Parts Express DOTD 20-0-20 200W transformer $5

officeboy · 23rd March 2004, 09:26 PM

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.

Peter Daniel · 23rd March 2004, 10:01 PM

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).

Bill Fitzpatrick · 23rd March 2004, 10:37 PM

What do you mean 30-0-30? The PE page says it's 20-0-20.

Aunkst · 23rd March 2004, 10:59 PM

is 20-0-20 at 90va adequate for a LM3875?

officeboy · 23rd March 2004, 11:11 PM

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.

Peter Daniel · 23rd March 2004, 11:13 PM

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.

leadbelly · 23rd March 2004, 11:29 PM

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").

Peter Daniel · 24th March 2004, 01:47 AM

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.

Peter Daniel · 24th March 2004, 01:55 AM

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.

leadbelly · 24th March 2004, 02:29 AM

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.

23rd March 2004, 09:26 PM	#1
officeboy diyAudio Member Join Date: Nov 2003 Location: NW Washington	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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23rd March 2004, 10:01 PM	#2
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	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).

23rd March 2004, 10:37 PM	#3
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	What do you mean 30-0-30? The PE page says it's 20-0-20.

23rd March 2004, 10:59 PM	#4
Aunkst diyAudio Member Join Date: Feb 2004 Location: PA	is 20-0-20 at 90va adequate for a LM3875?

23rd March 2004, 11:11 PM	#5
officeboy diyAudio Member Join Date: Nov 2003 Location: NW Washington	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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