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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
6550c
393 posts
 
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?
bifwynne OP
2,206 posts
 
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.
hifigeek1
770 posts
 
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
bifwynne OP
2,206 posts
 
Hifigeek1: have you heard the new KT120 in ARC gear yet? If yes, any comments about sonics, e.g., compared to 6550 "Winged C"?
hifigeek1
770 posts
 
No I haven't personally however I have received feedback from people I trust. It's great! It should be understood that ARC listens to the tubes for a long time as well as life tests the tubes before they give their ok. If the tube sounded bad, they wouldn't be using it in their products. Your going to get a bit more slam and impact with the KT-120 and not in a bad way. It has an effortless quality. Very musical. The funny thing is I remember my old Dyna MK III's with the tung sol 6550 Coke Bottle tubes in them, and they were awesome. More slam, more impact w/o sacrificing any detail. By more slam I mean better transient impact. I think it's going to be a win win but only time will tell. G
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