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Old 20th March 2005, 01:47 AM   #1
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Default trying to find a torrid

I'm working on an OPA549 bridge/paralel amp. Right now, it uses 4 OPA549 chips, but the board supports up to 8 of them in case I ever need more power or ability to drive low impedence speakers.

So, I'm assuming that with 4 chips into a 4 ohm speaker, It'll be pushing about 300-400W, so I'm thinking a 600-800VA transformer, to have plenty of power if I ever decide to add more chips.

OPA549s also need a +/-30VDC supply or lower, so I'm thinking 40VCT.

Where can I find a 40VCT 600-800VA torrid transformer, for a reasonable price (hopefully around $30-40), because I still have to buy heatsinks and the materials to build a case.

I don't care if it is new or used, as long as it works and is of decent quality.

Thanks!
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Old 20th March 2005, 01:53 AM   #2
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Why not ask where you can get it for free? Since you're dreaming you may as well make it the best dream possible.
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Old 20th March 2005, 02:29 AM   #3
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Well then what is the largest wattage I can get for that price?
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Old 20th March 2005, 03:13 AM   #4
Moose is offline Moose  Canada
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ebay

or try apex jr. They have some 21-0-21 toroids, which are $12.95 for somwhere around 100VA so you could get 4 of those.
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Old 20th March 2005, 03:37 AM   #5
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Default Re: trying to find a torrid

Quote:
Originally posted by soundNERD
I'm working on an OPA549 bridge/paralel amp. Right now, it uses 4 OPA549 chips, but the board supports up to 8 of them in case I ever need more power or ability to drive low impedence speakers.

So, I'm assuming that with 4 chips into a 4 ohm speaker, It'll be pushing about 300-400W, so I'm thinking a 600-800VA transformer, to have plenty of power if I ever decide to add more chips.

OPA549s also need a +/-30VDC supply or lower, so I'm thinking 40VCT.

Where can I find a 40VCT 600-800VA torrid transformer, for a reasonable price (hopefully around $30-40), because I still have to buy heatsinks and the materials to build a case.

I don't care if it is new or used, as long as it works and is of decent quality.

Thanks!

Apexjr has plenty of trafos in stock, including the 42vct. However, I don't think it'll provide the current you need. However, you could use a pair of their Signal EI cores (The BL1752).. Each one is a 24vct transformer when hooked up to a 115v line. I think each one is roughly 200VA. They're $8/each, and they're monsters -- i have 3 or 4 laying around here myself. You can also try calling Steve.. Sometimes he has one or two that aren't listed on his site, and he might have exactly what you need.

Ebay is another good bet. I've picked up some pretty nice toroids there pretty cheaply (including a dual 22v secondary 300VA for $15 + shipping).

Otherwise, check the usual places like Parts Express and look at their avel lindberg line. They have a dual 25v secondary 330VA avel for $47, the 500VA is $60.
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Old 20th March 2005, 12:36 PM   #6
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Thanks everybody.

I'm looking at that ebay one Moose suggested.

Wouldn't 32VCT be a little too low, even though it is a 300VA? Could anybody approximate the power I would get from this amp with that transformer?

edit: looking some more and found this:

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW

2x24V at 21A per coil. My only worry is will 24V, after rectification, ever exceed 30V?

another edit: forget it, It's not worth it with $20 shipping. Either way, I'd still like to know if the voltage is too high.
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Old 20th March 2005, 04:05 PM   #7
Alcaid is offline Alcaid  Norway
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yes, it will exceed +/-30v.

Vout = VAC * sqrt(2) - (Diode Drop)
Vout = 24 * 1.4142 - 3
Vout = 30,94V

And the trafo will deliever higher than 24VAC with lower loads.

You're dreaming about the price for such a big toroid.
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Old 20th March 2005, 06:47 PM   #8
Apex Jr is offline Apex Jr  United States
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Default Transformers

I do have 3 each of a 42Vct at 250Va-300Va in stock
there $27.50 each. 70 Vct 600 Va not yet listed on
the website but pictured on the marketplace, "Audio
Vendors Bazzar" there $29.95. And plenty of the
BL 1752's and there $7.95ea
Steve @ Apex Jr.
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Old 20th March 2005, 10:57 PM   #9
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steve, sent you an email.

Whats the Audio Vendors Bazzar?
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Old 20th March 2005, 11:05 PM   #10
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It's a forum on here where folks like Steve, BrianGT and Peter Daniel list their commercial products for sale. I think its in the "Market Place" forum off the main page.
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