suggestion for a SS class AB amp that sounds like a class A ... if such a thing exists

Looking for an amplifier below 2K for my Altec 620A (99 db efficiency). My actual amp is a Sugden A25B, which has 34 watts/chanel in class AB. Although quite musical, it lacks transparency and details. Of course, the best amplifier would be tube or class A but I'm trying to avoid these because of the heat and the electricity bill (my amp is on all day long). My short list include :

  • Audio by Van Alstine Set-120
  • Ayre AX 7e (used)
  • Sugden Mystro (class AB)
  • Benchmark AHB2 (used)

NOTE : please, no class D since I'm not familiar with it (and pretty skeptic too).
Your Sudgen is a respectable amp, and have worked on some Altec related custom designs with a few friends, they can be transparent with great crossover parts inside, once upgraded.  While I hate to open this can of worms, what sort of source and cabling are you running for ICs and speaker wire?  

Are you already running silver plated interconnect or speaker cabling,  sometimes a simple move from OFC to OCC crystal copper cabling can add transparency.  OCC can be really open and smooth too.  Maybe some other areas to check too while considering replacing your amp, fwiw.  
I listen mostly to digital sources... a 16 feet long standard USB cable goes from my computer to the Benchmark DAC1, and another 12 feet long cable goes from the DAC to the Sugden... I used a standard USB cable because the guy at Benchmark told me there was no need for a better one. I don’t know much about the second cable but it looks like a good one. As for my speakers wire, they are OFC Audioquest... I used to have a much better cross over made with oil condenser and other military grade parts, but I had to sell it in order to buy my actual Altec... The sound was better but I also had a different amp...
I was curious about my Atoll A/B integrated and I wrote to Atoll about this question. They responded right away. They said,

"The IN200 works in Class A up to about 40W under 8 Ohm. The switch to Class AB is quite slow."

Possibly of interest.
The Benchmark will be by far and away the least class A-sounding, so delete immediately from your list.

But are you looking for an integrated or a power amp?

Alongside the Ayre integrated, you could look at the Belles Aria.
Big fan of Ayre.  It's got a unique sound, like it sucks noise out of the room. :)

I love them, but because it's so unique you should listen, and in particular, listen with your speakers.
I have the Benchmark. Its behavior is dependent on what you connect upstream. The closest you can get to a “straight wire with gain.” 

I run mine with a Schiit Freya Plus which, in passive mode, measures nearly as well as Benchmark’s LA4 preamp. If you want the buttery-smooth class A sound from it you merely need pair it with a class-A preamp.
The Unison Research Unico Primo is a little above your price target but is worth a look as it has a lot of what you’re looking for and you might find one used.  The Primo has tubes only in the input stage, and the amp section is biased to emulate a Class-A type sound.  There was a Stereophile review a few years ago that describes its sonic attributes nicely.  Just another potential option, and best of luck in your search. 
thank you all for your thoughts and suggestions ...

hilde45: I did a quick search on the Atoll because there's an IN 100 on canuckaudio for cheap ... it has been there for some time and the price has been falling steadily for a few months (which seems suspect) ... from what I've read, the build quality doesn't feel first class to me and I've also read some stuff about the sound that doesn't give me confidence in this product ...

twoleftears : the Belle Aria looks promising even if it's difficult to get infos about it from elsewhere than here ... Any idea about it's power consumption ? I'm looking for an amp but wouldn't mind an integrated if the price is OK...

helomech: the Benchmark is on my list - especially since I have a DAC from this brand and I'm very happy with it - but I probably won't be able to afford one ... also, I don't like having to use balanced inputs even though I know it's better ...

soix: I had thought of Unico but I dropped the idea because I no longer want to deal with tubes ... I had my share of tube amps in my youth but now I don't want to have to deal with it anymore ... also, my amp is on all the time and it doesn't make sense to wear out tubes in these conditions...

@alaindexe  I think the other brands mentioned here (Belles, Ayre, Benchmark) all sound great. Out of curiosity (in case I try to sell mine), what specifically about the build quality of the Atoll doesn't feel first class to you? I posted a photo of the Atoll on my system for you to take a look:
@hilde45 ... thx for the picture... the model I look for wasn't the same, it was the IN 100 so my comment may not apply to yours... in one article I read (I forgot which one) the reviewer explained that the chassis was made of pretty thin metal and that it bent when he was plugging the cable at the back... this is a problem I've had with my Hafler DH 101 and it usually isn't a good sign...
Before changing amps you should rearrange your system for shorter cable lengths.  Your USB cable is at the max recommended distance for non-active USB.  Plus your 12 foot unbalanced interconnect from the Benchmark to the Sudgen is very long.  Your should also re-read Decooney's response.
Quad 405 and its later iterations: the 303 and 606! Truly innovative circuitry and excellent SQ! I have a 405 and it does sound like the proverbial "straight wire-with-gain"! Something the Benchmark amp has been compared to!
@onhwy61 it is true that when I play vinyl, it sounds much better although I don’t have a truly high-end turntable. I just have an old Garrard 401 with an Ortofon OM 20 and it does sing... I guess I’m gonna have to refigure my whole setting... this won't be easy since my computer is on the opposite wall from my system, and my room, 14’ long...
if your vinyl sings then maybe your amp is fine, and your digital chain has some issues. Not only cabling,  but try another DAC, not necessarily a more expensive one...
@jl35 : it does seem logical... I'm gonna start with the cable and if that isn't enough, I'll try another dac... if the problem comes from the dac, I'll be greatly disappointed about Benchmark... I spent so much time searching for a decent dac...
@decooney : it seems that you were right... (read above)... thx...

Thx, we will see. Said the old way, "the proof of the pudding is in the eating".

Disclaimer:  Assuming your current amp is factory original Sudgen and not a copy clone, some have copied that circuit in the A25B, read on if interested.  

"Transparency" and "details" is the Goal, correct?
Was thinking before you move past the cool Sudden A25B amp, are your Altec 620As original, 43 years old? Old dried up caps in the crossovers? Time for updated crossovers, maybe? Speaker surround stiff, maybe needing a refresh or proper update. As many like to say, start with the speakers. It applies here too, worth re-checking.

Contact these guys, maybe send them your crossovers inside your speakers or send your crossovers and the speaker drivers, both. If you are not sure, have a local shop pull it all for ya, box it up, ship it out. Hey, gotta tell ya...You might love that "musical" Sudgen amp all over again with some other upgrades first starting with your speakers, then some good speaker cables and really good IC interconnect cables after, wallah! A modern speaker crossover update, with really good parts can be transforming for a 40+ year old speaker. Followed by great cables after.

If this does not interest you, and you "MUST" jump right now and go buy another amp, send me a message, maybe I’ll take that Sudgen amp off your hands so you can go buy another amp - which might NOT help gain you more transparency. Maybe start here as option-B, just a thought. Root cause analysis can truly pay off some times, start here just for grins :)

@decooney : yes it’s an original A25B... and I just change the Alp potentiometer (with an original part - no worry)... I will eventually have to change the caps on this one...

The Altec 620A is the enclosure model... speakers are 604 8G (Alnico magnet) ... never heard of surrounding becoming stiff with that kind of speakers... but the cross over needs work, that’s for sure... I’ve wanted to upgrade it for quite some time but it’s quite an investment.... I know of Great Plain Audio, thx...
The Sugden is a great little amp... As I mentionned before, it does play quite well with my vinyl set-up... but it still isn’t as transparent as my previous amp, a CM lab 911 that I got rid of because it required too much maintenance (I had it entirely rebuilt twice). I bought the Sugden because I need an amp until I got something to replace the CM lab but end up keeping it... Even if I were to get something else, I’d probably keep it as a back up amp...

thx for taking the time to kick my a--... and sorry for not selling the Sugden : )
No worries, @alaindexe , all in good collaboration - you have a nice amp and speakers worth investing in. Fwiw, a few years back, helped a few locals to spec/design/build some very large Altec (Onken, custom) fridge size speakers (3 pairs). It was another new learning experience, before & after results with updated crossovers and GPA updated drivers, along with some other JBL drivers in another project. Listened to two pairs driven by 2-watt to 8-watt true class A amps. The results were beyond expectations. Much of the credit went back to the upgraded speaker components.
The Benchmark will be by far and away the least class A-sounding, so delete immediately from your list.

That's an interesting comment, since Class-A "sound" is far more influenced by design goals. A low feedback Class-A will have much different distortion products versus Class-A with more feedback, and that is not even taking into account voicing.

If someone makes a transparent sounding Class-A, i.e. neutral, not voiced, and no intentional distortion, then it would be closer to the Benchmark who has very low distortion at low power, somewhat negating any advantage of say Firstwatt and the justification for most ClassA, i.e. removing zero crossing distortion.

Why not just buy a class A integrated and turn it off when not in use? Why are you leaving it on 24/7? I have a sugden A21se and am very happy. I hardly notice an increase on my electric bill. It’s no different than leaving maybe 2 60 watt bulbs on for long periods, ok maybe 3 60 watts....🙄. When not listening I turn it all off. It only takes about 30 minutes for mine to completely warm up and sound its best. This question reminds me of another on here....mainly, what dac sounds most like analog....ugh, you know my answer to that one....

alaindexe OP
Suggestion for a SS class AB amp that sounds like a class A ... if such a thing exists
Great way that will sound very good, would be a $799 Schiit Aegir 20w Class-A for the highs and a $699 Schiit Vidar 100w a/b for the bass, horizontally bi-amped. Which if you look at the Altec xover is a snack to do.


You will need though a Schiit $49 Sys passive on the Vidar input as it has more gain than the Aegir and needs to be lowered just a bit, and this will allow you to tune the sound a little to your room or yourself.

Cheers George


are the purest sounding high power ss amps i have come across

at lower power/current delivery level it is the audiosector patek se gaincard clone of the original 47 labs unit

i have not heard a dagostino, goldmund, symphonic line amp in my own system
In taking a closer look at your setup I noticed the Sugden only has single-ended inputs and you’re running a 12’ interconnect between it and your DAC.  I’m not sure how much impact this might have on your sound or if the Benchmark has the juice to push the signal that far without it degrading, but if I was running interconnects that long I’d be using balanced interconnects — obviously not possible in your case.  Maybe others can opine more in depth about this, but just thought I’d bring it up as a potential issue. 

That aside, I think you’re pursuing something of a unicorn given what you’re looking for at under $2k and excluding both Class-A amps and tubes.  
@audioguy85 : my place gets way too hot in summertime to use a class A... also, it seems pretty irrational to me to waste so much electricity... I was told by a tech that what damages an amplifier was everytime you turn it on and off... when an amp consume very little at idle (or on a stand-by mode), why not simply leave it on all the time?
at lower power/current delivery level it is the audiosector patek se gaincard clone of the original 47 labs unit
@jjss49 thx for introducing me to Audiosector... I will definitely check that out...
@soix : I will change my set-up today and get rid of the 12 feet cable... I should have done that a while ago but I'm getting lazy...
Extra long speaker cables and extra long interconnects with high capacitance can be impactful. Particularly as noted earlier when gear/voltages are not designed to be used with long runs.   

A simple test is to pull all the gear super close together in a room, even with short low grade cables, make everything super short (for a test).  Listen and see if you can hear any difference.      
@soix @decooney @onhwy61 I just changed the cable going from the DAC to the Sugden and it did make quite a difference... next step, the cross overs... but that’s gonna take a bit more time... thx all...
next step, the cross overs...

FYI, for some added inspiration - peeking over on the DIYaudio site, members were commenting about before and after results from upgrading and refreshing the old Altec 604/620 crossovers with GPA crossovers and replacement parts. Quote, "it added a sense of spaciousness and clarity to the speakers", unquote.
@decooney I hear you... I used to have very good cross overs that a friend did for me, when I had Altec Stonehenge III (also with a 604 8G)... they we’re made with oil condenser and military grade parts and weighed about 20 pounds each... they we’re SO MUCH better then the junk that came with the 620A... I’ve been missing them greatly ever since... I sold the Stonehenge III because the inner volume of the enclosure wasn’t sufficient... I had to sell the cross over as well in order to get the money to buy the 620A... it was heart breaking because I built them myself (they were grooved)... but the 620A are MUCH better since they have the perfect volume for the 604 8G...
I have an Audio Analogue Puccini Settanta Rev 2.0 that compares very favorably to the class A amps I currently own (Line Magnetic, First Watt). It is by far the most euphonic solid state integrated I’ve had (others would say “colored”), extremely warm and rich in the midrange. Not the last word in transparency, of course.

A brand that flies under the radar here in the states, but a beautiful sounding amplifier IMO.   Hand made in Italy, first rate build quality.

Which FirstWatt model are you comparing to?

Each of them have a different circuit topology and output transistor types, SE, PP, different impedances, and wattage power output. Interested if your AA Pucciini sounds more like a SIT-3, F6/F7, or J2, etc. Also dependent on what preamp you are using too. Thx.
@decooney I am comparing to an F2/J, which is an F2 modded by Nelson Pass to replace the Mosfets with power Jfets.  
I have an SIT-3 coming on Tuesday, after which I will be able to comment on any comparison there.

Preamp is LTA MicroZOTL MZ2. 
@zm Thx... the Pucini was on my list for quite some time... but after reading reviews about it, I concluded that it was pretty similar to my Sugden...
The BellesAria is 75watts, is really open sounding and has good grip on the bass.  Its a beefy 75 watts for sure.  It might be slightly rolled off on top but has a nice warm sound that is not fatiguing at all.  
It is lightweight and unassuming but is of great quality.

@hilde45, the inside of that atoll is top notch 👍
Audia Flight Stremento #4 mk 2 sounds like the best class A plus its very musical with plenty of power.
alaindexe’s Altec 620A speakers are close to 100db sensitivity @1w, 4-feet away, right?. Can operate well with two (2) really good watts. Low watt delicacy of targeted 20-30w musical amplifiers like Firstwatt, Sugden, Pucini sound would be the ticket for these speakers.  Quality watts needed more than quantity watts in this case.  

Audia Flight Stremento #4 mk 2 sounds like the best class A plus its very musical with plenty of power.
Good grief, is that 28 Mosfets (14 per side) in that Stremento #4? 250/500 watts?

@ decooney according to the Altec catalogue, their sensitivity is 100db with 1 watt at 4’ on axis... when I had VOT (A-7), I had a pair of 14 watts Leak mono tube amps and it was plenty... and the VOT we’re 101 db... so yes, a low wattage amp if fine... Any thought on the Audio Sector products (gain clone) ?
Pass Aleph 3.  Yes, I know its class A.

I pair mine with Altec Malibu.

Good luck in your quest, and enjoy in good health, 

Well there is no such thing as a Class A sound.I have owned several Class A SS amps and they sounded as different to each other as Class A/B amps. .
Any thought on the Audio Sector products (gain clone) ?

I’ve never built one and read up on some stuff Darko was doing years back. Reviewed the DIY LM kits, not much help to ya. Maybe check the DIYAudio site, folks there can possibly help a bit more on that one. Good luck.  
@jtgofish +1
On the other side of four Class A amplifiers, I found the amps I was looking for, and they run in Class AB.
Class A amplifiers are not necessarily better than anything else and maybe not with all speakers or on all music.  Decide what sonic attributes you value most and then find an amplifier that delivers those while providing enough power to really make your speakers really come alive. 
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