll need an EQ. The SHO is designed to be a clean boost, with clean meaning an unaltered boost of your original signal; not one with filter coloration.  The filter cap changes aren't going to magically create sound where there is none but rather allow lower frequencies through when they are present (ie. from a bass).

Except if you play djent, then maybe the filter caps are what you're looking for.  :)

[induction]

What layout did you use for the SHO?

[induction]

The reason I ask about the layout is that IvIark's compact SHO layout includes a 1M pulldown resistor on the input. This reduces the input impedance from ~5M to ~800k and may reduce some treble sparkle. So if you used that layout (and the same mosfets in both builds), and you prefer that tone, try adding a 1M pulldown to the Super Duper input and see if it sounds better to you.

[DaSt]

You're right to ask as I used the compact layout. I'll try that pulldown resistor addin and will let you know.

Thx

[DaSt]

Hi,

I tried adding a 1M pulldown on the input and also tried replacing the 10M pulldown with a 1M.
With the first i don't notice any change and with the second i just dont have any sound no more on the modified stage.

Any idea ?

Thanks

[induction]

A couple questions:

1. Where exactly did you add the 1M input pulldown?

2. Did you replace both 10M resistors with 1M, or just one (you probably need to do both).

3. Are you using the same mosfets in your Super Duper as you used in your SHO? Any other differences in components?

[DaSt]

Hi,

I replaced only one, the one going directly to ground.
I also tried adding one on input jack directly to ground (also tried different values there with no more success)
I used the same components, and same mosfets. They are from the same order so possibly from the same batch.

I'll try to change both 10Ms for 1Ms anyway and will let you know

Thanks

[induction]

Ok. Yes, you have to replace both 10M's with 1M's if you want to try that trick. Those resistors set both the input impedance and the bias. If you only change the one going to ground, it seems you are biasing the mosfet into non-operation.

For the input pulldown: putting it on the jack is ok as a test, but putting it there will also color the bypass sound, which can confuse your testing. Better to put it on the board for a fair A/B test.

With the input pulldown in place, the first stage of the Super Duper is exactly the same as a single SHO. So if your builds sound consistently different, there may be some other problem. If you post some pictures of your boards and all the offboard wiring, maybe we can spot something.

It would be good to measure and post the voltages on the legs of the mosfet for each one as well.

[DaSt]

Hi,

By changing both resistors i could modify the tone the way i wanted. Thanks a lot !
I think i'm gonna use a stereo pot to add kind of a tone control to that SD2i1 ^^

Another question tho. I was given a custom SHO, here is its layout :



(Sorry i could not make it using traditionnal tools).

Point is that pedal has a much noiser sound with tremendous bass presence. Any luck someone could pinpoint the difference between that one and the usual compact SHO layout ?

Thanks

[induction]

Three differences:

1. The diode is a 1N4148 instead of a 9V1 zener. It's there to protect the mosfet from static damage. Don't know if it will change the sound. It's worth a try swapping it.

2. The power rail has no filter cap. This could account for the noise you mention. It's easy to pop a 100u in there and see.

3. The output pulldown resistor is 47k instead of 100k. In principle, this should cut volume and bass, not add it. This resistor and the 10u output cap form a high-pass filter. By reducing the value of the resistor, you increase the cutoff frequency of the hi-pass filter, cutting more lows. In either case, the corner frequency is below the threshold of human hearing, so it really shouldn't matter. Again, it's easy to swap it and see.

[DaSt]

OK Thx now i see.

Thing is that pedal sounds better to me than the compact layout. but the problem is it doesnt work for long..

Two times already it suddenly (when triggered, not while functionning) does the inverse it is supposed to do. There is a massive volume drop when engaged and no crackle when pot is played with.

Any idea ?

[induction]

I would suspect the diode first. A zener and a standard diode are very different things.

The diode is there to prevent excessive voltage between the gate and source. 20 V is enough to punch a hole in the gate and kill the mosfet. A zener diode will reverse conduct when the reverse voltage is greater than the zener voltage (9.1 V in this case). So if excessive voltage builds up on the gate (from static discharge that happens from plugging in the input cable, not from the battery), the diode will drop it before it gets to dangerous territory. Otherwise the diode doesn't do anything and shouldn't affect the sound or operation of the circuit. If you use a 1N4148 there, it won't discharge this excessive voltage, and the mosfet may get damaged. (A 1N4148 can handle up to 75 V reverse bias before it breaks down.)

So it's possible you damaged the mosfet. I'd try replacing it and using the 9V1 zener instead of the . Then see if you still get the sound you like from it.

This is all just a guess, though. Feel free to post pictures if you can't figure it out.