psu transformer choice ?

bdm47 · 26th June 2011, 11:12 PM

need help to make right choice psu transformer for 405 clones i have very well made old toroid 2 secondary out 58 v 80 v dc the other 30v ac / 42 v dc out i am not sure of va 3.5 amp on mains 5 amp on psu 400 -600 ? also 2 maplin 35 v sec 42 v dc out 160 va also any advise on psu position respect to amp boards placed each end of amp case the case to be made from white 6mm thick perspex i am new to the forum as you will have gathered cheers bernard

bdm47 · 27th June 2011, 12:12 AM

sorry wrong specs re transformers 1 secondary 58 v ac 80 v dc on rails 2 sec 35v ac 50v dc out

sreten · 27th June 2011, 12:31 AM

Hi,

VA rating is very related to physical size. +/- 80V TBH sounds like a recipe
for an amplifier blowing up, +/- 50V a lot more reasonable, if they are of
similar size, go for the latter as its far more sensible.

As its Vsquared/R, +/- 80V is good for 2.5 times the power of +/-50V.
the 405 AFAIK simply is not designed for +/- 80V rails.
As +/-50V is good for 100W or so, +/- 80V is heading towards 250W.

So the latter needs to be far bigger than the former, or it won't work.

rgds, sreten.

Michael Bean · 27th June 2011, 12:40 AM

Hi bdm47,
Just as I was going to post a reply, sreten beat me to it. But anyway, I totally agree, +/- 80v way too high, use the other one.

Mike

bdm47 · 27th June 2011, 01:16 AM

thanks for you help the old transformer also has sec 30v = 42vdc size w/110mm h 45mm cheers bernard

26th June 2011, 11:12 PM	#1
bdm47 diyAudio Member Join Date: Mar 2011	psu transformer choice ? need help to make right choice psu transformer for 405 clones i have very well made old toroid 2 secondary out 58 v 80 v dc the other 30v ac / 42 v dc out i am not sure of va 3.5 amp on mains 5 amp on psu 400 -600 ? also 2 maplin 35 v sec 42 v dc out 160 va also any advise on psu position respect to amp boards placed each end of amp case the case to be made from white 6mm thick perspex i am new to the forum as you will have gathered cheers bernard

27th June 2011, 12:31 AM	#3
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, VA rating is very related to physical size. +/- 80V TBH sounds like a recipe for an amplifier blowing up, +/- 50V a lot more reasonable, if they are of similar size, go for the latter as its far more sensible. As its Vsquared/R, +/- 80V is good for 2.5 times the power of +/-50V. the 405 AFAIK simply is not designed for +/- 80V rails. As +/-50V is good for 100W or so, +/- 80V is heading towards 250W. So the latter needs to be far bigger than the former, or it won't work. rgds, sreten. __________________ There is nothing so practical as a really good theory - Ludwig Boltzmann When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

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27th June 2011, 12:12 AM	#2
bdm47 diyAudio Member Join Date: Mar 2011	sorry wrong specs re transformers 1 secondary 58 v ac 80 v dc on rails 2 sec 35v ac 50v dc out

27th June 2011, 12:40 AM	#4
Michael Bean diyAudio Member Join Date: Sep 2004 Location: Minneapolis, Minnesota, USA	Hi bdm47, Just as I was going to post a reply, sreten beat me to it. But anyway, I totally agree, +/- 80v way too high, use the other one. Mike

27th June 2011, 01:16 AM	#5
bdm47 diyAudio Member Join Date: Mar 2011	thanks for you help the old transformer also has sec 30v = 42vdc size w/110mm h 45mm cheers bernard

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