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
Yikes! Looks like the new tubes come with a little price increase too. I wonder if this is why I see a few dealer floor samples for sale too?
Hey Hifigeek1: I believe the KT120 is branded by Tung Sol. I think one or two tube outlets on the web advertise the KT120. If the tube is matched, do you think it's worth trying out. The price is about $90/pair. ARC will charge twice that amount, when the tube becomes available from ARC in the Spring.
Bifwynne,

The problem is, all ARC tubes are matched for current draw so that all tubes draw the same current. Also the ARC tubes that I use are run for 24 hrs. at bias to cull out the bad ones and to make sure the tube won't majorly drift over time after you install them. One more very important point, if an ARC tube ever goes bad within the first 60 or 90 days, I don't remember off the top of my head, the damage is covered by ARC. If you buy your tubes elsewhere you are on your own. I would wait till ARC makes them available. You can contact me if you wish. I don't want to make this an advertisement for my business as I don't have that type of account. gary.mf1@gmail.com. Hopefully the admin won't mind a private email. G
Hifigeek1: have you heard the new KT120 in ARC gear yet? If yes, any comments about sonics, e.g., compared to 6550 "Winged C"?