2. amps-preamps
  3. 1073538602

Hurricane Owners - Biasing Question

I have been running the latest iteration of the ASL Huricane tube monoblocks (w/ the green PIO caps, triode switch, stronger chassis, upgraded parts, and new biasing system(??))over the last few months, and it seems that I'm spending an awful lot of time re-biasing the power tubes. I'm wondering if I'm just being too anal with the biasing, or if there is a better method or strategy to this madness.

When I start the amps up, the bias current starts low (low to mid 400s) then work their way up to over 500 over the course of a half hour or so. Over the next hour, they will drift down to the correct bias of 480. They stay there for a while, especially if I continously play music through them. If no music plays, then continue to drop to the 450s, or if music is playing, it takes a few hours to get down that low. So I find myself tweaking down when they're over 500, then I'm tweaking back up to 480 when they drop below 470, etc. etc. etc...Then at the next start up, the biasing is all wrong, and the cycle starts again. BTW, the tubes (KT88-EHs)are all burned in.

Is this normal (hey, this is the first time I've owned tube amps...)? What is the net effect if the bias drops too low (less power output?, sonic quality?) or of bias goes too high (reduced life?, sonics?).

Anyways, I think these are great amps despite the continuos fiddling around with the bias, and I'm enjoying them immensely!

Thanks....
1markr

Showing 1 response by denf

denf
241 posts
 
Hello Lmarkr -

I own the 2nd version, and am also "constantly fiddling" with the drifting bias. I don't hear any negative artifacts on the sound, however, as long as it stays in that 480-ish range.

I even have 30 amp dedicated lines (for EACH amp) and they still drift down if a major appliance is used in my house! (new house, 200 amp circuit box).

Bottom line is that I think it's just the nature of these beasties, and as long as they pump out the great sound, (which they certainly do!), I would focus on the music, and not on the meters (turn 'em off!)

Cheers!
More to discover