What amps are out there that are Class A, 50 wpc into 8 ohms?


This is NOT a buying advice question.

This is a purely theoretical question. A friend and I were trying to figure out what is available that is:

(a) Class A 

(b) 50w into 8 ohms or better

My guess is that the answers will be Pass, Sugden, and then very very expensive things like Gryphon. I'm curious to see what folks come up with.

Just for fun.

Thoughts?

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Monarchy SM-70. I owned a pair and they were very good. There's a pair for sale right now on USAM.

Manley Snappers are 100W, I think their other amps are in the same range.

Cary Makes some 100W-ish amps as well.

 

Class A watts are very expensive, I doubt you will find anything over 25W that is not expensive

The CODA #16 (100 watts Class A, 150 watts total@8). The CODA is not much of a heater. Just warm to the touch.

The KRELL Duo 175XD (175 watts Class A). Westminster Labs (100 watts Class A). These 2 use a biasing scheme. The KRELL runs cool, I expect the Westminster Labs to be similar in temperature.

Pass Aleph 5, 60 watts at 8 ohms. There’s a lovely moment about 40 minutes after power up, where all the music goes from good to amazing.

There’s a few Plinius that would fill the bill.

anything 50W that doesn't heat the room up significantly I would be very skeptical of claims of pure class a. 

I have a Richard Brown Brown Electronics Lab BEL 1001 (serial no. 0001). 50wpc Class A - rear heatsinks get quite hot! Cost new $3500 in 1982. TAS put it in the top category for sonics! I bought it from the original owner, who was a friend of Mr.Brown. 

The Luxman integrateds are kind of a fit in that they are Class A up to 50 W I believe. 

Luxman class A are up to 30w in class A if I am not mistaken,

after that they are a/b.

Clayton Audio has a stereo amp I owned S40. It can put out 50 watts channel into 8:ohms with the more robust power supply upgrade.  

Zesto BIA 200 - 100 wpc Class A tube amp.

The ad copy says "Class A". I can’t tell if "Class A" is it’s operating mode

or if is just "Really good".

Found another: Zesto Audio EROS 300 Class A Mono Power Amp.

 

@grannyring Do you have a current website for Clayton? I cannot find a working one using search.

A few past NorCal USA units, old/new, +others:

  • Threshold SA/3
  • Forte Audio 1A
  • Forte Audio 3 w/conversion
  • Forte Audio 4a
  • Coda s5.5

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  • Pass Labs XA-25 (50w peak @8ohm)
  • Pass Labs XA 60.5 (60w)

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  • Krell KSA-50
  • Mark Levinson No. 29

 

Doing a Forte Model 3/1 50w Class-A conversion and various upgrades now with help from Jon Soderberg, local, he use to work at Threshold. VintageAmpRepair.org (new site) 

 

I was gonna recommend Clayton too.  They used to be distributed under triaudio.com but that’s apparently not working.  Not sure what’s going on, but they’re great amps. 

Anything over 30-40 watts being sold as Class A is not pure class A, it’s class A biased. And the majority of the amps mentioned here are good examples. If Pure Class A is what you’re after (sounds alot better) don’t waste time with most of the amps mentioned here. And yes anything Pure Class can get pricey. Sugden and Pass might be the only exceptions, and they both make Pure Class A products. Most of Sugden’s product line is Pure Class A and it sounds superb.

 

The trade off to a Pure Class A amp and the sound it produces is the limitation of the wattage and it's ability to drive a wide array of speakers. 

I'll add another mention for Clayton Audio. I have a S100SE, very sweet sounding with a wonderful midrange.

@jc51373 not true, the Belles SA30 was tested by a British Hi-Fi magazine and measured around 50w in true class A. I can believe that as the amp gets very hot.

@gryphongryph

 

SA 30 is a 30 watt amp (SA30= 30 watts) measure to 50 watts into 8 ohm load?  You have a link for this article? If it’s 4 & 8 ohm loads you are referring to?

Great list gentlemen.  Of the list, I'll take the Luxman any day, and I dont need 50W or greater.

Anything over 30-40 watts being sold as Class A is not pure class A, it’s class A biased.

Really???

Anything over 30-40 watts being sold as Class A is not pure class A, it’s class A biased.

This statement is misinformation. If an amplifier is class A biased, its a class A amplifier. The output power has nothing to do with it.

The trade off to a Pure Class A amp and the sound it produces is the limitation of the wattage and it's ability to drive a wide array of speakers. 

Here are some simple facts about class A operation:

Class A simply means that the output device or devices do not shut shut off at any point during the waveform to be amplified. 

A class A amplifier can be made of any power. We make one that is 500 Watts/channel (So the quote above doesn't make any sense).

The output impedance of the class A amplifier can be quite variable- depending on if the amp is tube or solid state and how much feedback is used.

On top of class A, if you are talking about tube amplifiers, there are three forms of class A: A1 in which no grid current flows, class A2 in which grid current is seen during part of the waveform, and class A3 (recently patented) in which grid current also flows.

Class A can be either single-ended or push-pull. It can be tube or solid state. Triodes and pentodes can be biased class A.

Any amplifier that is class A to a certain output power and then is in class B above that power is an AB amplifier, regardless of how 'enriched' the bias on the circuit actually is. IOW an amp that is class A to 50% of full power is an AB amplifier.

I miss my Velleman Class A K8010 Tube Monoblock Amplifiers.  They were amazing, but the heat was too much for the summer so I sold them.  I also wasn't a fan of the look.

 

Any version of the Aragon Palladium mono blocks will exceed 100 watts Class A power. The newer Iridium mono does not have a class A rating, but idle draw is 120 watts per mono block. It is probably safe to say that it is over 50 watts of Class A power.

It is probably safe to say that it is over 50 watts of Class A power.

😁 What is safe to say is that it draws 120 Watts at idle.

This is a sort of 'who cares' thing since the point at which the amp goes from class A to AB isn't important; the amp is a class AB amp regardless. What is important is how well distortion is managed by the heavy bias (that's the reason for class A in the first place).

Vitus Audio MP-S201 » Audio Serum | HiFi to fall in love with

Vitus MP-S201 stereo amplifier delivers 25wpc in class A into 8ohms, or 50wpc class A into 4 ohms.  It can also run in class AB for 500wpc, 1000wpc. Class A or AB mode is user selectable.  We have one here at our shop.  It is a Beast! More importantly it sounds amazing - 

For about 15 years I had 3 Class A Amps.Two modified Threshold T-50's that were originally owned by a former Threshold employee. The amps were modified at Threshold to work as 90 wpc mono blocks. Also a classic Forte 4A 50 wpc amp. If you can find one on line pick it up. Always regretted selling that amp.

Old Sumo Nine, Pure Class A to all impedance loads. 60 watts to 8 and 120 to 4.