The simplistic Salas low voltage shunt regulator

[Salas]

My experience says that you never know sonics before you listen. For long in different systems, secures conclusions. All well with foreconclusions, but I still consider everything as ''wishful thinking'' until I solder something, won't smoke for 2 days power on, and enough people say its a plus in enough systems. Even if I have a good score in planning I am still reserved. Have experienced many akward things. Because there is aways that something that maybe lurking and manifests after. Of course with the benefit of hindsight all is very explainable. Many film over electrolytic bypasses are a disaster for instance. Just ask the GC snubber crowd.

[HiFiNutNut]

I agree. Usually bypass inappropriately causes more problems than it can resolve. This happens more on rail bypass where higher inductance cause ringing in the RLC circuits. In the C2 position, however, I can not see much issue. Even in rail, in my tube preamp, the sonic improved dramatically after I bypass the 300uF/450V electrolytic with a 20uF/630V MKP.

[Salas]

Then try it. It looks like it will be better. But I just can't say before. I only talk certain or recommend things that I have made and used. That's my rule. Imagine the long film and bulk and legs and boosted BW of the film one picking and adding RF noise directly on the Vref for instance. Can foresay?

[HiFiNutNut]

I have just got Spencer's note that 100 x 2SK170 was sent today and would arrive within 2 weeks.

While Futurlec sent me a cancellation note last week, and they even gave the transaction ID with which they credited my credit card, no money has been deposited into my credit card, and today a parcel from Futurlec arrived!

In that order, I had only 18 x 2SK170.

I was going to do the Idss tests using the method recommended, but I could not pull out the lead plug from my DMM after 4 years without doing current measurements (I always did voltage measurements to work out currents), even with heavy machine tools. So I connected 14VDC in series with a 100R resistor and then the JFET (g connected to s). Measuring the voltage across the 100R and dividing the number by 100 give the current. Let me know if this method is not good.

I got the following readings converted to mA:

(1) 7.34
(2) 7.51
(3) 8.05
(4) 8.17
(5) 8.39
(6) 8.44
(7) 8.58
(8) 9.14
(9) 9.88
(10) 9.92

The rest are not good, reading from as low as 3mA-6mA and as high as 10mA-18mA.

I read that they should be 7-8mA. So I have only two that are qualified. For +/-13V rails,
can I use (1) for CCS+, (2) for the CCS -, (3), (4) for shunt+, (5) and (6) for shunt-?

Or perhaps I should use (5) for CCS+, (6) for the CCS-, (1), (2) for shunt+, (3) and (4) for shunt-?

If so, I won't wait for the batch from Spencer and can get it done once I get the remaining a few parts.

Regards and thanks,
Bill

[Salas]

Use 9.88 & 9.92 under the 3 Leds. 8.39 & 8.44 for 550,560 active loads.

7.34 & 7.51 under Vrefs

Good luck.

[HiFiNutNut]

Thanks, Salas.

Hey, what is the time in Greece? You never sleep?

[Salas]

13:28 noon

[AndrewT]

if you add a 1k pot (or maybe a 500r pot) in series with the 100r current measuring resistor, you can adjust your fixed 14Vdc supply to give Vds of 10V. That lets you test to the manufacturers specified voltage.
The pot should be set to vary between 200ohm and 400ohms to drop the extra ~3.1V that you need to achieve that 10Vds.
You will reduce slightly the power dissipated in the FET and thus reduce it's temperature. This will help move the FET temperature towards the Tc=25degC specification temperature.

You will find only a small difference in your Idss values and I think your will find that most will remain in the same order of ranking.

[HiFiNutNut]

Andrew,

Thanks. I bear that in mind when I do my next round of test of 100.

For now, it is 9:41pm Sydney time. I am not going to bed yet but will need to get my 3 kids to bed. Will log back in tomorrow.

Regards,
Bill

[jkeny]

Bill,
I had the same issue with SK170s I got from Futurlec - readings all over the range - let us know how well they work or not!