freestompboxes.org

Recently got a commission to convert this EQ to 1/4" jacks, new power supply caps and NE5532 upgrade to make it less noisy. I took a bunch of photos to post here for tracing if someone wants to have a go. I have one of these of my own too if I need to check any part values.

Maybe also get rid of the tantalum, and bypass the electrolytics with filmcaps? Tack caps on the power pins of each opamp to ground?

Wat values are the carbon resistors?

I already did the upgrades. The NE5532s made a huge difference. It's more than twice as quiet now and in front of gain you can barely hear any white noise. The only issue is the channel 1 input is right next to the transformer in the case and picks up 120hz from the magnetic field but I have no idea how to address that.

Either a transformer with a smaller stray field (toroid), or some kind of mu metal shielding.
I had a Dean Markley guitar amp which had the transformer right up against the spring reverb, causing reverb to hum, so I moved that to all the way down in the (combo) enclosure, is there more room in the MXR unit?

Or what we do for superconducting MRI magnets, add windings to create an opposing field

Yeah I was wondering if there was some kind of shielding that could be used. But I'm not aware of anything that will block it currently.

I'm happy with how it sounds other than that. I wish there was enough space to move it or the input jack, but there is not. Also the screws for the transformer and the toggle switches are underneath the aluminum back plate which I'd have to heat with a heat gun and risk damaging it in order to get that plate off. It is glued down with contact cement.