Very noisy Ultra-Lead

Amps & Cabs Pittbull Ultra-Lead
1

Hello, I just bought a used Ultra-Lead w/EQ (I believe its from 2004) that I’m finding to be very noisy. When first turning the amp on there is a low level electrical hum even when on standby. It could be just from how much juice this amp is pulling, but it’s definitely something that I can hear with this amp that isn’t present on my other amplifier (a 50watt EL34).

Furthermore, I’m finding the amp produces a lot of “fizz” when turned up loud. I know this is normal, but I like to run a noise gate in 4CM with my amps to keep them dead silent and even when doing this, my Pitbull sill has a lot of noise coming through that gets louder as its turned up. I’m using the FX loop in serial, though I’ve tested with parallel as well. This kind of fizz is completely eliminated on other amps with the same gate in 4CM.

Before taking it to a tech or anything like that, is there anything I could try at home or be aware of? The amp currently has Tung-Sol 6550 power amp tubes, JJ ECC83S in V1-4, a JJ ECC803s in V5 and a JJ ECC81 in V6. I know these aren’t the recommended tubes in the manual and they are probably old. Would replacing these according to whats suggested in the manual help at all?

Edit: I should add that I’ve tested this with multiple power and patch cords, multiple cabs and at home as well as in my rehearsal space. Thanks for any help you can give!

2

If you are hearing a hum even with the amp on standby, that could indicate a ground loop in your setup, since on Standby, the power amp stage is not operating.

JJs can sound fizzy in this amp. Hard to say what to recommend these days. Shuguang 12AX7s generally sound really good, but they don’t seem to be sufficiently stable in production as yet since the factory got up and running again.

How do you have the global master set. We recommend keeping that up around 2:00 or higher and turn the Lead and Rhythm channel volumes down instead. That may help.

Dave

3

Hey Dave, thanks for your response. A grounding issue was my first thought too, but I’ve tested with multiple power cables, multiple outlets and two different locations. Here is what it sounds like:

The hum happens as soon as the amp is turned on, but only amplified after being taken off standby, obviously.

4

The fizz is only really prevalent when the master volume is up around 2-3. Here is a clip of the clean channel. Master at 2 and channel volume at 0 with no loop or eq engaged. You can hear me flip the ground switch near the end.