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Old 17th January 2009, 03:17 AM   #1
kop89 is offline kop89  United States
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Default L values in Aleph2 CLC supply

Hi,

I am building this power supply for my Aleph2:

http://www.kk-pcb.com/power-2.html

However, I am going to replace each one of the 2x47000uF caps with 4x15000uF. So a total of 240000uF per channel.

1. Should I leave the L at 2.2mH, or do I need to change it? How do I determine the correct L value?
2. Same question as above for the 4.7uF MKP capacitor
3. I am not sure what kind of "L" should I use, can anyone recommend a Digikey or Mouser part number for question #1 above?
4. This seems like a dumb question, but I am not sure what is the difference between inductor, coil, and choke.

Thanks!
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Old 17th January 2009, 04:29 AM   #2
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Default Re: L values in Aleph2 CLC supply

Quote:
Originally posted by kop89
Hi,


1. Should I leave the L at 2.2mH, or do I need to change it? How do I determine the correct L value?
2. Same question as above for the 4.7uF MKP capacitor
3. I am not sure what kind of "L" should I use, can anyone recommend a Digikey or Mouser part number for question #1 above?
4. This seems like a dumb question, but I am not sure what is the difference between inductor, coil, and choke.

Thanks!

1. 2.2mH is fine. Each channel Aleph2 draws 300W, you need big inductors. I'd be more concerned about wire gauge, 14ga or lower....the larger they are, the more expensive they are. You can also make your own.

2. High frequency PS bypassing, 4.7uF MKP is standard. I built my Aleph 5 with/without them, personal preference I guess.

3. Not sure about DK, or Mouser. I'd check PartsConnexion, or PartsExpress. Solen makes nice large inductors, $$. You can just as easily use large power resistors in place of the inductors, say 0.22R/25W. They serve the same purpose (reducing ripple), and they're cheaper.

4. Coils, Chokes etc are inductors . There are various types/sizes of course. For this particular power supply, you'll want to use large "air core" types.
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Old 19th January 2009, 06:06 AM   #3
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I remember that someone (maybe even Papa Zen Master himself) liked the Erse inductors (available from http://www.zalytron.com). I haven't done a lot of shopping, but the price seemed to be pretty fair. (And, no I am not affiliated with zalytron, and I do not intend this to be a shameless plug.)

I also have a related question for "someone who knows what they're doing". In my case, I'm collecting parts for a F5 and I want to try it with a CLC as well as a CRC PS. If the original CRC filter uses four 0.47 Ohm resistors in parallel (~ 0.12 Ohm), which inductor should I choose. I believe that Papa recommended 0.2 mH in the past, and what papa says is good enough for me. But... The Erse 14 Ga, 0.2 mH inductor has a DCR of 0.08 Ohm, while the inductor corresponding to 0.12 Ohm is 0.4 mH. Where's the trade-off (not considering cost, size or weight)? Do I benefit more by increasing the inductance to match the original resistance, or by using the 0.2 mH part and decreasing the resistance over the original (F4) PS circuit?

Thanks,
Looney
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Old 19th January 2009, 12:36 PM   #4
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I noticed a change for the better going from CRC to CLC, although I couldn't exactly tell what it was. Nelson has even said that he preferred CLC, but couldn't exactly say why. Ideally you want an inductor with zero resistance. Higher resistance, bigger voltage drop, lower voltage to the amp. The difference between 0.08 vs 0.12 is negligible, I wouldn't get too caught up in getting the exact R value. I'd go for more inductance, I suppose its analogous to using an engine with more torque. If you use a variac before the transformer with a slightly higher voltage rating, you have the freedom of testing various PS configs and the ability to dial in the exact voltage. I'm currently using CRCCLC for my 3 amp Zen, with the variac, I can vary the voltage from 20V-45V, with good results.
-john
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Old 19th January 2009, 04:27 PM   #5
kop89 is offline kop89  United States
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Default Re: Re: L values in Aleph2 CLC supply

Quote:
Originally posted by MEGA-amp



3. Not sure about DK, or Mouser. I'd check PartsConnexion, or PartsExpress. Solen makes nice large inductors, $$. You can just as easily use large power resistors in place of the inductors, say 0.22R/25W. They serve the same purpose (reducing ripple), and they're cheaper.

4. Coils, Chokes etc are inductors . There are various types/sizes of course. For this particular power supply, you'll want to use large "air core" types.
Here are the list of 2.2mH air-core inductors available at Parts Express:
1. Jantzen 15 gauge, DCR 0.52 ohms (P/N 255-432) - $25.12 each
2. Jantzen 18 gauge, DCR 0.84 ohms ohms (P/N 255-268) - $11.65 each
3. Erse 14 gauge, DCR 0.33 ohms (P/N 266-375) - $26.36 each

I am using a 100VA transformer with 2x35V secondaries. Would it be fine to use #2 above? I am worried about the voltage drop.

Thanks
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Old 19th January 2009, 04:51 PM   #6
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100VA? NO WAY!! 300Watts draw per channel, requires, at the absolute minimum 600VA per channel. The voltage is fine. I would suggest, possibly 800VA minimum per/ch. The bigger the transformer, lower the voltage drop when it loaded, better regulation.

The voltage drop across the inductor isn't really a big deal. No big deal if your input voltage is not exactly as stated in the schematic. The 18ga inductor will not work, they will get too hot, and quite possibly may smoke you out of the room.....14ga minimum.
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Old 19th January 2009, 05:46 PM   #7
kop89 is offline kop89  United States
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Quote:
Originally posted by MEGA-amp
100VA? NO WAY!! 300Watts draw per channel, requires, at the absolute minimum 600VA per channel. The voltage is fine. I would suggest, possibly 800VA minimum per/ch. The bigger the transformer, lower the voltage drop when it loaded, better regulation.
Ooops sorry... missing one zero there. I meant ONE THOUSAND VA.

Another question: whay would you recommend air-core inductors, instead of something like this:

http://www.parts-express.com/pe/psho...number=266-906

This is lower-cost and very low DCR.

Thanks!
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Old 19th January 2009, 06:17 PM   #8
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You can try them. I believe an individual here used them in his AlephX, but i think he mentioned, that they were saturating .

More importantly, a quote from that link:

"In electronic circuits, transformers and inductors with ferromagnetic cores operate nonlinearly when the current through them is large enough to drive their core materials into saturation. This means that their inductance and other properties varies with changes in drive current. In linear circuits this is usually considered an unwanted departure from ideal behavior. When AC signals are applied, this nonlinearity can cause the generation of harmonics and intermodulation distortion. To prevent this the level of signals applied to iron core inductors must be limited so they don't saturate. To lower its effects, an air gap is created in some kinds of transformer cores."



Not that you can't use iron core inductors, but for the size needed for this PS, you'd be better off with air core. Or you can dispense with the inductors, and use resistors. The Aleph circuit is very well designed, as long as you have large transformers(which you do), and a healthy supply of capacitance(don't know), The performance of inductors vs resistors in the PS is minute IMHO. Nelson didn't use L or R in the commercial version. My various Aleph versions were supplied with 400,000uF per/channel. If budget is a concern, and you want good performance, use tons of capacitance, save a buck or two and use resistors in the PS to reduce the ripple.
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Old 19th January 2009, 06:38 PM   #9
kop89 is offline kop89  United States
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Thank you for your advice. I think I'll go with 14ga Erse air core inductors ($15.58 at Zalytron):

If I would like to use bleeder resistor for the power supply caps, what value and watt rating would you recommend?

I put the PS schematics again for reference - I assume I need to use two bleeder resistors per channel, one connected between "+" to ground, and the other one connected between "-" to ground, correct?

http://www.kk-pcb.com/power-2.html
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Old 19th January 2009, 07:45 PM   #10
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Quote:
Originally posted by kop89
I assume I need to use two bleeder resistors per channel, one connected between "+" to ground, and the other one connected between "-" to ground, correct?
Not absolutely necessary, but good practice. Generally 10K/3W.

Aleph2 Project
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