Toroidal Amp Question :

DaveSail · 23rd July 2010, 07:02 PM

I am planning to build a Chip Amp using two LM3886 chips .
Separate power supplies and bridges .

" NUUK " has a list on his page for dummies . For 8 Ohm
speakers , 20 to 25 Sec. Voltage . 80 to 300 VA per channel

Plitron site . Standard list . # 077016201

2 x 25 VAC . 300 VA

Would a pair of those be correct ? [ I can work out dual
switches . ]

They also list " Low Noise For Soild State Amps " .

Would a pair of those be prefrrable ??

TIA ; David V. Webber

AndrewT · 23rd July 2010, 07:50 PM

two 300VA 25+25Vac transformers for two 3886 chipamps is about as good (best) as that anyone would recommend.
Most are built successfully with far smaller transformer/s
Go ahead if you think these give you value for your money.

DaveSail · 25th July 2010, 01:52 AM

I don't know a lot about electronics . Just felt as a V - 6 or a V - 8
gets less wear / sress than a V - 4 doing the same work , it might be
the same with TFMRs ! David

DaveSail · 25th July 2010, 07:27 PM

This amp will be for my " Bedroom " speakers . They are very efficient .
JBL LE14A Woofer and LE85 Mid / High . May add a pair of Slot Radiators .
They both have massive magnets and large voice - coils . My 1 Watt
Clock Radio will drive them such that they shake the walls !
However , quite often folks ask to borrow an amp . Perhaps for a Audio - Video
presentation or for an outdoor picnic or such . So , for those occasions I think
it would be good to have the larger XFMRs . David

infinia · 25th July 2010, 09:41 PM

Dual over sized XFMRs are not the most Eco friendly solution. IMO
well if you can coax 70W/channel of audio output from a chip amp at 60% eff I would shoot for ~150 VA / channel taking into careful consideration the rail voltage droop under load. If you combined the 2 into one 300 VA XFMR the rail will be stiffer ie better regulation.

abraxalito · 26th July 2010, 12:02 AM

Quote:

Originally Posted by DaveSail

I don't know a lot about electronics . Just felt as a V - 6 or a V - 8
gets less wear / sress than a V - 4 doing the same work , it might be
the same with TFMRs ! David

As far as I'm aware, transformers do not wear out. I agree with AndrewT and infinia - 300VA is overkill here. My active speakers have 150VA for two LM3886 per channel (bass/mid and tweeter) and work just fine.

DaveSail · 26th July 2010, 03:59 AM

Super . What would be the PLITRON part number for those ?

There are a LOT of units in their catalog ! TIA DVW

infinia · 26th July 2010, 04:46 AM

You could buy a single 300VA or 2x 150 Antek brand for saving big $$.
AFAIK they are equal to PLITRON at the standard ship now series.
Spend a moment at their site its really not too hard to figure out the P# scheme.

23rd July 2010, 07:02 PM	#1
DaveSail diyAudio Member Join Date: Jul 2010	Toroidal Amp Question : I am planning to build a Chip Amp using two LM3886 chips . Separate power supplies and bridges . " NUUK " has a list on his page for dummies . For 8 Ohm speakers , 20 to 25 Sec. Voltage . 80 to 300 VA per channel Plitron site . Standard list . # 077016201 2 x 25 VAC . 300 VA Would a pair of those be correct ? [ I can work out dual switches . ] They also list " Low Noise For Soild State Amps " . Would a pair of those be prefrrable ?? TIA ; David V. Webber

23rd July 2010, 07:50 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	two 300VA 25+25Vac transformers for two 3886 chipamps is about as good (best) as that anyone would recommend. Most are built successfully with far smaller transformer/s Go ahead if you think these give you value for your money. __________________ regards Andrew T.

25th July 2010, 09:41 PM	#5
infinia diyAudio Member Join Date: May 2005 Location: Californication	Dual over sized XFMRs are not the most Eco friendly solution. IMO well if you can coax 70W/channel of audio output from a chip amp at 60% eff I would shoot for ~150 VA / channel taking into careful consideration the rail voltage droop under load. If you combined the 2 into one 300 VA XFMR the rail will be stiffer ie better regulation. __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

26th July 2010, 04:46 AM	#8
infinia diyAudio Member Join Date: May 2005 Location: Californication	You could buy a single 300VA or 2x 150 Antek brand for saving big $$. AFAIK they are equal to PLITRON at the standard ship now series. Spend a moment at their site its really not too hard to figure out the P# scheme. __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

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25th July 2010, 01:52 AM	#3
DaveSail diyAudio Member Join Date: Jul 2010	I don't know a lot about electronics . Just felt as a V - 6 or a V - 8 gets less wear / sress than a V - 4 doing the same work , it might be the same with TFMRs ! David

25th July 2010, 07:27 PM	#4
DaveSail diyAudio Member Join Date: Jul 2010	This amp will be for my " Bedroom " speakers . They are very efficient . JBL LE14A Woofer and LE85 Mid / High . May add a pair of Slot Radiators . They both have massive magnets and large voice - coils . My 1 Watt Clock Radio will drive them such that they shake the walls ! However , quite often folks ask to borrow an amp . Perhaps for a Audio - Video presentation or for an outdoor picnic or such . So , for those occasions I think it would be good to have the larger XFMRs . David

26th July 2010, 03:59 AM	#7
DaveSail diyAudio Member Join Date: Jul 2010	Super . What would be the PLITRON part number for those ? There are a LOT of units in their catalog ! TIA DVW

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