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Old 23rd March 2004, 10:26 PM   #1
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Default Parts Express DOTD 20-0-20 200W transformer $5

http://www.partsexpress.com/pe/pshow...30&dotd=032304

Figured some here might be interested.

Esp with all the gain clone kits being sold and all.
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Old 23rd March 2004, 11:01 PM   #2
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With specified dimensions, it can't be 200VA transformer.

I have exactly same size unit from Frost and it is 90VA, which seems more appropriate for that size (its 30-0-30 VAC BTW).
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Old 23rd March 2004, 11:37 PM   #3
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What do you mean 30-0-30? The PE page says it's 20-0-20.
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Old 23rd March 2004, 11:59 PM   #4
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is 20-0-20 at 90va adequate for a LM3875?
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Old 24th March 2004, 12:11 AM   #5
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Well an LM3875 can't pull more then 5A. With a 4ohm load that's what you have at max power. It's about 3A with an 8ohm load.
(btw this is max power consumption at 29DCV)

So you would be better off with a 120va transformer per channel but I think you would have no problems getting this to work.
I have a GC that uses 1 75va per channel, but at normal listening levels only draws 0.3A from each secondary.
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Old 24th March 2004, 12:13 AM   #6
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Quote:
Originally posted by Bill Fitzpatrick
What do you mean 30-0-30? The PE page says it's 20-0-20.
My Frost is like that.
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Old 24th March 2004, 12:29 AM   #7
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Quote:
Originally posted by Peter Daniel
With specified dimensions, it can't be 200VA transformer.

I have exactly same size unit from Frost and it is 90VA, which seems more appropriate for that size (its 30-0-30 VAC BTW).
Peter, how sure are you about this? I was always under the impression that the guidelines for rating transformers on dimensions or weight were very broad, like +/- 50% or more (I'm not trying to be argumentative, I know a lot of surplus parts are spec'd by "eye").
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Old 24th March 2004, 02:47 AM   #8
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I've seen many transformers, and 200VA can't be that small.
I just happen to have few 200VA rated EI transformers and they are twice as big.

Of course I may be mistaken, but I rather doubt it.
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Old 24th March 2004, 02:55 AM   #9
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Quote:
Originally posted by Aunkst
is 20-0-20 at 90va adequate for a LM3875?
The amp will work with that, but you might use separate transformers per channel.
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Old 24th March 2004, 03:29 AM   #10
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Quote:
Originally posted by Peter Daniel
I've seen many transformers, and 200VA can't be that small.
I just happen to have few 200VA rated EI transformers and they are twice as big.

Of course I may be mistaken, but I rather doubt it.
Yeah, I guess I buy that. I have a couple of those that I bought last year from PE. They are slightly larger and heftier than other 100 VA xfrmrs I have, but are dwarfed by the 300 VA units I own. But at $5/each, even using 2/channel looks mighty good, if you can live with the cosmetics.
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