VSi60 Tube Amp Startup Power Needs

I have an ARC VSi60 integrated amp that is rated to use 350-500 watts of power to generate 50 watts RMS to the speakers. I'd like to purchase an online/double conversion UPS battery backup to isolate it from the rest of the house (puts out pure sine wave AC) because I noticed that when I was checking its bias voltage and the dryer kicked on, the bias voltage dropped by 5 VRMS. The dryer is on a different circuit entirely from the amp, but it's clear to me that when the AC, dryer, dishwasher, and garbage disposal run at the same time, with an oven thrown into the mix, there will be a much larger draw and this will not be good for the amp. I've also had trouble with the bias voltage drifting lately, and this was immediately after we had some power dips in our area (lights dimmed). Anyway, the UPS backup I'm planning to get is an Eaton EX1000, 900 watts. I talked with ARC tech support to find out peak power at startup for the VSi60 amp, and they don't know. The tech rep said it could very well exceed 900 watts when the caps are filling, but he doesn't know for sure. Does anyone have any experience using UPS's with their tube amps, and if so how much startup power do they need compared to their rated power? I would have thought that a 900 watts UPS would be sufficient for an amp rated at 350-500 watts (of input power). I also called Eaton's tech support and they said that their EX series UPS's can handle any startup power need without a problem, as long as it's within the rated 900 watts of the UPS. Alternatively, is there a way to measure startup power for the amp? Thanks. -Stuart
Hi Stuart, this issue has come up before. A while ago, I also spoke with Kal, ARC's customer service rep, about the wisdom of using power regenerators and conditioners for my gear. My amp is the ARC Ref 150, which is rated at 150 wpc (8 ohms). My amp idles at 375 to 400 watts and will draw 800+ watts when "working." Incidentally, I checked the specs on the VSi 60, your amp is spec'd to draw 300 watts at rated output, 500 watts maximum, and 200 watts at "idle" which does not impress me as being that excessive.

I would not be too concerned about your amp's power draw at start up unless you're blowing fuses. As the ARC rep told you, the power caps are charging at start up and you really should wait at least 15 to 20 mins before using the amp until the rest of the circuits settle down.

In addition, it's normal that bias voltage will drift a bit. You mentioned 5 VRMS. I assume you mean 5 mV DC?? Per ARC information, your tubes bias at 60 mV DC. I assume bias is within spec if it measures +/- 5 mV (check your manual or call Kal). If so, 5 mV fluctuations do not impress me as being hyper-critical.

All of that being said, here's what does concern me. Kal previously suggested to me that I do NOT use a power conditioner or AC regenerator because my amp may draw more current on dynamic transients than the conditioner or regenerator can deliver.

The result will be a diminution of the amp's ability to delivery "clean" power to the speakers when needed. Further, if the amp's power supply is starved juice, distortion may increase if the amp is called upon to deliver more power than it can deliver.

Your case is even more critical than mine because the power supply of the VSi 60 is spec'd at 166 joules. By contrast, the Ref 150 is 1040 joules. What this means is that your amp's ability to call upon its power reserve is limited. So, providing your amp with ample power access is very important.

In short, I think you should plug your amp directly into the wall. I encourage you to call Kal and hear it directly from him. And if you do hear it differently, please post it here or send me a PM to correct my misconception.

Next point about the power draw when using all of your appliances. If you check the A'gon Forum, you'll see that folks have discussed this issue many times already. I believe the consensus is that if possible try and run dedicated lines from the fuse panel for your rig. Seems like your integrated amp might take its own line. I assume you have other components, like a CDP/DAC and maybe a turntable and phono pre. Separate line(s) for those components (especially the digital gear) might make sense.

Hope this helps.

Bifwynne really gives an excellent answer. Very good advice. The only thing I can think to add is, do you notice a difference in sound quality when the other appliances in your house turn on? That's what would motivate me to make changes (at least in your case).
You might want to upgrade your service entrance if your household power needs are that significant. Running amps through power conditioners will close in and degrade your sound so best if you can avoid. I know someone who even installed a separate dedicated entrance just for the audio equipment.
Gosh. That's an excellent response, Bifwynne. I appreciate you taking the time to respond. That clinches it for me to skip the online/double conversion UPS for the VSi60. Kal didn't actively discourage me from using it, but he did mention that inrush current could well exceed the manufacturer's recommendations for the Eaton EX1000 UPS. I talked to Eaton's tech support and they said the EX1000 could take no more than 7.5 amps, at which point the UPS would overload and the load would drop. Not sure if that's entirely a bad thing. What didn't make sense to me about using a separate breaker for the amp (per the VSi60 manual and per Kal's recommendation), is that it really isn't isolating the amp from the rest of the house because everything is tied together at the breaker box and into the same ground stake outside. The only way to truly isolate a circuit is to ground it separately with its own ground stake at least 10 feet away from another ground stake. I do have some new questions after making several calls to Kal and to Eaton, and after reading your comments. First, if inrush currents are high at startup, doesn't it make sense to limit them with an external device like the Ameritron ICP-120? Any thoughts on this to save on tube life? Second, although I only saw a 5 mVDC drop due to the dryer, I'm assuming that when the AC is on in the summer, the fridge compressor is running, and the garbage disposal kicks on, this 5mVDC could end up being more like a 15 or 20 mVDC drop. Top this off with one of my kids vacuuming their room upstairs, and it could have a detrimental effect on the VSi60, I assume. I'm not that concerned about sound quality at this point because with all that noise, it won't matter. I'm more concerned about amplifier integrity. Third, we had our lights go dim and flicker several times on New Year's eve due to a winter storm. I had music playing. When I checked the bias voltage a few days after that, it had drifted up to 80mVDC on one tube and down to 50mVDC on another. I'm not sure if the flickering did this, but the last time it had been set to 60mVDC was three weeks before that. So, I have a concern about bias drifting long term (not just momentarily due to surges in the house) and I'm still in search of a clean AC source without having to get a new breaker box with a separate ground stake just for the amplifier (unless this is the least expensive option, which I doubt). Fourth, in my conversation with Eaton I asked whether their UPS could keep up with transients, and they said that its response was instantaneous and possibly better than the house receptacle. Their tech said the house outlets will have more time delay since they are tied in with other breakers at the circuit box, and these are supplying the instantaneous demands of the rest of the house. So, I'm not exactly sure if other people's experience with acoustic quality degradation with UPS's is due to overload of their particular unit or due to psychoacoustics. Regardless, a UPS battery backup for a power amplifier isn't the right tool for the job for no other reason than (that) an amplifier doesn't need a battery backup, plus the fact that it could overload a UPS at startup. So, I'm still looking for an economical clean AC solution that won't break the bank. Thanks. -Stuart
Your welcome Stu.

First off, Kal is the expert and he knows his gear backwards and forwards. So you should follow his advice. Second, I understand your question about separate circuits and ground wire issues, but I think a separate house circuit is proporational to your concerns.

Now, if with a separate dedicated circuit, you are still experiencing "brown-out" type problems when using other applicances, it may very well be that you need a larger electric service. That's a horse of another color.

As to whether you may be harming your amp with power surges and the like, unless Kal was concerned, who am I to say more. ARC gear is pretty robustly built stuff and holds up pretty well.

You mentioned that you see tube bias drift at different times. Yes, line voltage conditions will affect tube bias voltage readings. Utility companies often adjust line voltage in reponse to unusual weather conditions or customer power usage demands. Nothing you can do about that.

What is interesting is that the bias readings went in different directions in response to line voltage changes. That's definitely strange. The only thing that comes to mind is that you might be ready for a tube change. ARC recommends retubing the power tubes at 2000 hours. I think the VSi60 also uses (2) 6H30 driver tubes. ARC recommends switching these guys out at about 3500 to 4000 hours. If you are approaching or have exceeded those number of hours, you're do. DO NOT wait until a tube blows. It may take out a bias resister and that means a service call.

Btw, can the VSi60 take KT-120s? I don't recall if you mentioned anything about your tubes. If you're still using 6550s and you're ready for a retube, ask Kal about using KT-120s. They sound wonderful.

So unless Kal is concerned about the unusual pattern of your amp's bias voltage drift, I wouldn't be concerned either. As I said above, ARC gear is very robustly built. Other than replacing tubes and an occasional blown bias resister, it's pretty maintenance free. At least, that has been my experience and my whole system is ARC.

Regards and let us know how you make out.

OK. The high end audio store in Indianapolis swears by Kal too. And, if your experience is that their amps are robustly built, then I'll go with that. I'll run a separate outlet to the breaker, as Kal recommended. I've only had the amp for a few months and got it used from someone here on Audiogon who just had the tubes and bias resistor replaced at the factory (had receipt of work done). The amp uses KT-120's. Kal didn't have an answer for the drifting in two different directions, but he said to keep an eye on it and call if it happened again. I should probably back up another step here. The entire reason I even checked bias voltage in the first place and found the drift was that the right channel volume was very low after I had made adjustments to the speaker wires and reattached them. I loosened a spade connector behind the amp and the right channel came back. This was after I had switched speakers, switched inputs, and switched interconnects to eliminate all the other possibilities. I've been able to repeat the issue when I tighten that connector too tight, so now I just keep it tight enough and not too snug. The post doesn't move like its loose or anything. Anyway, this is an issue that may or may not have affected bias. At this point, I'm going to reconnect the amp and let it do its thing. If an issue makes itself known, I'll make sure it's repeatable, call Kal, send it in if for repair. I just love how this amp sounds. It really rocks my ML's.
If you want a tech to check out your VSi60, ask Kal if there's a local ARC authorized tech close to your home. He might come to you for a small fee, or at the least, you can ship the amp to him and hope for a quicker turn-a-round. For the rare occasion when I needed to replace a burned bias resister, a local ARC authorized tech came to my house and one ... two ... six, was in and out -- all in about 40 minutes, of which 15 minutes he and I schmoozed about stereo.

My gut instinct tells me that whatever the cause is of your amp's bias anomoly, it's not a big deal. Maybe an intermittent resister or tube related issue, maybe another passive in the circuit. I doubt the cause relates to the power transformer because it would likely affect all the tubes.

One other thought. Perhaps Kal suggested this, but if not, try switching around the tubes. If the anomoly moves, it's likely the tube. If not, it's somnething else. And that all assumes that the anomoly is even replicable.