3 terminal Jung Super Regulator Kit

[ALW]

A couple of points, whilst it is basic engineering science, it's also an audio product, hence listening comes in somewhere along the line

I'd be curious as to what references you feel are better, the LM329 is inexpensive and has low noise relative to it's output voltage.

This allows less noise gain within the system, resulting in less noise in the system as a whole.

Aboslute accuracy of the reference is irrelevant here as is long-term stability.

There's few, if any, bandgap devices that would beat it, sonically, and not many sub-surface zener alternatives.

And there is LOADS of tweaking in there.

But to test your authoritative statement, please tell us of the SONIC effects of altering various circuit parts

Andy.

[peranders]

Originally posted by ALW
There's few, if any, bandgap devices that would beat it, sonically, and not many sub-surface zener alternatives.

This design can afford sufficient LP-filtering so the noise is less important I would say. You could use almost anything but if you required low tempco, low drift, etc you have to look at the reference itself. I still think most of the design is normal, nothing weird and not very tweaked in the sence in being weird.

[ALW]

This design can afford sufficient LP-filtering so the noise is less important I would say. You could use almost anything but if you required low tempco, low drift, etc you have to look at the reference itself. I still think most of the design is normal, nothing weird and not very tweaked in the sence in being weird.

Well, here's a few questions to ponder: -

1. Why is the divider impedance around the op-amp still so low, when on the AD825 FET-input op-amp current noise would dominate (and hence imply a higher impedance)?

2. What are the disadvantages of trying to filter a noisy reference sufficiently, what effect does this have sonically, with the circuit as-is?

There's more, but it's easy to make the mistake that because a circuit looks simple, it is simple.

Measurement, Kirchoff or anything else will not answer those questions for you, but your ears will.

Andy (playing Fred's agent-provocatuer game)

[peranders]

1 Jung used the AD797 and to get low noise he used low resistor values. A basic rule is also to have as low values as possible so noise will be low and stray caps don't interfere too much. 1 kohms (if I have seen it right) is not very low, rather low.

2 No disadvantage at all! Possibly slow startup.

The reference Jung used is pretty much average, like the 431 but 6 dB lower noise. I think also Jung's text is straight forward, I agree to everything.

[Fred Dieckmann]

"The real benefit comes from the bootstrapping the op-amp."

Well................
This is really only true at frequencies where the PSRR of the op amp is high. As the PSRR drops with increasing frequency some issues arise. Here lies the paradox. The whole point of a very low impedance supply is to keep the voltage at the supply pins free from modulation. In this regulator the op amp supply is intimately coupled to the op amps (via two followers) output currents modulation of its own supply.

That is the very antithesis of the principle reducing the modulation of supply by load currents that regulation is designed to do. An additional RC filter for the op amp in the regulator seems prudent to me. The supply AC currents to the op amp would seem to be small enough (the AC load current demands of the regulator divided the Hfe of the two followers) to make the supply for the op amps increased impedance less important than the very significant improvement in the PSSR for the op amp.

The PSRR issue becomes very interesting at the point where the inductive output impedance of the regulator resonates with output capacitor and extremely interesting with a high Q low ESR capacitor! The very low inductance with a high gain bandwidth op amp pushes this to a high frequency where the PSRR for the op amp is poor.

This is more than just an academic exercise and is what seems to be a real life issue with the topology. The behavior of audio circuits at RF frequencies can have real implications for the sonics. This has been an area of some discussion on the forum in the area of diode bridge switching noise on audio circuits.

There is no such thing as a free lunch.


"2. What are the disadvantages of trying to filter a noisy reference sufficiently, what effect does this have sonically, with the circuit as-is?"

Leakage current in electrolytic capacitors can contribute to noise and voltage drift of the reference voltage seen by the op amp.

http://www.analog.com/UploadedFiles/...tion_V-Ref.pdf page 18

I will now sit and wait for the fur to fly in the ensuing cat fight.....

* Andy is quite sharp but is too modest to call himself an expert.

[Fred Dieckmann]

"Its only 1.75" wide by 1.5" tall. I don't think thats very big.
I blew up the layout for readability.

Thanks for your comments,
Craig Beiferman"

ummmmm...... How high do the components stand off the board?

Pretty tight fit for even brand X

Yes Peranders I do have further information on the regulators pictured. Why give them free advertising here?

Meeeyowwww!

[Elso Kwak]

Originally posted by dipchip
peranders,

The real benefit comes from the bootstrapping the op-amp.

This means that the op-amp is powered directly from the regulated output voltage of the circuit.

Normally, if the op-amp were powered from the supply, any ripple on the op-amp supply would show up as noise on the output.

But now, the regulated output powers the op-amp,
and the regulated output is also the feedback to the op-amp.
So the noise is now much more common mode, and hence the
big 30 to 35 dB improvement over typical regulators.

Thanks,
Craig Beiferman

Hi Craig,
Sonically I found no advantage in powering the opamps from the regulated supply i.e. the output of the regulators.
RC filters on the supplies of the opamps as also suggested by Walt Jung seriously diminished the bass slam of the supply. This is done in the Mark Levinson PLS-150 powersupply for the ML-1 preamplifier with detrimental effect. A LM317/337 combo sounded better!
This one is interesting I think..........
http://headwize2.powerpill.org/proje...lmore3_prj.htm
Though I found sound is better without preregulators......

[Fred Dieckmann]

"RC filters on the supplies of the opamps as also suggested by Walt Jung seriously diminished the bass slam of the supply.'

bigger cap, smaller resistor....... Actually the bootstrap gives extremely good input noise rejection at low frequencies. I think line noise rejection may be more important than output impedance. It may be the reason for the popularity of shunt regulators which also can be bootstraped.

[fdegrove]

Hi,

I think line noise rejection may be more important than output impedance. It may be the reason for the popularity of shunt regulators which also can be bootstraped.

Series regs do even better in that department...

Not surprisingly, really.

Cheers,

[stokessd]

Originally posted by janneman
Do yourself a favor and buy the 1995 backissue series of AudioXpress. Well worth the 20 $ or so it costs.

That must have been an outstanding year, then.

I buy issues from the news-stand a couple times each year when I am traveling. I have yet to be impressed by that magazine on an issue to issue basis. There's nuggets of greatness (like the Zen, Thor etc) but then there is things like low voltage biased tube headphone amps designed for lots of distortion, silly Macintosh amp output tube modification plates when simple socket rewiring would be better in every way, and on and on. Then there's articles like the moving coil transformer project which entails putting a transformer in a plastic case with RCA jacks (not even balanced inputs for god's sake!).

Then there's a project with some meat, and instead of pushing the marginal crap out of a particular issue, they spread the article over several issues.

$20 for all the back issues strikes me as "well worth it"


Sheldon