Newb question...Center pot'ed transformer and rectifiers

Stasiu · 30th November 2006, 02:02 AM

I've been lurking about this web site for months, learning here and there, and thinking up more projects than I have the time or money to do. The main area of interest of mine on this site is the DIY amplifier section. My goal is to eventually put together some type of class A amp (Aleph, Krell clone, etc.).

My question today is about an old Realistic STA-2100 amp that I inherited from an uncle years ago. I've stripped it down to it's PSU and dual amp PCB's and am hoping to bypass the whole pre-amp section. The plan was to rebuild the PSU with separate full wave rectifiers and a bank of 30,000 uF caps (currently 15,000 uF per side) for each channel and and make it a dual mono block after the toroid, but I just realized it has a center pot'ed torroid. Is it possible to wire two full wave rectifiers for each channel? Could I wire the secondaries from the transformer to the AC diodes of the rectifier in parallel and wire the 0v common wire of the torroid in parralel between the capacitors that need to be in series per side?

shirazmacuff · 30th November 2006, 06:07 PM

Hi Stasiu
I would like to help, but your description is a little fussy
If you could post a sketch of what you want to do, I think that will help us understand more clearly.

Stasiu · 30th November 2006, 07:19 PM

I'm actually working on a schematic right now....just have to download some software.

Stasiu · 30th November 2006, 08:18 PM

I drew this up in eagle. Does any of it make sence?

Stasiu · 1st December 2006, 12:50 AM

any thoughts?

motherone · 1st December 2006, 01:17 AM

If you have a center-tapped transformer, you should probably only use a single rectifier. There's numerous threads in the chip amps section about wiring up single versus dual rectifiers on center tapped an dual secondary transformers.

Stasiu · 1st December 2006, 06:28 AM

I understand how to wire one rectifier to a center pot'ed transformer, but will what i posted work? I've read on these forums that having two rectifiers will help stabalize the + and - DC lines and would like to hear the difference for myself. I'd like to separate the power supply to the separate sides as much as possible.

motherone · 1st December 2006, 09:18 AM

As far as I know, it will not work. In order to use double rectifiers, you need two completely separate windings. I believe that in itself is part of the improvement that you get when going that route.

pinkmouse · 1st December 2006, 10:43 AM

The only way this will work is if you can get into your transformer to split the centre tap. Dual rectifiers will not work at all with a single centre tap.

Stasiu · 1st December 2006, 06:42 PM

Thanks for the help

30th November 2006, 02:02 AM	#1
Stasiu diyAudio Member Join Date: May 2006	Newb question...Center pot'ed transformer and rectifiers I've been lurking about this web site for months, learning here and there, and thinking up more projects than I have the time or money to do. The main area of interest of mine on this site is the DIY amplifier section. My goal is to eventually put together some type of class A amp (Aleph, Krell clone, etc.). My question today is about an old Realistic STA-2100 amp that I inherited from an uncle years ago. I've stripped it down to it's PSU and dual amp PCB's and am hoping to bypass the whole pre-amp section. The plan was to rebuild the PSU with separate full wave rectifiers and a bank of 30,000 uF caps (currently 15,000 uF per side) for each channel and and make it a dual mono block after the toroid, but I just realized it has a center pot'ed torroid. Is it possible to wire two full wave rectifiers for each channel? Could I wire the secondaries from the transformer to the AC diodes of the rectifier in parallel and wire the 0v common wire of the torroid in parralel between the capacitors that need to be in series per side?

1st December 2006, 10:43 AM	#9
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	The only way this will work is if you can get into your transformer to split the centre tap. Dual rectifiers will not work at all with a single centre tap. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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30th November 2006, 06:07 PM	#2
shirazmacuff diyAudio Member Join Date: Jul 2006	Hi Stasiu I would like to help, but your description is a little fussy If you could post a sketch of what you want to do, I think that will help us understand more clearly.

30th November 2006, 07:19 PM	#3
Stasiu diyAudio Member Join Date: May 2006	I'm actually working on a schematic right now....just have to download some software.

1st December 2006, 12:50 AM	#5
Stasiu diyAudio Member Join Date: May 2006	any thoughts?

1st December 2006, 01:17 AM	#6
motherone diyAudio Member Join Date: Apr 2003 Location: Seattle	If you have a center-tapped transformer, you should probably only use a single rectifier. There's numerous threads in the chip amps section about wiring up single versus dual rectifiers on center tapped an dual secondary transformers.

1st December 2006, 06:28 AM	#7
Stasiu diyAudio Member Join Date: May 2006	I understand how to wire one rectifier to a center pot'ed transformer, but will what i posted work? I've read on these forums that having two rectifiers will help stabalize the + and - DC lines and would like to hear the difference for myself. I'd like to separate the power supply to the separate sides as much as possible.

1st December 2006, 09:18 AM	#8
motherone diyAudio Member Join Date: Apr 2003 Location: Seattle	As far as I know, it will not work. In order to use double rectifiers, you need two completely separate windings. I believe that in itself is part of the improvement that you get when going that route.

1st December 2006, 06:42 PM	#10
Stasiu diyAudio Member Join Date: May 2006	Thanks for the help