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Old 26th June 2013, 06:31 PM   #1141
AKN is offline AKN  Sweden
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Quote:
Originally Posted by jcx View Post
not if you're half competent, know what to measure - even a good US$150 sound card could "see" the various capacity PS differing loaded ripple through a LM3886 ~100 dB -PSRR with fc rignt at mains frequency

and that's just if you restrict "measurement" to audio input test signals, look at audio output under load
Hi,
One can measure PSU output under like I did Here, quite revealing.
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Old 26th June 2013, 07:12 PM   #1142
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Originally Posted by AndrewT View Post
Give a hint for some values.

Say 60VA & 4700uF+4700uF for a 60W amplifier, then 180VA & 15mF+15mF (for 3times the current for the same 60W amplifier and finally a pair of 180W SMPS, or should that be a pair of 30W smps for the dual polarity supply?

Is that what you mean?
Hi Andrew . I think Dvv and I would deliberately make it so that it measured the same yet sounded different . As others will say if carefully measured the difference will appear . My feeling is the measurements would be beyond what ordinary people can do on the money they can afford to spend .That's assuming they have the knowledge to know what to look for . This was especially so when we had the bland attitude of the past that a few chosen measurements told us all we wanted to know . I remember review after review saying yes it is hi fi . Never did anyone say I think this is rather good . In the case of a few budget amps they had room for comment . They were dreadful and that was it . None of those ever get discussed these days . Amstrad IC2000 was a treasure of badness . Now if we worked on one how good could we make it ? Amstrad the guilty amplifier . If I remember Amstrad reviews were in watts per pound rather than any hi fi virtue . Sorry Mr Sugar , you are a Millionaire and some ( me not ) . So what do I know ?

I will give you my take on this . I suspect that class B amps given the PSU for class A work better . This is because we no longer have to use common mode rejection to clean up the signal which would otherwise be ripple modulated . The big illusion is ripple is almost zero at idle . Thus we do not imagine it to be a problem . Turn the bias up and suddenly it is there at idle . Now if the majority of the amp is regulated with the output dumpers given raw DC that will get very close and can use a small PSU . Small PSU's usually have capacitors better suited to HF . Not always big is best . Lots of transformer always works well . Also well designed transformers .
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Old 26th June 2013, 08:05 PM   #1143
dvv is offline dvv  Serbia
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Originally Posted by nigel pearson View Post
Dvv . A challenge for anyone who has bits in the shed . Find a chip amp with a circuit reasonably like the blameless design in the handbook . Build three amps all identical . Three power supplies . One , the minimum required , Next the best you can with lets say 200% spare current . The third a switch mode . I bet they all measure the same ? And the next question is , do they sound the same ?
Nige, you know how I do it.

Assume an amp rated at 50/100 into 8/4 Ohms. Assume energy requirements, 1-2 Joules/10W, to be 2 Joules/10W of dissipated power, meaning an evil load. That means 20 Joules per channel. Assume my supply voltage is say +/- 37V. This means I would need to use roughly 30,000 uF PER SUPPLY LINE PER CHANNEL.

Where else but with me do you even see such numbers?

But I'll bet it would pump out around 200W into 2 Ohms in impulses.

No wonder. I am not happy with just one pair of power tranmnies at the output, so it would have to be two pairs. And since I practically use only Motorola/ON Semi MJL 3281/1302, rated at 200W per device, you could say I have the balls for the job.

As a matter of fact, that's exactly what I HAVE done, the schematic is with the PCB artwork guy, I expect them around July 10 or so. Which means you and I are going to have a very interesting automn, because there are TWO 100WPC projects also with the same guy. I decided to test two different topologies for the hell of it.

Once finished, I'll post it here as well, just to yank the chain of the local topic radicals and naysayers.
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Old 26th June 2013, 08:12 PM   #1144
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What I notice is we now have an agreement on things which we can leave to measurements and things we might have fun in using our ears as substitute test gear ( Remember the English and irony here ) . Sometimes the sound of a great amp was the power supply . Why we got deceived was the designer was an obsessive and we though knowing the circuit would save us the expense of paying the costs of retail distribution . Now with that secret known we can do exactly that . LAB 47 is how to do it . The power supply is from another planet . Not technically which is superb . No , it is a work of art .
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Old 27th June 2013, 12:05 AM   #1145
davebtw is offline davebtw  United States
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Just received my copy of the Sixth Edition, via Amazon today (Wednesday 26 June,2013). Gotta get reading!
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Old 27th June 2013, 06:55 AM   #1146
dvv is offline dvv  Serbia
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Quote:
Originally Posted by nigel pearson View Post
What I notice is we now have an agreement on things which we can leave to measurements and things we might have fun in using our ears as substitute test gear ( Remember the English and irony here ) . Sometimes the sound of a great amp was the power supply . Why we got deceived was the designer was an obsessive and we though knowing the circuit would save us the expense of paying the costs of retail distribution . Now with that secret known we can do exactly that . LAB 47 is how to do it . The power supply is from another planet . Not technically which is superb . No , it is a work of art .
No idea why is Lab47's power supply art - perhaps a picture, or a link?

You and I disagree on several things, Nige, but the one thing we have never ever disagreed over is the importance of the PSU for audio circuits. The only question is how to do it.

One of the tricks I have found to work each and every time is to add a mid sized capacitor (ma favorite size being 2,200 uF) to each and every output device's collector, as near to the device as possible. This always seems to clear the sound up and subjectively make the amp faster, more nimble.

The first time I saw that done in practice was an Italian made Galactron (a hell of a company!) amp sometime in the 70ies. I tried it and liked it.
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Old 27th June 2013, 10:17 AM   #1147
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This doesn't do it justice .
6moons audio reviews: 47 Laboratory Model 4706 GainCard

I found out about them when I repaired a FAL speaker they were using . The magnet had slipped and I put it back on centre .

The guy is a neighbour of yours from Bosnia . I lent my pair of FAL ( loaned to me also by FAL via my freind Martina ) to his partner Ishvan . He died and that was by by FAL's . It was the repaired ones . I didn't loose money . I lost an opportunity . My boss loves LAB 47 , he knows nothing of my history with them .
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Old 23rd July 2013, 01:38 AM   #1148
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Just received my copy of the Sixth Edition, via Amazon today (Wednesday 26 June,2013). Gotta get reading!
Just ordered mine from Amazon today. Had enough points to cover the entire cost. :banana:
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Old 27th July 2013, 11:39 AM   #1149
Mooly is online now Mooly  United Kingdom
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My copy arrived this morning... I can tell its going be a great read.
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Old 2nd August 2013, 05:05 AM   #1150
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At long last, mine turned up too, after an initial delivery estimate that was even a month more!
After an initial scan of the new chapters, I realised something had changed (and they really are new chapters in most respects). It shows quite a metamorphosis from neatly clipped prose in the early editions to something we might read here in some of the pro. posts - 'not that I mind either style but the contrast amongst mixed chapters perphaps gives the impression of a different author/editor as much as new ideas and material.

The content of these chapters also seems in direct response to some criticisms often voiced here. 'Flattering to those who made them, I guess, so never let it be said that authors are disinterested in reader feedback. The response in this 6th ed. is good but I'm a little surprised that some material is so devoted to defence of previous data, model choice and opinions. This isn't critcism, since there can be cultural and scientific divisions at all levels of even DIYAudio membership, so you could expect different groups to stack up their own evidence in their own preferred order of significance, as we find on the EEs' threads even, so I'm steering clear.

On a basic level, I have to say it's good to see some real ink on the pages. The QC of the last edition (the first by Focal Press) was b..... awful! At least my copy of this Focal edition, though finer print, is readable....which is what I intend to get on with
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