Do you use them simultaneously in different systems? It may be a worthwhile experiment to have ARC retube one amp, and retube the other with tube depot.
I have a VT100 mk II. When I bought it, the tubes were going bad. I tried to retube part of the tube compliment piecemeal via tube depot. I got frustrated because of bad luck and inexperience, and eventually had ARC retube it and replace a few of the other internal components as well (an advantage of sending to the factory is that they can check the whole unit, beyond the tubes).
Not sure if I won't try tube depot again when it comes time to retube, but for what it's worth, I haven't had any problems with the tubes ARC supplied at all! |
Nothing wrong with tubes from Tube Depot. Pay for matched sets. The trick is knowing how to bias an ARC amp, especially the VT series. You have to bias your amp(s) and you should be doing this often as they will shift as the tubes age. Before you temp to bias your amps be sure you know what you are doing or you'll have big problems. You might want to post this on the amps preamps forum. What ARC amps do you own? Do your research on how to bias your amps. If you post what models you have I'm sure many ARC users will help you out. If you're going to own several tube amps you should invest in a tube tester. There are plenty of junk tube testers out there so do your research and find one that's been gone through and calibrated. Good luck |
Not sure about the newer ones, but I would stick with ARC's tubes if the newer amps are anything like the older ones. They were very hard to bias correctly and tubes often would fail on first use because of that. Andy Bouwman told me years ago that he couldn't guarantee any tubes he sold if they were being used in ARC amps, for that reason. Personally, I'd stick with ARC's tubes, unless the biasing is easier nowadays. |
adg101 - intersting, so it is possible for my ARC installed tubes in my vt100 mk II to fall out of proper bias over time? |
In the old, old days, the amplifiers designed by William Zane Johnson, founder of ARC, were well known to run the tubes very hard, and failures were common. To deal with this issue, ARC was known in those days to "update" their amplifiers quite frequently. I never knew whether they were trying to convince customers that the newest version of whatever amplifier was "fixed" or what they were really doing. But tube failure, sometimes catastrophic, was a price you paid for great sound. In any case, Mr. Johnson has long been out of the ARC design picture, and I have not heard in many years that modern ARC amplifiers were particularly unreliable. If you know what you are doing with bias adjustments, you could source the tubes from Tube Depot, or one step up the scale would be to buy selected tubes from Kevin Deal or Jim McShane, which might cost a bit more but those guys really do test the tubes before selling them. Even the latter sources might be less expensive than buying tubes from ARC. Then you can start at bias point where the plate dissipation is at first low-ish and let the tubes break in for several hours before turning up the current, if indeed the tubes are stressed in modern ARC designs. But Tube Depot is a reputable source, far more reliable than eBay might be, for example. Keep in mind that tubes age and change parameters over time, no matter who sold them to you. So, long term, there are no guarantees regardless of source.
Yes, marktomaras, ALL tubes will require re-biasing once in a while over time. |
Thanks for all the great advice. These are the amps I have:
Phono Ref 2 SE
Ref 5 SE PreAmp
Ref 75 Power
The Ref 75 has easy access bias from the front panel so that's probably pretty safe. I'd definitely have to do some homework on how to bias the tubes on the other units.
I had a Ref 110 before the Ref 75 and the recommended tube run is 2000 hours. I pushed my luck and squeezed another 300 or so hours out of it before frying the fuse and fuse connector, about $200 repair. I guess that's the price we pay for loving tubes and for me not believing the specs. |
marktomaras - yes your ARC amp will in time drop out of bias; the VT100 is not a self biasing amp... double check but I'm pretty sure it's not. I know the VT50 is not and my dad checks his often and checks his tubes as well on his tube tester's.
moryoga - your preamps are simple. Your Ref 75 is another animal but as you mentioned easy to bias over older ARC amps. I agree probably best to buy from ARC on your Ref 75. For your preamps I have had great luck buying tubes from Cryoset Certified. I'm not sure if you can bias your preamps manually as I would guess they are self biasing but not sure. You have some very nice equipment - I'd invest in a tube tester. Not sure how people with tubes survive without one unless they have a friend or shop close by. |
How does one check the bias on a vt100 mk II? Is it also necessary to check bias on the LS-25? |
Preamplifiers, both linestage and phono stage, generally do not require any bias adjustments. Nor do the tubes in the input and driver stage of any amplifier I have ever known about. It's the output power tubes that generally do or do not need occasional checking for bias. (I say "do not", because some amplifiers have an autobias circuit that takes care of this issue.)
I am not sure I agree that one really "needs" a tube tester to get by with tube equipment. If you keep rough track of the hours of use, and if you pay attention to how your stuff sounds from day to day, the question of when to re-tube is typically based on subjective judgement of those two aspects. If a tube tests bad on a tester, it will sound really lousy. However, tubes can test "weak", but within spec, and still sound fine. There is no need to change them out unless the sound has gone noticeably off. The problem with a tube tester, even some of the best ones, is that they test tubes at currents, voltages, and bias settings that may not at all apply to the operating conditions in your amplifier. This can result in a false sense of security or insecurity, depending upon what the meter says.
Mark, Don't you have an owners manual for your VT100? If not, it seems unlikely that you could not acquire one for free (check on line for a pdf file) or for a pittance from ARC.
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lewm and marktomaras you might want to read up on this. http://mycollins.net/audio/artube1.htmlAs far as a tube tester goes I bet Upscale Audio and ARC use a tester before they send out tubes so saying a tester isn't an important necessity for a tube user is questionable especially if one likes to roll tubes often. I agree to keep track of your hours but a tester does much more than just test the strength of a tube. Just curious if you own a tester - lewn? The driver tubes in an ARC VT100 do require biasing I believe. |
ARC VT 50, 100 MK I, II and VT200 amps are difficult to bias. If you don't have highly matched tubes it is almost impossible to bias one of these which likely you will if you're lucky only lose a tube and a resistor in the process. If you're not knowledgeable on basic electronics, know how to read a schematic and comfortable with a soldering iron I suggest not tackling one of these amps as you'll likely send it in to ARC to get it fix. The VT100 is a great amp and this is the reason they're on the used market so often, or were several years back. For what it will cost to send a VT100 in to ARC to get retubed and biased by them you couldn't buy a new amp for the money to replace it. If you don't know what you are doing I'd send it in to ARC.
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Dear ADG, Yes, I own a Hickok tube tester, and the number of times it has served me to detect truly defective tubes is near to zero, because such tubes gave away their condition just by listening to them. It is not that useful for tube matching, either, because it tests all tubes at the same plate voltage and current, which is typically very different from the in-circuit parameters. Tubes that "match" at one voltage/current setting very often do not match at other settings for voltage, current, grid bias. Some of the best Hickok testers (e.g., 539B and C) do offer a choice of some of these parameters; those models are to be preferred and are both scarce and very expensive these days. Further, if you own one, it needs to be calibrated and kept that way. As an alternative and perhaps to your point, there are available modern tube testers that can actually trace curves. (I forget the brand and model names, but the internet will tell what they are.) That's the valid way to match tubes. Those are the types used by reputable pros who sell tubes, like Jim McShane and Kevin Deal. If you want to spend a few thousand bucks on such a tester, that's in a different league from the vintage testers, but are you seriously suggesting that we all need to go out and buy such a device?
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Upscale Audio has a very rigorous tube testing and matching process. Unless you have money to throw away, I’d definitely purchase tubes from Upscale Audio, or Jim McShane. I have more experience with Kevin at Upscale Audio, but Jim McShane also has a top-notch reputation and I’ve received great tubes from both of them as well as Tube Depot. But Upscale clearly has a more rigorous screening process then Tube Depot, that’s for sure. Kevin told me at the Newport show a few weeks ago that he rejects 65% of the Russian tubes he receives as the Russians sell everything they manufacture regardless of how they spec out. Have no fear buying tubes from Upscale or Jim McShane. Btw, I own a ARC VS-55 and I use the hell out of it. It’s a daily driver, and as such, I go through tubes regularly.
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I have just got tube amp, AA VSi75 integrated, with KT150 tubes. The tubes are very easy to bias on this model, select the tube number on the display screen and use the thin plastic screw driver through the access hole in front of each tube. Of course I am now planning for tube replacement albeit probably 18 months in the future. I cannot afford to get them from AA as a set of 4 are in the region of $1,500 CND so I will probably go for a matched set from The Tube Store that seems to have a good reputation. And of course we have Upscale which are more expensive than the Tube Store but offers more burn-in and testing which I'm not sure is worth it. Anyway really enjoying the change to tubes from SS. |
ARC's earlier tube amplifiers had a deserved reputation for tube failures and collateral damage that was fixed in later models.
There is a great post over on AK about a D115 that Dave G acquired as a sort of "kit" and built to ARC’s specs. As built under test it had some nasty habits. He carefully modded it to remove all of the nasty habits that would cause failures.Later model amps had all of his mods already incorporated or were redesigned to get rid of those problems.
The last few pages of the post covers all of that and why it was common for the tube amps of that era to fail. Seems there were a lot of "performance" mods that folks were doing that caused the same kind of failures that ARC had experienced. Once it was understood "why", steps were taken to fix the problem.
BillWojo
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