Overdrive Pro, a couple questions about mods.

[erick4x4]

So I just built this and I have a few questions about mods.

First I really increased the cap parallel to the diodes because the high end was way extreme for me. Could this of hurt my output volume? I went to a 2x2 config, but the output still is probably unity gain to high output guitars. But without it I always had the treble all the way down as it was ear splitting to me?

Second, on his website Jack mentions upping c5 to remove "fizzyness", just curious what is this doing?

Third, he mentions upping c8 to go from a scoop to a traditional mid response. Does this mean if I keep going say a 3 position switch, I could do scoop, traditional, and a mid boost?

Lastly, on the tonepad site (which is the PCB I used), it talked about changing r2 and r4 (both with pretty dramatic changes in value), but I can't find any reference as to what that does?

Sorry for all the questions I am just trying to learn more, and learn how to tweak this, as I have been wanting a typical heavy diode clipping distortion, but can never get one that has an EQ I like, which is what drew me to this. I am just wanting to really fine tune the eq so it fits for the sound I am trying to get.

Thanks!!

[erick4x4]

Sorry for the bump I am just so curious. Anyone have an answer to any of these?

[mojotron]

So I just built this and I have a few questions about mods.

First I really increased the cap parallel to the diodes because the high end was way extreme for me. Could this of hurt my output volume? I went to a 2x2 config, but the output still is probably unity gain to high output guitars. But without it I always had the treble all the way down as it was ear splitting to me?

Second, on his website Jack mentions upping c5 to remove "fizzyness", just curious what is this doing?

Third, he mentions upping c8 to go from a scoop to a traditional mid response. Does this mean if I keep going say a 3 position switch, I could do scoop, traditional, and a mid boost?

Lastly, on the tonepad site (which is the PCB I used), it talked about changing r2 and r4 (both with pretty dramatic changes in value), but I can't find any reference as to what that does?

Sorry for all the questions I am just trying to learn more, and learn how to tweak this, as I have been wanting a typical heavy diode clipping distortion, but can never get one that has an EQ I like, which is what drew me to this. I am just wanting to really fine tune the eq so it fits for the sound I am trying to get.

Thanks!!

Here's a few things to try:
1) I think that C3 is pretty small, and this tightens the low-end too much IMO - I used a .068uF cap for this. It's not a matter of shunting the low-end at the end of the circuit, it's a matter of allowing more low-end into the clipping stage - that will offset the high-end responce and even it out.

2) That isn't enough though, now that C3 is bigger, you should even-out the opamp's responce by shunting more low-end in the negative feedback loop. To do this up the value of C4 to 2.2uF and perhaps lower the value of R6 to something between 100 and 50 ohms - I just used a pot for this, but I keep it right around 70-80 ohms and really have not adjusted it very much. The important thing is to raise the value of C4 to 2.2uF - that adds low-mids to the sound to offset the high-end that is still there.

Also, I used an LM833 and made C5 30pF - I played with a lot of opamps and caps (I mean a lot) and that's the combo I liked.

3) This is minor, but C6 can actually be a smaller non-polarized cap. The problem with the larger polarized cap is that there is a difference in impedance for the + and - swings of the signal - replace this with a non-polarized 1uF cap - you should not loose any audible low/mid responce and to me it just sounds cleaner.

4) Get rid of C7, I hate shunting signal like that... IMO I think it sounds better to control the high end in the tone stack controls. With the extra mids and low-end you won't need C7.

5) Play with the diodes and see what you like. I use a Ge diode and a 1n914 on one side, and a single 1n914 on the other.

6) I played with the cap values in the tone stack too, I thought C8 sounded better being in the .022-.01uF range.

Hope this helps.