Gainclone power supply options/questions

trespasser_guy · 27th April 2003, 04:24 PM

The building of the GC is nearing... I will be building the whole thing, case and all, unless I can find a suitable enclosure. I will also be building a pair of speakers and subwoofer to match. (horn loaded, of course...

)

Anyway, I will be using OPA541's in my GC because I have them laying around and am on such a tight budget that I will not allow myself to splurge and buy two LM3875's for $10. So, I will be using Nichicon UPW caps (which are spec'ed almost exactly like Panasonic FC...), Solen metallized and Dayton non-metallized polypropylene caps, and Vishay/Dale 1/2W resistors. I will also be using a preamp stage, which will have my active xovers for the speakers/sub. There will be a buffer stage at input (opamp in unity gain) then a 12dB, 100Hz high pass for the mains, and a 12dB, 120Hz low pass for the sub, followed by a sub preamp with gain=6. Volume controls on mains and sub preouts. These will use Vishay/Dale 1/4W resistors and Dayton polypropylene caps.

Ok... so, now on to power supplies, which is where I was going... I have a 17-0-17VAC@4.7A transformer, which I will use. Do I simply hook up the power to recitifiers, then straight to the power chips with the 1000uF caps? Or do I buffer the PS in the PS section with high capactance (I might have some 27,000's coming) caps, then run this out to the chips which have their own 1000uF caps?

Thanks (note, if you see anything in my preamp, etc. areas that won't work, PLEASE tell me... I kind of know what I am doing, but could really use your help)

joensd · 27th April 2003, 10:54 PM

Quote:

Ok... so, now on to power supplies, which is where I was going... I have a 17-0-17VAC@4.7A transformer, which I will use. Do I simply hook up the power to recitifiers, then straight to the power chips with the 1000uF caps? Or do I buffer the PS in the PS section with high capactance (I might have some 27,000's coming) caps, then run this out to the chips which have their own 1000uF caps?

That´s one of the questions circling in my head as well.
Still haven´t found the time to through the whole TINJAG-thread where I might find some answers.

I´d say the AC coming from the PS to the amp enclosures is worse to the signal circuitry than DC would be but that´s just my guess.

Jens

Peter Daniel · 28th April 2003, 12:05 AM

When using separate PS, place the rectifiers there and some small value caps (like 4.7u BG N) for filtering. 1000u caps are directly at the chip's pins. I didn't find using more capacitance to improve sound, it actually diminished my listening pleasure. If you not sure about that, leave some space in PS section and after getting used to the sound of just 1k uF try to add more capacitance and compare the difference. If you building multiple amps, the subwoofer amp will probably benefit from more caps.

trespasser_guy · 28th April 2003, 02:52 AM

Ok... so no big caps. The seller of these caps is hard to contact anyway... I really don't want them anymore... grr

Does anyone have a comment on my active xover arrangement? I wonder if it will work... and how well it will work. The total cost of this project has exceeded that which I wanted to spend, so I may have to cut everything back further... if that is possible.

Question: If I use 3.5uF os capacitance on the input of the power amp section, technically, the preamp does not need any input coupling caps, right? Any DC amplified there will be caught by the power amp's coupling caps?

27th April 2003, 04:24 PM	#1
trespasser_guy diyAudio Member Join Date: Aug 2002 Location: USA	Gainclone power supply options/questions The building of the GC is nearing... I will be building the whole thing, case and all, unless I can find a suitable enclosure. I will also be building a pair of speakers and subwoofer to match. (horn loaded, of course... ) Anyway, I will be using OPA541's in my GC because I have them laying around and am on such a tight budget that I will not allow myself to splurge and buy two LM3875's for $10. So, I will be using Nichicon UPW caps (which are spec'ed almost exactly like Panasonic FC...), Solen metallized and Dayton non-metallized polypropylene caps, and Vishay/Dale 1/2W resistors. I will also be using a preamp stage, which will have my active xovers for the speakers/sub. There will be a buffer stage at input (opamp in unity gain) then a 12dB, 100Hz high pass for the mains, and a 12dB, 120Hz low pass for the sub, followed by a sub preamp with gain=6. Volume controls on mains and sub preouts. These will use Vishay/Dale 1/4W resistors and Dayton polypropylene caps. Ok... so, now on to power supplies, which is where I was going... I have a 17-0-17VAC@4.7A transformer, which I will use. Do I simply hook up the power to recitifiers, then straight to the power chips with the 1000uF caps? Or do I buffer the PS in the PS section with high capactance (I might have some 27,000's coming) caps, then run this out to the chips which have their own 1000uF caps? Thanks (note, if you see anything in my preamp, etc. areas that won't work, PLEASE tell me... I kind of know what I am doing, but could really use your help)

28th April 2003, 12:05 AM	#3
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	When using separate PS, place the rectifiers there and some small value caps (like 4.7u BG N) for filtering. 1000u caps are directly at the chip's pins. I didn't find using more capacitance to improve sound, it actually diminished my listening pleasure. If you not sure about that, leave some space in PS section and after getting used to the sound of just 1k uF try to add more capacitance and compare the difference. If you building multiple amps, the subwoofer amp will probably benefit from more caps. __________________ www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

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28th April 2003, 02:52 AM	#4
trespasser_guy diyAudio Member Join Date: Aug 2002 Location: USA	Ok... so no big caps. The seller of these caps is hard to contact anyway... I really don't want them anymore... grr Does anyone have a comment on my active xover arrangement? I wonder if it will work... and how well it will work. The total cost of this project has exceeded that which I wanted to spend, so I may have to cut everything back further... if that is possible. Question: If I use 3.5uF os capacitance on the input of the power amp section, technically, the preamp does not need any input coupling caps, right? Any DC amplified there will be caught by the power amp's coupling caps?