oil chokes

[richidoo]

Excellent!! Thanks a million Maxamillion!
Rich

[mgalusha]

'Tis amazing what chokes can do for a power supply. I modified a friends Cyber 845 amps as he found they had too much noise. Since they chose to use DC for the 845 filaments, I changed it from just a bridge with a 10mF cap to a CLC with 10mF/4H/10mF. The DCR on the choke was about .156R, so it dropped the voltage a bit but it was a little high to start with and ended up almost dead on the 10V the 845 is supposed to have.

While they measured quieter on the bench I didn't get a chance to listen to them before he picked them up so I was a little concerned. I received a call that went something like "what did you do, these are not the same amps". He was delighted, which of course was a huge relief.

I am on the lookout for some oil chokes to play with for my stuff but even 'dry' chokes can work wonders. I wholeheartedly agree with Maxamillion about using Duncan's PSU sim. 
 
Duncan Amps PSU sim charts. First is stock, second is CLC. Scale on left is volts.

[rollo]

  Ok then Mgalusha, You got my Nervosa perking you devil. What about the Cyber 211 PS ? Same thing just a different voltage for the 211 tube ? just installed Jensen .47 PIO coulping cap of driver  to 211 and so far a different amp. Liking anything oil these days.


charles

[richidoo]

Impressive demonstration Mike. Adding one coil and another cap gives almost 10,000x reduction in heater noise. I often think of coils as expensive tweak, but that's getting into regulator territory. How big was the coil? The coils Max used in his preamp look pretty big. Do they have a magnetic core?

[Maxamillion]

Those chokes have a C core of Lundahl's construction; they don't state what the details are. It's most likely silicon steel with maybe some nickel thrown in. They also have the same model with an amorphous iron core, but they cost $280 each and I'm not sure it's worth it in a power supply. I do use their amorphous cobalt core output transformers in my preamp, though - outstanding!

Their chokes use two coils on the single core, which allow them to be hooked up in several different ways, such as series for highest H, parallel for lower H but more current capability, and in a special common-mode noise reduction mode where one coil is in the + leg and the other is in the - leg. The latter is supposed to give some CM noise reduction while retaining the same high H value as the series hookup.

In my preamp I have the first choke in series and the second in CM hookup, in a CLCLC configuration.

[richidoo]

And you could simulate all those variations on Duncan's app? Neat!

Lundahl importer and tube amp designer Kevin Carter lives in the next town over. Funny I haven't met him yet. Good stuff.

[Maxamillion]

Well, using PSUD I only simulated with the series configuration, since both ways measure the same inductance. I had no intention of using the parallel hookup as I had plenty of current capability as is.

[mgalusha]

  Ok then Mgalusha, You got my Nervosa perking you devil. What about the Cyber 211 PS ? Same thing just a different voltage for the 211 tube ? just installed Jensen .47 PIO coulping cap of driver  to 211 and so far a different amp. Liking anything oil these days.

Charles, I bought 4 of the chokes just haven't gotten time to work them into my 211's yet. The 211 uses the same filament supply at the 845.

I have the AmpOhm copper foil/paper in oil caps in the amps, I like the results. I also installed Cinemag input transformers so could have a real balanced input and kill the ground loop caused by 25ft interconnects.

[mgalusha]

Impressive demonstration Mike. Adding one coil and another cap gives almost 10,000x reduction in heater noise. I often think of coils as expensive tweak, but that's getting into regulator territory. How big was the coil? The coils Max used in his preamp look pretty big. Do they have a magnetic core?

Rich, in my case they were just regular old Hammond chokes. Unfortunately I just demonstrated that running a PSU simulation at work without the real data in front of me is dumb... I put 4H as the inductance but the 4 was the current rating of 4A.   The real value was 15mH. I reran the sim and it's attached. Not quite so good but still works out to about 20mV p-p, so still about 1000x better than before. I used the biggest iron I could physically get in the chassis. These were Hammond 159ZG, $26 each from radiosupply.com.

Mike

[richidoo]

Very cool. Thanks Mike.

For heater impedance is no biggie, but for B+ how do the more complex passive filter schemes (with coils) affect source impedance?

What are the sonic differences of a coil filtered B+ vs. a super regulator like Hynes or Belleson. I know the technical differences, but wondering if anyone has compared the two for sound quality / emotional effect in a preamp or source.
Thanks

[Maxamillion]

That's one reason I used the LL1638's. 10H inductance, up to 215mA DC current, and only 36ohm DCR. My stock 10H coil was 165ohm DCR. I was able to shoehorn in 2 Lundahls, double the inductance, improve the filtration by a factor of more than 100, and reduce the DCR by 93 ohms.

If my preamp didn't have a phono stage (and thus higher DC current), I could have gone for the LL1673, which can give you 20H in a single unit with 60 ohms DCR, but saturates at 140mA.

[rollo]

 OK then Mgalusha, You got my Nervosa perking you devil. What about the Cyber 211 PS ? Same thing just a different voltage for the 211 tube ? just installed Jensen .47 PIO coupling cap of driver to 211 and so far a different amp. Liking anything oil these days.

Charles, I bought 4 of the chokes just haven't gotten time to work them into my 211's yet. The 211 uses the same filament supply at the 845.

I have the AmpOhm copper foil/paper in oil caps in the amps, I like the results. I also installed Cinemag input transformers so could have a real balanced input and kill the ground loop caused by 25ft interconnects.

Thanks for the response so then [ just to make sure] what value choke should I buy for the 211 ? Just installed Jensen PIO, copper at the 5687 coupling position and had a V-cap Teflon at the input, liking it so far, trying a new Deuland ' "Alexander" PIO next.
  BTW what 211 tube are you using ? Using GE 4TC with Tungsol 5687 driver and Matushita  6DJ8 as input. Have you tried the Pavane 211 ?


charles