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Old 22nd December 2002, 03:35 AM   #51
ungie is offline ungie  Canada
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Default Pliron Surplus Trannie?

Has anyone investigated using the surplus Plitron trannie that was mentioned on page 2 of this thread? It's 1500VA, 4x18V @ 21A. It looks to me that this would work well for a stereo Aleph-X with CRC filtering. The question I would like to ask the gurus is this:
Assuming I purchase 4 of the r-theta heatsinks from the group buy, will this be sufficient to handle an 18-20 DC supply rail? If not is there anything that can be changed, ie. biasing resistors to reduce the output device dissipation?

Andrew
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Old 22nd December 2002, 11:36 PM   #52
hifiZen is offline hifiZen  Canada
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Just a quick report:

I've had the chance to use my VM trannies now, and I have to say, these things are really nice!

...oversized core, magnetic shield included (!), consistent windings and wrapping, and very good quality lead wire. I couldn't be happier with these trannies.

These trannies are just over 5 inches in diameter (maybe 5 1/8).

My Aleph-X configuration is to use 11.5V rails, at 5A total bias per channel. So I ordered a trannie with 11V secondaries, and use a single bridge per channel, made from discrete Shottky rectifiers (more efficient than other types), through a 62mF-0.25R-100mF CRC filter. At the moment, I'm powering the amp directly from the first 62mF stage, and have found that the variac output needs to be around 99V to give me 11.5V rails. I've got about 430mV ripple on this cap. Accounting for R losses when I apply the CRC filter, the 11V secondaries look to be just about right for maybe 12V rails or slightly higher, so it appears I've made a good choice for secondary voltage. Switching to a different rectifier type and/or increasing the R value will yield lower rail voltages.
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Old 23rd December 2002, 02:03 AM   #53
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Default Re: Pliron Surplus Trannie?

Quote:
Originally posted by ungie

Assuming I purchase 4 of the r-theta heatsinks from the group buy, will this be sufficient to handle an 18-20 DC supply rail? If not is there anything that can be changed, ie. biasing resistors to reduce the output device dissipation?

Andrew
I'm using two of those sinks per channel with 15V rails and 6A bias. If you increase the rails the heatsinks will be rally hot and might not handle the dissipation. You can always reduce the bias to get less heat. (I'm assuming you want to use 2 sinks per channel).
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Old 24th December 2002, 01:49 PM   #54
ungie is offline ungie  Canada
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Default Peter:

What temperature are your heatsinks running at on your Aleph-X?
Is there a safe maximum, assuming that Tj is safe?

Andrew
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Old 24th December 2002, 02:29 PM   #55
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Around 55 deg. You can probably go as high as 65deg without much trouble.
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