Is it big enough?

Wombat2 · 2nd September 2005, 07:27 AM

I'm building a tri-amp 5.1 surround system. I'm using ESP P03A for the 12" woofers,(except centre) LM3876 for the mids and LM4752 for the tweeters. ie 4X 60W and 6 x 50W at +/- 35V (the LM4752 run on a single rail 24v supply for which I already have a 3A regulated PSU)

Would a single 600VA toriod be big enough for the 35volt supply? I'm thinking of running a snubberised regulated supply for the LM3876s and and unregulated for the bigger amps. If I split the tranfo I could go for a 42 v supply and get 100w out of the P03As

David L

rinox · 2nd September 2005, 08:45 PM

In my opinion the best is to use at lest two transformer, one dedicated for the bass and the other for the mid-high.... they will cost less then a single trasfo and the results will be better.

AndrewT · 3rd September 2005, 08:35 AM

Hi,
42Vac will give a lot more than 100W into 8r. 35Vac should achieve 100W.
Your 600VA transformer will be undersized for 6 * 50W + 4 * 60W.
the rail voltage will sag badly on peaks and make the sound quality suffer. This will be particularly revelevant on long bass notes.
I would recommend a minimum of 2 by 500VA for your loading and further if you can find them cheaply then use a pair of secondaries for each channel. More easily achieved, a pair of secondaries for the bass and the other pair for mid and treble. Then have separate rectifiers for every channel with their own smoothing and snubbers.

richie00boy · 3rd September 2005, 09:21 AM

He means 42 V DC

On the 35 V supply, your output power is 540 W, so a 600 VA transformer would be a bit undersized for continuous duty. Class-b amps typically demand VA = 2x amp power for continuous duty.

2nd September 2005, 07:27 AM	#1
Wombat2 diyAudio Member Join Date: Nov 2003 Location: Brisbane	Is it big enough? I'm building a tri-amp 5.1 surround system. I'm using ESP P03A for the 12" woofers,(except centre) LM3876 for the mids and LM4752 for the tweeters. ie 4X 60W and 6 x 50W at +/- 35V (the LM4752 run on a single rail 24v supply for which I already have a 3A regulated PSU) Would a single 600VA toriod be big enough for the 35volt supply? I'm thinking of running a snubberised regulated supply for the LM3876s and and unregulated for the bigger amps. If I split the tranfo I could go for a 42 v supply and get 100w out of the P03As David L

3rd September 2005, 09:21 AM	#4
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	He means 42 V DC On the 35 V supply, your output power is 540 W, so a 600 VA transformer would be a bit undersized for continuous duty. Class-b amps typically demand VA = 2x amp power for continuous duty. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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2nd September 2005, 08:45 PM	#2
rinox diyAudio Member Join Date: Oct 2004	In my opinion the best is to use at lest two transformer, one dedicated for the bass and the other for the mid-high.... they will cost less then a single trasfo and the results will be better.

3rd September 2005, 08:35 AM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, 42Vac will give a lot more than 100W into 8r. 35Vac should achieve 100W. Your 600VA transformer will be undersized for 6 * 50W + 4 * 60W. the rail voltage will sag badly on peaks and make the sound quality suffer. This will be particularly revelevant on long bass notes. I would recommend a minimum of 2 by 500VA for your loading and further if you can find them cheaply then use a pair of secondaries for each channel. More easily achieved, a pair of secondaries for the bass and the other pair for mid and treble. Then have separate rectifiers for every channel with their own smoothing and snubbers.