Question For Those In The Know About Audio Research Power Amps

I've flirted with ARC gear over the years, owning an LS5 preamp some years ago but never trying their power amps.

I've always had the idea that ARC tube power was a little lean and sterile and not in the Conrad Johnson style of presentation, with tube bloominess and that glorious CJ midrange.

Of course, I realize not all ARC amps sound the same and that some are warmer and more tube-like than others.

Anyway, I recently purchased an ARC Reference 110 SE, and really like a lot about what it does. Stage depth and imaging are excellent, it's detailed and dynamic. As if to reinforce the negative stereotype, it is a little on the lean side, but not horribly so. It's a musical amp overall, and that's what counts.

Questions -
1 - this was sold to me as a "SE" model, which I understood to mean that it was modified to allow the use of KT150's, which my amp has. Was this an 'official' factory modification, and if so, is the SE designation something which can be used when I try to resell the amp? I can't seem to find others running KT150's referring to their amp as the 'SE'. Or is the SE designation relating to a different upgrade altogether? 

2 - is this 'SE' amp backwards compatible with any other tube types?

2 - what's the next model up from the Ref 110 that might exhibit a little more tube bloom (warmth) than the  Ref 110? I wouldn't want to lose the wonderful transparency and soundstage ability of this unit, but if it could be fleshed out a little more then that would be a plus. The amp is only a couple weeks old, to me, so I'm still trying cables and supports etc, to see if there's more to be had, but I would say at this stage that this is a pretty amazing amp.

Any insights would be appreciated!


Rooze, Please list your system, speakers’ preamp, source, cables have you tried the amps different impedance taps?
Is there a carpet or area rug? Size of the room send a room set up pic with a link otherwise, there will be a lot of stabbing in the dark.

I recently purchased an ARC Reference 110 SE ... this was sold to me as a "SE" model, which I understood to mean that it was modified to allow the use of KT150’s, which my amp has. Was this an ’official’ factory modification, and if so, is the SE designation something which can be used when I try to resell the amp?
I don’t see any reference to the SE model designation on the arcdb site, which is usually pretty reliable. Nor does it mention using KT150s in the Ref 110.

I suggest you contact an ARC dealer or ARC directly to get a definitive answer, but it looks to me as though you’ve bought a unit that has modifications not approved by the factory..

Origin Live Resolution MKIV with all factory upgrades
Origin Live Illustrious tonearm with hybrid silver upgrade
Zyx Ultimate 100Z
Allnic Audio H-1202 / iFi iPhono3 (both review samples)
Allnic Audio L-5000 DHT with V-Cap upgrade (Linestage)
Cambridge Audio 851C (used as transport)
Aurender N100H
Sim Audio Moon 380D Dac
Thor TPA-60w monoblocks with KT77's.
Sonus Faber Cremona Auditor M
Castle Harlech floorstanders (in use)
Dunlavy SC-III (haven't tried them yet with the ARC)
3 x Aerial SW-12 subs
2 x HSU VT-2/VT-3 subs
SRA Platform for Allnic L-5000DHT
Symposium Acoustics SuperPlus platform for turntable
ESP The Reference Power Cords
Various cables - Synergistic Research, Tara Labs, Harmonic Tech, Acoustic Zen etc. Preamp to power amp is a Audioquest KingCobra with an Acoustic Zen Matrix XLR on the way.
Various tweaks and room acoustic treatments.

@cleeds - thanks for the suggestion and for checking out the arc website. I couldn’t find anything there either.

@erik_squires - thanks for that link! I’ve been googling but didn’t come across that particular thread. [EDITED - It seems to be conclusive on other ARC amps getting the 'SE' sticker and the KT150 seal of approval, but not my Ref 110. ]
I had a REF110 with KT120's.  I called ARC and asked if I could run KT150's and was told not it could not.  There never was a REF110SE.  I had a D115-mkII before the REF110 and a REF150SE after (and now want a 160S).  The REF150SE is definitely a better amp.  Thicker, more colorful and fleshed out, plus more detail that lets you hear deeper into the music.  Try to listen to one.
arc has took tube choice out of the hands of its customers unfortunately

you want this amp?  then buy this tube, only this tube, and oh, you buy it from me...  

too bad
Arc is sold by dealers who love the smell of their own farts. They are just overpriced traps. 
What an rude chap you are andrewkelley.  Your bigoted opinion has no place here.  ARC has traded successfully for around 50 years.  I have owned and still own a lot of their pieces and all have performed very well and been reliable over many decades.  I have no connection with ARC except as a very satisfied long-term customer.
Which snake-oil hardware do you favour?
Since these threads live online for all eternity, I thought I’d post an update on the KT150/SE issue.
 I contacted ARC yesterday via their website and they responded very quickly and courteously. ARC say the stock Ref 110 can run KT150’s without the need for any modifications. I know this conflicts with at least one statement in this thread. [@docknow]So there is no official Ref 110 SE and apparently no need for one. Obviously my next move is to decide what to do about my interaction with this particular dealer, who upsold this unit over a stock Ref110 on the basis of mine being a modified SE version and thus a “better deal”.
They also stated that “the SE upgrade was done in-house”, further confirming their narrative that this unit was modified from stock.
For the record, this really is a great sounding unit, and, when I’ve optimized the cabling, will work very well in my system, should I choose to hang on to it. Frankly, it’s tainted my experience somewhat, knowing that I was misled, so I will have to see if that passes, or not.

I run a small review website at and will post additional information on that website as I untangle my interaction with the local ARC dealer.

Thanks for all of the helpful input. I’m still interested in power amp recommendations from ARC, if you have them.

Your Thor amps are just wonderful.  A couple of internal upgrades and they would give you exactly what you want. Do you need more power? Love those Thor mono-block amps. Very musical with that rich and full tube sound. 
Well if this ARC dealer ends up taking the unit back and refunding your money because he flatly mislead you (I would make sure ARC knows all about it), then the Ref 150SE becomes possible - its a great amp.  If you can get by with less power a used Ref 75SE is awesome.  If you're considering the Ref 150 you might also consider what I'm running right now and enjoying tremendously - a GS150.  My only regret is that I didn't try ARC tubes earlier.  I'm fairly certain my next temptation will be to replace my Aesthetix Janus with an ARC Ref 6 preamp but not quite ready at the moment to make that particular expensive jump especially when I consider the fact that I'll need a new phono stage as well.
One thing to take into account as you sort this out is that some unapproved "mod" by the dealer (if in fact the dealer did anything and isn't just blowing smoke) may render whatever factory warranty you otherwise have invalid. One possible approach is to ask ARC to investigate this since it is their "franchise" at stake. In the old days, ARC was pretty intolerant of shoddy dealers. Ultimately, it may require ARC to open up the amp and inspect it for themselves to see what was done to the amp. That means you'll be out of an amp while that process is going on- perhaps ARC can arrange a relationship with another dealer or accommodate you directly through the factory while they address this. 

First, I'm pretty certain that the factory warranty for REF 110 amps is long past. 

Second, this is a clear example of us needing to do our homework before purchasing.  a quick initial inquiry to Audio Research before purchasing would tell one whether a REF 110 amp was offered as an SE model.  It also would address the use of KT150 tubes.

Third, most Audio Research amps were not designed to accommodate KT150 Tubes.  This has absolutely nothing to do with allowing customers to tube roll.  It had to do with some pretty extensive modifications to equipment to allow for the extra power handling capabilities of KT150 tubes.  Transformer upgrades are one thing that the REF250 amps required among other things.

Since KT150 tubes didn't exist at the time the original amp was designed/built, it is hard to blame Engineers for not allowing for the amp to be used with KT150 tubes.  You design around certain parameters. It can't be open ended designs.

The REF 110 amp in and of itself is a very nice amp, even to today's standards.  If Audio Research tells you that it is okay to use KT150 tubes in it, that is great.  However, I do have an issue with the "dealer" telling you that it was upgraded to SE status.  Since upgrading to SE status for most Audio Research Amps took way more than just changing tubes.

@minorl -thanks for correcting me on the vintage of this amp as it relates to warranty coverage. I'm obviously not up to speed on current or even recent models--- I was a long time ARC customer in the early days, from the SP-3-a-1 up through the SP 10mk ii and the last amp of theirs I owned was the Classic 60. I still have my Dual 75a that I bought new back in the mid-'70s. (It needs a go-over before I'd power it up again). Back in the day, ARC was terrific on service, parts and updates. 
Hi Rooze:
I was in the same boat as you. I had a Ref 110 and loved it but found it a little bit on the lean side. I thought that might be the price for the ARC bloom and holographic presentation. When I purchased the Ref 150--that all changed. Now there was meat on the bone. Images had more substance but without any loss of the other ARC attributes.That was exactly what I had been looking for.
With a  helpful word from the "inside" at ARC, I replaced the stock KT 120s with KT 150s and that was another slight foot forward (although not nearly of the magnitude of the difference between the Ref 110 and the Ref 150). A move to the Ref 150, Ref 150SE or GS150 from the Ref 110 will provide what you are looking for.
BTW, you cannot put KT150s in the Ref 110.
Well, you didn't mention what you paid and that isn't necessary, but you did get a tube upgrade.  Those 150s are about a $600 upgrade over 120s and even more $ over the 6550s.  You definitely got an 'upgraded' amp, but the use of 'SE' was wrong.  Have you spoken with your dealer?  Many are crucifying this guy and it would be nice to get their response to the situation.  Most have probably not heard a REF110 with 150s so your sound is pretty unique and maybe less 'lean' than what any others are sharing from their experience with the stock tube choices.  I have Classic 120s so have only heard 6550s.  I have a friend that has heard many ARC amps and recently added a REF75 to his system with the KT120s and he has been blown away at what those 4 tubes can put out.  I can only imagine the REF150 is better but you lose the cool blue meters.  I really don't think you can go wrong with the REF 75, 150 or 250 series of amps.  These were all introduced 8-9 years ago and are still in production which says a lot.     


Not sure where your getting your info but all the REF's you mention are NOT still in production nor have they all been for quite some time now. Even the REF10 Pre Amp hasn't been produced in over 9 months now.

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I have owned ARC amps for fifteen years, first a NOS VS110 that some wealthy guy just kept in his closet for about ten years as a spare before selling it to me and then three years ago moving up to a Ref 150SE paired with a Ref 6.
My VS110 killed tubes semi-regularly. I bet I went through an octet of various KT88’s or 6550’s annually. I also blew the protective resistors two or three times-just one on whichever tube failed. At some point on the advice of a regular on this Board, I upgraded the coupling caps, and the difference was subtle.
I bought my Ref 150SE as a dealer demo with only 30 hours on it and yet ironically enough, it shipped with one bad KT150. I replaced it with a single KT150 from Upscale Audio after providing then with the readings I was getting on my Fluke from the other tubes so that they could provide me with a matching tube. This is not optimum, but I have had no problems since with almost 1000 hours of use.
Keep in mind that the VS110 provided for biasing each output tube. ARC went to slave biasing with the Ref 150SE-you can only adjust bias on four of the eight KT150’s and then just hope that the tube coupled to the one you are biasing falls into acceptable range.
I immediately searched out a new octet of KT150’s to have as a back-up when I bought the single tube from Upscale.
Over the years I have purchased tubes from many suppliers, all of them "established" in terms of reputation. Though I have never met him, I consider Jim McShane to be the elite among the elite of tube authorities. Jim has little to say that is positive about New Sensor’s QC with the Tung Sol KT150. He flat out refused to source me an octet saying that it was not worth the trouble to buy a huge batch and sort out the duds from the winners. I eventually sourced a back-up octet from Tyler of TCTubes who was willing to buy the huge batch and sort out the better tubes and then return the bad ones.
I believe that this, in part, explains ARC’s very high prices on the KT150’s that it sells.
Btw, when I needed a back up set of KT150’s I sent three emails to ARC and they never responded to a one of them. From my fifteen years of owning ARC I can tell you that they go in spurts of being responsive and non-responsive. Their new business model is to try to insist that you engage a dealer rather than bother them.
All of this drivel, and I have not discussed the sound of the Ref 150SE with Ref 6. I believe the choice of XLR cables is critical (and you do not want to compromise with a single ended-only preamp and the true balanced Ref 150SE). I am using Cardas Clear Beyond. ARC warns the user in their manual that running balanced and using the best XLR’s one can afford is critical. The sound is definitely not of the "melting midrange with one note bass and recessed highs" that is common with classic tubed gear. It is very close to sounding like the best solid state. My Ref 6 and Ref 150SE have been perfectly reliable-after the one dead tube described above. They are a joy to use. I do hate removing 16 or so tiny set screws to remove the amp cover to check and adjust bias. The contact points for the bias adjustment are awkward to reach-so that aspect of "joy to use" is not so joyful.
But that aside, they together seem to push the aspects of a somewhat artificially widened (but not deepened) soundstage, pin point imaging, great dynamics (but not micro-dynamics) and bass slam at the expense of liquidity, tone, and timbre. I am quite content with the gear all the while not being in love with ARC now that they have been acquired under the McIntosh Group umbrella. For example, the dealer I purchased my amp and preamp from are both no longer ARC dealers. So when ARC tries to hand me off to "my retailer", I find that problematic. Also, ARC bet the ranch so to speak on the KT150 and as I said above, for the last three years New Sensor has not been able to get it’s act together to insure quality control. only source is their website.  I thought models still listed in their product sections meant they are current models in production?

Nope. 150/250's haven't been made since last year. All their remaining inventory for those models was wholesaled out to various dealers who are now offering them for 50% off or more. I know Audio Salon in Florida has many of the 250SE and Paragon in Michigan has some 150's,
@fsonicsmith response it very telling.  ARC goes through many tubes in order to produce "matched" tubes.  they probably re-sell they non passing tubes to other's.  however, that says a lot about Audio Research and their level of expected excellence.

I made the mistake of purchasing tubes for my REF 250 amps from a "reputable" tube supplier in Southern California.  They claimed that the tubes were matched and to specifications for the REF 250 amps.  Not cheap, but much less than what Audio Research sells them for.

Well, approximately $3000 in repairs later, I learned my lesson.  Tubes failed after they were correctly biased.  I was sitting there and actually saw the tube go up spectacularly and the circuit board.  It took out other parts of the circuit, not just resistors.  It costs $3000 to repair. 

If I had purchased the tubes from Audio Research directly, they would have repaired the amp free of charge if their supplied tubes caused the failure.

The authorized Audio Research repair center that did the repair work, told me to never purchase tubes from that supplier as although they claim that they are matched and to specification, they are not.  They proceeded to test all the remaining tubes and showed me the readings vs Audio Research's standards for that amp.  These brand new tubes weren't even close.  They were way outside the acceptable range. Also, when the tubes arrived, they listed clearly on the labels what the specs were.  That is so wrong.

I never contacted that tube supplier, because, what is the point?  If anything they would have replaced that one tube.  But no way would they have repaired the amp.

When I repair solid state amps and I have to purchase transistors, I typically have to purchase many just to find matching ones and also ones to match the "good ones" still in the amp.  Often, I just replace all the transistors, just to be safe.

So, I can see why the costs of tubes from Audio Research is so much higher.


OMG!Didn’t know ARC was in the Mac group. Ironic in view of the intra- staff battles that raged in our 70’s hifi emporium about the fact that they sounded SO DAMN DIFFERENT! I was with David Beatty Stereo in Kansas City. He was rightly a much respected early hi-end dealer who swore that ALL amplifiers sound the same if they do 20-20K. The D-76 hit we young freaks like a B-26! Then the SP-3 and the first Maggies and DQ’s arrived and the rest is history--and the financial ruin of many a young man. Maybe I’ll open a store called "The House of the Rising Sun."


Great posts/info, thanks.

I wrote a long update on the situation but the whole post was taken down by admin.
I’d forgotten we’re all children here and need to be protected from such profanity.
Does anyone know how to get a post reinstated so I can update on what’s transpired between dealer/ARC/myself?

Thanks everyone I’ve learned a lot from this thread.


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I talked to my AR dealer this morning. ARC is evidently charging $275 for the KT150's. That is EACH. So in case you are not good at math, with shipping and tax, you are looking at close to $2400 to re-tube a Ref 150SE like mine. It tempts me to seek a trade for an ARC Ref 75SE. They are not necessarily scalping-they need to buy huge batches of tubes to find suitable ones, expend the time to perform the testing, and can't simply return the rejects for a refund. But I stick with what I said previously, ARC bet the ranch on the 150 tube and the consumer is left to pay for that choice. The situation is slightly ameliorated by the toughness of the good KT150's that will go 3000 hours, but only slightly, 
ARC has never been a value-driven product but now under McIntosh they seem to be a lifestyle-based product-for show and bragging rights. One could argue that AR had no means of predicting that New Sensor would have such QC problems with the 150 tube but AR has done nothing to guide their buyers on the topic of alternative tubes. I intend to try Genalex Gold Lion KT88's and see what happens/hope for the best. 
Yep, that is the case for KT150 tubes.  I imagine that one could use KT88, KT90, KT120 tubes instead if you desire and they fit the sockets.  You would have to know the new bias points.  But, a simple call to Audio Research would confirm this. 

Audio Research equipment was modified to accept KT150 tubes, this meant upgraded transformers to hand to power handling/draw capabilities of the KT150 tubes.  If they can handle KT150 tubes, they can definitely handle tubes that came before with lower draw characteristics.

But as I mentioned earlier, since most manufacturers can't possibly know what new technology or tubes will be produced in the far future, it is impossible to design for them that far in advance.  You design for what you know now.

If you can find an alternate tube supplier that will supply matched tubes within Audio Research's specifications for that amp, for a lower price, well,, go for it. 

I can tube roll to my hearts content with my REF 250 amps and my REF6 pre-amp and REF 2SE phono stage, up to the current level of tubes that they can handle.  'For my REF250 amps, I just can't go above KT120 level.  not big deal.

its like with supercars or Mercedes or high end cars.  The maintenance costs is very high. People find themselves in hot water when they purchase something without investigating the maintenance costs first. 

That is a serious shock when the bill comes.  not a big deal with pre-amps or tubed phono stages, but for large powerful tubed power amps,  This could be a down payment for a new car replacing the tubes.  

thinks the REF 150 tube replacement is bad?  or my REF 250?  Look into tube replacement for a REF 610 or 750 amp.  or other manufacturers that make large tubed power amps.  Tube replacement costs is no joke.

not for the faint of heart.

Re: tube replacement costs. Apologies for the digression.

when I bought a Mesa Baron c. 1996, they offered half-off the cost of new, matched tubes (I understand their tube-matching is second to none) to original owners. Not a trivial expense, with 12 power tubes and 4 12ax7a’s.  They still honor that promise, 24 years later, long after withdrawing from the audiophile market.  Now THAT is customer service!  AR seems to take the opposite approach.
I enjoyed an AR linestage and and still have an upgraded ph3SE phono stage, but their power amps were always said to be difficult to bias and burn through tubes quickly.  I just couldn’t take it.

Not to beat a dead thread, but I have my (original owner) Mesa Baron being refreshed at Mesa right now (12/2021), and they are honoring the half price tube offer. Though the subtext was that they might not in the future, now that Gibson has bought Mesa.

I'm glad they're honoring the tube deal. When companies take over another's assets, they also assume the preexisting contracts and obligations. Or should.

I'm looking forward to getting the Baron back, and hearing it with new caps and tubes.