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Old 5th June 2003, 03:14 PM   #1
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Default Building a 5 channel BLS

Right, as part of my ongoing efforts to build my ultimate Hi-Fi/HT rig I need to get 5 channels of unbalanced pre balanced to feed into my active crossovers. As I have a 300VA 55-0-55 traffo and lots of other suitable bits in my spares box, I obviously thought of breaking my PassLabs virginity and building a BLS.

So, the questions-

1) Would I be better building a psu stage for each pair of amps, as per the normal design, or can I upgrade the existing PSU to provide the required power?

2) Is there any benefit in providing more capacitance on the PSU rails, or is 10000uf more than sufficient.

3) I was looking at the Onsemi website a few days ago, and I noticed they have a new range of mosfets, has anyone used them yet? I'm just wondering if they would sound any better.

4) Anyone got any specific component recommendations for the BLS?

Thanks a lot

Al
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Old 5th June 2003, 04:26 PM   #2
Mad_K is offline Mad_K  Norway
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1) 1 psu (in your case regulator; just one toroid right?) per channel is best (the pass transistors gets HOT). Or you can scale it (ZV3.pdf)

2) 10000uF is what I use for C101/102 (really overkill, I know..) and 1000uF for C103-105, else as original , as I recall Nelson recommends to double all C's.

3) try the IRF510 -very nice.

4) 750/1500 ohm: Caddock MP915/930. Good, low impedance C's. Ultrasoft diodes. Elna/DACT I/P selector, DACT attenuators/homebrew with Elma/ 0,1% resistors.
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Old 6th June 2003, 12:45 AM   #3
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Thanks for the reply K

So, I need to build a reg stage for each channel, fair enough, it probably keeps the isolation between channels.

But, do I need the bridge and the big caps per channel, or can I have a big reservoir bank and feed the seperate pass regulators on their own boards. I know what the purist answer would be, but I am not well off at the moment, and I need to be in the Frugalphile (tm) frame of mind!
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Old 4th July 2003, 09:07 PM   #4
Mad_K is offline Mad_K  Norway
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whoops! sorry for late answer, but I didn't notice your reply until now. I would make one (dual) bridge and a pair of bigguns (or better CRC or CLC). Then you make one reg per channel (without b101/b102). I would recommend to toss in a 10-220uF for c101/b102 though.

I would take: toroid, dual rectifiers (StealthTM from Fairchild), CRC (10000uF*/10 Ohm 5W (wirewound)/10000uF*(=Rifa PEH200, 100V), and 1000uF* for C101-106, but this is overkill.

Having a reg for each channel helps to minimize crosstalk between channels.

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Old 5th July 2003, 08:58 PM   #5
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Thanks Mads

Project is temporarily on hold due to possible house move, and therefore shortage of funds, but it is high up the list for when I get settled down again.
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