I built a nasty little dual chip-dual stage op amp based on the Ruby amp that turned out very good.

Here's a schematic if anyone is interested in building their own.

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Those pics are from the first version that didn't work out and had to be modded to the schematic I listed here. Just wanted to show what it looks like.

I got the parts and have built it on a breadboard. It works and sounds pretty cool, but I'm getting some high-pitched squeal and squwacks; I notice noise when I adjust the knobs, which leads me to believe I've got a grounding problem.
When you linked up your potentiometers, did you wire the ground back to the negative battery charge on the circuit board, or did you ground it to something on the unit itself independent of the circuit?
Do all the grounds go back to the battery loop? Thanks for all the help your providing on this!

The pots, jacks, battery input ground and circuit board ground are all linked together.

Check all your soldered joints and make sure they are soldered together, had a similar problem and it was a chip pin that wasn't soldered good.

Did you use mini pots? If you soldered the ground wires directly to the back of the pots, the heat can be too much and damage the pot. I always solder to the side to keep from damaging the pot. Also a good idea to scuff the area of the pot with a file, sandpaper or Emory cloth/board first.

Let me know what happens/find.

What did you build this in? How good is your ground?

I think the pots are standard sized (they're not particularly small) but this was my first time doing the "ground the leads to the back of the pots" bit and it's very possible I applied the heat for too long. It took several takes to finally get everything attached and it was a messy process. I was going to take a multimeter to the pots this evening to see if the resistance is still what it should be. I have spare pots, so I'm only out a few bucks if I burned the ones I'm using.
I see from your pictures how you soldered to the side, and I may give that a try. It can't be worse than what I did the first time (even resorted to a glue gun once I felt they were finally attached).
Right now the build is on a breadboard; duct-taped to some cardboard. Does a circuit on a breadboard inherently have more noise than one in a build? That may explain some issues I'm having with other projects.

This picture was taken before I mounted the pots on a cardboard frame so I could solder them together more easily. I was breadboarding the circuit first so I can get it right before doing it for real.

Haven't used breadboard before, so I can't offer an opinion about that.

I was just wondering about how good your ground circuit is and what it's grounded to?

I built mine in a tin box, the ground circuit goes to the tin box and to the walwart. But the walwart is only a 2 prong, so a ground wire going to the wall socket plate mounting screw wouldn't hurt.

I'm guessing your problem is a bad solder joint.

But wait a minute, my duh. Not a lot of solder joints to work with using a breadboad,  So a bad joint at the pots, bad pot, bad final ground or loose breadboard connection.


Also check how the Jfet is positioned. Make sure the correct pins are going where they should.

With flat side pointing up: left pin will be G which connects to input and 1M5 resistor to ground, middle pin S to toggle/input caps circuit and to 3K9 resistor to ground on other side, right pin D to batt+ circuit.

Oh yes, I had the JFET backwards and the circuit just made a clicking sound which went faster when I switched the toggle to use the other capacitor. That was one of a few mistakes. It was such a thrill after fixing the third or fourth goof and hearing it work and get a pretty decent tone! And significantly louder than the single-LM386 circuits I've built.
I'm pretty sure I've got a problem with the pots 'cause when I touch them it makes a buzzing, crackling sound. And the breadboard nature of the whole construction isn't helping. I'm sure when I finalize the whole thing into an enclosure (with everything soldered), it will sound a lot cleaner. I might just jump to that step now that I've proven I can make the circuit work.

Most of my creations run on 9 volts and are encased in wooden cigar boxes. That must do something to the grounding. Would it make sense to fix some hunk of metal in an isolated corner of the box to run a ground to it? Thanks again for all your help!

Yes a piece of metal in the box would be good. Think about big amps, every thing is mounted and grounded to a metal chassis inside the casing and then to the plug ground. The final part is a necessity with large voltage amps for safety, but with 9volts you don't have to worry about that. So a piece of metal to act as a chassis ground would be good.

I would put it in the box with the "chassis" and check it out before replacing any pots.


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