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Old 27th June 2008, 04:33 PM   #1
5150ed is offline 5150ed  Thailand
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Default Transformer problem...

Hi I am about to build an invert gainclone using OPA 541. I have a problem finding a good quality transformer in my country. As we know transformer does effect the sound of the amp so much. So I decide to use an old transformer from my old class A Electrocompanient amp which shold be very good quality.

But the problem is its secondary are 35V-0 3.5A 35V-0 3.5A too high for my use I want it like 16V to 20V.
Is there any way can I reduce the voltage to 16V-0 16V-0 without trade of the sound quality???

And the primary of the transformer is 110V-0 but my country use 220V AC, anyway, in the amp has a circuit to reduce the ac input voltage to 110V. My question is is it gona reduce the sound quality if I use that circuit with my gainclone too???

Please help
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Old 27th June 2008, 05:24 PM   #2
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hi 5150ed,

3 options:

1. rewind transformer
2. use autotransformer
3. buy proper transformer

regards
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Old 27th June 2008, 05:56 PM   #3
AndrewT is offline AndrewT  Scotland
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4th option:
refurbish the ClassA Electrocompanient.
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Old 27th June 2008, 07:00 PM   #4
Nuuk is offline Nuuk  United Kingdom
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5th option. Pay for me to fly out to Bangkok with a decent traffo!
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Old 28th June 2008, 09:08 AM   #5
5150ed is offline 5150ed  Thailand
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Hmmmm... Thanks you all.

From ur five options you all suggest, I may have to ask u a new question .

Is there any online store which provide a high quality transformer and ship worldwide???
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Old 28th June 2008, 09:36 AM   #6
Nuuk is offline Nuuk  United Kingdom
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Try here .
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Old 28th June 2008, 10:34 AM   #7
5150ed is offline 5150ed  Thailand
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Thanks so much Nuuk.

I just went through the web and found MULTICOMP Toroidal transformer.
It quite expensive, around USD120.
Does anyone has experiences about this brand of transformer???

And what should be the voltage using with OPA541 inverted schematic?
I plan around 14V-18V coz I aim for more natural and relax sound like SET amp, Is it too low?
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Old 28th June 2008, 10:46 AM   #8
Nuuk is offline Nuuk  United Kingdom
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What speakers will you be driving with this amp?
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Old 28th June 2008, 10:57 AM   #9
5150ed is offline 5150ed  Thailand
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I am not sure but should be 6ohms minimun and 89db up.
May be Fostex F200A I had.

I like bass, power, soundstage but not too much dynamic and attact.
My music is 80% old jazz and vocal and the rest is classical and pop.
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Old 28th June 2008, 11:05 AM   #10
Nuuk is offline Nuuk  United Kingdom
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OK, I would still aim for around 27 volts using an 18VAC transformer. If you can afford it, go for two at around 120VA and build dual mono. If not, 225VA will be fine.

I run my OPA541 amps at 27 volts and they sound very much how you want yours to sound.
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