Informant overdrive 470 -> 430 ohm substitution

Fama

Well-known member
Hello!

I built the Informant overdrive, but I didn't remember to order 470 ohm resistors and I'm planning to not order more stuff for a bit, so I substituted them for 430 ohms. The pedal sounds nice, but it's a bit on the thin/bright side - it's fine if I keep the cut control maxed or almost maxed most of the time. There is nice heft to palm mutes, but no way to make the pedal bassy.

Just wondering if it's normal or did the substitution matter for this? I'm using low output single coils in a Vintera 50's strat, so if the pedal "keeps your guitars natural tone" that could also be it. I didn't have any problems getting tons of low end with other pedals though.
 
I'm assuming you are referring to R8 in the below.
1684784340861.png

Do a google search about non-inverting opamps. A writeup of one is overdue here, but inverting opamps have been covered in the Resource section. That resistor is in the feedback loop and does 2 things: controls the amount of gain in terms of the relationship between it and R9/DRIVE combo. R8 in combination with C5 complete the feedback loop and control the corner frequency of the gain stage. In other words, it selects what frequencies get boosted in this stage. Any old RC calculator will tell you the corner frequency got raised from ~1550Hz to ~1700Hz. Not huge, but noticeable. Increasing R8 will bring in more low end and vice versa to this stage.
 
I'm assuming you are referring to R8 in the below.
View attachment 49087

Do a google search about non-inverting opamps. A writeup of one is overdue here, but inverting opamps have been covered in the Resource section. That resistor is in the feedback loop and does 2 things: controls the amount of gain in terms of the relationship between it and R9/DRIVE combo. R8 in combination with C5 complete the feedback loop and control the corner frequency of the gain stage. In other words, it selects what frequencies get boosted in this stage. Any old RC calculator will tell you the corner frequency got raised from ~1550Hz to ~1700Hz. Not huge, but noticeable. Increasing R8 will bring in more low end and vice versa to this stage.
Thank you!

That does sound like it might be worth changing even at this point. What about the other two 470 ohm resistors? One is directly on the bypass out, and one is right before the volume pot.
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I would venture a guess that the buffered bypass one means I have a smidge more gain in the bypass signal, but if it wasn't already obvious I'm very much a beginner when it comes to schematics, so I'm not sure about that. I guess the volume one would seem to limit the maximum volume a tiny bit? There must be some other function to them too? Or I'm just completely wrong.
 
I really like this pedal but would also agree that it can be a bit on the bright side. I generally have the cut about 3/4ths or thereabouts to get it sounding right to me.

That said I also find it’s definitely one of those pedals that feels more tuned for “in a mix” than soloed/isolated (and at full stage volume rather than bedroom, etc?). Can be a little thin sounding on its own but tends to sit pretty nicely in a full band mix. And I suspect if it were voiced a bit bassier it’d likely come at the expense of clarity/definition/“cutting” when it comes to a full mix.
 
I changed the 430 ohm to parallel 1k resistors for a total of 500 ohms, I think it has a bit more beef now. That part is fine - but it definitely is a bit too bright for me.

Or to clarify, I can get great tones out of it. But rolling down the guitar tone seems to be the key there. If I have tone at full blast and use the Cut control to control the top end, the tone is broken up on the high end in a rather unpleasant way (for me). However, if I turn the tone and Cut both down (so tone down -> less high end, cut down -> more high end to compensate) I can get some really nice sounds out of it. Only with the gain very low can I run both guitar tone and Cut so they let out a lot of high end.

So what I'm getting at is that I'm wondering if I should try to mod in a low pass at the start of the circuit. However, using the buffered bypass seems to make it pretty tough, since I can't just add it before the pedal itself. Is there maybe some cap or resistor I could change to achieve a low pass, or if there is one already, make it lower?
 
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