Older PURE CLASS-A Amplifiers

I am looking at some older Pure Class A amps and am curious as to are they as good as some newer amps like the Pass X150, and which ones are recommended, and have they been compared to each other anywhere? Thanks much for the recommendations.

I am considering the following PURE CLASS A amps:
Threshold T-50
Monarchy Audio SM-100 Monos
Monarchy Audio SM-70
Forte Model 4
I owned an SM70 and currently own a pair of the Monarchy SE100Delux's. The SM70 was a sweet little amp. I just sold it but it was hard to let it go. Was looking to buy another one and run them as monos but could not find another one with matching faceplate. The only problem I had with the SM70 was that it ran hot. It doubled as a space heater in my little 10x9 office; good in the winter but not so good in the summer.

Hope this helps,
Personally, if I were going to get an older Class A amp I would wait for a Threshold SA series 1 or 2 (both mono's) or a 3, depending on power requirements. The original SA3 is a real sweetie and a bargain at typical sales prices. Apart from that I would also consider the Classe DR3 either the regular or HC depending on speaker requirements. These are great amps, different perhaps, even compared to todays products. Of your list the only one I'd think about would be the Threshold T-50 and, before I thought about it much, I'd want to be sure the output devises are still available in case of a failure.
Threshold sa-1 or sa-2 mono bloc amps are still considered the best of class a sound today. They are just very tough to find.

I know of one who owns some 20-plus year old Classe model D-25 (I believe) and really enjoys them. He also has had much exposure to and has owned some outstanding amps.

Gryphon mono blocks DM-100. Excellent amps.Threshold Amps are too bright for my taste.
Don't forget the Krell KSA-250. This is a superb amp.
There are a number of folks on this site who own or are big fans of the Forte Model 4, which I thought was a great little amp when I heard it years ago. You might want to check the archives.
I should have put, that wanted to spend less than $1000, which is why I am looking at older gear. Thanks for the responses!! Keep em coming...
Consider checking out a Stax DA-80.
Pure Class A.
Runs hotter than hell.
You could fry an egg on it.
Sounds great.
It will be in your price range or below.
Classe Audio DR3 or VHC
The Forte 4 IS a great amp and will cost you about 1/2 of what you wanted to spend, I think.
I'm pretty sure you can get the Monarchy SM70 and run it as a mono amp. Two of them run as mono blocks would be relatively inexpensive, and very good sounding.
Look for a Bedini 25/25. They go for around $450-600 on the used market. John Bedini also will rebuild them for around $400. Lucious midrange! Your speakers will need to be at least 89db efficiency if you want to listen at higher volume.

Swamp - The pure class A 50 watt version or the 100 watt A/B version?
Levinson made a pair of very nice class A amps, monoblocks, rated at 25 per channel into 8 ohms....and 50 into 4...and 100 into 2...and 200 into 1..and 400 into 0.5..think they were the ML2 but not sure...one of them is at least as large as the stereo 100wpc 27.5. If a pair ever pops up for sale I'd give them serious consideration; they'll drive anything around probably.

Cut down on your heating bills, too.
Ever consider a tube hybrid like Lazarus H-1A?

You mentioned "older" amps, but the two Monarchy amps that you mentioned are still current products.

You don't mention what speaker you will be using. The Monarchy Audio SM-70 or SM-70 Pro are only about 25-30 watts/channel in stereo mode. They jump up to 70 or 80 watts/channel in mono mode.

At their used price, the SM-70 or SM-70 Pro are EXCELLENT amps, if you can live with 25 watts/channel. Heck, I think you can get a single SM-70 for under $300-$350 used.


The SM70 has been discontinued. The SM70Pro is still a current product. The SM100's were replaced by the Se100's. Monarchy is very slow to update their webpage. I was trying to purchase a second SM70 about two months ago. I called Monarchy and they informed me that it had been discountinued.
Andy Rappaport amp one, along with the Levinson ML-2 (when owned by the man, not the marketing machine)are both teriffic amps. The Rappaport sounds smoother and more dynamic to me. As an interesting side light, it was rumored that Rappaport was put out of business because of the law suits from people burning themselves on the outside of the amp. Now that's what I call class A. Realize that these beasts are now 30-40 years old and that nothing really kills electronic components like heat.
Tpk- I had the 50 w Class A model. A very sweet Class A.
I am looking to drive Platinum Reference 1 monitors, similar to the Solos. They are very power hungy, so I guess I would need at minimum 50 watts. I liked the Monarchy cause it looks like they double down with each increasing ohms load.
Hi Gang. I see a couple of posts on the original Mark Levinson ML-2 mono's. Indeed they were amazing amplifiers, however....Your chances at finding a working pair for a $1000 are "Slim and none". cheers
I second Ramy here (Gryphon DM100), the only caveat would be the intensive wear that class-a design brings to output transistors, Is there any technical trad-off in that?


Why not go with a pair of Monarchy SE-100 Delux's. They are an improvement over the Sm70's and they fit in your budget. Also, they run cooler than the SM70's. There's a pair for sale here for $989. Why not make an offer.

Ecclectique, None, if I ever see them first. Its the only SS amp I've ever heard w/Quad 63's that I have enjoyed as much as tubes. It really is great.
I owned a pair of Mark Levinson ML3 - similar to ML2's but double mono in one chassis which I loved. Very few for sale though...

The other class A amp that I really enjoyed was my Musical Fidelity A100, a higher power version of their well respected A1 with a rich warm, fluid sound. They later introduced an even larger version A200 and mono-blocks A50 which occasionally become available on the market but I have never heard them. However the best of the A series was definately the A1000 (not A1001) - this was awesome ( a Tim e Paravicini of EAR design I believe) if you can find one.
How come nobody mentioned Plinius? Older SA-50 amp is extremely good for the money.
nobody's mentioned the Pass Aleph series amps, amongst the most famous of all class a solid state amps...are they not considered to be in the same league as the above mentioned amplifiers??
The Aleph-3 is the best amp I have ever owned.
Too bad I bought some Thiels and had to go to a bigger amp.I wish I would kept the amp and bought different speakers (for power only as I love my Thiels) Although this thread asks for CLASS A bias amps only.I would like to add,my Threshold A/B S/300 is a killer amp!
It drives my Thiels with ease,and then some.
The Platinum Reference I is the biggest chanllenge to power amps. I have yet to find anything that make it sound acceptable to my ears.
I have matched it with about a dozen amps 5 years ago (from $$$$ SS amps to tube amps )and gave up at the end. No matter what you feed through it, it never sound as open and relax as some other better monitor speakers. I ended up ATC SCM10s as it sound much more realistic, relax and open ( very dynamic without the constrain I felt from the Platinums.)
What is your experience of intensive wear that pure Class A designs impose to output transistors? Does Class A amps were at a faster rate than a/AB?, which are the sonic implications of such "wear" in older Class A designs?
The older Threshold S and SA series amps can still hold their own against the newer equipment. I am quite familiar with them and have heard many of them over the years at a local dealer that used to sell Threshold. I currently have the S350e Class A/AB model. As someone else had mentioned, I think I would shy away from the T-50 model because I also have heard that the IGBT ouput devices used by the T series are no longer available. All of the older Threshold amps that I have heard, including my own have delivered a relatively neutral presentation, depending on what other components were also in the chain. IMO they have a similar sound to the Pass X series amps. If you happen to see one of the class A SA series for sale GRAB IT!
Don't forget about the Sugden A21ap, excellent 25wpc pure Class A. They show up here occassionally for well under $1,000.
Threshold SA/1's & SA/2's set the standard in Pure Class A sound.
I own a Threshold T200 and I would not consider selling it. Poweful beyond its 100W/channel rating and still one of the sweetest sounding SS amps I've heard. Put a pair of MIT Oracle Cables on it or Transparent Ultras or Refs and you will stop searching for power Nirvana.
Elinor: You should try your Threshold with some Goertz MI-2 Veracity cabling. Just make sure to use proper impedance compensation i.e. Zobel networks and see what you think. The results are extremely complimentary and natural sounding for a staggeringly low price. Sean
Pass labs Aleph series have to be in there with a shout. As David 99 says, the Aleph 3 has to be one of the great power amps out there, not the most dynamic, but such a sweet, detailed sound. I have been using it into my Living Voice Avatars for 3 years. You need 50 watts, then there is the 5, I believe at 60 watts, or the 4 that comes in at 100, something for everyone
Classe DR3. Hands Down!! (Having owned many pedigree amps (McCormack DNA2, Jadis Defy 7 among others)
- A good old CLASSE DR3 VHC this amp is a small power house and deliver 45 WPC of pure classe A and it is reliable and sweet souding, weighting in at nearly 90 pounds....
Threshold SA -1 mono block power amps are my choice for great pure class a sound. Also the SA-2 mono blocks and even the stereo SA-3 amp. All of these amps are timeless and have incredible sound.
I have two of the Lazarus highbird mark III amps and the Cascade Classic MKII pre amp.
The system sounds awesome. It is a work horse. I have it since 1993.

As for Greg. His last name is miller.
The last I heard about him was back in the nineties that he was planning to go to Japan.
Apparently, the high-end audio market over there liked his products.

I am looking as well for copies of the circuit for the above.

Currently using an older modified Adcom 535-II to drive new Paradigm Studio 100 v3. I find the sound to have a hard top end which is almost hurtful (my previous speakers did not have as much treble extension).

Wondering if a better power amp is required. Would it be possible to use a Pass Aleph 3? Specs seem to indicate the Paradigm 100's are not super easy to drive.


I have the chance to get the levinson ML3, is it still a good amp considering its age or should i consider a later model, if i do purchase it what pre amp should i match with it.
Krell KSA-100 MK11 gets my vote.
These Clayton aren't too old, but here's any interesting review:

The Levinson ML3 is definitely not a Class amp.
It's a AB with only enough biascurrent for approx. 6 Watts @ 8 Ohms Class A. The ML2 has 25 - 40 (European model) Watts Class A and consumes 400 Watts at idle.
You can bridge two ML2 monos to get 100 Watts Class @ 8 ohm.
The Krells with forced cooling were not my favorites with their flimsy covers and coolernoise. I had the KMA 200 Mk II and the consumed 2300 Watts just minding their own business.
Krell made real good amplifiers starting with their plateau biasing models (KSA 300 and forth)
Threshold SA/1 is a classic. Nice sound beautiful crafted but lamps for meter-illumination have to be replaced now and then. If you don't need the slamming power of a Krell this would be one of my favorites although I wonder if they are hard enough biased to deliver 160 Watts Class A @ 8 ohms. I turned down the biaspot anyway to thermally distress the amp.
Class A is not an indication of good sound anyway.
In most cases it's a waste of energy.
I had the Krell KSA 100 & the KMA 200 Mk II and found them both musically inferior compared to the Rowlands 7 (series II and IV) and 8T which are Class AB designs.
For power and musicallity I found the Rowlands 7 a real "bargain".
Threshold SA/4e is one of the greatest ever pure class A amps.
There are a lot of Class A tube amps too- any reason they are not on this thread?
Don't think you can get the Threshold SA-1 mono blocks for $1000, I've looked.
SA-3 would do, the Forte #4 is a good amp and you would have enough left over to get it upgraded be Jon Soderbreg.
You could even get 2 Forte #4 and biamp for your price.
Aragon 8008BB.