Regulated vs. Traditional

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Best of both worlds.

I say use a fully regulated supply, but have really *big* filter capacitors at the supply output where it connects to your amp. These capacitors will be able to supply the current peaks the amplifier may draw on transients just like an unregulated supply with these same size caps, yet the whole thing will have the normal advantages of a regulated supply too.
 
My opinions - by no means authoritative, but mine nonetheless:

For small signal applications -- preamps, signal processors, instrunentation, perhaps even for the opamp in power amps using an opam based input section -- go regulated. In each case, the principal advantage being supression of ripple and noise.


For power amps -- unregulated. More efficient, potentially more headroom from a given transformer, simpler. And since regulated supplies involve a feedback loop, avoids the possability of two feedback loops in conflict. The exception is amps with poor PSRR wich tends to include single ended designs.

I would say there are trade-off's involved: On one hand to get some desired qualities you may have to accept a design that is sensative to power supply noise which argues for a regulated supply, but if you don't feel a need for those qualities then a design with high PSRR may make a regulated supply superfluous.

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Of course some people just are turned on by power supplies. As an example I'm thinking of a particularly expensive commercial headphone amp (which I'll leave nameless) I once saw the inside of. About 3/4 of the space (and it seemed like a rather large enclosure for a headphone amp) was taken up by the power supply. The amps boards themselves seemed to be little more than a single opamp with current boot, which can make an excellent headphone amp. The opamps were good units, probably OPA134s, and while a regulated supply was appropriate, the one used was way more elaborate for what was needed. The quality of construction was very good, but nontheless I failed to see the rational (as oppossed to marketing) rationale.
 
I've done both fully regulated and just the input/driver regulation and find that just doing the input/driver is 90% as good as full regulation. Full regulation is also much more costly and takes up a lot of room. Another good idea is to use two transformers on for input and one for output, that way you can use a higher voltage and regulate it down for the input/driver.
 
I'd prefer regulated

Hi, although I've built my J-amps with fully regulated ps both times
one thing that I've noted is that no COTS regulators are available for voltages over 35v with a decent Amp rating.

My J-amps are Class A so adding a regulated ps isn't nice for the overall efficiency :hot: but it' seemed a good idea to have. Sound wise I have not made a comparison with unregulated psu's.

I have some ideas about a setup which will be able to regulate over 70V at 5Amps but these are waiting on my next diy project.

A disadvantage of using a lot of buffer caps after the regulator is the current limitation in the regulator itself. The regulator might shutdown on the in-rush current.
 
Always keep in mind that a regulator is essentially a single ended amplifier. Most regulators are only pull, not push-pull though. As SAM-9 said, you now have two feedback loops to deal with. Many low current regulators are designed with quite high bandwidths, outside the audio range. Some of the higher current ones are not. Some regulators also have lots of feedback, and others have very little (and heck, a Zener and a pass-FET has as little as you can get).

So, the answer is not as easy as which is better. The design of lower current regulators coupled with the low current draw of pre-amps often makes for the best combination. However, when you get into a power stage, there may be no benefit.

Alvaius
 
ClassA Power amps

Does not this statement imply that for ClassA power amps full regulation is the best option?

qoute:-
The voltage section of the power amplifier runs in pure class A, hence drawing constant currents; since it amplifies voltages, its current requirements are both fixed and low. On the other hand, voltage gain stages should have no idea what kind of load is being driven, and they introduce voltage drops over every stage, thus forcing us to increase power supply lines in order to realize the full potential of the amp.
So, we could - and I believe should, always! - use full regulation for supply lines to our voltage amplifier stages.
end quote.
from http://www.tnt-audio.com/clinica/ssps1_e.html
 
Does not this statement imply that for ClassA power amps full regulation is the best option?

I think yhat applies if you limit your discussion to single-ended class A. Some people may tend to assume that the class A always implies single -ended because that is a popular configuration. A dual rail class A would behave a lot like a class AB except for the output section, and thus have the potential to be fairly isolated from power supply noise, etc.
 
Is this not for a dual rail amp?

Mind you what this person calls regulated may not be what you mean.

I suppose fully regulated means zeners or transistors used clip a high voltage down to a lower voltage and thus supply a regulated power supply.

Were he is just using full smoothing.

Or have I got it all wrong?
 

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For small signal applications -- preamps, signal processors, instrunentation, perhaps even for the opamp in power amps using an opam based input section -- go regulated. In each case, the principal advantage being supression of ripple and noise.

Beware though as some voltage regulators put out quite a lot of noise in the audio band. I recently measured the AC output of an L7812 3 terminal v reg and found about 800uV peak to peak noise!

Gordon.
 
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