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I repair music equipment and one of my clients tries things and flips them, letting me try them before they go. I've encountered effects like this and think I actually tried one. They are often clever and original, but like you - I struggle to find a musical application for them.

For reference, I have an early 1980's grey-box DoD 280 compressor. As I understand it, the DoD250 had tweaks in its evolution. I acquired this in 1992 (disassembled), from a friend and revived it / modified in the past few years. My Mods: - R5 is the resistor in parallel with the...

'Live at Pompeii' is a great recording! Yeah, an 1176 derivative is not squishy or noisy, like an OTA or VCA compressor. Studio engineers describe the 1176 as making the music jump off the page and when the effect is turned off, it is very noticeable that it doesn't sound as big. I built the...

A Strat into a Dynacomp (squishy and muted treble), into a 100w Hiwatt (stiff and wide dynamic range) sounds about right for early Floyd. 'Breathe' would be a good example. However, that was probably on a light setting enhanced by a Fairchild or a mixing desk studio compressor before tape...

My neighbor had one and I took a peek under the hood. Like the Wampler Ego 76 (Median Compressor on PedalPCB), it is a simplified Urei 1176 FET compressor.

RESOLVED: Thanks to @bean and @Erik S, I resolved the original problem. The short story is, the schematic was drawn incorrect. It had the (-) polarity of the 4.7uF cap facing pin #10, when it should have been facing pins #15 & #16. This corrected the pin voltages. The original NE571 compandor...

@Erik S , this would easily run on 18 VDC and I am guessing 40ma. Just undo the diodes and insert the 18 VDC in one of the holes, at the 470uF cap. Then just undo the AC clips, the strain relief and then use a plastic hole cover. I was thinking converting to true bypass, as it has tone suck...

@Erik S , one more thing: be careful of handling the lead wires. Many pedals of this era used aluminum wire and soldered with acid-rosin solder. It corrodes the wire at the joint and they easily break off, or look connected but are actually hanging by threads. I've found this same condition...

That is extremely helpful and ties into what @bean provided! Thank you! Indeed, my only problem appears to be pin #10 where I am over voltage by 8v to 9.5v. Per Bean's advice, I am going to rebuild the 33k resistors and 10uF cap at pins #10 & #12. I can tell from your gut-shot, that your...

Most appreciated. The device in question is the NE571 IC. A reading of DC voltage to ground for all the 16 pins would be extremely helpful, in conjunction with the info @bean kindly gave! I've had this pedal since 1986, as it was gifted to me by a friend who was terminally ill. One of those...

Is that from doing the math from the datasheet? Vout DC = (R DC1 + R DC2) / R4

My DoD Chorus 690 wasn't working. The LFO, Flip-flop SAD512D bucket-brigade chip and the compression half of the NE571 compandor was operating, but the expansion wasn't and the Vcc was about +14.2VDC (below the threshold of the LM78L15 regulator). I assumed the electrolytics were all bad and...

To mitigate eddy currents keep the signal circuit ground in a 'star' (emanating from one point), then connect that to 'earth' (chassis ground) via a very low ohms resistor (10 ohms works, I typically use a 5 ohm). It keeps the junction of the dissimilar metals of the enclosure (typically...

I appreciate the tip! I haven't gotten around to peek inside to see what can be done in that regard. Not sure if it is a discrete device, like a transistor or FET, or an SMD op amp. If I skip the looper-switcher's input, the pedals behave better. Using the standard buffered input sounds...

Correct. I typically connect the ground 'feed' to the pedal with the highest power requirement (typically a digital delay or reverb).

What is the status of this offering? I have a Joyo PXL-Pro and have tried a bunch of others, like the Boss switcher and the loop input buffers mess with my FET based pedals when other pedals with buffers are engaged in the same memory program selection (Klon, delay with tails, etc.).

If each AC transformer winding has its own isolated ground, then keep the rectifier-regulator-filter circuit isolated. Your ground of your pedal-to-pedal instrument cables will serve as the 'star grounding system.' I utilize a simpler method of star-ground in the supply, with the positive...

They are all pretty much based from the same dual op amp circuit. Timmy / Zendrive derivatives. These have been designated 'Dumble sounding' pedals, mainly because Robben Ford once made claims that his Zendrive got close enough for gigs which he could not take his Dumble Overdrive Special...

Yep - not all the LT1054's are the same and not all the 7660's are the same, when it comes to hearing sub harmonics of the internal clock / switching oscillator. IDK if it is shielding, filtering or both. All will step up the voltage exactly the same, but only particular suffix types will be...

I've restored one around 2017. Any parts in specific?