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Old 27th August 2004, 03:56 AM   #21
DougL is offline DougL  United States
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Quote:
Could You be more specific about the one You said that different ps should be used for phono and different for, say, line stage.
A phono stage with 60 db of gain to line level needs an ultra quiet supply. Nothing less will do. However, because of the small voltages, the dynamic load is very small.

The other end of that spectrum is a push-pull output, where the high signal levels and high PSRR tax the current capabilities of either shunt or series regulation, but noise is not the overriding consideration.

I am saying that there is not one perfect supply for every circuit.
You need to look at a number of variables and choose the supply that makes the most sense to you.

I was trying to decide between the PS I posted on my 6H30 preamp or a Tube shunt regulated PS. After thinking about it a week, I concluded that either had the potential to sound fabulous.

Doug
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Old 27th August 2004, 06:57 AM   #22
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DougL-
thanks for the reply

For all of You-
thanks for all Your replies in this thread- I will have to, after all, try at least few different designs to find something suitable- first of all the two easiest ones (bipolars/ mosfets) and then some with tubes regulators- I will make two identical prototypes of my line to compare them more easilly.
Thanks again a lot
regards
daniel
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Old 27th August 2004, 09:37 AM   #23
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Frank, Frank... rationalize.... I've said it before and I'll say it again, it's all in your head...

Quote:
Originally posted by fdegrove
You knew I'd have to respond to that so here goes:

...

Zout is consistent throughout the frequency range we envisage of using.
What's that have to do with anything? We aren't looking for a Zo match, we're looking for invisible Zo (zero ohms ideally). Consistency is no problem, add 20uF and a series resistor to tune to taste. At F's below where the 20uF does anything, the regulator can handle it. It's made to.

Quote:
If we consider the fact that series regs are Class B devices
HWA!?

Face it, it's class A, there always has to be a bias current in the thing. Well, if you unload it, it might be possible to call it AB, depending on how it's wired. But chances are, it's also wired to be "linear" (I put in quotes because the next part, NFB, is true, and we're near cutoff, so I'd rather use the word "responsive") at these levels too. So that also breaks down.

Quote:

heavily depending on NFB and the response time of the error amp it becomes clear that any series reg will be relatively "slow" no matter what we do. This can become painfully obvious with loads operating in classes other than Class A but I digress.
Two things: 1. error amps handle 100kHz easily. And that's worst case. 2. BYPASS CAPACITORS.

Quote:
- Noise, no big deal: VR tubes are often quieter than common Zener diodes and far more reliable in operation too. Whatever noise is left it's far less obtrusive than Zener pops and crackles and when operated and filtered correctly the VR tube will be rocksteady noisewise.
Which of course can be squashed by using far more C than gas tubes can handle.

Quote:

- Solid state does better at DC. Fine by me but that hasn't convinced me in view of a tube load attached to it which opearates quite likely in Class A at about 30mA anyway.
And what's this BS about regulating a class A amp anyway, it doesn't even give a $@*&!!

Quote:
- With a tubed regulator, provided it's wired correctly, you can remove the load: no problem.
You can pull the series pass device: no DC pass, no problem.
You can pull the error amp or VR, ditto.
- With a SS regulator, provided it's wired correctly, you can remove the load: no problem.
You can pull the series pass device: no DC pass, no problem.
You can pull the error amp or VR, ditto.

(Of course, such is not necessary because the devices are more reliable = semi-permanent. If one fails, it doesn't really matter if it takes the house down with it, because it doesn't happen nearly as often. Not to say that's good engineering practice, of course.)

Tim
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Old 27th August 2004, 12:02 PM   #24
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Hi,

Quote:
Frank, Frank... rationalize.... I've said it before and I'll say it again, it's all in your head...
It obviously isn't in yours yet....Maybe if you'd look beyond the basic function of a series re you'd understand it better?
I can only hope, right?

Quote:
What's that have to do with anything?
Quite a lot, actually...

Quote:
If we consider the fact that series regs are Class B devices
Should have said: Act as if they're class B devices.

Quote:
And that's worst case. 2. BYPASS CAPACITORS
Response time of the regulator itself is heavily dependent on the AC feedback cap's value, it's a matter of fiddling between ripple suppression (if you want that) and speed.

Quote:
And what's this BS about regulating a class A amp anyway, it doesn't even give a $@*&!!
Which goes to show that you seem incapable of looking beyond the basic function of a regulator?

Cheers,
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Old 27th August 2004, 02:53 PM   #25
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Frank,

The nice thing about using a LM317 is it's simple to use, few parts and it works well and will last along time. I redesigned several old MARANTZ preamps with LM317 what a nice improvement and still working over 20 years later.

I guess the debate is if a tube regulator can perform as well as a transistor regulator. I really can't see that happening, as you know amplifiers circuits like low impedances over their frequency range, low noise, and fast response tubes just donít perform in that application as well as their transistor counter parts. However, I am not saying that a tube regulators are bad, they can be quite good.
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Old 27th August 2004, 08:57 PM   #26
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Hi,

Jim,

Quote:
I guess the debate is if a tube regulator can perform as well as a transistor regulator.
To me it's not just a matter of what performs best on paper.
I realize quite well that if it's a regulator and nothing else you're looking for, the semiconductor based regulator will quite likely show the better specs.

Audio design however is a little less straightforward and if that regulator has a very distinct sonic fingerprint then I need to look elsewhere or at least find a way to get rid of that aspect of it.

After all, if it's just paper performance we're looking for, we'd probably all be designing with semi-conductors....

Anyway, it's good to know you had excellent results from using a LM317.

I'm not saying this or that is better but from experience I just know that every single regulator I ever designed was optimized for the load and task at hand...
In the end I did always arrive at what I wanted to "hear" from it but it didn't come from just looking at a spec sheet if you catch my drift.

Cheers,
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Old 27th August 2004, 09:04 PM   #27
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Alright Mr. Smartypants, HOW does it act class B then.

I've only ever seen it as exactly what it is, a class A cathode (or emitter, or source) follower.

Tim
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Old 27th August 2004, 09:44 PM   #28
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Hi,

This is what is said:

Quote:
Act as if they're class B devices.
This is what you make of it?

Quote:
I've only ever seen it as exactly what it is, a class A cathode (or emitter, or source) follower.
Ask yourself:
What is a series voltage regulator?
What does it have do to?
Is it an amplifier?
If so, how does it respond to changes at the load?

Cheers,
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Old 27th August 2004, 09:58 PM   #29
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Ehm Frank,

A pre amp usually draws an almost constant current. No matter what kind of pass device you use, whether hot glass or cold sand, it passes almost constant current. It only has to cope with small current deviations.

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Old 27th August 2004, 10:13 PM   #30
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Hi,

Pjotr,

Quote:
A pre amp usually draws an almost constant current. No matter what kind of pass device you use, whether hot glass or cold sand, it passes almost constant current. It only has to cope with small current deviations.
The pass device is not the issue anyway...
We don't even know what this regulator is going to be used for, neither do we know what class of operation the load is working only that the current range will be about 30mA tops.

The point is however that the series regulator will only react when the load is causing an error, in that respect it acts on demand just as a class B stage would...Hence the analogy.

Nowhere have I stated that series regulators are biased for class B operation as seems to be the assumption.

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