Audio Research VS 115 bias Adjustments


Any A-goners familiar with setting bias on the ARC VS115 power amp??

Just checked and set the bias on my VS115 amp. For those who are familiar with the process on this amp, I checked and adjusted the 4 "Set" ports to 65mV, as specified. However, the bias readings from the other 4 "Check" ports ranges from 63-71mV. While technically in "spec" (i.e., 57-73mV for the "Check" ports), I would have thought the range of bias readings from the "Check" ports would not have been that much. As you know, the bias voltage for the "Check" power tubes cannot be adjusted.

As an aside, I only use ARC matched tubes.

Does anyone know whether the range of bias mV readings on the "Check" tubes is normal (whatever that means) or otherwise could result in a denigration of sound??
bifwynne
Well..see my comments above. Those sonic changes were due to the KT-120. I can only assume it will sound the same in your amp. G
I Purchased a matched octet set of Tung-Sol KT120's from parts Connexion for my ARC VS115. Good people to deal with. Tubes were well matched and arrived promptly.I put them in the amp biased them ,same as 6550 biasing, and as is well. Listened briefly and what was apparent immediately was: could see into the music better,better dynamics and micro dynamics,better mid-bass and overall better resolution.
Tomj2617. Awesome. they will take approx. 20 hrs. to break in so they should only get better over time. No need to run the amp non stop for 20hrs. however. Enjoy
Tom: I believe Tube Depot also sells the KT120 for the same price as HiFiConnexion, $89.95 for a matched pair. Any reason why one should prefer one vendor over another?

I know Hifigeek has a strong bias for buying from ARC, and for good reason. However, ARC will not be selling the KT120 for replacment until March/April or later. Also, I understand that ARC will charge more than twice the price than Tube Depot and HiFiConnexion, $100 per tube. For two quads -- that's a lot! Thanks. BIF