Op amp choice

[J M Fahey]

IC6, at least on my schematic is being used as an audio mixer twice, first receiving master volume outputs and then mixing main signal with reverb return, so DC on pins 1 and 7 is WRONG.

Now left half of IC6 receives Master signals through a CMOS switcher, maybe it´s sending DC where it shouldn´t.
Read and post DC voltage on all IC6 pins.

[Steve Blackdog]

Hi JM Fahey

I have just realised that my hard copy schematic has different IC numbering. My IC6 is IC8 on your version. Here is the correct schematic as provided by John Cooper of Pro-Amp.

Sorry for that.

By the way the problem with the channel 2 switching now solved- the f/s was the problem. Now f/s rewired and switching channels ok. Massive hum when pre volume turned up. Hum might be single coil telecaster, will try with signal generator.

Also low volume still “in and out”. So something is not right. I am wondering if the pots are responsible.

thank for your help.

[Enzo]

If you think the hum comes from a pickup, turn the volume control on the guitar to zero. Does that make the hum go away?

[Steve Blackdog]

If you think the hum comes from a pickup, turn the volume control on the guitar to zero. Does that make the hum go away?

Thanks Enzo - yes the hum is the guitar. Standing further from the amp also makes a big difference.

The only remaining concern is that there seems to be a bit if a tremolo at lower volumes. This is really noticeable on clean channel. If you play a note, the sound does not sustain as the note decays. Rather, you get the note, but it quickly drops off completely. Any ideas?

cheers

Steve