Do I really need to rebias an amp?

[davidd]

Afternoon,

I have recently acquired a blackstar ht40 which is nice. There is a slightly odd hum which I'm pretty sure is one of the pre amp valves and so I've ordered new ones, whilst I was at it I bought new power amp valves (and a speaker).

Swapping the valves is simple enough but I have read that I might need to adjust the bias on the power amp valves to make sure they are not to hot or cold.

Technically I can do this but I won't have time before the weekend and I need to use the amp tomorrow evening.

Will it kill everything if I swap the valves out and run it for a couple of hours without biasing it?

Cheers

D

[Tom_C76]

Depends how far out they are. Why not run with the existing power tubes?

[davidd]

Tom_C76 said:

Depends how far out they are. Why not run with the existing power tubes?

That's a fair point, I probably will this evening and then sort it all out properly later in the week.

[davidd]

Just in case anyone is interested.

The amp is a blackstar ht40

I swapped all the valves last night for JJ's the bias was 50% high (75mv instead of 50mv) which might have been why the amp sounded so horrid.

Anyway I let it warm up and set it to 50 and put a vintage 30 in it. Then went to band practice, it sounds much better than it did and has much better headroom than the tubemeister 18 (unsurprisingly).

I just need to spend a bit of time with it learning how to get the tones I want from it.

D

[Tom_C76]

That V30 speaker will have a fair bit to do with the improvement. Great speakers, I put one in my Laney cub 12 a while ago.

[davidd]

Tom_C76 said:

That V30 speaker will have a fair bit to do with the improvement. Great speakers, I put one in my Laney cub 12 a while ago.

I've had another play with it this evening, all at low volumes. Really pleased with the sounds I can get out of it, I just need to work out how I manage the channels so I can switch volumes/clean/od etc without too much faffing between songs.