Any info on the new Audio Research VS115 tube amp?

I have just bought a VS115 with LS17. This is an addition to my Jeff Rowland Concentra Integrate MK2. My speakers are Sonus Faber Guaneri Homage (the original one). My CD player is Audio Resolution modified by Great Northern Sound.

Without running in the new pre and power amps, I noticed some significant improvements in the sound qualities, deeper depth, wider stage, clarity, transparency, tighter bass, and most important a very neural sound allowing hours and hours of un-fatigue listening. I am listening with a big smile :)

I have a question regarding the bias adjustment. There are 8 x 6650C tubes, and there are 8 pairs bias checking ports (4 of them for V1, V5, V2 & V6 are marked 'Set V# 65mA', and 4 of them for V3, V8, V4 & V7 are marked 'Check V# 57mA-73mA' where # is the corresponding valve number) at the back. But there are only 4 bias adjusting holes at the top of the cover. So how does the bias adjusting work? When I am adjusting the bias, which bias testing pair should I be using? FYI, there are bias adjusting holes between V7 & V5, V3 & V1, V4 & V2, and V6 & V8.

Normally, I expect to have one bias adjusting hole for each pair of bias testing port. Maybe VS115 bias adjustment is for a matched pair?

Your advise is appreciated

[Hi, at 20 hours I checked the Bias and every thing was ok all tubes 065 mV. After 45 hours I measured again.
The V2 had 067 mV and V4 was at 064. All other tubes were at 064-065. I adjusted the V2 back to 064-065 and I measured then on V4 only 059 mV
After 2 hours I measured again 066 on V2 and 062 on V4.
On first use the VS115 matched with LS26 was very close to REF110. Then after 10 hours – it exhibited a darkish character, without the tubey warmth, dry and mechanical sound. After roughly 55 hours things began to change and soundstage opened up, detailed and smooth.But i think i have to wait for ca. 150 hours to break in for full improvement. The sound of LS26 also evolved during the break-in period and i heard no further changes after 160 hours/]

Hi Basile,

So, you can only adjust 4 of the 8 tubes. In fact, I adjusted V1 to be 65mV but V3 then measures at 77mV. Do I then tune down V1 so that V3 falls within the advertised range of 57mV and 73mV?

Anyway, I found out that my VS115's right channel is causing my speaker to crackle (noises within the hiss), quite noticeable even during the day time. I even swap all tubes between right and left channels. The crackling still comes from the right channel. So probably not faulty and bad tubes. I tried all sort, changing power cable, use different sockets in my house. With my Jeff Rowland, no crackling just very low hiss.

Anyway, it is going back to the dealer, a 5 hours round trip though.

[Hi Zekor,yes, you can only adjust 4 of the 8 tubes and check if the matched parallel tube falls within the range.
For my V4 at 059 i asked the Customer Service of ARC. They told me that its ok in the range, but if i don't like the sound i can change the tube v. my local dealer. Now after 60 hours the V2 stabilised at 066 and V4 at 062.
I would say it is better to contact directly to ARC and don't swap the matched tubes.
Good luck, looking for your reply/]

My amp now is nearing 1000 hours... I decided that would be an appropriate amount of time to have elapsed and decided to check the bias. At first, I too was a little confused about the test points and adjusting screws, but it became obvious after a few minutes of thought and testing the various points.

I "set" the bias to 65mV on the appropriate tube, then checked the matching tube and found it fell very close to, if not directly on, 65mV. The amp was on for several hours before I did this ensuring everything was warmed up and stable. For three of the four set points, the bias was very close to 65mV, only off a couple mV at best. On the fourth point I found the value to be 59mV, and the matched tube was at 73mV. When I adjusted the "set" point up to 65mV, the matched tube came down to 66mV. Not having had the pleasure to measure bias for anything before, I was happy to see this was quite simple with good results. I just wish the plastic adusting screw driver thingy had a bigger end for my fingers -- as I lingered over the hot tubes my palms got a little sweaty and it was hard to get a grip on the adjuster.