PDA

View Full Version : Bad Cat bias


Ken Ho
12-13-2007, 06:47 PM
OK, So I have a BAd Cat Hot CAt 30, Class A PTP etc etc.
When I replace power tubes, do I need to bias, or does a Class A not have a bias ? Or is it self-biasing ?

Probably an old question, but I'm new here.

JimmyR
12-13-2007, 07:19 PM
A Hot Cat is cathode biased, which some people call self-biased. I like Bad Cat amps, but then I'm biased. Anyway, just replace the tubes and you'll be fine. There are no bias pots to tweak.

BTW you can try JJ KT77s in there, which cost about the same as EL34s, but I find they sound fuller and smoother to my ears. They are a straight drop-in. If you prefer to stay with EL34s might I recommend the SEDs? Bad Cats are quite hard on output tubes, so expect to change them at least every year.

Ken Ho
12-13-2007, 07:38 PM
A Hot Cat is cathode biased, which some people call self-biased. I like Bad Cat amps, but then I'm biased. Anyway, just replace the tubes and you'll be fine. There are no bias pots to tweak.

BTW you can try JJ KT77s in there, which cost about the same as EL34s, but I find they sound fuller and smoother to my ears. They are a straight drop-in. If you prefer to stay with EL34s might I recommend the SEDs? Bad Cats are quite hard on output tubes, so expect to change them at least every year.

THank you very much, I had a feeling it was cathode biased.
I'm happy with the EL34's, and I quite like Ruby tubes, perversely. My H&K had them as stock and I liked them in that too.
I run 5 amps in rotation, so I don't wear out tubes too quickly luckily. It's a deliberate ploy, and a great excuse to own mucho gearo. I like Mesa for the ease of tube replaement as well, no easy tech access for me, so it's a significant thing to consider.
I'm only playing at home, so I don't flog the slot out of it either.
I'm pretty biased toward it as well.
Thank you again.

FFTT
12-14-2007, 04:33 AM
The SED's really do hold up well and are highly recommended.

JJ EL34L's also seem to hold up well, so I'd try both and keep one set
for back-up.

vibroverbus
12-14-2007, 10:05 AM
I run 5 amps in rotation, so I don't wear out tubes too quickly luckily.

VL - that's excellent! I'm going to steal that as my excuse next time I get crap for having too much gear...
"guys, the reason I HAVE to have so many amps, is to save on TUBE REPLACEMENTS. it's just being frugal really!"

Ken Ho
12-15-2007, 06:18 AM
VL - that's excellent! I'm going to steal that as my excuse next time I get crap for having too much gear...
"guys, the reason I HAVE to have so many amps, is to save on TUBE REPLACEMENTS. it's just being frugal really!"


It's great logic innit ?
I had only two this time last year, and sold one to buy a guitar, thinking 2 was a waste. Well the very next day, ny main amp crapped out and facing Xmas time off with nowt to do but play guitar, I was not happy. So, I went out and bought another immediately, and vowed to never sell anything again, especially for a silly reason like economics.