What s the best Class A integrated tube amp over 80W

Bruce

I agree with you. But, these speakers have an EQ dial for treble (as well as Mid and low) to adjust this attenuation/augmentation. There is no Sound Labs dealers near me, but I have been told that most use tube amps. There are no Atma-Sphere dealers around hear either, but one dealer has one on trade-in. I will try to see when it will be ready for demo.

@chungjh,

I am surprised by the anecdotal advice Sound Labs gave you.  The part about lots of power is ok, but the part about Atmasphere versus JC-1 amps is curious.

As I explained above, Atmasphere amps have "high-ish" output impedances.  See for example  Atma-Sphere M-60 (atma-sphere.com).  Per the Atmasphere website, the M-60 has an output impedance of 4.1 ohms.  By contrast, most SS amps have near ZERO output impedance.  

I surmise that of you drove your Sound Labs ESLs with the M-60, the amp would attenuate the high end of the ESLs.  By contrast, I would expect that the JC-1 would augment the high-end harshness. 

In the end, YOU have to be happy with the match.  In an optimal world, you should plus each amp into your rig, ... in your house,... and take a serious listen.  

Given the advice given by Sound Labs,  maybe you should have another chat with Ralph. He will steer you in the right direction.

Good luck.

Bruce   

I have talked to Soundlabs and they don't have any specific preference, except for a lot of power. Soundlabs often plays Atma-S tube amp on shows. For SS, they have used JC-1's and others.

@bifwynne

good advice given to op

speaker maker will know best what works well with their product(s)

they may not have tried every amp out there but they have tried what they have tried and hopefully are willing to share (most are) info on what works synergistically

at a minimum they will tell you what attributes of high compatible amps are for their speakers...

Check out new BC 2180i (i stands for INTEGRATED)

You may want to look at this amp. 
https://www.bobcarvercorp.com/crimson-raven-features-specs
It may just be the one. 

@chungjh, ... if that Q is directed to me, the only brand I know about is Atmasphere OTLs.  I suggest that you make a call to Sound Labs.  They know what electronics are the best fit for their products.

Ironically, most dynamic speakers on the market have fluctuating impedance and phase angle curves, ... but are voiced to be driven by SS amps having near zero output impedances.  Fortunately, most ARC amps have "low'ish" (but not zero) output impedances and mate, for the most part, pretty well with most speakers that have moderate to high sensitivity levels. 

The impedance curve of my speakers fluctuates between a low of 4 ohms in the bass region and have an impedance peak in the high-teens/low 20s in the 2200 kHz mid/tweeter cross-over point.   Because I use my amp's 4 ohm taps, I calculate (as echoed by John Atkinson in his review of the Ref 150) that the SPL delta between the high and low impedance points of my speaker is roughly between .8 to .9 db.  Not too bad for a tube amp.

I would call Sound Labs. 

What are some highish impedance tube amps? Regardless of Class.

@chngjh,

I would never contradict Ralph.  However, I think you may have somewhat reversed what Ralph may have said about amps that operate under the so-called voltage paradigm (i.e., constant voltage at varying speaker impedance levels -- most SS amps which have near zero output impedances) versus amps that operate under the so-called power paradigm (i.e., constant power at varying speaker impedance levels - generally, tubes amps that have high'ish output impedances).  Ralph wrote a white paper on this topic.

Just an fyi, the reason the ARC Ref 150 SE operates as though it has "low'ish" (but not zero) output impedance off the 4 ohm taps (.55 ohms in the lower frequency region) is because the amp uses 14 db of negative feedback (NF).  Some folks and manufacturers prefer amps that use zero NF.

In the case of a SS amp, voltage generally remains constant at all frequency levels, but power output (wattage) will increase as speaker impedance decreases and amp power will decrease as speaker impedance increases.  So, for dynamic speakers that present low impedance levels in the bass region, a SS amp will produce more power than in the frequency regions where the speaker impedance is higher (often at driver crossover points). 

The reason the SPL of a good speaker remains relatively flat at most frequency levels if driven by a SS amp, despite the varying speaker impedance levels, is because the speaker was designed and voiced to be driven by a SS amp. 

You posted that: 

SS output doubles with every doubling of impedance. Therefore my Pass Labs X250.8 SS amp produced about 60W at 30HZ with 30 ohm impedance. On top of that bass frequency takes more power to make the sound than treble.

That seems somewhat odd and contradictory if you were using a SS amp with near zero output impedance.  This is because your ESLs present 30 ohms of impedance in the low frequency region and just 3 ohms of impedance in the high frequency region.  If you used a SS amp, I surmise that bass would be attenuated and treble bright, ... which you kinda indicate in the quoted text below.   

That said, you also posted that:

Soundlabs sounds too bright at treble with most SS and sounds better with tubes which don't double output with halving of impedance.

On the other hand, it may be that your ESLs were voiced to be driven by a tube amp that has a "high'ish" output impedance.  For example, I think many Atmasphere amps have an output impedances in the 4 ohm space. 

Rather than me being disagreeable for the sake of being disagreeable, I think what is important in the end is whether a particular tube amp will mate well with your ESLs.  Aside from electronic stability issues of mating a particular tube amp (or any amp) with your ESLs, I would expect, if it was my setup, that the amp/ESL combo would produce a relatively flat SPL over the audible sound spectrum.  

So returning to your original question, your OP asked for Class A tube amp suggestions to mate with your ESLs.  I think there have been several suggestions already offered.  I do not think ARC amps are Class A, but some type of hybrid Class A/Class A-B variant.  Further, if your ESLs mate better with high'ish output impedance amps, ARC amps may not be a good fit because many of the amps in the ARC line have low'ish output impedances.

In any case, I'll add to the list Atmasphere tube amps, especially if Ralph thinks they would mate well with your ESLs.  I would also have a chat with Sound Labs.  The manufacturer may have some good suggestions too.

Good luck with your amp search and happy listening.
         

I have talked to Ralph (AS) about this. SS output doubles with every doubling of impedance. Therefore my Pass Labs X250.8 SS amp produced about 60W at 30HZ with 30 ohm impedance. On top of that bass frequency takes more power to make the sound than treble. Therefore, Soundlabs sounds too bright at treble with most SS and sounds better with tubes which don't double output with halving of impedance.

I don't know why but I don't know anyone who uses an ARC amp with SL but many who use Atma Sphere amps.

@chungjh ... do a search in the Forum for old posts about the ARC VT 100.  I recall that some years back, a couple of techie members explained why biasing the VT100 is so hard, ... and a tad dangerous for non-experienced, non-techies. 

I don't recall if you mentioned your budget, but someone mentioned the ARC Ref 150SE as a possibility.  I own that amp and it is a stunner.

I have question for you that should be answered by a techie.  If your ESLs have an impedance of 30 ohms in the low end of the spectrum and 3 ohms in the treble, is a tube amp a good choice for you?  Your ESLs operate almost like a giant capacitor.

I ask because many tube amps have high'ish output impedances.  Even the Ref 150SE has a "low'ish" (for a tube amp) .55 output impedance off the 4 ohm taps in the bass region; the amp's output impedance creeps up with frequency. 

I mention this because a tube amp's output impedance may color the sound based on Ohm's Law principles.  See, e.g., John Atkinson's bench test report on Ref 150 at: 
Audio Research Reference 150 power amplifier Measurements | Stereophile.com   

Based on the impedance figures you mentioned, I calculate that if you used the REF 150SE as your amp, the treble could be shelved down by approximately 2 db as compared to the bass.  Check with a techie.  You could even call ARC customer service. 

Or, if Ralph Karsten (Atmasphere) catches this thread, perhaps he could weigh in.  Ralph manufactures high quality OTL tube amps.  I recall that Ralph posted a while back that he uses his amp to drive ESLs.  Maybe Ralph could explain the whole impedance matching business. 

Good luck with your search.

Bruce
       

I’ve heard the VT100 a few times but never biased it so I do not know the process. But one of the tube amps I have is a Canary 301 mk 2. To bias the Canary, I need to flip the amp and remove the bottom cover. Then with a volt meter, put the probes on specific locations in order to bias each power tube. The first few times I did this convinced me to sell the amp. But I missed the Canary so  I purchased one again. Now that I’m more familiar with biasing the amp, its not an issue for me. I set the bias only once per year and that’s good enough. Canary has since made biasing procedures easier on all their amps.  I like easy biasing but sometimes you can’t have everything. Also, most of my amps are very easy to bias so if I have 1 or 2 that involve a little skill, I can live with that and it makes this hobby even more interesting. 

I read that biasing VT100 tubes is a big headache. Why is it such a headache?

I read that biasing VT100 tubes is a big headache. Why is it such a headache?

Just another thing to think about when we compare new technology to older designs.  The best things that were ever created to make music sound its best were invented very long ago,  Vacuum tubes, LPs and Reel to Reels. 

Lancelock, why would you post amps that are so expensive?   I believe the majority of people that are reading here and in this discussion don’t have money like that. I looked up the David Berning 211 amps and saw they retail for $75,000. I didn’t bother looking up the 845 OTLs.  Of course there are a lot of super expensive components out there that are only for those that are wealthy. If you are fortunate to have money like that, then you’re lucky but for most people $5,000 to $10,000 is a whole lot of money to spend on an amplifier.  I think I could have easily pick a number of amplifiers that are over $50,000 and posted how good it is. Just trying to find your reasoning.

Thrax Enyo - I personally have not listened to it, but some friends of mine have listened to it and said it is wonderful.  Might be worth checking out.

David Berning 211/ 845 OTL amplifier but the best isn’t cheap.

lowtubes

Something like these amps made today would cost so much money and might not have the same high quality parts and workmanship.

well the grandson of the vt100-2 or 3 is the current ref150/se @ $13,000, so you are on point ...

https://www.arcdb.ws/model/REF150

91490 likes the LS 22-classic 150 combo. How about others? What preamp-older AMP combo do you like?

When someone compares what they get purchasing an older pair of amps like the Conrad Johnson Premier 12s or Audio Research VT-100 to todays amplifiers, it just makes sense.  Something like these amps made today would cost so much money and might not have the same high quality parts and workmanship. And, a well made and designed amp will last many many years.  Yes the VT-100 series 2 or 3 are the better ones.  Jjss49, I agree with you about the different sonic characteristics of CJ and AR.  I’ve mixed matched between them throughout the years. 

Audio Research LS 22 preamp and Audio Research Classic 150's this combination drives my Martin Logan Quest Z's better than anything else I have tried in my 50 years of hifi!  Obviously not an integrated but why bother?
I have been using these uninterrupted since 1995 with only occasional tube changes.

i would agree that an arc vt100 series 2 or 3 amp would be excellent, and makes no apologies to many newer tube amps that are multiples of its price presently

brilliant, powerful, wonderful sounding amps... not super tubey in a rolled off romantic sense but great imaging, extension, bass control (for a tube amp) and midrange magic

i have tried cj tube amps in the past, they are a touch more romantic than the arc's and substantial weaker in terms of bass output and speaker control

Hello chungjh, you are on the right track. For the money, you can’t do better than what you did. And the 6550/KT88 tube design should sound fine on Electrostats.  From my memory, the Premier 12s have a hardwired power cable. That may be the only issue limiting your options to tweak the amps.  But those amps are beautiful, powerful, and gorgeous sounding. I have a very big collection of amps going back 30yrs to current products products and I can honestly say that sometimes my vintage items outperform my more current stuff.   For my systems, I stock up on fuses so my systems are never down for long.  

@lowtubes.   That is what I was thinking. I am trying out an old CJ Premier 12. Just got Svetlana 6550 NOS tubes for it. Unfortunately, fuses on the bias pot for my ESL speakers went out. I will report back once I am set up again.

Hello Chungjh, if I were to tell you, you probably wouldn’t believe me or it.  I’m assuming because I didn’t, but learned the hard way. Spent a ton of money and got me almost there: But not to where my system was perfect.  Now I currently have 3 setups where they sound perfect to me.   What am I talking about?   Older items.  People, including myself discounted older items because in my belief, there couldn’t  be any way something older could sound better than something new-  I needed to learn.  I’ve listened to a lot of “state of the art” current products and many of them fall way short of some of the classic designs.  I have many great tube amps to recommend that are a little old but are truly killer. Do you want my advice? Been in this hobby for 30 yrs.   I’ll just leave you with 2 different sounding amps but extremely fine items. Conrad Johnson Premier Four (100 watts)
Audio Research VT-100 (100 watts). 

please give the Rogers High Fidelity EHF-100 or EHF-200 tube integrated amplifier some thought.
a definite plus is that Roger G. (in MA) always answers the phone and is extremely helpful without being overly pushy.

Leave you Pass Lab amps ON. I have heard of a sound studio left theirs on for over 20 years without a failure of any kind. You may find a nice integrated amp but will probably not sound as good as Pass equipment.

I’m two months in with a new Rogue Audio Cronus Magnum III. It is 100 wpc integrated that can switch from linear to triode mode, is built in the US and is a terrific value. Nice on board phono stage (the MoFi Ultradeck sounds fabulous through it) and a separate headphone circuit too. Runs not too warm which matters in a room your size. My Line Magnetic 508ia cooks me in the summer although I admit it is a better sounding amp all around. The Rogue is well built and has a flat, clean, industrial, exposed tube look. I am paired with easy to drive Klipsch Heresy IVs so I can’t speak to how it will handle the ESLs.

"Primaluna Dialogue Premium HP 75w using EL34’s or higher wattage with KT88, KT120, or KT150."

rushfan71-
The PLHP is a class A/B as some of the others mentioned. I have the PLHP. Good stuff for the money. Perhaps like most decent amps the PL HP's first few watt(s) or so is "class A"? Just a  guess.


An amplifier operating at true "class A" producing 80 WATTS would be as big as a car and produce massive heat. No one would be able to stay in the room. If they did, they would be deaf!
https://www.electronics-tutorials.ws/amplifier/amplifier-classes.html

Hopefully, a qualified member will step in to shed light?

i agree the primaluna’s sound good and are an excellent value for performance and features... but i would not say they are with quite with the top tier of tube amps such as audio research and vac

Primaluna Dialogue Premium HP 75w using EL34’s or higher wattage with KT88, KT120, or KT150. This amp can use all these tubes and their variants.
The Primaluna EVO 400. Same as above. Plus these amps have and auto bias circuit for ease of use.
Ultra linear or triode operation.

The best class A tube I ever heard is: Ear Yoshino monoblocks 509 (100w), I have the Wavac 805m (56W)and is great to!

This is great. Thanks for all the responses. Keep them coming.

Vinni Rossi L2ise which uses 300B DHT tubes in its preamp section. 100 watt into 8, 170 into 4oms. Fabulous sounds 10 year warentee US made. I have the unit and it replaced and beat fine mono amps with separate preamp. Also has optional DAC and phone pre modules you can add if wanted

Check out a cayin h80a integrated. You can find them used for about 2-2.5k. I’ve heard them and they sound excellent. Dual mono design as well. 
Good luck 

Getting my new VAC sigma 170iq delivered next week. Can report soon. Demoed VAC separates and loved the sound

"I have a thread on Agon on this topic, but now I would like some recommendations on the best Class A tube integrated amp with >80"

sigh....

Yup, looks like a case of reading too many internet threads. You're not listening to more than a handful of watts at any given time. Read a electronics 101  book on amplifier operation.

V 70 Class A by OCTAVE ... a bit limited bandwidth @ 70 watts / 4ohms and V 80 SE with 120 watts @ 4ohms.

pure class a - pass i would think

hope your listening room is cool, or has excellent a/c

I have been considering VAC sigma 170i? Has anyone heard it?

How about the VAC Sigma 170i?

Actually, SL speakers sound great once the amp is fully warmed up. 

Such a thing does not exist! Your room is too small for those electrostats! A Pass amp can't take that long to reach optimal temperature! My Bedini class A amp reached maximum temperature in about 30 minutes.