I agree with mulveing, Check your manual and you will probably find that it has automatic muting on turn on to protect it tubes. With my amps I let them warm up for a couple of minutes, then set the bias, let them run for about 20 minutes and check/reset the bias as necessary. Then I check the bias the following day after running the amp an hour or so to make sure the tubes hold their bias. If they do I check the bias about every three months.
Tube amplifier - tube bias and time to warm up
Power Amplifier
I have a Cary Rocket 88R tube power amp, it is not an integrated, power amp only, but my questions are pretty basic.
The specs for biasing my amp are 195-220 Milliamps.
Currently it has:
- Quad set of KT88's
- Pair of EL84's for the voltage
- Pair of 12AX7's for the preamp drivers
Status
All tubes light up.
No tubes are glowing hot.
All fuses (2) are working.
When I power up my amp to do the tube biasing, I'm not getting any milliamp reading on my Multi Meter. Am reluctant to leave amp on after 30 seconds with no milliamps showing. Worried I'll blow something.
I get a rise up to about 40 Milliamps when I turn the amp off. But nothing within 30 seconds when it is on. The Bias LED's are lit, which indicates that there should be bias current available.
When I remove the Bias headphone jack, I do not get any sound out of the amp.
All tubes light up - but no sound. But again, I'm shutting the amp off after 30 seconds for worry that I don't have the Bias set properly and I could damage it.
I've had the amp in the shop months ago and I don't recall how long it takes to warm up to get a bias read, and long enough to put out sound.
Questions:
- Should I have some reading on my meter after 15-20 seconds?
- How long before I should have some Milliamps showing?
- How long before I should have music coming out?
- Could a bad tube cause this situation?
Thanks for any thoughts.
Graham