It's difficult to tell remotely, but it does sounds like you ran into a bad tube. But since the tube worked for some time, it's somewhat possible that somehow your replacement tube didn't make good contact in the socket or some other odd thing went wrong.

As for output tube re-bias, you don't need to do it unless you change the output tubes so you are OK there.

You should be able to get a replacement 12AX7 at the store where you got it from. Typical guitar stores wouldn't have the equipment to test tubes (a number of them orders from people like me), and big franchises, as you know, couldn't care less. But if it's a friendly shop, you might be able to get them to try the replacement tube in their house amp for a while. At least that'll give you some level of comfort.

If this problem does happen again with another replacement, I'd take the amp into a tech though.

Aki

It’s amazing the difference the tubes make though. When the amp freaked out I plugged in the bass via the effect peddle to the board. Nice and clean but no balls. I'm starting to see why tube heads are so obsessed with the sound of tube amps.

John

It's difficult to tell remotely, but it does sounds like you ran into a bad tube. But since the tube worked for some time, it's somewhat possible that somehow your replacement tube didn't make good contact in the socket or some other odd thing went wrong.

As for output tube re-bias, you don't need to do it unless you change the output tubes so you are OK there.

You should be able to get a replacement 12AX7 at the store where you got it from. Typical guitar stores wouldn't have the equipment to test tubes (a number of them orders from people like me), and big franchises, as you know, couldn't care less. But if it's a friendly shop, you might be able to get them to try the replacement tube in their house amp for a while. At least that'll give you some level of comfort.

If this problem does happen again with another replacement, I'd take the amp into a tech though.

Aki

The amp is solid state; the only tube in it is the one pre amp tube, hence my assumption to re-bias it.

I'm a bit sketchy on the idea of going back to the shop. Its one of those guitar shops with used gear that’s WAY too old and beat up. I'm willing to cut my losses at $20 for the tube and be grateful the amp didn't permanently roast. I'll try order another replacement from a specialist (I’ve heard of this company named BOI AudioWorks…) and not chance smoking a bass amp in order to save $2-3. I have my eye on the 12AX7EH-GOLD you stock. I'm hoping it will fill the bill. Clean is what I am looking for.

John

I know what you mean about tube gitfiddle amps. I used SS for a while and then bought my first tube amp when I started playing gigs 6 years ago--a Peavey 5150 combo. I still have that amp, but haven't used it much cause since we moved to TX. I usually use an old early 70's Fender Vibrochamp I picked up from an 80 year old man at church for $25. Best buy I ever made. Couldn't get him to part with his old Bandmaster head or Leslie speaker.

Hopefully next practice will be a bit more subdued and I can get some critical listening done with the new tube sound.

John