Ampeg SVT-CL line-out noise

[aengberg]

Hi

I’m having a problem with my Ampeg SVT-CL amp’s balanced line-out. When I use it to plug in to a mixing console I get a buzzing static noise, that is so loud that the engineers prefer to use a DI box. This is without an instrument even connected to the amp.

I don’t hear noise from the speaker, except for a low humming noise when the amp is turned on, which gradually disappears when the tubes warm up. The noise from the line-out seems to be different, and a lot louder.

Any suggestions to what my problem might be? Could this be due to low quality tubes, or maybe the line-out is bad?

Thanks.

/Andreas

[lem8r]

it is not tubes. May be bad cable or wrong connection inside the amp.

[beans-on-toast]

There is a chip that contains two op amps, IC1A and IC1B on the schematic, that drive the balanced out signal. The chip is an NE5532.

Noise problems on the balanced out have been reported to be cleared up by replacing this chip.