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Old 28th August 2003, 03:06 PM   #11
Mikett is offline Mikett  Canada
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There is something about PSRR. Many ICs claim high figures that I do believe is justifiable. However, whenever a wide bandwidth (e.g. Jung Didden super regulator) is utilized, they noticeably sound very different and always for the better. This leads one to suspect there are interactions that PSRR does not take into account.
From an engineering standpoint one questions the need, but practice deems otherwise. The key to regulated supplies in audio is bandwidth as was known since the 80's. Hang a poor PS on a better amp and it is for the worse.
By the same token, why does short wiring sound better? In theory, the few cms on a PCB should not make any perceivable difference. Judging by the gainclones being built it is obvious that many have discovered that it does and now seems the accepted norm.
Everyone is still learning, experimenting and listening .
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Old 28th August 2003, 03:13 PM   #12
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when i built my gainclone, i had 2 15v regulated power supplies in my scrap bin, so i decided to use these. having not heard a non-regulated supply, i cannot comment of the differences.
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Old 28th August 2003, 04:48 PM   #13
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Quote:
I have been thinking that since the amp chips work so well as amps perhaps they also work well as regulators as the application notes also describe. So why not build a gainclone with the same chip as ps regulator? It is a simple and elegant solution.
Protos

I was thinking the same. For some reason though, all Jung-type regulators i've seen seem to have very low closed loop gain for dc and sometimes even lower at ac. As the 3875 is not stable at low gain it might not be suitable. Or maybe it can work with a lower reference voltage and higher gain?
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Old 28th August 2003, 05:35 PM   #14
Mikett is offline Mikett  Canada
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amplifying a low reference might not be a good thing.
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Old 29th August 2003, 11:05 AM   #15
protos is offline protos  Greece
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Quote:
Originally posted by analog_sa


Protos

I was thinking the same. For some reason though, all Jung-type regulators i've seen seem to have very low closed loop gain for dc and sometimes even lower at ac. As the 3875 is not stable at low gain it might not be suitable. Or maybe it can work with a lower reference voltage and higher gain?
The opa power chips are designed to work as regulators.
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Old 29th August 2003, 08:50 PM   #16
ukram is offline ukram  Finland
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I did some power testing for my dual LM3886 amp. I have non-regulated power supply. 8 parallel 33 ohm / 5W resistors were used as a load (= 4.125 ohms). I only tested one channel. I could only get 1 V p-p signal from my USB card. This was enough to get 18.9 V RMS or 55.2 p-p signal into load. This equals 86.6 Watts into one channel! The resistors soon got very hot, and i had to turn down power. The peak current was 6.6 A, still smaller than the 11.5 A current limit. There was no clipping. The ripple was 1.6 V. The supply voltage dropped from 33.0 V when idle to 31.4 V at full blast. I have 4*4700 uF capacitors on the PCB for power supply filtering and 2*24 V / 250 VA toroid transformer. The LM3886:s did not get very hot while testing.

See http://hepso/misc/Lm3886_amplifier.html for more details about the amp.
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Old 30th August 2003, 03:32 PM   #17
jkeny is offline jkeny  Ireland
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Has anyone got report on how regulated supply sounds in comparison to no reg supply and if it worth buying parts & building

Pedja doesn't give much info - simply says it does all he expected it to do?

John
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Old 30th August 2003, 03:38 PM   #18
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Thanks Ukram for posting that....I am in the middle of comparing the LM3886 and opa 549/541
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Old 30th August 2003, 04:31 PM   #19
ukram is offline ukram  Finland
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Correction: the input signal was 2V p-p (400 Hz sine wave).

And i agree that it might be a good idea to use regulator to make sure the amp chip is working at best possible voltage, to get maximum performance out of the chip. Just for this purpose a rather simple transistor circuit might be enough.
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Old 30th August 2003, 09:27 PM   #20
JoeBob is offline JoeBob  Canada
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ukram, that's exactly what I am using and why as well. So far it works well, although I'm still assembling it (tested it without a chasis) and I'll put it through some listening tests in the next week. I just put together a zener/emmiter follower type regulator and haven't tweaked it yet, but at first listen it looks promising.
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