Class D
Possible Chinese firework design?
Certainly doable. One downside of relatively high voltage power amp rails i= s that the power trans tend to have lousy beta. Another issue is that opamp= s seldom like >40v. You also need isolation between mains and speaker side,= and optoisolators are far from linear, so it has its challenges.=20
NT
Quite. However, what happens if you exceed the maximum current rating of a voltage regulated supply?
We're talking power amps here - where the power supply is the most expensive part. Make it fully regulated and you add cost and complexity which simply isn't necessary or beneficial. Have you never built a power amp?
Depends on the design of the supply. In this case there's no reason to use an under spec psu, so I'm not sure its relevant
It doesn't add cost, the cheapest option will be an smpsu which is bound to be regulated, since regulation is a necessary part of how almost all smpsus work. You could probably find exceptions if you looked hard, but not in standalone psus.
If the OP had the one cheaper option, an old basic iron lump psu in their bits box, they wouldnt be asking the question.
Lol :)
NT
I have, more than 40 years ago though. I used a simple regulator as the transformer I had available gave too high a voltage. I used a simple zener and a 2n3055 (IIRC) transistor. Despite the then current recommendations that you never used regulation as it added noise it worked really well with no audible hiss at full volume.
SMPS ain't the norm in power amps. Or rather wasn't - even when pretty well everything else was using them.
And you used a SMPS?
But would you have done the same if starting from fresh - or simply bought the correct transformer?
I was at school, I couldn't a££ord the correct transformer.
Given its success I might well do it again.
No, but it is probably whats being used in this instance. They come regulat= ed.
I've used all sorts of things. Mostly 50Hz transformer, BR, C, and another = RC for earlier stages, sometimes with embellishments.
I've done some odd ones too though. The oddest one I cant really remember t= he details of, it was a fix rather than a new design, of a stage amp. The 5=
0Hz transformer was either twice or half the required voltage, and I made t= he supply fix the problem on the assumption the power consumption was symme= trical. I don't remember how, it worked fine though.NT
The whole point of the thread is it comes without a PSU and the OP is asking about a suitable one. ;-)
Quite. Again.
That again is making do with what you have. My point is there is no need to use a regulated supply with a power amp when starting afresh. And there are plenty reasons not to do so - like increased noise from the PS when approaching its limits. So unless you have a vastly oversized regulated PS
- costing considerably more - so this can't happen, it's actually a retrograde step.
I'm glad you've noticed that
Yup
We all know that, don't we?
There are pros and cons. The obvious pro is better energy efficiency, as lo= ng as the regulation is switched mode.
Traditional iron lump, BR, C supplies also present the amp's output trs wit= h plenty of crap. They're charged every 100th of a second, and they dischar= ge the rest of the time. This doesn't stop excellent fidelity being achieve= d. PSRR is plenty with discrete amps, and even better with IC amps as the O= P is using.=20
(FWIW I've deliberately fed a small IC amp with high levels of psu crap to = find out when it became noticeable, and it took huge ripple before anything= was noticed.)
No, it has pros and cons, and in this example its the logical choice for on= e simple reason: the pros and cons are fairly trivial, so price & availabil= ity rule.
(If you're truly concerned about the hf noise output of an smpsu, which it = is of course designed to remove, you can always add a simple passive filter= , but I wouldn't suggest the OP worry about it.)
NT
Sigh. But not if an analogue type? Where it will be less efficient? Are you just arguing for the point of it? ;-)
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