21Fretter
I think my Laney VC30 is due for a tube swap but I am unsure if it is power, pre-amp or both, I have zero experience. I have no changed them since I bought the amp, easily a year and a half ago and unsure when they were changed previously.
The clean channel is running like a dream, no hissing, popping, volume swelling etc.
The drive has no balls to it/volume. There is hissing, if I play quite hard I can hear a bit of the 'full' sound coming through but intermittent.
Running 4x EL84
3x Sovtek 12AX7
I was given two spare JJ EL84's when purchased.
AlanRatcliffe
Usually the power amp valves and phase inverter wear out every couple of years, while preamp valves last for decades. However, if you are having a problem with only one channel, it's most likely to be one or more of the preamp valves in that channel.
21Fretter
Thanks Alan. Few questions:
How can I go about determining the bad tube?
If it is a preamp valve issue, should I considering replacing the output valves regardless?
Am I going to die a horrible death?
AlanRatcliffe
Get a 12Ax7 and simply swap out the preamp valves one by one until you find the culprit. if you still get problems, then it's more likely to be a dry joint or something else ideally handled by a tech.
To be honest, if it still has the stock valves in, I'd change 'em all and keep the stock valves as emergency spares. IIRC the VC30 is fixed bias, like the AC30 (just check the manual on that one), so no need to do anything other than replace the valves - no further adjustments necessary.
21Fretter
Am I able to mix Sovtek 12AX7WXT+'s with Sovtek 12AX7LPS's without issue?
Edit: It seems the preamp valves are already a mix of 2 * Sovtek 12AX7LPS and a Ruby 72055/12AX7A
AlanRatcliffe
Yup you can try any 12AX7 in any position.
The LPS is a well regarded valve - especially for phase inverter (V3 in your amp). They have a warmer sound with good low end, which to some makes them too dark. They have a tendency to go microphonic in higher gain circuits, so a lot of people don't like them in V1 or V2.
21Fretter
Edit:
I have swapped 2/3 valves and the configuration is different than the original, no luck. Tech time?
