Grounding Scheme Question

[Ripthorn]

Some of you may have seen the schematic to my MIAB circuit called the Beatdown. For those of you who haven't, please see below. As you can see, the opamps are all biased with VREF and all the signal components go to VREF instead of ground. A question I have is how that will react when used with other pedals. I've had the circuit on my breadboard and it's been working fine in isolation, but I'm wondering if I will mess anything up by doing that. Would it be better to take the output and just reference it to power ground? If so, do I need to put a DC blocking cap in there? Any light you can shed on this would be greatly appreciated. Thanks!

[Rob Strand]

You probably should reference the input and output to gnd. In that case you will need to add a coupling cap and anti-pop resistor to the input. Good idea to add an anti-pop resistor on the output to ground as well, and perhaps a low value resistor in series with the output to prevent oscillation issues with capacitive loads.

[Ripthorn]

So Rob, if I were to take my 1M pulldown and reference it to ground, put in a large-ish input cap, and do the output cap and resistor referenced to ground, should that be ok? The original design had a bipolar power supply, so ground was fine. I want to avoid using two charge pumps (one to pump the voltage up and one to invert), though I suppose I could breadboard it up and just use the charge pump to give me the negative voltage and then reference everything to ground. Hmmm.... Breadboard, here I come.

[Rob Strand]

if I were to take my 1M pulldown and reference it to ground, put in a large-ish input cap, and do the output cap and resistor referenced to ground, should that be ok? The original design had a bipolar power supply, so ground was fine.

You will need to keep your existing 1M going to Vref to bias the opamp.   Then add another from the input to ground (2M2 if you like); see the GGG website for the pattern.   If you want to keep a 1M input impedance you can raise the 1M to 2M2.    The input cap goes between the two resistors.


Single supply should be OK, provide the headroom is enough for you.

[antonis]

IMHO, too much "garbage" on Vref..

[ElectricDruid]

IMHO, too much "garbage" on Vref..

Antonis makes a reasonable point. The R3/C2 and R10/C7 legs could go to ground rather than Vref.

[Ripthorn]

Thanks for the thoughts guys. I've rethought the entire power scheme and will be breadboarding it hopefully today to test out. It would reduce component count and simplify the grounding scheme issue. I'll keep you guys posted.