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Refreshing take on external power supplies.

I would be more worried about a design that does not respond to a measurably better power supply. The power supply is the heart of an amplifier, the transistors are directing the power available to the speakers, you are listening to what the power supply provides including the noise generated by it. Change the power supply, you change the sound, simple physics that can be observed on a scope ...
 
Alexh said:
I would be more worried about a design that does not respond to a measurably better power supply. The power supply is the heart of an amplifier, the transistors are directing the power available to the speakers, you are listening to what the power supply provides including the noise generated by it. Change the power supply, you change the sound, simple physics that can be observed on a scope ...
Click to expand...

There's so much more to it than that as to make that wrong on many levels...
 
Not a power supply as such, but the Intona usb isolator only made an audible difference on an Audio Note UK Dac ,all the other equipment-mentioned we tried it with no audible difference.
Keith
 
Purité Audio said:
Not a power supply as such, but the Intona usb isolator only made an audible difference on an Audio Note UK Dac ,all the other equipment-mentioned we tried it with no audible difference.
Keith
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Thats interesting, which model was it, and what effect did it have ? I am not on a troll here I genuinely would like to know because most of the AN Dacs have an input transformer ?
 
I'll have a go.

Let's assume that any circuit has a certain amount of power supply noise rejection ratio. The higher this PSRR is (assuming equal bandwidth) the more immune to noise on the incoming PSU voltage rails it will be. So a great amp with great PSRR will be immune to all but the craziest of mains variances, it doesn't matter if you give it a wall wart of a massive over specced power supply, as long as it can fill its psu capacitors it's happy because the circuit after the psu is so good it can deal with anything without audible effects, my Modulus 86p is one such amp is has over 90db of PSRR, you could feed it with a square wave and it wouldn't care. The opposite end of this spectrum is something that has woeful PSRR, like a Naim 72 gain card which only has a cap and a resistor as the power rail filter. So my mod 86p doesn't benefit from a better psu, but Naim pre-amps (of a certain age) do.

Obviously it's way more complicated than just that as there are myriad ways the noise can manifest in the output signal, but basically there's circuits with high PSRR over a wide bandwidth and then there's the other stuff.

Now some people try to make the argument that only a better amp can resolve the audible benefits that come from a better PSU, but honestly that's a logical fallacy of the first water. If the measured performance, (sound) of a circuit is easily affected by changes the quality of the power supply entering the box then the circuit has poor PSRR and can be improved. Some people say " ah but does it sound good just because it has high PSRR", well if it has low measured distortion and load invariance, and all you really want is fidelity to the source, then yes, it should/must sound good. If low distortion doesn't sound good to you then you're after an effects box not a hifi.

In truth, most people want a bit of an effects box, even if they won't admit/accept it. (Only Serge is immune)..
 
Alexh said:
Thats interesting, which model was it, and what effect did it have ? I am not on a troll here I genuinely would like to know because most of the AN Dacs have an input transformer ?
Click to expand...

Hmm I hope they're not still using the HagUSB module as the site suggests. It was good for its day (I used one years ago), but is now outdated & easily improved by asynchronous USB. It is also self-powered, so any power supply modulation, EMI etc. could impact clock jitter. Note that the HagUSB has an output transformer, not an input transformer.
 
sq225917 said:
I'll have a go.

Let's assume that any circuit has a certain amount of power supply noise rejection ratio. The higher this PSRR is (assuming equal bandwidth) the more immune to noise on the incoming PSU voltage rails it will be. So a great amp with great PSRR will be immune to all but the craziest of mains variances, it doesn't matter if you give it a wall wart of a massive over specced power supply, as long as it can fill its psu capacitors it's happy because the circuit after the psu is so good it can deal with anything without audible effects, my Modulus 86p is one such amp is has over 90db of PSRR, you could feed it with a square wave and it wouldn't care. The opposite end of this spectrum is something that has woeful PSRR, like a Naim 72 gain card which only has a cap and a resistor as the power rail filter. So my mod 86p doesn't benefit from a better psu, but Naim pre-amps (of a certain age) do.

Obviously it's way more complicated than just that as there are myriad ways the noise can manifest in the output signal, but basically there's circuits with high PSRR over a wide bandwidth and then there's the other stuff.

Now some people try to make the argument that only a better amp can resolve the audible benefits that come from a better PSU, but honestly that's a logical fallacy of the first water. If the measured performance, (sound) of a circuit is easily affected by changes the quality of the power supply entering the box then the circuit has poor PSRR and can be improved. Some people say " ah but does it sound good just because it has high PSRR", well if it has low measured distortion and load invariance, and all you really want is fidelity to the source, then yes, it should/must sound good. If low distortion doesn't sound good to you then you're after an effects box not a hifi.

In truth, most people want a bit of an effects box, even if they won't admit/accept it. (Only Serge is immune)..
Click to expand...

Good stuff Si. The main thing I would add to that is that some topologies with intrinsically shite PSRR can sound very good indeed if the effort is made to provide them with clean and stiff enough volts.... A pentode valve for example has virtually no PSRR as a simple single ended amplifier, a cascode stage whether built with transistors, valves, FETs or whatever is just the same. A simple triode valve common cathode circuit as used in innumerable bits of hi fi kit has only the PSRR derived from the r,a of the valve type. The ECC83 is about the most commonly used triode in small signal amplification, mainly due to its high mu of 100, but this results in a very high r,a of 68K and so poor PSRR. It's unusual to find a basic triode circuit with more than 10-15dB of PSRR.

A basic common emitter bipolar transistor stage is the same as a pentode valve with virtually no PSRR at all and most of the collector impedance being defined by the Early voltage and internal capacitive feedback mechanisms.

There are ways ameliorating all this of course but sometimes low noise and other consideration mean that now and then you end up with an incredibly simple gain stage with no PSRR being by far the best solution and you then have to use a supply thats often vastly more complex than the actual amplification circuitry in order to get the best results from the amplification stage... the onus on PSRR etc then being passed to the voltage regulator!
 
Purité Audio said:
I agree, I feel that if a device requires a ‘better’ power supply then intrinsically it is not a good design.
Keith
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Not necessarily, it may be a good design with a "simpler" PSU to allow the manufacturer an extra profit by selling a "more complex" PSU for the same model. :cool:
 
It's all design choices really isn't it Jez? Either you decide to go all in and make something the best you can, or you design to a price point and perhaps make 'quality via-addition' a product feature.

I think Keith's position is way too binary, life's not like that
 
tuga said:
Not necessarily, it may be a good design with a "simpler" PSU to allow the manufacturer an extra profit by selling a "more complex" PSU for the same model. :cool:
Click to expand...
So, a poor design, deliberately hobbling one’s own product.
Keith
 
Purité Audio said:
So, a poor design, deliberately hobbling one’s own product.
Keith
Click to expand...


No keith, a design built to a price point that is attractive to customers and has an upgrade path that allows for future improvements and in doing so works with the way the customer plans their finances and purchases their hifi.

I'm sure it's all sweetness and light in the esoteric echelons of hifi that you operate in, but for many buyers £1000 this month and maybe another £500 down the line offers them the flexibility they require.

We can't all be living on a diet of foie gras canapés and purchasing final-destination hifi on a whim ;-)
 
RME does that all for £850 Simon, superb measurements, incredible versatility, there really is no excuse for poor design.
Keith
 
But I only have 500 quid to spend, so they've fukked up and missed me as a customer.

See how it works now?
 
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