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Old 30th June 2011, 03:36 PM   #1
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Default Oversized transformer - Any problems?

Hi All,

I'm considering a 'Lovely Cube' headphone amp but to keep costs down I was intending to use a toroid I already have. The amp design calls for 15V and ~25-30VA. My transformer is 18V & 60VA. I'll unwind it down to 15V but will the higher capacity cause any problems? I thinking inrush current destroying rectifiers etc.

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Mike
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Old 30th June 2011, 04:07 PM   #2
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Shoudn't be a problem. You might want to use some surge suppression on the primary or just use rectifiers which can handle the increased initial current surge as the capacitors are charging.
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Old 30th June 2011, 04:14 PM   #3
Atilla is offline Atilla  Norway
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You shouldn't need to do anything special. And if your caps have good enough voltage rating, there shouldn't be a need to rewind the transformer. Or you could regulate it, after rectification to drop a few volts with something simple, instead of rewinding. What's the Voltage rating of the caps?

Last edited by Atilla; 30th June 2011 at 04:18 PM.
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Old 30th June 2011, 04:18 PM   #4
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Should work just fine with the transformer you have.

BTW, the rectified voltage will be 3*1.414 = 4.25V DC higher than with the intended transformer, you should check if you application can handle this.
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Old 30th June 2011, 04:42 PM   #5
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I Googled 'Lovely Cube' headphone amp and it appears that it uses 35 volt filter caps, and is voltage regulated already. So you could probably use the larger transformer without any problems. Only possible issue I see might be whether or not exising heat sinking is adequate for slightly higher power dissipation for regulators.

Mike
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Old 30th June 2011, 09:27 PM   #6
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Thanks for the replies all. Much appreciated.

I'll check the pcb layout to see how much space there is for bigger heatsinks. It'd be good not to have to unwind the transformer.

Mike
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Old 30th June 2011, 09:42 PM   #7
Atilla is offline Atilla  Norway
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I saw the actual board itself as well. I don't think you'll have much problems. Given the very low currents that'll flow, a few volts more on the regulators shouldn't be too much of a heat problem either. Assemble it and give it a go and you'll know
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Old 17th July 2011, 06:24 AM   #8
troyo is offline troyo  Guyana
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if i have lets say a 6 500w into 4 ohms amp circuit working in a triamp format would there be any problem working with one single appropriate transformer or do i need several transfromers
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Old 18th July 2011, 04:40 AM   #9
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Quote:
Originally Posted by troyo View Post
if i have lets say a 6 500w into 4 ohms amp circuit working in a triamp format would there be any problem working with one single appropriate transformer or do i need several transfromers




Providing that you have a transformer with 4000VA rating it should work okay!

jer
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