The simplistic Salas low voltage shunt regulator - Page 534

Salas · 26th September 2012, 03:47 AM

Lets hope it will open the Mosfet gate less capacitive at least.

Dr.H · 26th September 2012, 01:10 PM

So I am building REFLEKTOR (probably 5V and 10V) tonight. Any things to watch out for (layout, oscillations, etc)?

Salas · 26th September 2012, 05:57 PM

If you got wire leads between rectification/main filtering to reg's input decouple the reg's input with 0.1u to 1u to ground. Tie the top shelf mirror BJTs face to face. Make it tight especially around the input CCS. Scope it for stability. Good luck.

Kazuo Ozawa · 27th September 2012, 12:52 AM

Quote:

Originally Posted by Kazuo Ozawa

Of course, I have observed that it does not oscillate.

I have to correct the previous report.
The attached photo shows that my regulator is oscillating.(Vertical X10)

First I thought that it was normal fluctuations.

Salas. I was searching low Cxxx MOS FET. The device you propose is the best as far as I found out. Now I am purchasing STP55NF06L. I will report later.

Salas · 27th September 2012, 01:03 AM

~50ns period, that is very high. 20MHZ. Also low in amplitude. Can it relate to any clock fundamental or harmonic since you use them for digital? Anyway put 0.1R at the +side on the DAC's particular power feed point and see if that waveform damps away.

Kazuo Ozawa · 27th September 2012, 02:01 AM

Your response is always quick.

I thought as same what you guess. But when I moved the board by chance, the waveform became quiet like a ground noise. So I found it oscillates.
In other words, I say Salas Reflektor is excellent regulator if it runs stably.

Salas · 27th September 2012, 02:09 AM

This is very high a frequency, if it is just a matter of moving it maybe you need shielded coax and/or to shorten/redress the wires loop. Or to dampen it as I mentioned. Maybe your new Mosfet with less capacitance will make it less sensitive, but it may very well be it just picks something over the wires so try to address that as it is made now. I see much loose wiring in #5326 as it is in test configuration now. In any account make sure that when the whole configuration is assembled as a final system the layout is economical for wire loops and there are no waveforms.

Dr.H · 27th September 2012, 05:27 AM

Hi Salas, built Kazuo Ozawa version (5V) of your reg. A few observations:
1. I am using the reg to power a shunt LDR on my balanced pre-amp. I was not expecting much, given that it's just a shunt. The shunt reg is being fed by a "ALW super reg" which takes raw dc (18V) and down regulates it to 10V. Your shunt reg is then fed the 10V to produce 5V output.
2. I was surprised by the mid-range, which seemed more present/live/real using this reg in this position. I listened till 130am this morning and only went to sleep because I had to be up at 530....
3. Very keen to try the reg with the transport, DAC but....
4. I noticed at start-up that the shunts voltage output would initially spike to around 5.8-5.9V before quickly settling at 5.00V. Is this normal? I do not believe my DAC's can live above 5.5V....
5. Second q: What is the reg doing that makes it sound so good? Is it filtering noise in a way that other regs cannot?
6. Thanks for the circuit, great performer!

roender · 27th September 2012, 06:08 AM

Hi guys,

I strongly recommend to all SALAS shunt regulator builders to insert a small value resistor between positive output of bridge rectifier and smoothing capacitor. This resistor should drop around 1V and it's value will depend of the designed current value of regulator.

Kazuo Ozawa · 27th September 2012, 06:30 AM

Quote:

Originally Posted by Dr.H

4. I noticed at start-up that the shunts voltage output would initially spike to around 5.8-5.9V before quickly settling at 5.00V. Is this normal? I do not believe my DAC's can live above 5.5V....

Hi Dr.H, congrats.

It is curiously, in my case output voltage becomes up slowly and few minutes later becomes down slowly almost from 5.1V to 5.0V.

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26th September 2012, 03:47 AM	#5331
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Lets hope it will open the Mosfet gate less capacitive at least.

26th September 2012, 01:10 PM	#5332
Dr.H diyAudio Member Join Date: Apr 2002	So I am building REFLEKTOR (probably 5V and 10V) tonight. Any things to watch out for (layout, oscillations, etc)?

26th September 2012, 05:57 PM	#5333
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	If you got wire leads between rectification/main filtering to reg's input decouple the reg's input with 0.1u to 1u to ground. Tie the top shelf mirror BJTs face to face. Make it tight especially around the input CCS. Scope it for stability. Good luck.

27th September 2012, 01:03 AM	#5335
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	~50ns period, that is very high. 20MHZ. Also low in amplitude. Can it relate to any clock fundamental or harmonic since you use them for digital? Anyway put 0.1R at the +side on the DAC's particular power feed point and see if that waveform damps away.

27th September 2012, 02:01 AM	#5336
Kazuo Ozawa diyAudio Member Join Date: May 2006 Location: Japan	Your response is always quick. I thought as same what you guess. But when I moved the board by chance, the waveform became quiet like a ground noise. So I found it oscillates. In other words, I say Salas Reflektor is excellent regulator if it runs stably.

27th September 2012, 02:09 AM	#5337
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	This is very high a frequency, if it is just a matter of moving it maybe you need shielded coax and/or to shorten/redress the wires loop. Or to dampen it as I mentioned. Maybe your new Mosfet with less capacitance will make it less sensitive, but it may very well be it just picks something over the wires so try to address that as it is made now. I see much loose wiring in #5326 as it is in test configuration now. In any account make sure that when the whole configuration is assembled as a final system the layout is economical for wire loops and there are no waveforms.

27th September 2012, 05:27 AM	#5338
Dr.H diyAudio Member Join Date: Apr 2002	Hi Salas, built Kazuo Ozawa version (5V) of your reg. A few observations: 1. I am using the reg to power a shunt LDR on my balanced pre-amp. I was not expecting much, given that it's just a shunt. The shunt reg is being fed by a "ALW super reg" which takes raw dc (18V) and down regulates it to 10V. Your shunt reg is then fed the 10V to produce 5V output. 2. I was surprised by the mid-range, which seemed more present/live/real using this reg in this position. I listened till 130am this morning and only went to sleep because I had to be up at 530.... 3. Very keen to try the reg with the transport, DAC but.... 4. I noticed at start-up that the shunts voltage output would initially spike to around 5.8-5.9V before quickly settling at 5.00V. Is this normal? I do not believe my DAC's can live above 5.5V.... 5. Second q: What is the reg doing that makes it sound so good? Is it filtering noise in a way that other regs cannot? 6. Thanks for the circuit, great performer!

27th September 2012, 06:08 AM	#5339
roender diyAudio Member Join Date: Sep 2006	Hi guys, I strongly recommend to all SALAS shunt regulator builders to insert a small value resistor between positive output of bridge rectifier and smoothing capacitor. This resistor should drop around 1V and it's value will depend of the designed current value of regulator.