Power amp suggestion

maxpou · 18th January 2012, 05:19 PM

Hi Guys,
I would like to built a new power amp. I have many parts here, 2 xformer 35-0-35 Vac 2500VA, Bjt output 8 mjl1302 and 8 mjl3281 onsemi, driver toshiba 20 2sa1930 and 20 2sc5171, 10 2sa1381 and 10 2sc3503, 20 MJE15030 and 20 MJE15031, many 2n5401 and 2n5551, many BC546B and BC556B, many 2sa970BL and 2sc2240BL and many 2SK170BL and 2SJ74BL.

I want can put a Dunlavy SC-IV on this amp without problem. Somebody can suggest me? Thank you! Maxpou

wahab · 18th January 2012, 05:44 PM

With such a transformer , the poor devices on the left
can only hope that such a question will stay unanswered....

a.wayne · 18th January 2012, 05:47 PM

Well , maybe all for one channel .....

maxpou · 18th January 2012, 06:02 PM

Quote:

Originally Posted by wahab

With such a transformer , the poor devices on the left
can only hope that such a question will stay unanswered....

Why?

maxpou · 18th January 2012, 06:06 PM

Quote:

Originally Posted by a.wayne

Well , maybe all for one channel .....

you believe I don't have enough parts to built 2 channel. Maxpou

AndrewT · 18th January 2012, 06:25 PM

With a 35-0-35Vac transformer you can expect a sinewave output of ~29Vac.
This gives ~100W into 8r0 and gives ~200W into 4r0.

Two channels of 200W into 4r0 would require a transformer from 400VA to 800VA.
Your transformer is wasted on that.

indianajo · 18th January 2012, 06:50 PM

With two transformers, you can stack them up end to end and make +-70 VAC. Of course, it would be incredibly heavy. Then your number of output transistors and heat sink size would limit your power. Better install good overcurrent (output) protection.
Cool Andrew says you can get 29 VAC out of 35 VAC rails. The amps I have been working on produce about 2/5 to 3/5 the rail voltage on the speaker output by specification. I thought modern transistors might be better.

maxpou · 19th January 2012, 12:40 AM

Hi guys!,
I don't know what wrong with my big transformer? I can't built a power amp with them? maxpou

a.wayne · 19th January 2012, 01:08 AM

Max you can and if you double the outputs it will be a monster at 2 ohm ...

tinitus · 19th January 2012, 03:20 AM

use monster classA rated heatsinks

18th January 2012, 06:25 PM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	With a 35-0-35Vac transformer you can expect a sinewave output of ~29Vac. This gives ~100W into 8r0 and gives ~200W into 4r0. Two channels of 200W into 4r0 would require a transformer from 400VA to 800VA. Your transformer is wasted on that. __________________ regards Andrew T.

18th January 2012, 06:50 PM	#7
indianajo diyAudio Member Join Date: Jan 2010 Location: Jeffersonville, Indiana USA	With two transformers, you can stack them up end to end and make +-70 VAC. Of course, it would be incredibly heavy. Then your number of output transistors and heat sink size would limit your power. Better install good overcurrent (output) protection. Cool Andrew says you can get 29 VAC out of 35 VAC rails. The amps I have been working on produce about 2/5 to 3/5 the rail voltage on the speaker output by specification. I thought modern transistors might be better. __________________ Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,SP2-XT's, T-300 HF Projs, Steinway console, Herald RA88a mixer, Wurlitzer 4500

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18th January 2012, 05:44 PM	#2
wahab diyAudio Member Join Date: Nov 2009 Location: algeria/france	With such a transformer , the poor devices on the left can only hope that such a question will stay unanswered....

18th January 2012, 05:47 PM	#3
a.wayne diyAudio Member Join Date: May 2008 Location: Front Row Center	Well , maybe all for one channel .....

19th January 2012, 12:40 AM	#8
maxpou diyAudio Member Join Date: Apr 2006 Location: Québec	Hi guys!, I don't know what wrong with my big transformer? I can't built a power amp with them? maxpou

19th January 2012, 01:08 AM	#9
a.wayne diyAudio Member Join Date: May 2008 Location: Front Row Center	Max you can and if you double the outputs it will be a monster at 2 ohm ...

19th January 2012, 03:20 AM	#10
tinitus diyAudio Moderator Join Date: Nov 2005	use monster classA rated heatsinks

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