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Old 31st October 2003, 08:42 AM   #1
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Default SOZ PSU & Fairchild MOSFET

Although some have dissuaded me not to do the SOZ as first time build, my previous experiences lead me to believe that i'm capable, and I feel pretty confident that I can tackle this project. Plus once I make my mind up there is little one can do to deter.
But some of the terminology is eluding me.
I plan on building dual monoblocks @ 35-40 w/each.
Would a Piltron 1500V with 50V dual secondaries @ 13A be sufficient? Or do i need one secondary. The exact model is #12703320. I am assuming i need it to be center tapped if dual secondary. Maybe 60 V secondaries? For capacitors i'm looking at 4 @ 47000 uF a piece, is this ideal? For the Mosfet I would like to use the Fairchild FQA70N15. The voltage is rated at 150V vs. the IRFP244's 250V, is voltage difference ok, and does anyone have any experience with this type of Fairchild MOSFET? As in Mark Finnis's SOZ he modified the circuit for dual FETs on each limb of the circuit, I like this idea, and since its proven and approved by Nelson Pass himself (Mark Finnis's SOZ) I would like to implement it. I am assuming this adds durability and redundancy to the circuit. I know i have to tackle such things as ridiculous sized heatsinks, the right choke, thermistors etc. With my limited audio knowledge i've been picking up information about circuit intracacies along the way to help me better understand the whole process. Slapping something together hastily and plugging it in is not what I have in mind, so I strive to learn. Although sometimes running around like a mad scientist can be fun, i'd like to eliminate the possibility of severe financial burden and build this thing correct before a penny is spent.

John Hepple
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Old 6th November 2003, 01:18 AM   #2
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Default too terrible

50vac secondary is too high for 30-40w/soz . I think you only need 36vac to get 50vDC. if you want to build 40w soz , the soz will dissipate 1000w for one channel ,so your transformer 1500w
wiil be small .above 2000w be better for one channel. by the way,
you will need 70kg heatsink for soz without fan . .
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Old 6th November 2003, 01:59 AM   #3
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John,

Have you considered the Zen Lite as your project. This Son of Zen amplifier is costly to build because the high power resistors are expensive and must have a heat sink. The Zen Lite uses normal incandesent light bulbs as the high power resistors and do not require heat sinking. If that does not suit your taste maybe the Penultimate Zen would be a good start. I am building one right now. The boards are available from Pass Labs for $50 and are of extremely high quality. The parts are much less expensive and the power supply does not have to be near as hefty. I am enjoying building the Penultimate Zen. I will post some pics soon. My next project will be an Aleph 5 or lower power Aleph X. I am pretty new at the DIY stuff and I have found that it is a good vehicle for me to keep my skills sharp having gotten my EE degree over 25 years ago. I am in awe at some of the stuff the guys on here have built. If my Penultimate Zen turns out half as good as some of the projects posted here I will consider it a success. Best of luck to you.
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Old 6th November 2003, 04:14 AM   #4
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Just for fun, I'd recommend locating and pricing the heatsinks you'll need before going any further. Either lack of availability or high cost is likely to be quite persuasive.
Or you could go water cooled, but that's another thread entirely.

Grey
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