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

[hearhere]

Once you’ve gone Class A, theres no way back other than deafness or stupidity or electrical costs.

Or the latest Class D of course - see my post above!

 

[newlash09]

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.

+1
Funny how my own amp upgrades , sound quality wise, have been dipping in power outputs :

2014 - 190 W - class AD
2016 - 160 W - class AB
2018 - 100 W - class A
2019 - 68 W - PP pentode
2021 - 24W - SET

 

[audio_PHIL_e]

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.

Probably down to the frequencies they amplify most (ie where the peaks are in the response curve) and how widely the speakers disperse their o/p (closed back 4 x 12s are known to be quite directional but an open-backed 2 x 12 can splatter signal over a wide area). I've also heard it said that Marshalls often sound louder because they are dirtier: I've often tried getting a clean signal out of a mid 60s plexi in studio conditions and it doesn't matter what you do the signal still seems filthy ... whereas live it just seems louder than everything else. Not that I mind, of course Funnily enough I also have an AC30 which although it puts out only 22W max I've never tried turning it right up as it would not only pin punters to the far wall it would push them through to the outside as well.

 

[audio_PHIL_e]

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.

I'm sure there are others but for me the best class D was the Amptastic. It really was excellent.

 

[Idlewithnodrive]

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.

I don't know your definition of 'budget' but you can't go wrong with a Sugden A21a, at about £600 or so.

 

[hifinutt]

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.

Having sold my high end class ab to pay bills I had class d icepower with my tannoys .They were warm , delightful and really musical with bel canto pre and were in situ for several years .

However the Joe Henry f5 monoblocks are better , can't quite say how but they are . The system sounds sensational imho ( tannoy Eaton monoblocks) .I like the jh amps as they are not big and easy to carry and accommodate .

Highly recommended at the price

 

[Monitor Gold Ten]

Audrey, my Audio Innovations Series 500 is Class A. Well that's what is written on the Polycarbonate Lid.

Nearly three years of ownership and enjoyment.

Heats the room up nicely too!

 

[audiohound]

XTZ A100-D3 owner here. Has the class A option. Definitely a good winter amp, and incredibly heavy (I imagine most of that 22kg is heatsink and transformer).
It's a great amp, especially for the price it was when available. But to be totally honest... there isn't a huge difference between class A and class AB mode. Certainly not enough to rule out placebo effect.
I've never really run it terribly hard though. Maybe there'd be a more pronounced difference at higher volume?

 

[Nopiano]

However the Joe Henry f5 monoblocks are better , can't quite say how but they are . The system sounds sensational imho ( tannoy Eaton monoblocks) .I like the jh amps as they are not big and easy to carry and accommodate .

Highly recommended at the price

Can I ask what the price is/was? I’m not familiar with his offerings, but I’ve seen the 6 or so different models on eBay, and there’s a f5 stereo turbo. Are yours the same, but in two boxes in effect?

They look very nicely built, but is this just a one man band - so if he keels over the warranty has ended?

 

[hiacedrifter]

I don't know your definition of 'budget' but you can't go wrong with a Sugden A21a, at about £600 or so.

Sorry, good point - an A21A would be right on the money!

 

[George 47]

Of course there is Class A and glorified Class A and Class A/B. But leaving that aside, there is 100w @8 0hms @1% at 1kHz and 30w @ 8 ohms and 60w @ 4 ohms and 120w @ 2 ohms @ 0.1%. And then there is the Crest Factor, as an indicator of amplifier headroom.

Guess what? Companies chose what works well for them in the numbers game. And as others have mentioned, people tend to use much less power than they believe. Some companies will show you, you need huge power to play a full-blown orchestra at full pelt. And then along comes a 'low power' Class A amp with enormous power supplies (expensive) and embarrasses them. As always, it is the sound quality that matters and if you luv what Class A does then great. As long as it is not seriously underpowered, why care?

There are good and bad amplifiers and the power supply is very important and 'normally' Class A PSUs tend to be big, heavy and pricey. As always try at home, you may be surprised.....and have been?

 

[Steveh]

This from Gramophone 1995(annual shortlist of recommendable hi-fi products)

Very high quality power amplifier using a switched-mode power supply. The power supply is arguably the most important part of a modern amplifier and this one is extraordinarily good. The result is a compact unit of remarkable anonymity and an ability to control almost any load.

 

[audio_PHIL_e]

Very high quality power amplifier using a switched-mode power supply. The power supply is arguably the most important part of a modern amplifier and this one is extraordinarily good. The result is a compact unit of remarkable anonymity and an ability to control almost any load.

Just for balance, see Morgan Jones on switch-mode PSUs

 

[savvypaul]

Never mind the watts, show me the iron...

 

[karlsushi]

Thanks for all the responses on this one. A lot of love for Class A around, but as ever, differing opinions.

I've made contact with Joe Henry through eBay today, so let's see where that heads. There's also a second-hand First Watt amp available from Emporium which might be worth a punt.

Then it sounds like it's onto SET/DHT valve amps from there. Good job I'm coming into some inheritance soon!!

What a great hobby

 

[hifinutt]

Can I ask what the price is/was? I’m not familiar with his offerings, but I’ve seen the 6 or so different models on eBay, and there’s a f5 stereo turbo. Are yours the same, but in two boxes in effect?

They look very nicely built, but is this just a one man band - so if he keels over the warranty has ended?

yes i believe they were originally 1300 pounds . f5 clone with better bits than normal . i am not worried about one man bands , there are so many in this game , graham tricker of GT audio , firebottle , joe henry , glen croft ... multiple folks . at some point i want another set of AB amps to use with the horns

 

[TLS]

It is easy to figure out the performance of a car because the engine specs shows horsepower and torque figures. A car with 200hp/250lbs of torque will be much faster compared to the same car with only 200hp/175lbs of torque.

IMHO, in a power amplifier, the size of the power supply will likely determine the torque. So yes, not all watts (hp) are created equal and it doesn't have anything to do with Class A or AB.

 

[hearhere]

A car with 200hp/250lbs of torque will be much faster compared to the same car with only 200hp/175lbs of torque.

Same top speead but the one with more torque will get there quicker!

 

[Nopiano]

IMHO, in a power amplifier, the size of the power supply will likely determine the torque. So yes, not all watts (hp) are created equal and it doesn't have anything to do with Class A or AB.

Would that equate more to maximum current availability in your amp, subject to any limiters coming into play? Or, in effect, the amp’s ability to continue to double its output with each halving of impedance.

 

[audio_PHIL_e]

Same top speead (sic) but the one with more torque will get there quicker!

Makes sense to me, as torque is angular force, and f=ma, so for the same m you get more a if you have more f. However I was shouted down for saying that on another forum, by someone who said that you get acceleration from an excess of power over the requirement for keeping the vehicle at a constant speed. I could blow off a Honda CB750 from the traffic lights on my Norton Commando as it would pull like a train from almost tickover whereas the CB engine had to be spun to at least 6,5k before it would do any work - plus I had a 4-speed box while the CB had 5 (according to its wikipaedia page) with a narrower torque band up with the power band, I didn't have to waste so much time changing gear. 's funny, both engines were designed by the same bloke! The said reference doesn't state who designed the engine but Bert Hopwwod said he did (in his book Whatever Happened to the British Motorcycle Industry?)