Pro-10 Green No Treble

[twbaucom]

Happy new year all!

I recently built a string of pedals and for some reason only this one is giving me trouble. It sounds like a wet blanket is over my amp as I have very little treble or presence with the effect engaged. Which capacitors/resistors would affect this element of the signal?

 

[twbaucom]

Or I guess another newbie question…where would I be losing top end due to user error? Ground connections? Bad solder joint somewhere?

 

[giovanni]

Hard to say. It could be any capacitor or resistor in the signal path. The fact that you get wet blanket sound may also hide some other problem. After visual inspection (check for cold solder joints) and verifying all component values, if nothing obvious pops up, I would go through the circuit with an audio probe to find out where the sound starts getting dark.

 

[giovanni]

Btw, do the knobs do what they are supposed to?

 

[giovanni]

@PedalPCB this one is missing the schematics which I think would help here!

 

[twbaucom]

Btw, do the knobs do what they are supposed to?

Thanks for the help!

They all “do” the task assigned to them *but* I have to have the volume pot all the way up to be unity. The gain pot goes from overdrive to almost fuzz which seems odd for this circuit. The tone knob gives me some top end back but it still pretty buddy.

Only component value issue I found was a 22n in place of a 27n but changing that out didn’t do much.

I’m going to go in with an audio probe once the kids go to bed.

 

[giovanni]

Check some voltages: if the drive takes you into fuzz territory, it’s possible that you have a short somewhere and the circuit is not getting the full 9V. Start from the op amp and transistor biasing.

 

[twbaucom]

Just took the MM to it and here is what I am seeing. Something looks up with Q1, yeah?

Voltages

IC1
1 -4.48
2 -4.48
3 - 4.47
4 - 0
5 - 4.46
6 - 4.48
7 - 4.49
8 -9.02

IC2
1 -4.49
2- 4.49
3- 4.48
4- 0
5- 4.42
6- 4.48
7-4.48
8-9.02

Q1 2N5457

1 9.02
2 .24
3 0

Q2 2N5088

1 3.39
2 3.97
3 9.02

 

[giovanni]

Yeah that looks a bit fishy to me, but it’s hard to say without seeing the schematics.

 

[twbaucom]

Agreed. The Nobleman schematic shows this going into Q1.

 

[giovanni]

The gate is not biased (DC voltage is ~0), which matches what you measured. So if the Pro-10 Green has a similar design, it would be fine I think.

 

[twbaucom]

Dangit! I thought we were onto something.

 

[twbaucom]

@PedalPCB how similar would the nobleman schematic be to the Pro-10 Green? Close enough for rock and roll troubleshooting?

 

[PapaBear]

Having built both I'd say it's pretty close

 

[PapaBear]

Dangit! I thought we were onto something.

That Q1 is part of the input buffer, I think that's right

 

[PapaBear]

How are you setting the Spectrum control, it can squash your high end if up too far, what guitar and pick ups?

 

[twbaucom]

The tone/spectrum control doesn’t currently have any setting that gives me usable presence or top end which was what first set off my alarm.

I have tried with a Les Paul and a Strat. The Strat has fairly low output pickups but it was still pushing this bad boy into a lot of drive.

 

[danwojaz]

@twbaucom I have the Protein and I can tell you that on the original pedal, I have to turn the tone control almost all of the way up. When using the protein, I typically don't use the green side unless I am boosting it into the blue side. Currently, the tone is at 4 o'clock. Also, the original seems to not be as loud as the blue side.