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Using the LM317 with higher voltages
Using the LM317 with higher voltages
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Old 19th November 2019, 03:47 AM   #81
carlmart is offline carlmart  Brazil
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Another thing: how many volts more does the booster zener have to be to consider the regulator's drop?
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Old 19th November 2019, 03:43 PM   #82
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by carlmart View Post
I imagine there's no way to, but can we trim the regulated voltage output on the single transistor regulator?
With the zener, there is no clean way: you will ruin some parameter.
An adjustable reference like the TL431 could do the job, except the 431 is limited to ~30V.
If you can find a 431-like circuit withstanding 70V, it would be possible

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That would certainly be a good reason to go back to the 3-transistor regulator, because we have a trimpot there.
Or the 2-transistor one

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Originally Posted by carlmart View Post
Another thing: how many volts more does the booster zener have to be to consider the regulator's drop?
Apparently, it requires about 10V dropout to begin to regulate.
Add 20% + 1V as a safety margin, and you are at 13V.

Since a higher voltage comes almost for free, use 15V to be on the safe side.

If you use the smooth, non-tracking version, the zener must be 15V higher than the highest possible V+ voltage.

The 2 and 3 transistor regulators are LDO's, and require <1V to regulate properly
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Old 19th November 2019, 07:01 PM   #83
carlmart is offline carlmart  Brazil
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Quote:
Originally Posted by Elvee View Post
With the zener, there is no clean way: you will ruin some parameter.
An adjustable reference like the TL431 could do the job, except the 431 is limited to ~30V.
If you can find a 431-like circuit withstanding 70V, it would be possible
So the resulting V+ and V- voltages would always have some difference. Which Luxman didn't seem to care, or they hand picked the zeners to null the differences.

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Or the 2-transistor one
Just compared them, adding the same RC input filter to both. The two-transistor reg is still 10dB worst than the single one @ 10Hz.

Increasing to 220 ohms /1000uF decreases that, but is it worth it?


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The 2 and 3 transistor regulators are LDO's, and require <1V to regulate properly
Which would be the drop with the 1 transistor reg?

In any case, would it make much of a difference, audio quality wise:

1) To have a slight difference between regulated V+ and V-?

2) To be 10dB worst at 10Hz?

3) None of them matters much.
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Old 19th November 2019, 07:42 PM   #84
carlmart is offline carlmart  Brazil
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Just for the fun of it, to see what did change, I added the capacitance multiplier used by Goldmund Mimesis 9 to the 2 transistor regulator.

This time I got -100dB at 10 Hz.

What are the pros and cons of capacitance multipliers?
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Old 19th November 2019, 08:50 PM   #85
Elvee is offline Elvee  Belgium
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Originally Posted by carlmart View Post
So the resulting V+ and V- voltages would always have some difference. Which Luxman didn't seem to care, or they hand picked the zeners to null the differences.
Both possibilities are plausible. An asymmetry of a few % normally makes no difference



Quote:
Just compared them, adding the same RC input filter to both. The two-transistor reg is still 10dB worst than the single one @ 10Hz.
That's unfortunate, but it is the price to be paid for the LDO, good DC performance and low output impedance.
Since the limiting factor is also the Early effect, you could use the same tweak as for the 3-transistor, and gaining 10dB without adjustment is probably possible, but if you want more, an individual adjustment will be necessary
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Increasing to 220 ohms /1000uF decreases that, but is it worth it?
I don't think so




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Which would be the drop with the 1 transistor reg?
Around 10V, as I said

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In any case, would it make much of a difference, audio quality wise:

1) To have a slight difference between regulated V+ and V-?

2) To be 10dB worst at 10Hz?

3) None of them matters much.
Normally 3), if the amplifier is designed correctly, but it is extremely difficult to be accurate without examining the actual circuit.

Quote:
Originally Posted by carlmart View Post
Just for the fun of it, to see what did change, I added the capacitance multiplier used by Goldmund Mimesis 9 to the 2 transistor regulator.

This time I got -100dB at 10 Hz.
You can stack regulators, passive & active filters ad infinitum and get -300dB PSRR, but what's the point?

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What are the pros and cons of capacitance multipliers?
You can find all the information on the net or this forum, but remember that cap-mults, in their simple form are just like simple regulators, except they don't regulate, and their PSRR is limited also by the Early effect
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Old 19th November 2019, 09:31 PM   #86
carlmart is offline carlmart  Brazil
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OK, things are getting to a nice closure over this power amp supply.

Let me tell you what I think it's worth using.

1) LDO, good DC performance and low output impedance are interesting. Point to the two transistor regulator.

2) Asymmetry is not essential, but easy to have with a trimpot. Point to the two transistor regulator.

3) Adding a CM adds one more transistor, but I get better specs than with the three transistor regulator. Point to the two transistor regulator with CM filtering.

The would provide me with an adjustable LDO, good DC performance and low impedance regulator. Am I right?
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Old 19th November 2019, 09:48 PM   #87
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by carlmart View Post
The would provide me with an adjustable LDO, good DC performance and low impedance regulator. Am I right?
Yes, it a good tradeoff for a decent regulator. Being fully discrete, it will be quite robust if you chose a sufficient pass transistor. You can also add a protection transistor if required, and the circuit has not been tweaked in any way: by optimizing the bias currents, E-B resistor etc., you can certainly scrape some dB's of performance here and there.
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Old 19th November 2019, 10:56 PM   #88
carlmart is offline carlmart  Brazil
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Quote:
Originally Posted by Elvee View Post
Yes, it a good tradeoff for a decent regulator. Being fully discrete, it will be quite robust if you chose a sufficient pass transistor. You can also add a protection transistor if required, and the circuit has not been tweaked in any way: by optimizing the bias currents, E-B resistor etc., you can certainly scrape some dB's of performance here and there.
First of all, thanks for your help in getting here. To all of you.

Currents will be quite low for me to worry about the pass transistor being "sufficient".

How and where should I add a protection transistor, and why? I will add DC protection circuit, also inspired on the one used by Goldmund, which also protects from oscillations.

Now I will open another thread, as I had mentioned, for the RIAA preamp's power supply. And your Denoiser and NoNoise design will be main contenders.
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Old 20th November 2019, 08:53 PM   #89
Elvee is offline Elvee  Belgium
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Originally Posted by carlmart View Post
How and where should I add a protection transistor, and why? I will add DC protection circuit, also inspired on the one used by Goldmund, which also protects from oscillations
A protection is always optional, and you could think that it is only needed in bench supplies, and you could be right -most of the times-, but it is inexpensive, easy, and can save the day when you are experimenting with your circuit, or if a cap goes short, etc.


Here is an example of such a protection, dimensioned for ~60mA:

Using the LM317 with higher voltages-carl62f-png

Thanks to a strange LTspice quirk, the first load is 200ohm and corresponds to the 24mA trace.
60mA is for 1K
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Old 20th November 2019, 10:09 PM   #90
carlmart is offline carlmart  Brazil
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Great. Of course I will add the protection. Thank you.

You had also suggested optimizing bias currents and the E-B resistor. Would that show on the simulation or only with the supply working?

BTW: I did open another thread for the RIAA preamp PS, and both your D-noisator and NoNoise are on the options. If you can go have a look it would be great.

Looking for a good power supply for a RIAA preamp

There's already a sim loaded, from the original supply, but it's not running as it should, probably because some variable is wrong. The regulated output voltage is showing, but now the curves I expected.

I would like to sim those supplies for PSSR, noise and impedance, if possible. Like you did with your NoNoise.

One thing I perceive with your regulators is that they are all positive types, and I am not sure I will have separate secondaries to use two positive regs. AFAIK only 317/337 have pos and neg versions. Is that so?
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