strange noise, can you help me find the correct term?

[deathruddles]

Hi all

I'm fairly new to building amps and i have a problem.

Ive built a single ended kt88 amp which sounds loverly...except.

When the gain is set to max, even on low master volume i get a kind of squel. almost like someone saying woooo high in pitch.

Its different from the normal feedback i get, this wooo cant be stopped by muting the strings.

The sound will not stop if i move further away from the amp/speaker.

It will stop if i reduce the gain, reduce the volume on the guitar or strangely, if i alter the tone control on the guitar.

Can anyone tell me what this type of noise is?

Many thanks for any help!
Nick

[selloutrr]

*SQUEAL*

http://www.geofex.com/ampdbug/squeal.htm

[Reeltarded]

High pitch? match the pitch on the guitar and tell us what note it is.

Not just feedback? WOOO at high pitch... could be howling. That points to a backward component or a ground issue or a freaky tube socket or a bad jack.. or so many other things you could break your head trying to guess..

What note is the WOOO?

[Jana]

WOOO is a bit lower in pitch than WEEEE.

It's oscillating. I would chopstick leads, make sure lead dress is all nifty, stuff like that.

[Andy Le Blanc]

Some times a simple grid stopper is all that's needed.

Welcome to the forum...

[deathruddles]

thanks for all your input!

and thanks for the welcome! ]

I'm not that technical on the guitar, kinda self tought so i have no idea what note it is!

Maybe if i record the sound, and attach it to a post...?

[deathruddles]

and here is the file.

when the wooo changes pitch im actually selecting through the pickups.

[VacuumVoodoo]

It's oscillating. Since the frequency changes when you switch pick-ups you'll need to reduce bandwidth of the first (input) gain stage.
- a grid stopper
- a couple 100pF capacitor parallel with plate resistor
- a small capacitor 10 to 30pF on the tube socket between grid and plate pins

one of the above should cure it.