Transformer shoping

[Richie V6]

I've just done a search and could not find a clear answer. Could some please explain the VA rating to me? I have a transformer that puts out +17V and -17V at 2 amps. Is this enough for 2 LM3886 gainclones? I really doubt it is enough. Thanks for any help.

 

[thomas997]

http://tinyurl.com/6atkw

Yours is probably alright for a single channel, depending on the speakers. But might be too weak for stereo.

 

[Richie V6]

Can a bunch of capacitors make up for a weak transformer? I have 250 10000uF caps comming.

 

[jawbreak]

Well Im a newbie to transformers myself so I cant be alot of help but here are two sites with information on transformers that might be of interest that I've used.

http://sound.westhost.com/articles.htm

http://www.tpub.com/neets/book2/index.htm

Both have transformer sections.

 

[Sherman]

Can a bunch of capacitors make up for a weak transformer? I have 250 10000uF caps comming.

The transformer "recharges" the capacitors during those times when the demand for power by the amp is less than the power the transformer is capable of putting out. You can think of a capacitor sort of like a very, very short duration but high output rechargeable battery.

So... the short answer is "no". A slightly longer answer is it depends. It depends on how much output you are expecting from the amp, how long you want to play it, whether the music you listen to has lots of transients where the power requirements are low, etc. etc..

For instance, if you put in a bunch of caps your transformer may take several minutes to charge them to the point that your amp will work. Then if you shut off the power supply the amp may keep working for several minutes. However if you get the caps charged and then call for more power than the transformer can deliver the caps will take up the slack and then the transformer will be unable to supply enough power to both charge the caps and power the amp and it will quite working until the caps are recharged. If the amp calls for power during this time the caps will discharge before charging fully and you will never develop the voltage required to run the amp.

(There are actually lots of other issues and this is extremely simplified.)