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Old 3rd June 2004, 03:41 AM   #1
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Default Leach Amp Power Supply Transformer

I'm a little confused about what kind of transformer is to be used in the leach amp power supply. On this page (near the bottom, under two channel power supply) he states:

" The power supply voltages should be in the range (+ and -) 56 V to 59 V with no load on the amplifier."

but then below that, he recommends a transformer from Victoria Magnetics that is rated for 80VCT@6A. Maybe I don't understand, but wouldn't this transformer put out 80V where he said earleir it should put out between 56V and 59V?

Also, could I use any transformers on this page for the power supply (always looking to save money =).
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Old 3rd June 2004, 04:16 AM   #2
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Quote:
but then below that, he recommends a transformer from Victoria Magnetics that is rated for 80VCT@6A. Maybe I don't understand, but wouldn't this transformer put out 80V where he said earleir it should put out between 56V and 59V?
Nope, 80v CT equals to 40v-0-40V AC.
After rectification, +56.56v - 0- -56.56v DC, not including the diode loss...

Hope it helps you a little to understand...
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Old 3rd June 2004, 01:22 PM   #3
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Actually it does, but only a little =). Could someone please define "VCT". Also, please explain how you found +56.56V - 0 - -56.56V DC after rectification? What is diode loss? And is it possible for me to use any of the transformers on the page I linked to in my first post as a substitute? Thanks for your help, I'm hoping to expand my knowledge in this area.
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Old 3rd June 2004, 07:04 PM   #4
jaycee is offline jaycee  United Kingdom
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CT means "Centre Tapped"... 40-0-40 (where 0 is the centre tap) would be written as 80VCT, ie the voltage you would get if you measured from one tap to another. Hope that makes sense

AS for why DC rectified voltage is higher than the AC voltage, that is because sinusodial AC voltage is specified as RMS voltage or "root mean square" voltage. The DC voltage upon rectification and smoothing is Vdc = Vac * 1.414, diode losses depend on what bridge rectifier you use but is normally about 1.1 volt.

Having quickly looked at ApexJr, none are suitable. The 93VCT one is the nearest but i'm not sure if the Leach amp would handle the extra rail voltage (this would produce about 65V per rail).
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Old 3rd June 2004, 08:12 PM   #5
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Thanks, very informative. Is $62 a good price for an 80VCT@6A toroidal transformer or would I do well to keep looking?
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Old 3rd June 2004, 09:05 PM   #6
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Parts express has a similar Avel transformer for a dollar or two less. http://www.partsexpress.com/pe/showd...number=122-670

I have not used Victoria Magnetics, but their reputation for build quality is very good. Avel is a good quality part, too, judgng by the ones I have. Build quality mostly equates to less mechanical hum from the transformer. I have some Radio Shack 50 VA transformers that I used temporarily for my BOSOZ preamp They hum with virtually no load.
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Old 4th June 2004, 08:30 PM   #7
K-amps is offline K-amps  United States
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Quote:
Originally posted by m0tion
Thanks, very informative. Is $62 a good price for an 80VCT@6A toroidal transformer or would I do well to keep looking?

Roger that. $62 is a little expensive. I would get a 600-800 va toroid for that money...

The parts express tip is a good one. I have been using Avels, not bad for the money.
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