small transformers?

[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.

 

[SkinnyBoy]

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

 

[roibm]

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?

 

[woody]

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 ?

 

[SkinnyBoy]

Re: Re: small transformers?

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

what are the transformers for?? lol

actually... make that 5 watts per channel..

 

[ped]

Decoupling bridges from a transformer

Hi Woody,

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

 

[CRFX]

Re: Re: small transformers?

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.

 

[Ricren]

Re: Decoupling bridges from a transformer

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

 

[woody]

I guess the decoupling resistors arn,t realy needed but they might
prevent any crosstalk between power supplys....

Woody

 

[azira]

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

 

[CRFX]

thanks so much, thats just what i'm looking for.

btw im using lm1875s, so 12V works fine for them. I have 6 drivers on 1 12V 3A transformer with no probs. 1A each will be more than enogh.
1 more question, how well would a 1875 work instead of the 3875 in BrianGT's gainclone.

 

[troystg]

Steve @ Apex.jr just got some new torids that may intrest you.

Troy

 

[Jay]

1 more question, how well would a 1875 work instead of the 3875 in BrianGT's gainclone.

OK, it's not the first time I hear people comparing 1875 with 3875. I really don't know what is going on. 1875 is still so far away from hi-end, no matter how hard I've tried (and I used tantalum resistors). I felt so stupid using expensive stuffs for that "cheap" IC

 

[CRFX]

Is it really "that" bad? Been using some for a while and they sound fine to me. Will I say "wow, thats so much better", or "It sounds a little better, i guess" I'm just debating spending another $80 for the 3875s

 

[troystg]

Don't spend $80 dolloars for the LM3875, spent $35 and get the basic kit from Brian here:

http://www.briangt.com/order/

http://www.briangt.com/order/

Troy

 

[CRFX]

I ment for 12 of them at $6 a pop.

 

[thomas997]

I ment for 12 of them at $6 a pop.

You could probably find them for a bit less than that. Nationals price is $2.40 per thousand.


So maybe if you found a group buy somewhere.