My discrete voltage regulator.

Zen Mod · 2006-08-30 7:56 pm

Russ White said:
Hmmm, would that also work with a center tapped trafo?

nope,because you don't want already established ground point on center tap;
what you want is that you make ground point on output of two regs - tying minus of upper reg and plus of lower reg;

Russ White · 2006-08-30 7:59 pm

Zen Mod said:
nope,because you don't want already established ground point on center tap;
what you want is that you make ground point on output of two regs - tying minus of upper reg and plus of lower reg;

Yes, I was mulling that over in my head and I was beginning to see it that way too. Thanks for the confirmation.

Zen Mod · 2006-08-30 9:45 pm

Russ,I have no intention to hijack the thread,but short off topic Q:
recommendation for SuperDuperCCCCCCSSSSSSSSSXccccSSScccSSSS BOSOZ from another thread regarding volume pot ?

on input (and values)

OR
on output (and values)

??

I have no time for reinventing the wheel about that and I know that ppl here are investigating that already...... too many posts in not so small number of related threads......

tnx

Nixie · 2006-08-30 10:27 pm

How about a nice op-amp driven shunt like http://www.diyhifi.org/forums/files/ccssr4_sch_687.gif
from the thread at http://www.diyhifi.org/forums/viewtopic.php?t=720&postdays=0&postorder=asc&start=0

Of perhaps http://www.wenzel.com/documents/finesse.html

Also look at http://www.tnt-audio.com/clinica/regulators2_impedance4_e.html and http://www.tnt-audio.com/clinica/regulators3_ripple_e.html

And of course, consider flattening the output impedance over the whole frequency range through the use of snubbers as in http://www.calex.com/pdf/3power_impedance.pdf

Russ White · 2006-08-30 11:00 pm

Zen Mod said:
Russ,I have no intention to hijack the thread,but short off topic Q:
recommendation for SuperDuperCCCCCCSSSSSSSSSXccccSSScccSSSS BOSOZ from another thread regarding volume pot ?

on input (and values)

OR
on output (and values)

??

I have no time for reinventing the wheel about that and I know that ppl here are investigating that already...... too many posts in not so small number of related threads......

tnx

Terry is more the expert on that amp, but I will do my best.

Funny thing. This VREG will be tested on just that preamp!!

With the amp circuit and PS as it is presented, the amp always sounds better with an attenuator on output. anything from 2.5K or higher input impedance is just grand. I used a stepped attenuator with 750R output impedance and an input impedance that varies from about 2.5K to about 5K.

I am hoping that with a new PS that amp may sound better with the attenuator on the input side. I think part of the reason you get hiss with it in that configuration right now is that is does not have very high PSRR. The input impedance of the amp is fairly high so I bet you could use a 20-50K pot/attenuator without a problem.

Cheers!
Russ

Russ White · 2006-08-30 11:01 pm

Nixie,

Thanks for the educational links. Very much appreciated! :yes:

That said, is there anything particularly bad about my design?

Zen Mod · 2006-08-30 11:11 pm

Russ White said:
.........
That said, is there anything particularly bad about my design?

looks good enough to me

except that is series ,not shunt reg..... :devilr:

my name can be ,in fact "Shunt Moderator" :clown:

AndrewT · 2006-08-31 9:29 am

Hi,
no one has directed Russ to the WJung site where in collaboration with JDidden he wrote a (definitive) series of articles on opamp regulated PSUs including the super regulator.

http://waltjung.org/PDFs/Low_Noise_...og_Circuits.pdf
http://waltjung.org/PDFs/IC_Regulated_Power.pdf
http://waltjung.org/PDFs/Regs_for_High_Perf_Audio_1.pdf
http://waltjung.org/PDFs/Regulator_...e_Rejection.pdf
http://www.alw.audio.dsl.pipex.com/...v2.9_iss009.pdf

Russ,
all you didn't know that you needed is in there.

Russ White · 2006-09-01 8:04 pm

First thanks to all for the valuable input. What a great group on this forum.

Ok, so I simulated my circuit, and it seems to be OK, but I am also wanting a series regulator for lighter loads.

What do you guys think about this puppy. It a simple series VREG but with a capacitance multiplier in front of the pass device.

R7 is there simply to help keep some small current flowing. It would be a high value.

Cheers!
Russ

metalman · 2006-09-01 8:43 pm

Originally posted by Russ White
With the amp circuit and PS as it is presented, the amp always sounds better with an attenuator on output. anything from 2.5K or higher input impedance is just grand. I used a stepped attenuator with 750R output impedance and an input impedance that varies from about 2.5K to about 5K.

I concur with Russ' recommendation. I have a stepped attenuator built with 10K impedance, and I find that if the input impedance of the amp it is driving is less than 20K then the music starts to lose a little life. THat being said, it still does a good job driving the GC Susy amp which only has a 2K input impedance.

Russ,

Great work with the regulator. I agree that the pre may benefit from a better power supply, and I have been investigating along that path as well. I would also recommend giving a read through the Blowtorch Thread where they talk about the benefits of a series reg followed by a shunt reg to achieve great noise rejection across a very wide bandwidth. You might find some gems there as well.

PS. How's the DAC coming. Need a beta tester???

Cheers, Terry

jan.didden · 2006-09-01 9:59 pm

Russ White said:
First thanks to all for the valuable input. What a great group on this forum.

Ok, so I simulated my circuit, and it seems to be OK, but I am also wanting a series regulator for lighter loads.

What do you guys think about this puppy. It a simple series VREG but with a capacitance multiplier in front of the pass device.

R7 is there simply to help keep some small current flowing. It would be a high value.

Cheers!
Russ

I like the idea of the cap multiplier before the reg, I haven't seen that beofre. I think it is more cost-effective than a full swing prereg.

One point: feeding the opamp from the output of the prereg gives a but more performance.

Jan Didden

Russ White · 2006-09-01 10:07 pm

metalman said:
PS. How's the DAC coming. Need a beta tester???

Terry, I think it's ready to beta test, and if you want a board all you have to do is ask. I would love for you to give it a go.

I have the PCB designed and will be sending it off to the fabricator no later than Tuesday after the holiday.

Cheers!
Russ

Russ White · 2006-09-01 10:08 pm

janneman said:
One point: feeding the opamp from the output of the prereg gives a but more performance.

Jan Didden

Hi Jan, and thanks.

It's funny you say that, because I first drew the circuit that way, but I was worried about the slow rise of the voltage after the multiplier, and possible negative effects that might have. If it would not have any negative effects, then I will definitely put it back that way.

Cheers!
Russ

AndrewT · 2006-09-03 11:29 am

Hi,
the slow charge up is the beauty of regulated supplies.

The few tens of mS it takes massively reduces the charging pulses both before the regulator and after it.

It helps stop blowing close rated fusing and reduces stressing on capacitors (which are dV/dT limited).

Russ White · 2006-09-04 8:52 pm

First VREG tested.

Here is the basic circuit... Some parts are not exactly the same, but here is what the simulation looks like... The opamp is OPA227 and the transistors are ZTX450s.

I built it as a 5V supply, and built 3 of them to test on an existing preamp. It is working quite well.

Here is the circuit as simulated.

Russ White · 2006-09-04 8:56 pm

And here are the simulated results for output voltage.

The load is a 100ma 1000hz sine wave. Along with a 10ma 1mhz sine wave in parallel. The input have 1V 120hz sine wave injected to simulate a lot of noise on input.

jan.didden · 2006-09-04 9:09 pm

Hmmm. You do interesting things with the reference. I would make R1 and R5 10k for more input ripple & noise rejection.

Jan Didden

sawreyrw · 2006-09-04 9:20 pm

Russ,

What are Q2, Q3, and Q4 and all the circuitry around them for? I think they can be deleted. Of course, you do need D1.

Rick

richie00boy · 2006-09-04 9:22 pm

You mean R2 and R5 Jan? Yes I agree with you.

Q2 & Q4 and Q3 form capacitance multipliers, and are an elegant way of achieving low noise operation.

Nice work Russ. Have you abandoned the MOSFET output device?

Russ White · 2006-09-04 9:25 pm

Q2 and Q4 makeup a Darlington pair for the main capacitance multiplier for the voltage input.

Q3 is a capacitance multiplier for the VREF and makes a significant difference in the accuracy (noise rejection) of the VREF.

Cheers!
Russ

My discrete voltage regulator.

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