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Old 6th June 2004, 12:29 AM   #31
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Hi,

Bricolo,

Quote:
-the amp's transformer becomes quiet -> DC on the line (that causes the core to saturate)
Let's suppose it is DC on the line for a minute and you won't be able to keep your friends' isoxfmr. What can you do?

1/ You could buy a new one in which case I'd choose one with an EI core or better, NOT a toroidal one, with an electrostatic shield that you connect to Earth.
Chosing one with a higher current rating will have a better chance to run cooler if you're lucky. Most xfmrs heat up due to copper losses in the wires.

2/ You could build a DC blocking circuit as explained on Thorsten Loesch's website and this one:

DA BLOCK.

Watch the diode and cap polarities, follow all the necessary safety precautions and it should work.

3/ if you think of investing in an isoxfmr, think 5KVA, not 500VA if you plan to run the entire system from a single unit, otherwise use smaller rated ones where it matters most, i.e. digital naughties.

4/ Whatever you build that uses a powerxfmr nowadays will likely benefit from a well built high quality xformer. Most toroidal powerxformers could double as decent OPTs which should tell you enough to know they'll likely let a truckload of RF junk riding on the mains through as well. This is why I almost always avoid toroidal powerxfmrs like the plague.

5/ A cheap powerxfmr is a cheap powerxfmr so don't expect stellar results from it.

I haven't read the entire thread so if I repeated someones elses' suggestions, my apologies.

Cheers,
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Old 6th June 2004, 01:16 PM   #32
Bricolo is offline Bricolo  France
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Quote:
Originally posted by Bas Horneman
here is a link to it...it is actually quite complex with all the transformers...sorry about that......


the isolation transformer actually looks like a better option.. ;-)

http://www.diyaudio.com/forums/showt...840#post191840

the problem is that I have only one transformer, with a single primary
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Old 7th June 2004, 03:51 PM   #33
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Default Topaz 5KVA on eBay

Bricolo, check it out:

http://cgi.ebay.com/ws/eBayISAPI.dll...819629512&rd=1

I have a Topaz 5KVA and am very happy with it. You can run this transformer in step-down quasi-balanced mode 240VAC to 120VAC balanced. I say "quasi-balanced" because I'm uncertain just how balanced the secondary windings are.
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Old 7th June 2004, 03:53 PM   #34
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Default eBay II

A smaller Xentek 1KVA model is also for sale on eBay. Looks like a repackaged Topaz, but in any event gives -146dB noise reduction.

http://cgi.ebay.com/ws/eBayISAPI.dll...820308409&rd=1
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Old 28th June 2004, 11:10 AM   #35
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I've seen an isolation transformer on ebay, relly cheap
but the picture shows a toroid

can an isolation transformer be a toriod??
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Old 28th June 2004, 07:16 PM   #36
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Quote:
Originally posted by Bricolo
I've seen an isolation transformer on ebay, relly cheap
but the picture shows a toroid

can an isolation transformer be a toriod??
http://www.toroid.com/index.html

http://www.equitech.com/products/products.html

While I prefer my Topaz Ultra-Isolation transformer
(.005 pf interwinding capacitance), toroids with
carefully balanced windings and Faraday shields
do make for compact isolation transformers.

That's the trick: it's got to be a quality component
designed as an isolation transformer for best
isolation results. Given a toroid's inherant wideband
capability, magnetic coupling can defeat electrostatic
shielding so carefully balanced windings are necessary
for best common mode rejection.

And I can still get some dimmer buzz even through
my Topaz, at some settings on the dimmer. I need
a dedicated 220 V line, but I doubt my landlord's
going to be sympathetic to major wiring changes.

I'm also using heavy-duty Isobars, but that's because
I originally lived in lightning-prone Georgia.

http://www.tripplite.com

--Damon
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Old 28th June 2004, 07:46 PM   #37
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There's no other info than "Isolation transformer, 850VA" on ebay

here's the picture
Attached Images
File Type: jpg 1c_1_b.jpg (21.6 KB, 103 views)
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