High gain, high pitched squeal oh no! Poor layout?

[Luke51411]

I built dead astro's spitfire tested it and boxed it up. Now there is a high pitched squeal at about 50% gain and higher. Is this just most likely poor layout/shielded wire needed? I thought that would just cause a noisy circuit not ear piercing screeches. Ouch.
Also, when I tested it before wiring stomp switch I used a battery but there's no room in the box. The power supply is meant for pedals and I haven't had an issue with it before. I'm sure I answered my own question but any help is appreciated.

[pappasmurfsharem]

I built dead astro's spitfire tested it and boxed it up. Now there is a high pitched squeal at about 50% gain and higher. Is this just most likely poor layout/shielded wire needed? I thought that would just cause a noisy circuit not ear piercing screeches. Ouch.
Also, when I tested it before wiring stomp switch I used a battery but there's no room in the box. The power supply is meant for pedals and I haven't had an issue with it before. I'm sure I answered my own question but any help is appreciated.

You can always try a large filter cap. Not sure it if it will help.

Are you saying that the squeel doesn't happen with a battery?

[Luke51411]

Well it didn't happen with the battery but I also didn't have the jacks or switch wired I just soledered wires for the in, out, power, and ground and plugged them into a breadboard as I usually do to make sure the circuit works. I think I will take it out of the box and move stuff around to see if it is interference from the wiring.

[pappasmurfsharem]

Well it didn't happen with the battery but I also didn't have the jacks or switch wired I just soledered wires for the in, out, power, and ground and plugged them into a breadboard as I usually do to make sure the circuit works. I think I will take it out of the box and move stuff around to see if it is interference from the wiring.

I believe batteries supply a fairly clean source of power. So it's possible that increasing the filter cap may be useful. What size cap do you have in there now?

[Luke51411]

100 uf

[Luke51411]

It's definitely the wiring. Tried a battery and there was still squeal. Removed the circuit from the box and if I moved components far enough from each other it stopped. I think I'll get some shielded wire and try that.

[ggedamed]

You can try a buffer before it - like a Boss pedal in the bypassed position. If it kills the squeal then it looks like the output signal finds its way to the input and then travels again and again through the Spitfire. Any method that increases the isolation between the tracks/wires/tracks and wires should help: shielded wires on input and output, decoupling caps on every gain stage (as close as possible to the supply pins of the stage), changing layout and so on. The easy way out could be adopting a buffered bypass, many commercial hi-gain circuit work like this.

[deadastronaut]

You need to shield the input....then when its boxed it,ll be fine.

[Luke51411]

That's my plan. Thanks!

[duck_arse]

try putting a 100R between your adaptor V+ and the point C1/D1, so as to make a power line filter. (I don't see one one the V3 diagram.) you could also try adding, like ggedamed (I always liked that name, it sounds to me like a real bad "cuss") said, another 100R and 100uF between R4 and Q3 as they are drawn on the V3 schem.

http://www.aronnelson.com/gallery/main.php/v/chickpea/SPITFIREV3.jpg.html?g2_imageViewsIndex=1

does the scream stop if you take a little off at the guitar volume knob?

[Luke51411]

I installed shielded wire on the input signal all the way to the board and to the modern/classic switch. Problem solved.

[deadastronaut]

Cool...