Ampeg SVT - Help!

[iandi.bass]

A few days ago I made sure my bias on my SVT amp was good and set (first time). I didn't mess anything up and both bias are lit green the way they should be. However, when I play my actually bass, as I hit the notes, the lights will flash red every time I play a note, not matter what kind. I do not know whether the amp did this before I re-biased it because it is fairly new and the first time I've done it. Is a red light flashing normal while hitting notes at loud levels? Or may there be some other issue?

[mikeldtl]

Hi iandi.bass -

This would be considered totally normal. A tube amplifiers "bias" is set measuring the tube at idle, i.e. no input signal present. So assuming your tubes are pulling (slightly making up numbers) 72 ma per side, your bias would be set to the correct SVT specs. As soon as you plug a bass into the input, this figure may get into the ballpark of doubling when you push it hard. This will absolutely cause the indicator LEDs to light red. As long as the tubes return back to a stable state in the range in which you set bias all is fine. The bias setting is not a hard and fast number as different AC line voltage will affect the setting and IME as an SVT warms up the bias will climb (over a span of about an hour). As long as everything sounds normal and the lights are green when the standby is flicked off, don't sweat it. If you don't have it already download the owner's manual from Ampeg and give it a good read. There is a whole section dedicated to the user setting bias and troubleshooting.

Cheers