Ampeg SVT 450H, problem

[AKI BASE]

Hello to everyone
After a 3 hour rehearsal, my Ampeg head start to make a noise (like fuzz) every time i played on bass.

I usually play with the master volume in the end and the gain in 9 o'clock.
I check everything (bass, cable, cabin), the problem is on the head.
Please, if anyone can help.......Thank you.!

[JimmyM]

maybe a bias issue? i know the svt 3 pro requires occasional biasing of the mosfets. maybe this one does, too.

[RickenBoogie]

How exactly do you "know" it's the amp, and not the speakers?

[craig.p]

Try isolating the head from the cabinet so it doesn't pick up any cabinet vibrations. If the problem goes away, then you have a loose connection or bad solder joint inside the amp. It could even be dirty contacts in the effects in jack, though I think that's a long shot. But you can eliminate that possibility by connecting the effects out and effects in jacks with an instrument (shielded) cable.

[AKI BASE]

Thanks everyone for the replies, i will try your advices......!

[Jerrold Tiers]

Originally Posted by JimmyM

maybe a bias issue? i know the svt 3 pro requires occasional biasing of the mosfets. maybe this one does, too.

The 3PRO needs it because the bias is especially sensitive due to the "zero feedback" design.

The other amps are not like that, and so the bias is less critical.

There are lots of reasons for a "fuzz-type" tone, ranging from dirty connections to amplifier failures, so any opinion here is pretty useless. Go to a technician.

If the technician does not have schematics etc, send me a PM with your email..... I should have them.

[AKI BASE]

Originally Posted by Jerrold Tiers

The 3PRO needs it because the bias is especially sensitive due to the "zero feedback" design.

The other amps are not like that, and so the bias is less critical.

There are lots of reasons for a "fuzz-type" tone, ranging from dirty connections to amplifier failures, so any opinion here is pretty useless. Go to a technician.

If the technician does not have schematics etc, send me a PM with your email..... I should have them.

Hello my friend,
What is the PM ?

[Jerrold Tiers]

Originally Posted by AKI BASE

Hello my friend,
What is the PM ?

Sorry...

PM = "private message" , a feature of this site..... If you click the name on a post, you get a list of actions, one of which is 'send a private message"..... that is what you want.

Send me your email address that way , and I will email the PDF files to you