2. amps-preamps
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Burn-in and Biasing

I just got a new VTL integrated (IT85) tube amp yesterday. Two questions:

BURNIN:
--Is it OK to leave it on, on a low level, overnight and during the day, running constantly? (Hope so! that's what I'm currently doing, but I can turn it off when I get home if I have to)

BIASING:
--The manual says that only a recommended VTL tech should bias the machine. It seems kind of complicated. The person who does the biasing needs to use some kind of digital multimeter equipped with autoranging feature. I guess I wouldn't mind trying it myself, but I have never done this.

The manual recommends that the amp is biased when it first is setup. What are people's opinion on this? Is biasing something I could do myself, with that meter?

TIA....
dennis_the_menace
viridian's avatar
viridian
4,184 posts
 
DTM be sure to recheck your measurements at night if you have not already done so as line voltage tends to climb at this time. You wouldn't want to be running the tubes hot part of the time.
dennis_the_menace's avatar
dennis_the_menace OP
467 posts
 
I just checked the bias again tonight (around 10:30pm), and it was actually a little under the amount I set it at yesterday afternoon. The acceptable reading is supposed to be anywhere between 275 and 300. I set the bias yesterday at around 285 on each tube. Tonight, when I measured them, they all read either 272 or 275.... I just left them as is... i guess they will vary slightly. VTL said that if the reading falls within 10% of the acceptable range, then that is OK...
marakanetz's avatar
marakanetz
5,473 posts
 
Dennis,
feed the tubes with 300 when they're in triode mode and 275 when they're in penthode.

don't do it too often. once in 400 hours will do.
dennis_the_menace's avatar
dennis_the_menace OP
467 posts
 
How do I know if they are in triode or penthode mode?
marakanetz's avatar
marakanetz
5,473 posts
 
all today's vtl product have that switch for triode or tetrode operation. I assume that 85W/ch is for tetrode(sorry not penthode) operation and you might have a switch to switch it to triode which nearly halves the output power.
in my case(Totem Forest) i always use tetrode.
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