Ampeg SVT-CL Bias Lights and slight buzz

[Eskimo Spy]

Okay, I just got my SVT-CL, and I have a question about the bias lights...

There are two lights, a red and a green for each set of three tubes. When I am playing, the red lights light up with the signal. This is normal behavior. But should the green bias lights remain lit under normal conditions?

Also, how much noise should I expect from the head? Running through a 4ohm cab, even after switching the polarity switch to all three positions, there was noticeable, but not terrible buzz.

[JimmyM]

Originally Posted by Eskimo Spy

Okay, I just got my SVT-CL, and I have a question about the bias lights...

There are two lights, a red and a green for each set of three tubes. When I am playing, the red lights light up with the signal. This is normal behavior. But should the green bias lights remain lit under normal conditions?

Also, how much noise should I expect from the head? Running through a 4ohm cab, even after switching the polarity switch to all three positions, there was noticeable, but not terrible buzz.

bias lights: every cl i've used has bias lights that stay green unless i'm playing.

noise: nothing beyond normal operating noise that you'd hear out of any other amp. it's possible you could be picking up interference from something in your house, though. dimmers, flourescent lights, tv's or monitors nearby...etc. also, being too close to the amp with the bass can cause noise. so rule interference out before you go tearing apart your amp.

[Eskimo Spy]

The bottom lights stay green, the top lights flash red with the signal.

I hear buzzing, and when I put it in standby, the buzzing goes away. It is plugged straight into the wall, no strip between it and the wall, but it's a 4 year old house, not a 40 year old house. And it's a brand new head, so I'm not tearing anything apart! If it's broke, they can fix it.

That said, I'll see if the buzzing still exists when I plug it into my new Aggie DB 410 cab when it arrives tomorrow. I ran it into my Ashdown ABM 410T cab tonight just to see what it sounded like tonight.

[JimmyM]

my house is only 2 years old and i can't get a clean signal in most of my house.

[Eskimo Spy]

Hmph. My Ashdown runs without much noise, but like I said, it's not horrible, just noticeable. It still sounds fantastic though.

[johnk_10]

it sounds like you're describing a normal amount of noise to me, but some preamp tubes can be noisier than others.
you bias lights are operating perfectly as described in the manual on page 7.

[Alexander]

The bias lights should stay lit green when not being played. You can adjust the bias screws until this is the case. Even when they are both green, you have some play and IME can adjust until they are both green AND the buzz goes away. If you cannot do this, or the bias adjustment does not hold over time, then you might need to get the amp serviced.

If both lights show (and stay) green and you cannot dial out the buzz with the bias controls, I agree with others that you might have a noisy tube somewhere or dirty signal.

[Eskimo Spy]

Well, my new cab won't be in until tomorrow. I'll connect it and see if the buzz is still there with a surge protector, if it is, I'll try adjusting the bias, then try swapping out the preamp tubes.

[ajunea3]

I've noticed that if I bias my CL too far in either direction I get buzz; and the more I over- or under-bias the amp the stronger the buzz gets. Try fooling more with the bias lights to see how they affect the noise.