My take on a discrete shunt voltage regulator

[HiFiNutNut]

Thanh, it should be Ikoflexer to answer your question. But the experts have been silent for a couple of days now. And I have my questions pending for answers, too.

I think the wima mkp10 2.2uF is good. You may try it without the padding resistor and report back. I have not done that yet.

When thinking about how my 1.1uF can be successful - the regulator has a low impedance until some hundreds of kHz. Below that an output cap / bypass cap would have little use. Since the frequency is high, we probably don't need a large cap in there. I am now thinking about perhaps a 0.1uF might do, as Ikoflexier suggested reading the post of JCarr and in his he used 0.1uF. I have not read the Blowtorch thread so I don't know what circuit JCarr referred to.

With regards to silver mica, I have a few of them but these days don't think of using them. They are good and linear and can work at high frequencies. But usually the frequency range concerned would be well above 1MHz region in which they may have an advantage over the ordinary MKP. But we can't hear that high. I would be happy to use a ceramic. I also read that an experienced guy adviced that silver mica should not be used for DC but AC only, because in a few years of time the silver mica would create a large leakage, or some other probelm which I can't remember any more.

Have you built a v1.5 or v2 yet? Used in analogue or digital circuit? If for digital, I would not worry about the output cap as much.

[Salas]

Try polysterene.

[Melon Head]

What do you think about this one?
LCR COMPONENTS|FSCEX 33000PF 1%63V|CAPACITOR, 33NF, 63V | Farnell Australia

[ikoflexer]

Sorry guys, when it comes different capacitors and such I can't be of much help, you guys are more versed in voicing.

[Melon Head]

Just having a look at this data sheet
http://www.farnell.com/datasheets/30215.pdf
The mixed dielectric are capable of 10,000V/us.
Is dV/dt important here, what are we looking for in this location.

[Salas]

Originally Posted by thanh1973

What do you think about this one?
LCR COMPONENTS|FSCEX 33000PF 1%63V|CAPACITOR, 33NF, 63V | Farnell Australia

Cool.

[ikoflexer]

Originally Posted by HiFiNutNut

Ikoflexer, Could you explain the purpose of C3 in your schematic? I am wondering if it has a sonic signature on the regulator or not.

OK, just got back from groceries shopping (what a pain!). Anyway, C3 has a funny role here. Some people call it a bootstrap capacitor. It boosts the psrr quite a lot. I don't have any comments about how it affects the sound.

[ikoflexer]

Originally Posted by HiFiNutNut

I replaced the output electrolytic capacitor with 0.5R + 4 x 2.2uF (MKT) ||. The sound further improved. The difference is not small.

Tomorrow, I will try 0.5R + 1.1uF (MKP). If it does not work, I will increase the uF until it works, otherwise,, I will reduce the R to 0.2R. If it still works, I will remove the R. If it still works (I don't think so), it will stay that way. The cap ESR is only 0.003R. Some of these will first be tested with no load because I worry about a severe resonance may kill the expensive OPA627 (or not?)

Good idea to test with a passive load first. I too always do that. It's different when you build something out of a kit, that's been built by hundreds of people and such. Here we're on the bleeding edge, so to say. So far I managed to build a prototype of each of these regulators and made sure it works as expected, but these are rough tests. I've had so many promising ideas for improvement lately that I couldn't stop at one version to test very subtle things like, say, the proper capacitor in a certain position. So I kept on moving. Hopefully I'm converging soon on a version and then start addressing these subtle issues. But you guys are already ahead, so I'll have a lot of catching up to do.

[HiFiNutNut]

Originally Posted by thanh1973

What do you think about this one?
LCR COMPONENTS|FSCEX 33000PF 1%63V|CAPACITOR, 33NF, 63V | Farnell Australia

I used quite a few of these in my active line level filter circuit and they are great. They are 1% so they fit my application very well.

Polystyrene sounds very good. Only about 3 weeks ago I compared a pair of 1uF polystyrene to the 1.1uF Vishay blue box as the output cap of my opa627 buffer (for test only, otherwise I don't use an output cap) and there are tiny differences but they are at the same performance level. That pair of polystyrene sounded maybe a touch more musical but also a touch "too much" high frequency sparkle therefore I still choose my 1.1uF. It may be more system dependant rather than one is better than the other.

If you look at the technical specs, polypropylene is better in some parameters and polystyrene is better in others.

[ikoflexer]

Some people use capacitor multipliers before the regulator. Something like this can improve the psrr even more, at the cost of a few parts and a voltage drop of a few volts. I haven't tried it yet in a real circuit, it's just to throw the idea in for discussion.