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Old 14th August 2006, 02:16 AM   #1
ostie01 is offline ostie01  Canada
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Default Is this transformer good for power amplifier

Hi, would like to buy this toroidal transformer on ebay and would like to know if they are good choice for a power amplifier project.

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1
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Old 14th August 2006, 03:43 AM   #2
singa is offline singa  Singapore
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Yes if you are building amp with 46V rails.At this voltage looks like it going to be over 100watts.But at 1000kva it's overkill and huge.Check whether is suitable for your country's AC line.
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Old 14th August 2006, 03:58 AM   #3
infinia is offline infinia  United States
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Hi
May be OK if using bridged into 2-4 ohms but overkill otherwise. Probably need higher voltages to get higher power into 8 ohms. Search for an amplifier firstly, then look to design the powersupply given your drive/load requirements. Another thing to watch out for is non-vacuum impregnated xfrmers can be audibly noisy.
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Old 14th August 2006, 04:27 AM   #4
ostie01 is offline ostie01  Canada
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Hi, I don't know why 46Vac which give 65Vdc on the rails would not be powerfull enough, I think this is about at least 200w of power.
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Old 14th August 2006, 07:21 AM   #5
djk is offline djk
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That transformer would give 300W per channel at 4 ohms in a stereo Leach type amplifier,
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Old 14th August 2006, 07:30 AM   #6
ostie01 is offline ostie01  Canada
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Hi, thanks for the reply, I'm looking at a 8 Ohm design which would give about 250w.
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Old 14th August 2006, 07:40 AM   #7
AndrewT is offline AndrewT  Scotland
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Hi,
I have seen this seller's data before.
The regulation when driving 1kVA seems very high (suspiciously high).
I queried it with the Seller but got no sensible response.

I think the transformer would do audio duty, just don't expect to get 600watts out of the amplifier.

Singa,
how did you work out (or not work out) the DC rail voltage?
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Old 14th August 2006, 09:20 AM   #8
djk is offline djk
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"I'm looking at a 8 Ohm design which would give about 250w."

In that case I would use something like a transformer rated at 55-0-55 at full load. AndrewT is right, the regulation figures don't seem good, especially for that much weight.
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Old 14th August 2006, 09:23 AM   #9
quasi is offline quasi  Australia
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The maximum power using this transformer is;

Available DC voltage = 46v - 5% regulation - 1v (diode bridge) * 1.414 = +/- 60v DC.

Even a great DC filtering section and solid state amplifier with transistor output stages will lose around 5 volts at full power, so the maximum voltage swing will be 55 volts.

55v * 0.707 = 38.8vrms = 190 watts into 8 ohms. Dynamic power will greater.

And this I believe is the at best result.

My $0.02

Cheers
Q
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Old 14th August 2006, 01:09 PM   #10
AndrewT is offline AndrewT  Scotland
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Hi,
you could use Quasi's predictions to guess at how many channels you could run off the one transformer.

I think you could run three channels into 8ohms each, or just about two channels into 4ohms each.
Into 4ohms the supply rails will sag but this can be partially compensated by increasing the smoothing capacitor bank up from the usual 2mF to 3mF per Apk of output current/channel to 3mF to 4mF/Apk/channel.

I seriously recommend a separate rectifier and smoothing bank to each channel fed from the common pair of secondary windings.
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