There is nothing difficult in biasing and it can be done by elementary school graduate.
Open the vtl page and surf through to find biasing instructions. A multimeter is a-must tool so you can get to the RadioShack and buy it.
The logical issue: Why would yuou buy a new amp from the dealer and send it right away to the manufacturer to bias???
Once you turn it into AC you should worm it up for nearly two hours before first playback but still you should check the bias prior.
Burn-in your amp by simply listening and drive the speakers on the different volume levels sometimes on high (if conditions permitting).
Dennis, biasing can be learned. You should probably find a tech in your local area that can show you and walk you through this biasing process for your particular amp. You will obviously need to know where the pickup points are for the meter readings. Some amps are biased using the volt reading and some are biased using the amperage reading. After you learn those few things, you will find yourself like many of us checking the bias levels on a regular basis. This as part of the fun of owning tube gear. Good luck........Bob
I agree with "two wheelin' Bob" up above. This is something that you should learn to do if you intend to own / operate a tube based system for any length of time. Keeping track of the bias will also let you know what state the tubes are in, as noticeable shifts in bias are also typically related to shifts in tube performance. If you notice that you have to adjust bias every time you check it, it's time to get some new tubes. This is not to say that the ones in use are "bad", only that they are not as stable as they used to be. They could make for great spares "just in case". Sean
Just from your experience, do you usually check the bias when you first buy a piece of equipment, fresh from the factory? I'm going to buy this meter from Radio Shack, and have sent a message to VTL, asking for advice and maybe for a tech person I could have come out to my place and show me "how to", but in the meantime, I'd like to hear some music! You think it's OK to do that while I'm still figuring out how to adjust the bias?
(PS... I re-read the directions; they were actually pretty clear, and I think I could probably figure this out by myself, but I'll still wait to hear from VTL...)
And be sure not to touch the contacts, there's a lot of juice in a tube amp.
Leaving the tubes burning all the time will not damage anything except for shortening the life of the tubes. Tube life is (normally) anywhere from 2,000 to 10,000 hours so figure on replacing the tubes at least once a year or as much as 4 times a year for some. Tube amps sound their best, IMO, after they're on for 48 hours.
As for biasing yourself, the only thing I can add is to be mindful of your warranty: it might not cover audiophile-induced shorts.
Gs5556, there is no reason to be affraid of shorts in VTL since it's very well engineered and protected equipment and easy as 1 2 3 to work with.
Even if Denis will short an output with the tester pin the worst thing he will spend $2 for the fuse(BTW Denis if you have glass fuses on your new amp call up VTL and order ceramic ones(a few per each slot for output and power to save on shipping) and the replace them for better performance.
Thank for the help... the fuses are actually ceramic already (according to the manual).
I'm getting the meter tomorrow. I've already started listening... and i'm really blown away. I just stop and stare into space listening to the music coming out of my martin logan's, in a trance... god, the VTL is SOOOOOOOO much better than that NAD i had.
Well, went to radio shack, got the product VTL recommended (digital multimeter with autoranging), and also got a plastic screwdriver...
read the instructions..
TOTALLY EASY. i was surprised.. this was no big deal. the tubes were actually a tiny bit under the recommended measurement.
thanks for the help...
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.
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...
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.
How do I know if they are in triode or penthode mode?
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.
i must be using it in tetrode... i didn't see any switch mentioned anywhere in the manual, and haven't found one, but i wasn't really looking either. I'll check it out when i get home... thx
BTW, Luke Manley emailed me a response today. At least it came from his email address LManley@VTL.com.... answered my questions about the biasing and burn-in, and really took some time to be thorough. i was pretty impressed...