Class DAmps

[Mr. C]

Anthony,

I would agree whole-heartily with the quality psu sentiment, we have some deigns, which produce a mere 120Wrms, yet can switch at 25n/s, ultra-quiet, yet supremely musical, fluid, and involving and generate serious amps of current, run little more then tepid in temperature.
They do require top spec cores, balanced design, we use 2 tx's, tie the '0' volts together and use each tx as separate '=' and '-' supply rails. This along with some special bridges and purposely designed smoothing caps makes for 'proper performance'

Ashely,

For every one who dislikes a product another one with make it work :-)
I cite a recent event that happened at an quality emporium, not too far from your good-selves close to 2 weeks ago. Were a gentleman went to audition a pre-power combination from yourselves, against a integrated class 'd' amplifier.
Consequently the owner of the emporium was so taken with the product (it had shown the door to the combo, comprehensively he was auditioning) he wanted the gentlemen to leave the product there! A true happening Ashely.
Perhaps there is no accounting for taste possibly!

[Nick]

I also had the RedWine Audio Sig 30.2 Now these baby’s really are special. I have to say very valve like in sound and presentation. A nameless person didn't actually realise he was listening to the RedWine amp rather than my normal Almarro 50125. One big advantage of the RedWine is they are Battery Powered and are disconnected from the mains during use. Therefore no mains to bugger up the sound.
Andy - SDDW

I would echo the comments on the RWA 30.2 a bona fide over achiever.

Nick

[Ashley James]

Mr C. At the risk of starting another fight I'd disagree, I don't see that choosing one device over another on the day as proving anything, because it's my experience customers often realise later that they've made a mistake. To my mind, if something measures right it is right and if it doesn't it isn't and people invariably eventually realise.

I'll cite an example. Some years ago we put a CD player into What Hi Fi for review, and as you know we design these things using the DAC manufacturers evaluation boards to make absolutely certain that ours sounds and measure the same, or that we've followed their instructions. There's no other way to do it, except wrong. Therefore we knew it was right and should do as well as the best. In the event it was described as: "Sweet sounding, laid back and more detailed than the others in the groups, but lacking their hard edge attack and excitement". In other words, ours was right and the rest were wrong and the reviewer had made a serious mistake. Needless to say a very good selling CD player stopped selling and we got numerous calls and complaints from people with a complete AVI system who substituted a five star CD player for ours and didn't like the harshness. They rather illogically assumed the amp's sound had changed and were reluctant to believe What hi fi could make a mistake.

It is for this reason that I've appeared on various message boards, not so much to sell AVI above all else, which I don't think would work for reasons discussed, but to counter dealers who argue that it's all lovely and that you must choose what's right for you. Bollocks and double Bollocks! say I, you're better offer armed with knowledge that helps you to understand the hearing process and that helps you select something that you can live with in the long term. Dealers need to stock and support a wide range of products and magazines need to sell magazines. We'd like you to buy AVI, but would still be happy if by using better methods to help the decision making process you buy something else that does the trick.

Ash

PS and this will cause grief - ADM9s have the highest customer satisfaction rate that we've ever seen, it might be 100%!!!! As you know, we've a strong following but this amounts to more.

[jcbrum]

I dunno about "tastes", some people are too "naive" (nice word for ignorant, due to insufficient education) to recognize a good thing when they see it.

Class D, is an old valve amp technology, which was in use primarily to provide servo amplifiers in control systems. It fell out of use about 40 years ago when digital techniques became popular, and solid state devices being smaller and more powerful took over.

Class D, just means it's a pulse width modulated amplifying device. It requires a high frequency oscillator approximating to a square wave which chucks out prodigious quantities of hash at all sorts of frequencies, which then has to be filtered out at the outpuy stages. Because of all this filtration and the inductive nature of loudspeakers, the damping factor or "grip" of the class d amp is poor.

You can't polish a class D amp, or not much anyway.

BTW Class D just means pulse width modulated, due to the bias state of the amplifying stages. It is nothing to do with digital amplifiers.

I'll return to being a grump old sod shall I ?

[jcbrum]

BTW for those who remember them, "Sinclair" "Radionics" used to sell 50watt amps that cost about £4-19-11d for DIY'ers to put in their own cases. They were class D.

[Marco]

Indeed. Pure Class A is where it's at, especially when the circuit is used in conjunction lovely glowing bottles...

Ashley,

To my mind, if something measures right it is right and if it doesn't it isn't and people invariably eventually realise.

Oh how I vehemently disagree with that!!

But I don't have the energy to argue with you today, after a long drive home late early this morning. I'm sure others will fill in for me, though.

Marco.

[jcbrum]

Class A is indeed very good, but impractical except at low power, this cause amplifiers to be designed with "acceptable soft clipping" which of course leads to considerable distortion and produces "musicality" amd "involvement" which many people like.

In modern ss designs this type of distortion is often re-introduced as "valve sound" or "British Eq".

There is nothing wrong with class A as long as you don't need more than about 0.5 watts with 10 watt peaks.

It's very suitable for a headphone amp but not much else.

[Marco]

Hahahaha...quite. As they say in Scotland, JC, 'Yer heid's full of broken bottles'

Marco.

[jcbrum]

After the lapse in time some of us can look fondly on this advertisement.

However at the time "Wireless World" refused to carry the advertisement as the advertising standards people said it was "not capable of being substantiated"

Some things in hifi never change .

[Ashley James]

Marco although it's no longer the case, Class A sounded better because it avoided crossover distortion and THEREFORE MEASURED BETTER. However, that's no longer the case and it now has no advantages only disadvantages. You just cannot get enough power out of one for modern recordings and clipping Class A is just as nasty as clipping Class B.

Measurements tell a good engineer everything and the rest of the world very little and therein lies the problem.