Audio Research Tube AMP Reliability

Without matched tubes from arc, the amps can be near impossible to retube. Mis-matched input/driver tubes can wreak havoc on the output tubes & other components. Many amps require hand selected / tested parts & ARC is no exception...

I wouldn't agree with the shop owner's statement, at least as a generality. Some Audio Research designs may require more service than others, but I have had a Classic 60 for about eight years and other than tube replacement haven't had any trouble with it. Based on what I've read the biggest issue is poor quality tubes. Audio Research designs their amplifiers so that a resistor acts as a fuse which can be messy, but is better than the whole amp blowing up. Some of the newer designs run the tubes at a higher power output which stresses them more and may lead to the problems the shop owner was referring to. I also heard the the horizontal tube layout of the VT100/200 causes some problems. With respect to preamps, I've had a LS-25 for five years with no issues and had an SP-9 for 10 years prior to that with no problems. For the most part the preamp tubes are not stressed as much as the power amp tubes. The build quality of Audio Research gear is excellent so I would not fault them there. Just keep in mind that tube gear will require more user involvement than solid state, but it's worth it!

As long as your shopping and open to other manu., try McIntosh, the unity coupled circuit is less critical of tube selection.....at least that's what they say and my experience so far confirms this.

I have owned many, and I mean MANY ARC products and have never had a service related issue with any piece. The amps do require retubing more often than the preamps, but no more so than any other brand. The ARC gear is built very well and sound superb.

I can't speak for the newer amps but I used to own a SP-6A in the late 70s for many years and had never had any problem with it. I also have friends who used to own different early model ARC tube preamps and none of them experienced any major problem other than normal problems due to aging like noisy volume control, dust collection, dry up capacitors, aged tubes, etc... So I would say the early models are quite reliable.

Never owned one; first time I have heard that "rap", but IMO, the horizontal, stacked output tubes in some of the ARC amps is asking for trouble for all but the bottom tube.

I have owned many ARC amps and preamps over the last 35 years. I have found them to be very reliable. The few malfunctions I experienced were tube related, not faulty circuit design or reliability issues.

A friend had the VT200, the tube blew, took out the resistor, but burned the board and replacement was not cheap...over 1K...I would never own one like that. Other designs of ARC seem more reliable. Jallen

I've been using a LS2BII pre and and VT130 power for 15 years. A resistor blew on the VT130 due to a faulty tube but Audio Research sent replacements within a few days. If you can solder, very easy to fix. I also use SED Winged C 6550s and 7308s in the VT130 with no issues. The LS2B has been flawless.

I currently own and use the following ARC products:

a). D75 - has been my old standby for 30+ years. I recently retired it till I have the time to change the filter and coupling caps it has never been serviced other than replacement tubes.
b). SP7 preamp - the mate to the D75 for the same time period currently retired but works fine and will probably rejoin the D75 when it is re-capped
c). CA50 - I did send it back to ARC once but it turned out to be an intermittent 6922 no problem with the amp itself
d). SP9MKIII another bad 6922 shorted and took out $250 worth of FET's and some resistors. It was an expensive way to learn that JJ6922's just are not suitable for use in ARC products.
e). SP3A1 - diodes shorted in the power supply board shortly after I purchased it which appears to be common problem. Currently awaiting repair or upgrade to SP3C (ihave not yet decided which)but it is even older than my SP7.
So that's one man's experience with a variety of ARC products over the years. Not too bad. I would say better than average. Probably McIntosh is the only brand better in my experience with names such as Counterpoint, GAS, NAD, Marantz, Dynaco, Sansui, Pioneer,Sherwood etc.

Good luck,Jerry

I have worked in service, and since the only units a serviceman sees are broken ones (not the other hundreds or thousands that are working) all they will ever have are negative comments. I have owned some Audio Research gear (VSi55 tube integrated, SP5 & LS3B solid state preamp, D52B & D100 solid state amp etc.) and my father started out with Audio Research equipment in the early 70's. He had an SP3A preamp with a Dual 51 and Dual 75 bi-amped driving some of the first pairs of Magneplanar Tympani speakers. He was high-end before such a term existed. Never had any trouble with anything. Recently we took one of his ARC tube amps - A Dual 79 which is a 110+ pound monster of a tube amp produced in very few numbers around 1979-1980. The amp sat for 20 years without being plugged in or powered-up. In bad practice we plugged it straight into the wall instead of using a variac to bring the voltage up slowly. We had no problems, unlike typical older equipment where something pops/smokes/glows red etc. After letting it warm up I connected it to my Magneplanar MG 1.6's and it quickly put to shame the McCormack DNA 0.5 amp I was using (no insult to the McCormack because it is a great amp). I don't know about the latest equipment (although my VSi55 was from 2006) and I could certainly not speak for all their models, but I believe ARC uses high grade components and their reputation is built on reliability and sound quality, instead of marketing and gimmics. Just my two-cents for what it's worth. From the serviceman's standpoint everything sucks when its broke.

I owned the ARC D76A for 12 years (1976 - 1988) with no service issues and still going strong in a friend's system, same for the ARC D115 MKII (1988- 2000 , which I owned for 12 years. I now have the ARC VT100 MKII since about 2000 with only needing to replace the fusing resistors which protected the amp from an arching defective output tube. However the VT100 requires input 6922 tubes that are very closely matched with tight triode balances. This is needed to properly bais the input section of the amp and to ensure proper functioning of the output tubes.

In general ARC tube components are very reliable.

I forgot to comment on the reliability of the ARC preamps.
I have owned the SP9, SP9 MKII, SP14, LS2B, LS2B MKII and now the LS25 MKII and the Phono PH2. I have never had any problems with any of the preamps. NEVER!!. Currently, I leave my PH2 and LS25 on 7/24 without any service issues. The PH2 is well over 15 years in my system without any issues (albeit it is solid state).

I have owned a VT-100mk111 for 7 years and have retubed it once. I have never had any service issues with it. I also have a LS-25 and PH-5 and have never had any problems. The reason I buy ARC gear is because it is reliable.

I guess my experience is different than the majority. I had a demo ref 110 for a couple of months. Had one tube failure and the next time the blown tube took the board with it too during LOTR - ROTK. I got so scared I sold my ordered unit without even taking it out of the box. Did I like the sound yes. Would I ever go back to ARC or tube amps no.

My 2 cents.

I've owned an SP-3a (upgraded to "c") since 1974. An LS-15 since 1999, a D76 (from 1975 to 1980), and a VT100 MkII since 2002. No problems with the pre-amps. No problem with the D76. Only problem with the VT100 is one of the output tubes died, which I could determine when I checked the bias and it was very low in one channel. I could see that one of the tubes was not glowing. No other damage was done. I then replaced all the output tubes, re-biased the amp, and it's been fine ever since.
PMOTZ ; I have heard just the opposite about tube layout. An experienced electronics tech I know says that with vertical output tubes, as the tubes age, metal flakes can come loose and find their way down to the bottom of the tube, where things can get shorted. This is less likely to happen with horizontal tube layout.

Almost forgot, I also own a PH-3SE since 2002. No problem with that either.

I own the LS-16 preamp for 3 years and never had an issue.

I owned the Sonic Frontiers Line 1 for 3 years, different story. It went into the repair workshop at least once a year without failure. After 4 failures in 3 years, I eventually got rid of it and lived a peaceful life ever since.

I can only comment about the LS-2 hybrid pre, and that little puppy has never let me down *knocks on wood*.

I had many Audio research amps and pre amps. They all worked beautifully. I blow a fuse in one once thats it.

Have owned several ARC units too numerous to list here. What i have now is REF2 MKI, REF Phono, Classic 120 mono's all modified by GNSC and all with vintage NOS tubes. Not once an ARC unit blew up on me and i have always done my own tube replacement and biasing. No reliability issues with the models i have owned over the years.
Hope this helps.

I was given an ARC Dual 75 gold front by a friend who found it on the sidewalk here in San Francisco after an estate sale. One of the power tubes had popped, all the filter caps were dead, and the power supply section of the board was fried. I replaced the caps and burned components, but I really didn't want to replace the power tubes. They had been a matched quad of old US tubes, GEs I think. Anyway, I found a nearly-matching single tube on eBay and biased everything closely. It did take me a few near runaways to get it all right, but since then it's been running fine. The boards are a little fragile, with small easily-broken traces, but the component quality is good.

I agree with what's been previously said.

I've owned a Dual 50 f, a Dual 51, Dual 76, Classic 120's and a pair of VTM 200's. In addition, I've had an SP-3, LS-2, PH-3, and PH-5.

The pre-amps are rock solid. Never a problem in 30+ years.

The amps are much more linked with the condition and quality of the output tubes. If there are the beginnings of minor noise or crackles through the speakers, or if a unit begins to blow fuses, or an individual tube seems to run hotter than the others, time to look at the tubes. If these little warning signs are ignored, a blown tube will take out a resistor and make a bad smell, resulting in a dead amp that is easily repaired.

If you use high quality tubes that have been run in before installation, you should be fine. ARC equipment is very well designed and built.

[I am interested in ARC because the sound is great intimate and truly beautiful.I am an original owner of PH5, CD3mkII and LS26 and over two years I never had troubles. They all work beautifully
But the few malfunctions I experienced with the amps were different.
My newer VS115 at approx. 165 hours during the warm up period suffered a fairly catastrophic failure.
The V1 tube was glowing with a white colour, a capacitor or perhaps a resistor became overheated and flamed out with blast and smoke.
Luckily the rest of the equipment were not damaged.
After two weeks the local ARC service repaired the unit and I had to pay for the tube.
At approx. 255 hours it happens again. This time I heard only a blast.I returned the unit to the local ARC and I am waiting but I am very disappointed.
(I checked the Bias and the wall voltage every time I heard music)
The same happened 2 years ago to my VS55 I previously owned at approx. 400 hours. At that case ARC had sent me through the local dealer a new circuit board. ]

The biggest problem isn't the fault of ARC. They rate their 6550's life span to be approx 2-3000 hrs. That being said most people don't keep track of the time they put on their tubes. A few ARC amps have Hobbs Meters on them (elapsed time on the tubes)which makes it easy to determine when a new output tube set is needed. As with any high current high voltage tube amp arcing can happen across a circuit board trace but this is usually not the norm. Most of the time a plate and/or screen resistor will open and require replacement prior to installation of a new output tube set and rebiasing. Remember, once that amp is on and the tubes are drawing bias current the clock is ticking.

I had a VT200 with a tube arc, because I bought tubes from a seller other than ARC. It took out a resistor, but contrary to a previous poster, that repair is about $165. It is the shipping that is expensive on that amp.
Your friend's amp has obviously not been repaired at ARC if it has signs of previous issues. After ARC repairs an amp, there is NO sign that there was a problem. The board is clean, and the traces are redone as needed to make it like new. I would say your friend is going to an unreliable repair person. He should send it to ARC. I have also owned, besides the VT 200, a Vt100 mk2 and a mk3, and currently have a Ref 110. Preamps have included SP9's and Ref2 and currently Ref3. The only problem I have ever had was from replacing tubes in my VT200 from a Canadian tube company. ARC is very particular about the tubes it sells. Live and learn.

I repair ARC on the west coast...Non ARC output tubes are always a very bad idea and should never be used.

I noticed that the ARC amps have high idle current, it looks to be about 4 times the amp rated power output.

I think that this indicates that the amp runs in single ended class A. Is that why people tend to like the sound? A Pass Labs XA amp also runs in single ended class A.

Has anyone ever compared a Pass XA 30.5 against something like a VT 50 from ARC to see if they have a similar sound?

I am surprised this blog even exists. The last time there was a serious discussion of the reliability of ARC tube amps, the postings were removed in less than two weeks, no doubt due to pressure from the manufacturer. I'll try to capture some of my previous remarks here and hope that it survives. First, let me say that I don't think reliability with tubes is a problem with anyone's pre-amps, including ARC. I own a Ref 3a and it is a joy to listen to and a delight to own. But high-powered tube amps can be problematic regardless of manufacturer. Someone said it best in a previous comment that when you own a high-powered tube amp, tube failure is something you just have to accept, period. If you are not prepared for this, perhaps you should consider SS.
My own experience with ARC tube amps has been similarly problematic. I owned D76A amps several decades ago, and then more recently ARC Ref 300 MkIIs. I prefer the sound of KT88s to 6550s and ARC does not support the use of KT88s in their amps. One might conclude that when installing non-ARC tubes, tube failures can be more common, but I do not accept this. I’ve had failures with both ARC tubes (Russian 6550s) and my preferred tubes (Shuguang KT88). The problem, as has been noted elsewhere, is that when a tube goes, it often takes out its power resistor. Most of us would rather repair it ourselves rather than ship these beasts back to ARC. Unfortunately, the repairs require replacing the resistor from the from side of the board unless you really want to take apart a good deal of the amp. Many of us who have had this problem have shared our experience with others via e-mails and in blogs such as this. It’s not fun, but it is a reality. Most recently, I purchased the ARC 610s and I was stunned when one of the maps blew up within 7 seconds of turning it on. I sent the amp back to ARC, only to find that my other amp blew 2 within 2 weeks while the first amp was being repaired. That was the final straw for me. Unfortunately, I am not alone as this has happened to several others. What I found particularly dumb, is that ARC should have been cognizant of these failures and at the very least, designed their latest amps so the power resistors can be easily accessed for “front of board” repair. At the very least, they should have raised the resistors high enough off the board so the board does not char when the resistor blows.
While the ARC amps are exceptionally fine sounding, I am simply not willing to live with their liabilities as tube failure probability is, as I said, a fact of life in all high-powered tube amps. My solution was simple. I bought VTL Siegfrieds. Not only does VTL support KT88s in their amps, but the amp has an absolutely stupendous and smart protection system that makes replacing a tube amp- are you ready- one of the most rewarding experiences in high end audio that I’ve ever had! When a tube fails, or is about to fail, the amp shuts down and a little light appears on the front panel that identifies which tube needs to be replaced. Replacement is accomplished in about 30 seconds, and the amp is simply re-started. Voila! No muss, no fuss. ARC claims this protection circuit degrades the sound of the amp but I have not found that to be true. I can discuss sonic comparisons of the amps but that is beyond the scope of this blog. Let’s just say I am not disappointed. Both amps are truly wonderful sonically. But for me, it’s a no brainer. If I would have kept the ARC amps and continued to experience the problems inherent with tube failure in high-powered amps, I would have no brains left at all.

I wonder if the root cause is not buying the ARC tubes, and not having a certified tech install them. ARC has been around a long time, and there are a ton of used AMPS still running, and many of them have non ARC tubes and were installed by the owners. I wonder if this is adding to this issue of reliability because of the volume of these amps still in use.

Do folks have any issues when they always buy direct from ARC so that the current balance is within their factory spec?

Most people do not want to spend the money for ARC tubes as they are expensive. I won't fix an ARC amp unless I can use ARC tubes pure and simple. I have had way too many problems with tubes from other vendors and it becomes a huge headache. And yes, it can definitely cause a reliability issue.

[I got my VS115 "repaired" from the local ARC service. They told me that the amp is fine, they couldn't find anything. I heard a blast after ca. 250 hours during the warm up period -- I checked the bias and i measured at all tubes 90mA. I also asked ARC about it but they wrote to me a short text "pls. adjust the bias to 65mA". Is there a logical explanation for that ? Ok the amp sounds great but could it happen again? Please advice - thanks for your feedback]

Well your bias difference is odd..What did you mean by "blast". Did a tube arc? Bias can fluctuate depending on your line voltage and the accuracy of your volt meter. BTW its 65 mV not mA as you are measuring across a resistor not in series with the resistor.

I've owned a SP9MkIII pre-amp for 13 years, from new, and the only problem was a rocker switch which failed, needing replacement. Used a variety of 6922s without issues, currently NOS Mullard.

Regarding power amps, had a D70 for a year, and then a D125 for 8 years(both second hand) - in both cases they developed faults which the local (Sydney, Australia)technicians could not fix, despite repeated costly attempts. Loved the sound, especially of the D125, but ownership was frustrating - for the last two years the D125 pretty much sat unused, and old Luxman SS amp filled the gap.

I'm afraid I wouldn't buy another ARC power amp.

That's a shame as the D125 is a very nice sounding amp. Being so far away from the U.S. makes it rather difficult to get parts/service etc.

[ok correct it should be 65mV and the multimeter is not defect, but this is not the point. By "blast" i mean a noisily explosion -- although i was scared i checked the bias and i measured at all tubes 89-90 mV. ]

[ok correct it should be 65mV and the multimeter is not defect, but this is not the point. By "blast" i mean a noisily explosion -- although i was scared i checked the bias and i measured at all tubes 89-90 mV. The same measured the local ARC service but they couldn't give to me a logigal explanation. I am using a Masstech mas830 multimeter ]

Because the ARC tubes are so expensive guys buy elsewhere.That is where 75% of the problems lie.ARC is in the top ten,maybe top 5 for reliability issues regarding their tube amps.Keep on keepin on and best of luck,Bob

well I suggest you contact the people who worked on it to go through the amp again and check the amp for proper output at clipping as this doesn't make any sense...

I have been using my ARC Ref3/Ref110 combo for the past 18 monts with no problems whatsoever. Amazing stuff.

Years ago, I owned a D-250 Servo. After a few months, with not that many hours on the stock ARC 'selected' tubes, a loud dramatic explosion occurred with smoke, etc. I had to send "Big Bertha" back to Minnesota for repairs. When it returned, I sold it.
I own a pair of M-100's and a custom modified D-79A. I've never had any problems with them at all. They have individual tube bias. I've retubed them with reasonably priced tubes from reliable sources.

The M-100 run very hot you might want to put a fan on em. Can you still get the 7119's from ARC?

I have a big stash of 7119's - enough to last my lifetime.

amperex?

Yes, Amperex. Some marked 'USA' and many marked PQ.

Well I havn't gotten in too many M-100 but if I do I know who to call...8o)

hi everyone!
here is the real story:
ARC gear that was produced in the 80s was the best ever made, period.
Problem: in those days premium hi fi parts with todays technologies where not available. Caps, resistors, volume pots, internal wiring, connectors, solder, plugs.
Huge progress in these areas made in the last 30 years.
If you have time ,money and basic skills, replacing above parts within ARC  gear of the time, will yeald incredible results.
As for tube supply, this is a big issue. Unless you own a tube tester, you are screwd.
NOS tubes are a gamble. Today's tubes  are best bet, provided you buy a large amount of the same production batch.
Here are some parts manufacturers: V caps, vandenhul wires, WBT connectors, TKD stepped attenuators (type C minimum), Caddocks tfts, vichay nude, Mills, fred diods.
Ps electolytic caps in ARC preamps must be replaced with polyprop
The sp10 has space on top and bottom of board to do so provided you lift the whole chassis. The 8s need an external box.
Hundreds of working hours, but then you have a killer, and W.Johnson will bless you from his other life. 

This is an old thread, but for what it is worth I owned an SP-6b and a D90 from 1980 until 2010 with zero problems.  I recently purchased an old, clapped out SP-6a and recapped it with Mundorfs ... sounds even better than my 6b did.