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Well, trouble in paradise. My brand new ARC Ref 150se which I bought as an unused store demo with 3 hours on the tubes (OK, almost brand new) does not check out bias-wise. The tubes are biased in sets of two. You adjust the lower numbered tube and a second tube is slaved to it. The "master tube" has a bias pot and the slaved tube does not. The master is set to 65mV and the slave is supposed to automatically be between 57 and 73. Well, three pair of my four check out just fine but on V5 (as labled inside chassis) when you set it for 65, the slaved V7 only reads 40 or so. The instruction manual is devoid of any advice as to what this means and what measures should be taken. Any advice short of taking it to a tech? As bought from third party for dealer, last thing I want to do is ship it back to the dealer.
Follow Ups:
Just to be certain that it is the tubes and not the unit insert know good tubes into the position that reads faulty. If there is still a problem then the unit is at fault, if not then the tubes are at fault.
Thanks for all the responses. My understanding is that ARC no longer wants calls from customers and instead wants the customer to try the dealer. The "new ARC under Sonus Faber Group" wants to focus on manufacturing and letting the dealer handle customer service much like VPI. I did that. The dealer didn't have an answer and spoke to ARC for me. ARC says one of my brand new tubes is likely failing-to swap a pair from the other side of the amp with the two in question and see if the problem follows the tubes or not. Makes perfect sense to me. I will do that tonight. I also bought a pair of new, matched KT150's from Upscale. It would cost me more to ship my amp to ARC than to just buy a new pair of tubes.
1) - If it were me, my first course of action would be to take it back to the dealer and have him make it right.
2) - As kootenay mentioned it could be a bad tube in the tube pair. Easiest thing to try is to buy a new matched pair of power tubes and try biasing them again.Excellent service from: TheTubeStore.Com and TubeDepot.Com and some others.
3) - If the dealer won't step up to solve the problem and if you don't want to try a new pair of tubes on your own, I would give ARC a call.
Edits: 08/03/17
Consult ARC as to not void any warranty.
I have found the factory techs very knowledgeable and helpful. Give them a call. Could be just a bad tube, or a pair that is not matched if required.
Good luck
According to a post by Ross in December, ARC no longer will discuss problems over the phone. Has to be done by email or VM.
I married the perfect woman. The downside is everything that goes wrong is my fault.
Edits: 08/03/17
However, if replacing the tubes and the issue persists then it the resistors.
If a thing's worth doing, it's worth doing well
(Proverb)
I have had four ARC pieces over the years going back to a D76 and SP3 I bought new. They only time any of my items went back to the factory was to be updated. Never had one fail. Good luck or damned reliable equipment?
Of which I bought used. The D-250 was very liable until after 15 years of owning of which it develops a one resistor problem. I replace the resistor and never had a problem again except for the fact that it cost me $1,200 for the retubing every 5 years or until it starts to sound hard than usual.
If a thing's worth doing, it's worth doing well
(Proverb)
+ 1 to the D250's reliability . Never had a problem w/ it .
My OP was not about ARC reliability, it was about biasing slaved tubes and what it likely means when one slave tube is showing lower current than it should. The answer seems to be that I have a failing tube. I don't blame ARC for that-I blame Tung Sol. The KT150 may be a great tube when the tube is good, but what about the variability of the tube? It seems to be a BIG and largely untalked-about problem. Over on Kevin Deal's website if you click on the KT150, you will see this comment from a customer;
"Prospective kt 150 buyers know this....many of the KT 150 Quads bought from small time operations cannot be used....they won't balance. I work at a custom tube amp builder. We now are ONLY buying your tubes or our customers MUST buy your KT 150'S or we won't set the AC/DC balance for them. Several customers have brought unusable "new KT 150" quads to us which after 10 hours, drifted so far, they would not balance....now unusable......and they saved 15.00/tube. Share this and save philes some money, and they will get longer tube life, and better sound.
Audiophiles, believe Uncle Kevin...his tubes are better. The 150's match so nice now......Only get "Real Matched tubes".........Jeff"
Now I know that "Jeff" could be anybody-reliable or unreliable but right now, I think he is legit. I think there is a problem getting matched sets of KT150's that are reliable.
I know Kooteney and I were just trying to be helpful. Always a smart move to look at the tubes first. Hope it solves your bias problem.
On my case, I always have a good reliability with my tubes as I bought them from ARC. They may be a little expensive on the side, but it does give me assurance that I won't run into problems of having bad tubes. Which is mostly the most common cause of tube not being able to achieve the bias specs.
If a thing's worth doing, it's worth doing well
(Proverb)
Is there anything over at the "Tubes" forum on reliability of the KT150? If so I missed it. I will do a search. If nothing comes up, I will likely start a new thread on the issue over there.
Give us an update- FSonic
Fantja-I appreciate your interest. Good timing too, my two new KT150's from Upscale Audio arrived yesterday. As soon as I got home from work I replaced the two tubes at issue with the new and let my Ref 150se warm up for an hour. The two new tubes biased perfectly and I then went to all eight KT150s with my Fluke and had to readjust bias very slightly on the three other "master" tubes with all four slave tubes checking out fine and showing similar readings (right around 61mV as opposed to the "master" tubes at 65 which is all within ARC spec as I set out in my OP).
After replacing the PITA 16 screws holding down the amp cover, I sat down to listen to some records. The sound was good before even with the one bad slave tube running at 40mV but with the new matched tubes the sound was-well, sorry for the flowery word, but "magnificent" is the word I choose. I don't pay much attention to 98% of professional reviews but in Mikey Fremer I trust. He described the Ref 6 perfectly in his November '16 review-and it is carried out consistent with his review by the Ref 150se-incredibly wide soundstage with lots of inner detail not perceived previously-the predecessor preamp was an AudioPrism Mantissa and the amp was an ARC VS110-and to borrow Mikey's words, "familiar music makes more sense". Voices and piano sound palpably present in my room for the first time. The attack of notes are lightning fast and as Mikey noted, ever so slightly emphasized over the decay. I think I would likely rather have it the other way around, decay over attack. My other minor nits are that clicks and pops on vinyl are reproduced with startling speed and clarity too-my old gear kind of glossed over them with everything else. Also, very deep bass is still just a tiny bit fuzzy but I have only 15 hours on both pieces of new gear-the Ref 6 and Ref 150se. Plus, I hooked up my speaker with the 8 ohm taps and I have yet to try the 4 ohm which may be a better match with my Acoustic Zen Adagios. This experience has confirmed a hunch I have had for a while-truly top notch electronics can transform decent speakers (properly, methodically placed in the room as per Jim Smith's method) much more than most of us ever think. I love my Manley Steelhead even more now that I have the Ref 6 and Ref 150se. The new gear shows off what the Steelhead is doing. Just incredible with my restored Thorens TD124 with VPI 9T arm and Benz Glider SL. Digital from an Aurender N100H into an Uptone Audio via Wireworld Platinum Starlight 7 into an Abbingdon Music Research DP777 is also similarly more rewarding than before and there is now closer convergence between the two-I am pretty much at a loss to say that one is better than the other now. Slightly different but so close. My digital files sound cleaner but slightly less warm and vivid.
I will end this with a shout out to Upscale Audio. Many years ago Kevin refused to sell me 6922's and told me he was reserving them for customers who had bought preamps from him-and I was a pre-existing customer. But I love the guy anyway because other than that one experience, he has always provided me with fantastic failure-free tubes. This time I dealt with Kevin's assistant because Kevin was in France. The only other guy I will buy tubes from is Jim McShane. Obviously, ARC's proclaimed vigorous testing procedures are not perfect. My new Ref 150se simply came with a bad tube.
from what I've read so far and given everything is equal and it's from a reliable manufacturer the KT 150 tube should last longer than any other power tubes. As long as it's being utilized within its given specs and parameters. Usually, the problem arises when some designer decides to cheat and make them work harder and deviate from what it's intended to do in the first place.
If a thing's worth doing, it's worth doing well
(Proverb)
Edits: 08/04/17
BTW, I sold it together with the Reference pre amp 6 years ago and replaced them with Krell Evolution system.
If a thing's worth doing, it's worth doing well
(Proverb)
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