Overdrive Build, High Treble+High Gain = Squeal

[drchek]

I finally got my Klon build working (bad IC) and it sounds great. Only problem is that if I crank the Treble and Gain there is a constant squeal. Reducing either control eliminates the feedback. Obviously a combination of treble and gain is always a recipe for feedback, but my question is this:

Is this a thing with the Klon circuit? I've watched many demos of the original units and they never max both the gain and treble at the same time. Is this why?

Another thought. I currently have the circuit going to a breadboard to test all the controls. That means lots of wire and unsoldered connections. Could that be the reason that the circuit is more susceptible to squealing at max treble and gain?

[GibsonGM]

Hi DR., welcome...

ANY high gain circuit can/will squeal and feedback!   It's just physics...you're amplifying a signal thousands of times, and it passes near wires and components that 'catch' the field that's radiated, bringing some of the signal back to an input where it is re-amplified.  This is called "Coupling", and it is most always not good.   

A magnetic field is radiated by each wire carrying a varying current...this field cuts into other wires, and induces a current to flow in THEM...the current is "jumping the line".

You MINIMIZE coupling by routing wires properly....keep ins and outs away from each other; if wires must cross, do so at right angles, use shielded wire for inputs/outputs, with only one end grounded.   Use  a good ground scheme ("star grounding" search topic).   

Right now, your circuit is on breadboard...it is NON-shielded (the metal enclosure you put it in acts like a shield...), so can pick up any room garbage floating around and make noise.  The wires are all over, coupling to each other, and the board itself has high capacitance, which also aids coupling.

Think about how you'd like to route all your wires (read up a bit), get your enclosure ready, mount the circuit in a box, and be done with it.  If you're playing, there will be no squeal...when you stop playing, you must turn the high-gain box off    That's sorta universal...yes, we try for as quiet a circuit as possible, but there's only so far you can take that....

[blackieNYC]

+1 to all above, but I wish I could tell you for sure. I don't have a Klon - yet. I was thinking that my breadboard wires are actually much further apart than my final builds. I suspect you have something wrong somewhere - or - you need to tweak a component to your liking.
BTW - I've recently started tacking my assembled perf circuit back on to the breadboard (where it started) for one last check before I stuff it in the box.  Good practice, eh?

[GibsonGM]

There's nothing *special* about the Klon Centaur from the schematic I just found...buffers, gain stages....it's all about the gain, the wire routing, and the ground plan, basically!   Taking care with those will get you an as-quiet unit as can be had.     Of course on the BB, all KINDS of noise are going to be observed, ha ha! 

I like to also test my PCB when done before adding switches etc....I use jumpers to attach jacks or plug them all into the BB, and test it before boxing.  Then you KNOW the error is with the switch, jacks or DC input...if it's built properly, you may find that the Klon is a little more cooperative when IN the enclosure, which will shield it, and well-routed wiring can help avoid oscillation....

[drchek]

Thanks for the replies. It put my mind at rest since I checked over the circuit MANY times trying to find an issue that wound up being a bad IC. The more I though about it the more I realized that the messy breadboard test is far from ideal conditions and so all sorts of feedback and signal leakage can happen.

Can't wait to get this thing installed in the box...