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Old 3rd April 2004, 04:58 AM   #1
CRFX is offline CRFX  United States
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Default small transformers?

Hey guys, been lurking on the board for a while diggin up ideas for my 12 channel GC.

Got the amp pretty much planed out, just looking for small transformers, 1 for each channel. Around 500ma or less is all i need. Don't really wana spend $20 per channel just for power.
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Old 3rd April 2004, 08:54 AM   #2
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Default Re: small transformers?

Quote:
Originally posted by CRFX
Hey guys, been lurking on the board for a while diggin up ideas for my 12 channel GC.

Got the amp pretty much planed out, just looking for small transformers, 1 for each channel. Around 500ma or less is all i need. Don't really wana spend $20 per channel just for power.

are you making a 10 watt per channel, 12 channel gainclone?

what are the transformers for?? lol
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Old 3rd April 2004, 09:25 AM   #3
roibm is offline roibm  Romania
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throwing them at some wise @ss(like a so called president) would be a good idea.

Really now, 500mA? You plan using those for headphones?
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Old 3rd April 2004, 09:48 AM   #4
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A small 500 ma transformer will have a high output impedience
as a guess 2 ohms or more.

So why not use 1 large transformer to feed your 12 bridges
each bridge being decoupled from the transformer by a pair of
1 ohm resistors ?
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Old 3rd April 2004, 09:53 AM   #5
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Default Re: Re: small transformers?

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Originally posted by SkinnyBoy



are you making a 10 watt per channel, 12 channel gainclone?

what are the transformers for?? lol

actually... make that 5 watts per channel..
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Old 3rd April 2004, 05:32 PM   #6
ped is offline ped  United States
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Default Decoupling bridges from a transformer

Hi Woody,

Quote:
So why not use 1 large transformer to feed your 12 bridges each bridge being decoupled from the transformer by a pair of 1 ohm resistors ?
Could you please explain the need to decouple the bridges from the transformer and how the value of the resistor is determined.

I was considering powering two bridges off the same secondary to get +/- rails.

Thanks
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Old 3rd April 2004, 10:22 PM   #7
CRFX is offline CRFX  United States
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Default Re: Re: small transformers?

Quote:
Originally posted by SkinnyBoy



are you making a 10 watt per channel, 12 channel gainclone?

what are the transformers for?? lol
actualy, yes.
10W per driver is more than enogh for me, and thats blasting to me. I barly use 10W for all 12 for normal listening. Also I'm using an active Xover so that 30W for my 2 3 way speakers and 20W for the 3 2 ways.

Power is a non issue for me, i just want it to sound its best.
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Old 5th April 2004, 07:41 PM   #8
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Default Re: Decoupling bridges from a transformer

Quote:
Originally posted by ped
Hi Woody,



Could you please explain the need to decouple the bridges from the transformer and how the value of the resistor is determined.

I was considering powering two bridges off the same secondary to get +/- rails.

Thanks
I second that. I really like to know why the decoupling resistor is needed.

cheers

Ric
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Old 10th April 2004, 08:33 AM   #9
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I guess the decoupling resistors arn,t realy needed but they might
prevent any crosstalk between power supplys....

Woody
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Old 10th April 2004, 06:12 PM   #10
azira is offline azira  United States
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Default Re: small transformers?

Quote:
Originally posted by CRFX
Hey guys, been lurking on the board for a while diggin up ideas for my 12 channel GC.

Got the amp pretty much planed out, just looking for small transformers, 1 for each channel. Around 500ma or less is all i need. Don't really wana spend $20 per channel just for power.
Math time...

500mA * 16 ohm speakers (worst worst case) = 8Volts peak or 16Vp-p that you'd have to drive. So that pretty much tells you waht you're looking for. 16 / 1.414 = 11.31V. So. you need at minimum a 12VCT 1A transformer (for a little headroom) per channel. The only problem is that a LM3875 needs minimum 20V rails. So now what you need is 20 / 1.414 = 14.14V. So you'll need something like a 14VCT 1A transformer.

All electronics has an 18VCT 1A transformer for $4. That might be a good candidate for your project.

But now you know what you're looking for.

All Electronics Transfomers

--
Danny
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