FAQ

Whenever you change power tubes, have the bias checked and adjusted if needed — regardless of bias type or class. Fixed bias doesn't mean the amp biases itself; it means a fixed bias voltage. Self-bias (cathode bias) still needs checking.

Part of checking bias is confirming everything inside is healthy. I've found bad screen grid resistors on 5150s where the owner thought the amp sounded fine — it was only running on three power tubes. On a 5150 the factory bias is very cold, so you're usually safe popping in tubes, but you can still miss underlying problems.

In most cases, an upgraded output transformer gives a tighter, more defined, articulate tone and helps balance frequencies so the low end doesn't turn to mud. It's not a cure-all — not every amp needs one.

A choke beefs up the power supply under heavy playing. Better filtering can improve noise, sustain, and reduce sag. Some players feel their tone gets muddy by the second set — a choke sometimes helps keep things consistent through the night.

No. That leaves the door wide open for disappointment. If you like another amp's tone, buy it. CDs are full of studio tricks. Tell me what you'd like to change about the tone you have now — more or less gain, brighter, darker, channels, switching — and I'll do it if I can.

Power tubes: I like TAD, Ruby, and Mullard for current production. Sovtek power tubes tend to be thin and bright for my taste. I'm not a fan of most Chinese power tubes except TAD and some Ruby — they can sound OK but often don't last. Many "boutique" brands are rebranded Chinese tubes. NOS can be great or garbage — buy carefully.

Preamp tubes: I mix and match — even the same brand can vary. Tubes are a starting point, not a cure-all; sometimes the circuit needs to change.

From me, of course — check the tubes page on the classic site. There are great dealers out there; if a dealer only sells one brand, guess what they'll recommend. Tubes aren't one-size-fits-all.