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Thinking about EQ type patch for the FV-1. What I need - bandpass filter with two notch filters. For example: 100Hz to 5kHz with notches at 500Hz and 2kHz. Each notch has fixed frequency, fixed Q and adjustable depth (from zero to -10dB). Is it possible? Any tips?

I suspect that Locrian99 has swapped the pin designations. S - ok.. D - could be this 7.18V G - should be 0

nothing..absolutely nothing. You can even not install Sag pot before setting the bias. Jumper pads 1 and 2 of the Sag pot, set the bias, install the pot. Looking at the schematic of the v1 and v2 there's no difference between Sag pot wiring, unless there is an earlier version of the schematic.

But you know you have to set 6V on a test points, right? And only when Sag does not limit the voltage?

First let's make sure you're doing everything correctly. 1. Set the maximum voltage on the pin 1 of the Sag knob. Sag should be probably at zero (max CCW) but it's better to measure the voltage than stare at the knob. From now on - do not adjust Sag. You want max voltage.. like there's no Sag...

Do not rely on the Sag knob position. Measure voltage in the circuit - you want max possible voltage on pin 1 of the Sag.

Because audio signal can affect the bias voltage.

No, I haven't even started yet. I would prefer to use the full schematic rather than with some modules omitted.

@Robert - any update on this?

Thank you for your offer. I think I already have everything I need to design a pcb. I like this part of the build and I like to lay a board in my own way :) I'll post an update here. Thanks again.

@Paul.Ruby thanks for the schematic and explanations. Now I have to find some time to process it and probably design a board for the O2.

I had a similar "issue" with fake 072s. https://forum.pedalpcb.com/threads/tl072-vs-tl072.12830/

Is the schematic similar to this one?

@Paul.Ruby - do you use a buffer between output of your AMT preamps and next pedal? Btw - O2 schematic omitts input buffer.

Vp 0.6–0.63V and Idss 0.5–0.52mA

Gain @ noon. Bat41 Bat46 Bat42 Bat48 Bat85 1N4148 Ge diode

Some oscilloscope shots from the O2 on a breadboard. Testing different diodes. Cyan trace - second stage output, yellow trace - third stage output. 1kHz sinewave, 200mv p-p Gain @ max. Bat41 Bat46 Bat42 Bat48 Bat85 1N4148 Ge diode

For me O2 is ok, but not amazing. Maybe because I connected it only to the audio interface instead of the power amplifier. I'll give it another chance in some time. Btw - I recommend Crunch channel of the AMT Bulava SS30. Schematic available here One comment about the diode in O2. Schematic...

Just tested O2 on a breadboard. Seems to be ok.

@Paul.Ruby - O2 schematic appeared today on freestompboxes