I own the VS-115. I can't say enough positive things about it. I've read old posts from other members who claimed it sounded 80-85+ percent as good as the now discontinued Ref 110. If you decide to spring for the VS-115, use KT-120 tubes. They make a big difference. If you check the A'gon ads, I recall seeing one or two used VS-115s for sale for around $4K or less, which is a very good deal considering a new VS-115 retails for $7K.
Two caveats. The VS-115 has been around for a while. I wouldn't be surprised if ARC comes out with a replacement model soon. Not to say that's bad. It may even put a downward pressure on the used VS-115 market.
The other point relates to maintenance. I've owned my VS-115 for about 3 years. So far only one maintenance issue, but I suspect this applies to most tube amps.
On occasion, usually when I replace power tubes, a new tube may arc taking out a bias resister. The part costs about a buck -- it's the labor cost and out of service time that is annoying. Fortunately, I live near an ARC authorized service tech who makes house calls. He charges me between $80-$100 to soldier in a new resister, usually within 1 day after I call him.
If you're handy with a soldiering iron and can stay away from lethal high voltage sources, you can replace the resister yourself. Otherwise, be prepared for the occasional blown bias resister. |
Smatsui, not sure you laid out all the relevant facts about your resister problem. But based on what you did say, I surmise the VS-115 was under warranty since the resister problem occurred within one week of taking delivery from your dealer. When one of my bias resisters blew, my amp was still under warranty. ARC sent a tech to my house to fix it -- free of charge.
Bias resisters do double duty as fuses when a tube arcs. Tube arcing goes with the territory with tube amps. Now . . . as to engineering, I understand some manufacturers make self biasing amps with mini fuses for each power tube. Don't remember the models - sorry. OTOH, it is my understanding that ARC intentionally passed on that configuration to keep as much artifacts out of the circuit as possible.
I have heard of bias resisters making quite the racket when they do their job. Can't say I heard one took a ride out of the amp, but I guess sh*t happens.
If the problem you experienced was indeed as I surmised above, ARC would have fixed it in your house, the fix taking all of 30 to 40 mins. And I want to emphasize, power tubes are glitchy when new and have a tendency to arc during break in. If they do arc, something has to give or the circuits could fry.
Here's my bottom line: as soon as I get beyond the "tube break in nervosa period," I have little if any problems with my VS-115. And the double bottom line is that the amp sings.
I'm glad you found another fine amp to pick up the slack. But all of my electronic gear is ARC and except for the occasional pesky tube arc, I have no complaints. In contrast, after tweaking this and that, my rig is very musical and enjoyable.
If Gary (Hifigeek1), an ARC authorized tech, catches this thread, perhaps he can weigh in with his comments. |
Smatsui, I'm sorry to read about your troubles. It's hard for me to react to your situation, other than I'm glad you found an amp that suits your needs.
Just a couple of responses to your last post. Yes, the power tranny does get quite warm, but that is normal for the VS-115. As far as humming is concerned, I wonder out loud if what you heard was the power caps charging. I've heard humming too at start up, but it goes away pretty quickly after warm up. Perhaps Gary (Hifigeek1) could add another comment or so to put your observations into perspective. |
Jake, what loudspeaker did you use when you tested the VS-115's FR? Also, what output taps did you use? |
@Jake, your results line up with the test results from Stereophile and Soundstage I posted above. Did you also have a chance to near-field mic the actual SPL outputs of the Theils. That would seem to be the ultimate test.
I switched over to the 4 ohm tap and am getting used to it. Very different acoustic presentation, probably because the 8 ohm taps has a higher output impedance than the 4 ohm tap, ergo permitting a touch more output variation in the high impedance parts of my speakers, mainly the 2.2K to 4K Hz region of the freq. band. Per Atkinson at Stereophile, the SPL variation is almost half. |
Jake, out of curiosity I googled to find bench tests of the Thiel CS2.3. May have looked at the wrong site, but the test results I found showed impedance remarkably holding at a near 4 ohms almost across its entire FR spectrum. As expected the impedance curve had the normal two spikes in the bass region, but that was it.
I'm not saying every amp could eat a constant 4 ohm load for lunch, but I was surprised that past 100 or 150 Hz, impedance hovered at 4 ohms. I must have looked at the wrong speaker. If you have a link to the bench test results you had in mine when you made your post, I'd be very grateful if you'd either e mail me or post it here.
Thanks.
Bruce |
Jake,
I re-checked the net to view the bench tests for the Thiel CS2.3 speakers. What I saw in fact was bench test results for the CS2.4s, which as I said had an amazingly flat 4 ohm impedance plot from 50 or 75 Hz through the audible acoustic spectrum.
Do you know whether the CS2.3 was configured differently? I ask because you posted that the 2.3s had modulating impedance plots? Do you have any idea what the SF Cremonas impedance and phase angle plots look like? Couldn't seem to find any hard data on the net.
The reason I am so curious is because I'm trying to gather some real life anecdotal information about how our amps perform when driving speakers with goofy impedance and phase angle plots.
Btw, how do you even measure the output performance of the amp and speaker combo? I have a digital meter that I use to bias the amp's tubes. But I have no idea how to check actual output with the amp hooked up to the speakers. Or how to check output impedance (with no load) off the 4 and 8 ohm taps. Can you advise?? I kinda would like not to damage my gear just to satisfy my curiosity.
Thanks and have a great Memorial Day weekend.
Bruce |
Thanks Jake. I think the impedance/phased angle plots are demanding as reported in Stereophile mainly because of the 2 ohm dip and general 4-5 ohm range. But other than that, the impedance is quite flat between 4 and 5 ohms across the freq. band. The low bass peaks are typical. Nevertheless, it does demonstrate the VS-115's impressive performance capability. How many amps out there can push power into such low impedance loads?? |
Paradigm Sig. 8 v3. I've had a devil of a time getting reliable and timely info about the specs, but finally got through. The S8s have a 21-22 max ohm peak between 1K and 2K Hz; and a 4 ohm min. in the bass region. I've been in private contact with one of our tech members and he did some math calcs that indicate the VS-115 should be able to drive the S8s with a relatively flat output response because the amp's output impedance is low for a tube amp. Soundstage and Stereophile bench tested the VS-115 and Ref 150 and they share similar electrical attributes re: NF (about 12-13), DF (about 7 or 8) and output impedance (approx. 1.1 ohms off 8 ohm tap; about half that off the 4 ohm tap). Based on his calcs, FR may be off +/- .5 db at the peak, which ain't so bad. |
VS-115 maintenance tip. Just replaced the four 6H30 cathode follower tubes. May have run them out to almost 4000 hours. BIG, BIG difference. The amp definitely sounds better: tighter bass, more transparent, and so forth. I think in the future I will switch out the 6H30s before they have 3000 hours of use. |
Gerald, for some reason ARC recommends using their parts, e.g., bias resisters. I don't know why. They only charge a buck so per resister. Selling "matched" resisters can't be a big profit center. So, I would order the resisters from ARC.
As to tubes ... I think the main stream brand is Tung Sol KT-120s, but there may be other KT-120 manufacturers. ARC charges about $100 a tube, which is twice as much as what other reputable vendors, such as Upscale Audio and so forth. I've gone both ways with tubes. I don't think ARC's KT-120s sound better than anyone else's KT-120s.
But there are two advantages going with ARC. One ... it has been my experience that ARC does a better job of matching tubes. An ARC matched pair biases very closely.
Two, if a tube arcs within 90 days of purchase, I believe ARC will replace it. They may also repair any damage caused, e.g., open bias resister. I'd check the last point.
Btw, I used to own the VS-115. Traded up for a Ref 150. I think the VS-115 is a super-duper amp. Enjoy.
Bruce |
