HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

Lurcher300b wrote: ↑Mon Jul 06, 2020 12:34 am Not a Albert quote.

Doesn't actually matter who said it, what matters is what it says. In our context; just because I can't explain why it works doesn't matter, what matters is that it works. As an example, when I was at college there was still argument over exactly how a wing produces lift. That doesn't seem to have stopped Boeing and Airbus from producing many thousands of aircraft

Lurcher300b wrote: ↑Mon Jul 06, 2020 12:34 am If you are following that subjective approach why not start just connecting one wire. Or put a pot of yoghurt on the top. Or any other entirely random thing.

Possibly, just possibly, because experience* tells me that connecting just one wire doesn't work?
Have you tried putting a pot of yogurt on top of an amplifier, does it make a difference?
There are people out there who firmly believe that supporting their speaker cables on little bridges makes a difference to the sound, others will spend a fortune on a super fuse. Both are actually harmless. Equally harmless is using a 20VA power supply in place of a 10VA power supply, as long as the output voltage is correct. If I connect a 90KVA power source to an an aircraft that requires 30KVA does it do any harm, no the industry standard ground power is 90KVA it is done all the time.

*Experience and training.

Daniel Quinn wrote: ↑Mon Jul 06, 2020 9:34 am Because we stand on the shoulders of giants.

Understandable quote Dennis,BUT

Is knowledge without understanding meaningless ?

At one level, knowledge without understanding is by definition meaningless, in the sense that you have nothing more than a fact with no insight into its underlying significance.

Doesn't actually matter who said it

Then why did you credit it to him?

what matters is what it says

Yep, but in reality it doesn't say anything. Its well known one horse can run faster, but which one, that's the important bit. So, some things can't be counted, but some can, it matters which camp the subject is in.

when I was at college there was still argument over exactly how a wing produces lift. That doesn't seem to have stopped Boeing and Airbus from producing many thousands of aircraft

Maybe, but the key word there is exactly. They had some good ideas how it worked and that was enough, but it was not zero understanding.

more than a fact

Actually you don't, you have an observation not a fact.

To grossly over simplify matters. I don't have to have a full, wide and deep understanding of how or why something works to exploit the fact that it does.

If you feel the need for a deep understanding of why using a larger capacity PSU may make an amplifier sound better please feel free to perform the experiments necessary to gain that understanding. If, on the other hand, someone is just happy to enjoy the benefits of a larger PSU, why not let them get on with it?

valvesRus wrote: ↑Mon Jul 06, 2020 10:09 am

Daniel Quinn wrote: ↑Mon Jul 06, 2020 9:34 am Because we stand on the shoulders of giants.

Understandable quote Dennis,BUT

Is knowledge without understanding meaningless ?

At one level, knowledge without understanding is by definition meaningless, in the sense that you have nothing more than a fact with no insight into its underlying significance.

You can't begin to answer such a question without defining your terms. I think your knowledge is dubious.

I don't have to have a full, wide and deep understanding of how or why something works to exploit the fact that it does.

Of course, that's fine, I am not saying they shouldn't. What we started this about was your statement:

As you know the capacitors also smooth the output waveform and a larger capacity PSU may well just use larger capacitors. Clearly it makes a difference otherwise the Phono 3 wouldn't use a higher capacity power supply, well four different PSUs which is effectively a four times larger PSU.

Which started with a description of a model as to why something did something. I was just arguing that your description was a simplification. So in your terms, you stared with counting something and there was a clear suggestion of a cause and effect.

Lurcher300b wrote: ↑Sun Jul 05, 2020 6:38 pm

So then, if having a bigger PSU for the input stage improves the sound, and there is no commercial reason not to, why not?

Because without knowing why it improves the sound we are just guessing. Now some may not worry or care, but some others do.

Lets imaging a situation, we start with a 75va transformer, we replace it with a 300va transformer. It sounds better, But what we don't know is will a 600va transformer sound better or would a 150va sound even better than a 300va. Would a 75va sound even better than all of them if we changes the cap or the rectifier, or would a 75va with a different voltage sound better. We can decide to try every possible variation, or we can try and create a model of what is happening and see what that suggests would be better, try that, if its better continue with the model, if not find a new model. Another name for that model is understanding.

Because the secondary and primary impedance is lower on the larger transformer you get better damping, often improved image and the top end seem sweeter.

Larger cap still need energy to charge them and if the output impedance and diode are not right, then it is waste of time choose the right value.
1 simple rule of thumb for 50Hz , 1A on 10,000uf has 1V ripple. So now if the cap is charged to 10V (easy numbers) the ripple at 1A only give us a useful voltage of 9V with out clipping and 100Hz ripple noise. Now if we make a stereo 6.3W/ch what is the current it need from the 10V supply running a 4ohm load, about 3 amps, whoop we now have a 3V ripple and useful voltage of 7W, oh dear it is now not 6.w/ch.
The above is simplified ,

Number to remember:-

3.143
0.707
1.414

and a useful formula for energy/current/time (i.e. frequency)

1/f = T

0.5C x V x V = A/S (columbs)

so (0.5C x V x V)/S = Amps this will give the peak current for the time you need i.e. 1KHz is 1ms

so (0.5 x 0.01Farad x 10V x 10V)/0.001S

You turn

All these and more are needed to just get the PSU right with a margins allowed for ageing, normally for most caps 3000 - 10,000 at given temperature. And mains input changes in this UK.

OK does this help a little ????

Awesome knowledge Colin.