Discovering pure Class A - It's true, not all Watts are created equal

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karlsushi

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Yes, this will all be old news to many of you, but wanted to share my relatively recent discovery of pure Class A amplification.

I have been reading about the virtues of using pure Class A power for a fair while, but had always been put off by the low power ratings, extra heat and bigger unit size. A few weeks ago, I finally pulled the plug on a second-hand Pass Labs Aleph 3 to put in my second system. Albeit I have some relatively inefficient speakers in there (Spendor S3/5R2 at 85dB/W/M) I figured it's in a small room and my listening position is quite close, plus it's winter so I could do with the extra warmth, so thought I'd give it a go.

Well, it was a complete revelation. Granted, it was replacing a little budget Class D amp (XTZ Edge A2-300), but even that little thing pumped out 150W into 8 Ohms, so thought the 30W into the inefficient Spendors might still struggle a bit, but it sounds absolutely wonderful (and even inspired me to go out and get some new speakers to replace the S3/5R2's).

Since getting the amp though, I have been meaning to try it in my main system in my living room. I figured this would be a very different kettle of fish, being a much larger room (9m x 2.5m), greater distance from the speakers and driving some bigger (albeit slightly more efficient at 88dB) floor-standers in the shape of my Spendor A7's (yes, I like Spendors!).

Notably, the amp I have been using in that system is also no slouch, a 400W per channel (into 8 Ohms) Nord NC500DM MkII. Yes, it is Class D, but it is a very impressive performer and handles the A7's with aplomb. I had convinced myself that I would need to spend a lot of money to improve on it.

Whilst the Hypex amp excels in clarity/detail (ridiculous specs for THD etc) and also control (the damping factor is through the roof), I must concede, I have been suffering a bit from listening fatigue in that system. Reading around, this is something that many people associate with Class D, but I have also read many reports suggesting that the Hypex/Purifi amps are a bit of a game changer in that regard. In fact, Nord's own marketing headline on the web page is "Class D, with Class A sound".

So anyway, I hooked up the Aleph 3 this morning, expecting things to sound nice with the volume down low playing some jazz, but convinced that things might start to lose grip when I turned it up with a bit of electronic music.

Well blow me down if 30W of pure Class A didn't knock me for 6!!

Having heard it in my second system, I knew it would have the edge in terms of smoothness and musicality, but I have been listening to that thing all day wondering how it's possible that such a low-powered amp could offer so much in the way of power and control. Even the area where I was sure the Nord would have the edge, that being transparency and detail, the Pass Labs highlights just how unnatural and edgy the treble on the Nord is.

Which brings me to the old adage about Watts not all being created equal. A cliche I've heard many times, but only today have I really understood how true that is.

Well, the Aleph 3 has been moved back into my second system and needless to say, all I can think about now is which Class A amp I am going to purchase to replace the Nord in my main system after being completely blown away by it.

So a question to those who use Class A, have I just got lucky with the Aleph 3, or is this what Class A is all about? And then, what to go for (once I've saved up a few quid)?

I've certainly got my eye on the First Watt or newer Pass Labs amps, but also interested in the Colin Wonfer designs being sold under 'EWA' (from ABC Audio). Any others to consider at maybe a maximum price of £3 or £4k?

(I'm planning on SS rather than valves at the minute, but I can always be convinced).

Cheers
 

Amormusic

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I have a Sugden A21a Signature. 23w of Class A heaven.

Despite it being low powered it drives my Harbeth M30 speakers (85db efficiency) with ease to plenty loud enough levels. I've also tried it with lots of other speakers recently and it had plenty of grunt to make them sing.

I love it and it is most certainly a keeper. A superb amp ♥️.

Certainly worth adding one of these onto your "must listen" list.
 

Amormusic

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Look for amps built by joeh283 on eBay. Joe Henry builds some stonking Pass clone (official Nelson Pass kit designs) plus other class A amps and sells at sensible prices. His workmanship is first class.
Just had a look. Really nice builds. They look great.
 

flak monkey

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I've heard some good class A and some bad some valve and some SS. Like a lot of things, depends what your preferences are.

I still prefer my MOSFET AB power amps over pure class A for my taste in sound and music.

And scientifically, at least, Watts most definitely are Watts, assuming you are using the same standard to measure them 😉 thing is, at modest listening levels most of the time a lot of people are using <10w so really don't need all that much power.
 

tackleberry

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Always been a fan .I have a21a and mf a1000 which I maintain is one of the best amps I’ve ever heard.

I’ve heard great things about the Henry amps too.👍
 
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rabski

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I've heard some good class A and some bad some valve and some SS. Like a lot of things, depends what your preferences are.

I still prefer my MOSFET AB power amps over pure class A for my taste in sound and music.

And scientifically, at least, Watts most definitely are Watts, assuming you are using the same standard to measure them 😉 thing is, at modest listening levels most of the time a lot of people are using <10w so really don't need all that much power.
This.
 

audio_PHIL_e

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I've heard some good class A and some bad some valve and some SS. Like a lot of things, depends what your preferences are.

I still prefer my MOSFET AB power amps over pure class A for my taste in sound and music.

And scientifically, at least, Watts most definitely are Watts, assuming you are using the same standard to measure them 😉 thing is, at modest listening levels most of the time a lot of people are using <10w so really don't need all that much power.
yes, but haven't you heard it said Marshall watts are twice as loud as anyone else's ... like you, I know the definition of a Watt, also that various speakers have varying efficiency, but if a guitarist is playing through a Marshall he is more likely to be heard (or asked to turn it down)
 

Lawrence001

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I've got a pair of Monarchy SM70 Pros waiting to be set up in my second system. Reckon they'll be the bees.
 

rabski

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The combination of low efficiency speakers and monster-power amplifiers can be very impressive, but to my ears, the most 'natural' sounds come from the opposite combination. High efficiency speakers and a few watts of class-A just usually sounds somehow 'right'. Do it with single-ended triodes, and it just sounds 'very right'.

IMO.
 

flak monkey

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yes, but haven't you heard it said Marshall watts are twice as loud as anyone else's ... like you, I know the definition of a Watt, also that various speakers have varying efficiency, but if a guitarist is playing through a Marshall he is more likely to be heard (or asked to turn it down)

There's more than 1x 100W valve guitar amp head here that have seen their share of big gigs 😉

It down to the design of the amp and not the power they are capable of delivering.
 

hiacedrifter

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Yes, this will all be old news to many of you, but wanted to share my relatively recent discovery of pure Class A amplification.

I have been reading about the virtues of using pure Class A power for a fair while, but had always been put off by the low power ratings, extra heat and bigger unit size. A few weeks ago, I finally pulled the plug on a second-hand Pass Labs Aleph 3 to put in my second system. Albeit I have some relatively inefficient speakers in there (Spendor S3/5R2 at 85dB/W/M) I figured it's in a small room and my listening position is quite close, plus it's winter so I could do with the extra warmth, so thought I'd give it a go.

Well, it was a complete revelation. Granted, it was replacing a little budget Class D amp (XTZ Edge A2-300), but even that little thing pumped out 150W into 8 Ohms, so thought the 30W into the inefficient Spendors might still struggle a bit, but it sounds absolutely wonderful (and even inspired me to go out and get some new speakers to replace the S3/5R2's).

Since getting the amp though, I have been meaning to try it in my main system in my living room. I figured this would be a very different kettle of fish, being a much larger room (9m x 2.5m), greater distance from the speakers and driving some bigger (albeit slightly more efficient at 88dB) floor-standers in the shape of my Spendor A7's (yes, I like Spendors!).

Notably, the amp I have been using in that system is also no slouch, a 400W per channel (into 8 Ohms) Nord NC500DM MkII. Yes, it is Class D, but it is a very impressive performer and handles the A7's with aplomb. I had convinced myself that I would need to spend a lot of money to improve on it.

Whilst the Hypex amp excels in clarity/detail (ridiculous specs for THD etc) and also control (the damping factor is through the roof), I must concede, I have been suffering a bit from listening fatigue in that system. Reading around, this is something that many people associate with Class D, but I have also read many reports suggesting that the Hypex/Purifi amps are a bit of a game changer in that regard. In fact, Nord's own marketing headline on the web page is "Class D, with Class A sound".

So anyway, I hooked up the Aleph 3 this morning, expecting things to sound nice with the volume down low playing some jazz, but convinced that things might start to lose grip when I turned it up with a bit of electronic music.

Well blow me down if 30W of pure Class A didn't knock me for 6!!

Having heard it in my second system, I knew it would have the edge in terms of smoothness and musicality, but I have been listening to that thing all day wondering how it's possible that such a low-powered amp could offer so much in the way of power and control. Even the area where I was sure the Nord would have the edge, that being transparency and detail, the Pass Labs highlights just how unnatural and edgy the treble on the Nord is.

Which brings me to the old adage about Watts not all being created equal. A cliche I've heard many times, but only today have I really understood how true that is.

Well, the Aleph 3 has been moved back into my second system and needless to say, all I can think about now is which Class A amp I am going to purchase to replace the Nord in my main system after being completely blown away by it.

So a question to those who use Class A, have I just got lucky with the Aleph 3, or is this what Class A is all about? And then, what to go for (once I've saved up a few quid)?

I've certainly got my eye on the First Watt or newer Pass Labs amps, but also interested in the Colin Wonfer designs being sold under 'EWA' (from ABC Audio). Any others to consider at maybe a maximum price of £3 or £4k?

(I'm planning on SS rather than valves at the minute, but I can always be convinced).

Cheers

What would be a good, low risk, budget way to get started with class A? Integrated or power amp is fine. My speakers are 97db btw.
 

Batty

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I have used a Pass ACA with 8 watts of class A to run through a pair of Lenehan LK1 diy standmounts of 86dB/W efficiency, surprising how little power you actually need. I also built s DIYAudio first watt M2X clone with 25 watts, which is very nice indeed.
 

hearhere

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Well, the Aleph 3 has been moved back into my second system and needless to say, all I can think about now is which Class A amp I am going to purchase to replace the Nord in my main system after being completely blown away by it.

So a question to those who use Class A, have I just got lucky with the Aleph 3, or is this what Class A is all about? And then, what to go for (once I've saved up a few quid)?
After using even lower powered SET amplifiers (6-18 watts) for many years, I agree with you that mega-watt amplifiers are quite unnecessary for most speakers. However, I'd like to challenge your applause for Class A!

After I decided to move away from valve amps on the basis that I'd listen to far more music if I found an equally satisfying solid state amp (which turned out very true), I bought or borrowed 12 amps that I thought may just match the SETs. I was expecting the Class A amps that I tried to be top dogs amongst that dozen. I was in fact hoping they wouldn't be best because I don't like the idea of burning up the world's recourses just to provide the daft level of AC that Class A (or valve for that matter) amps demand!

The Class A amps were Sugden Masterclass FPA-4, Valvet e2se, Bakoon 13r and the very costly Accuphase A-36. All between 12 and 30 watts and all nice sounding and polite, though the Accuphase was by far the best amp. The borrowed Sugden, Valvet and Bakoon were quickly returned but I kept the bought (used) Accuphase for a longer time as it's such a lovely amp. However, even the Accuphase offered less "tingle factor" than I was looking for, so my search continued with Class AB (Mark Levinson, GamuT, Micromega, Quad, etc) and Class D (Lyngdorf, NAD and earlier Devialet).

Despite my expectations that Class A would beguile me, no it was a Class D that swept me away. Not either of the technologies you mention, but first the "DirectDigital NAD M32 and then the even better Purifi Eigentakt NAD M33 that won me over – and much better value than most of the others too.

All I’d say is don’t fall in love with inefficient and environmentally unfriendly Class A until you’ve given the latest Class D a decent trial. The NAD C298 uses the same Purifi module but it’s only a power amp, as opposed to the M33 that includes streamer, phono stage, DAC, headphone amp, Dirac Live room correction, preamp and power amp. It really does provide the tingle factor (if your speakers are up to it) that I’m sure you will find even more pleasing than a softer and warmer Class A amp.