Help needed in solving high pitch noise

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tubeswell
Posts: 2337
Joined: Thu Mar 27, 2008 6:42 am
Location: Wellington. NZ

Re: Help needed in solving high pitch noise

Post by tubeswell »

stephenl wrote:If I pull the guitar cable out, grounding the input, the noise goes away.
Bad old deteriorated cable?
He who dies with the most tubes... wins
Tillydog
Posts: 462
Joined: Thu Jun 17, 2010 9:29 pm
Location: Wales, UK

Re: Help needed in solving high pitch noise

Post by Tillydog »

stephenl wrote:The screens are fed from a mosfet amplified zener stabilizer...could that be inducing the noise?
*Could*, yes - do you see any oscillations on the screen supply?

Are the screen resistors on the socket, too?
stephenl
Posts: 383
Joined: Wed Aug 13, 2008 10:21 pm
Location: Clinton, MA

Re: Help needed in solving high pitch noise

Post by stephenl »

I scoped the screen supply - its stable as a rock.
Steve
stephenl
Posts: 383
Joined: Wed Aug 13, 2008 10:21 pm
Location: Clinton, MA

Re: Help needed in solving high pitch noise

Post by stephenl »

The cable is good, relatively new mogami.
Steve
stephenl
Posts: 383
Joined: Wed Aug 13, 2008 10:21 pm
Location: Clinton, MA

Re: Help needed in solving high pitch noise

Post by stephenl »

Mystery solved :oops:

It wasn't the cables, but I did have a boost pedal in the circuit. The pedal was off and has a hardwired bypass. The pedal is powered from a OneSpot supply - once I unplugged the OneSpot the noise disappeared.
Steve
Stevem
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Location: 1/3rd the way out one of the arms of the Milkyway.

Re: Help needed in solving high pitch noise

Post by Stevem »

First rule of trouble shooting, just the guitar or a signal gen gets plugged into the amp!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
stephenl
Posts: 383
Joined: Wed Aug 13, 2008 10:21 pm
Location: Clinton, MA

Re: Help needed in solving high pitch noise

Post by stephenl »

Heh, yep - I should have known better.
Steve
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