The simplistic Salas low voltage shunt regulator

[Kazuo Ozawa]

Salas, You pointed out correctly that I was worried before.
Simulation shows that wire loop effects to occur oscillation.

 

[Salas]

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!

Nice news. What output Mosfet did you use for that Reflektor? Any pics?
In my experience they don't jump up at start. Can you see with out the pre-reg? (And also listen without).

 

[Salas]

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.

I had used CRC with rather big R (4.7-10R) for pi pre filtering some times, what did you observe with a small one?

 

[roender]

I had used CRC with rather big R (4.7-10R) for pi pre filtering some times, what did you observe with a small one?

CRC dose not reduce peak diode current, hence switching noise and EMI

 

[Salas]

Ah OK you chased EMI better with RC. Did you use soft recovery diodes or normal ones?

 

[roender]

soft and very fast ... uf4007.
Also, using resistor right after the rectifying bridge it will unburden the diods for very high transients if a low ESR smoothing cap is used, which is good for the shunt but not for the bridge

 

[Salas]

Good diodes. Also BYV27 are nice in my experience. What you use the reg for?

 

[roender]

One 5V25 for Buffalo DAC pre-regulator, one 5V for SDtrans and two 15V for my I/V stage http://www.diyaudio.com/forums/digi...-v-stage-sabre-reference-dac.html#post3147840

 

[Salas]

Very nice I/V congrats.

 

[roender]

Very nice I/V congrats.

Thank you

 

[Salas]

Salas, You pointed out correctly that I was worried before.
Simulation shows that wire loop effects to occur oscillation.

Don't bother much with simulating the loop, just solve it practically to get the soft line with less or no sensitivity to movement and orientation. That nice Tek scope you got will be much faster than theory. Twisting the pair you change a bit and the sim goes off.

 

[Dr.H]

Hi Salas, will build a lower Voltage raw DC supply and measure/listen with that. The mosfets are exaclty those used by KAzuo (IRF9610, IRF640). I noticed that the resistor values he uses are very different to those you used in the intial REFLEKTOR.

Salas, why does the reg sound so good?

 

[Salas]

Thank you

Big caps I saw on the pics... 10mF? What kind of CCS settings?

 

[Salas]

Hi Salas, will build a lower Voltage raw DC supply and measure/listen with that. The mosfets are exaclty those used by KAzuo (IRF9610, IRF640). I noticed that the resistor values he uses are very different to those you used in the intial REFLEKTOR.

Salas, why does the reg sound so good?

OK the original Mosfets. We changed some resistors from the beta and in the Zobel we allow some tuning down to taste. The trimmer he had to use lower due to lower voltage region. And he did some YAM combinations for inventory reasons. Not that different.
Sounds good because we love it.

 

[roender]

Big caps I saw on the pics... 10mF? What kind of CCS settings?

Yes, 10mF. As per currents, for digital I used 100mA extra (450mA total for DAC,
330mA for SDtrans). For I/V stage only 70mA extra, 200mA total.

 

[Salas]

@ Dr.H
P.S. Put a small R as Roender recommends in your raw psu, he tested in digital app for minimal emi.

 

[Salas]

Yes, 10mF. As per currents, for digital I used 100mA extra (450mA total for DAC,
330mA for SDtrans). For I/V stage only 70mA extra, 200mA total.

Heavy for 1A diodes indeed. We usually put MUR TO-220s for 10mF. I measured some Nippon KZH, very low DF btw. Recommended.

 

[Dr.H]

0.3R? Between bridge and 1st cap?

 

[Salas]

Got to go, Roender will tell you more I am sure. See ya!

 

[roender]

0.3R? Between bridge and 1st cap?

Well, If your shunt is designed for 3.3A then yes, the resistor should have 0.3ohm. The voltage dropped over this resistor should be around 1V