Strange sound when I turn the drive pot

[Tdale]

My Hybrid-a (I followed the schematic) sounds good most of the time.

I found that when I put the volume, drive, level and master in the 10-11 o'clock position, it sounds great.

But if I turn the drive pot past 12, up to about 1-3 o'clock, the sound gets a bitt strange. When I play a single string, it sort of resonats like it does if you pick two strings at the same time, and one of them is out of tune, or they sort of dissonate.

Any ideas of what it can be?

I'll try to make a sound clip...

[Bob-I]

My Hybrid-a (I followed the schematic) sounds good most of the time.

I found that when I put the volume, drive, level and master in the 10-11 o'clock position, it sounds great.

But if I turn the drive pot past 12, up to about 1-3 o'clock, the sound gets a bitt strange. When I play a single string, it sort of resonats like it does if you pick two strings at the same time, and one of them is out of tune, or they sort of dissonate.

Any ideas of what it can be?

I'll try to make a sound clip...

I had an amp do that once. Turned out to be a very high frequency oscillation. I used a scope and connected to various point throughout the ckt until I saw a sine wave at about 30K at the PI. Redressed some leads and resolved the issue.

[Tdale]

what does redressing a lead mean actually?

Tommy

[Bob-I]

Lead dress refers to the way wires are routed inside the chassis. Basic rules are that signal leads should cross power leads at right angles, connections to the tube sockets should be laying flat against the chassis, cathode and grid leads should cross at right angles and many more rules.

I'd start by duplicating the noise, then shifting some wires around using a chop stick or other non-metalic object. If you find a lead dress issue you'll know because the sound changes, not necessarally better, but different. Then you know you're in the right area.

[Tdale]

Thanks

Hehe.. I always thought that lead dress referred to the inslutation of the wire.. plastic, silicon, cloth.. like the way the copper lead is "dressed"

Not easy for a norwegian..

Tommy

[Bob-I]

Thanks

Hehe.. I always thought that lead dress referred to the inslutation of the wire.. plastic, silicon, cloth.. like the way the copper lead is "dressed"

Not easy for a norwegian..

Tommy

Not easy for an American either

I saw the pics of the completed amp, do you have pics of the internals?

BTW, I spent about 4-5 hours troubleshooting an amp that had a bad tube. You might cover the simple things first, tubes, guitar cable, speaker cable, speakers.

[Robert]

Could be a bad pot.

[tomrasdf]

I second the idea that you check the lead dress. A Klemt Echolette I was just working on had the same problem. One of the grid wires was picking up a stray oscillation. I got that same wierd out-of-tune undertone. No fun. I'd double check everything between the first and second OD triod. Best of luck tracking it down.