What to build with 2x22V 160VA tranny and Heatsink

transducer · 20th August 2002, 12:42 AM

I've got a Plitron 160VA 2x22V secondary transformer lying around, plus ONE heatsink measuring 10" wide by 4.75" high with fin depth of 1 5/8" on a 5/16" thick base, 22 fins total. I'd like to try a small 2 channel class A amp, is there anything I can do with these two parts that is worth it? My new speakers will be pretty efficient, around 90dB 4ohm load. This is just for fun, and to get a taste of a Pass style amp, I don't want to spend a lot of money on it though. Maybe a Mini-A? I lost track of what was happening with that one.

Thanks,
RonS

AudioFreak · 20th August 2002, 01:25 AM

The rails will be too high for a Class A Power Amp given a 4 ohm load and the VA rating of the transformer. Your really limitted to a class AB power amp of about 40W/channel into an 8ohm load, a line level circuit (perhaps a preamp) or a (possibly Class A) headphone amp.

Variac · 20th August 2002, 01:30 AM

I was gonna say a gainclone, but noticed we are in the Pass area,
http://home.attbi.com/~greggbaker/invertedLM3875.gif
Edit- I think it is too small for your chips, but it might sqeak by for a 25w/ ch
Wot's Planet 10 say?, ask him

transducer · 20th August 2002, 01:40 AM

Audiofreak, So the VA rating is too low for a class A amp using these rail voltages? (by the way, I estimate around 29VDC) This tranny actually came out of a preamp that I had done years ago, based on Corey Greenbergs buffered preamp.

Variac, I had thought of a gainclone, I actually have 7 LM3886's lying around, had also thought of a paralleled bridged configuration for 200W but the tranny is too small. Would this tranny be fine for a pair of gainclones using the 3886? I guess my overall power would be lower than full potential.

RonS

Peter Daniel · 20th August 2002, 01:44 AM

If your transformer has option for 110/220V you could connect primaries in series and effectively reduce secondary voltage in half. Mini A would be tempting then. Too bad Grey's not around.

transducer · 20th August 2002, 01:47 AM

Unfortunately there is only one set of primaries for 117VAC

RonS

AudioFreak · 20th August 2002, 01:58 AM

Loaded voltage will be about +/-25V i suspect which leaves +/-20V swing assuming you use LM3886's. Now, the transformer is good for about 4.5Amps rms output which equates to 50W max rms per channel into 4ohms or about 40W rms average into 4ohms assuming a normal stereo musical signal. This drops to 20W rms per channel into 4ohms if the input signal is mono.

Nelson Pass · 20th August 2002, 02:19 AM

How about a nice pair of Zen channels? You should be
able to put two 10 watt originals on that sink, or better
yet, a pair of 10 watt channels with the Zen Variations 2
circuit and a little value adjustment.

One secondary per channel, isolated as with the Zen Lite.

AudioFreak · 20th August 2002, 02:22 AM

Now that is a good idea!!!

transducer · 20th August 2002, 02:37 AM

Hi Nelson,

Wow, an answer from the man himself, and to my first ever question on this forum!

I'm interested in the Zen variation 2, but I cringe at the thought of that big ol cap on the output

My source is single ended, so I can't do anything there. Any other thoughts?

Cheers,
RonS

20th August 2002, 12:42 AM	#1
transducer diyAudio Member Join Date: Mar 2002 Location: Toronto, Canada	What to build with 2x22V 160VA tranny and Heatsink I've got a Plitron 160VA 2x22V secondary transformer lying around, plus ONE heatsink measuring 10" wide by 4.75" high with fin depth of 1 5/8" on a 5/16" thick base, 22 fins total. I'd like to try a small 2 channel class A amp, is there anything I can do with these two parts that is worth it? My new speakers will be pretty efficient, around 90dB 4ohm load. This is just for fun, and to get a taste of a Pass style amp, I don't want to spend a lot of money on it though. Maybe a Mini-A? I lost track of what was happening with that one. Thanks, RonS

20th August 2002, 01:30 AM	#3
Variac diyAudio Editor Join Date: Dec 2001 Location: San Francisco, USA	I was gonna say a gainclone, but noticed we are in the Pass area, http://home.attbi.com/~greggbaker/invertedLM3875.gif Edit- I think it is too small for your chips, but it might sqeak by for a 25w/ ch Wot's Planet 10 say?, ask him __________________ Burning Amp Festival Sunday, October 28th, 2012 in S.F. We need Volunteers & sign-up's for what you're bringing!

20th August 2002, 01:44 AM	#5
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	If your transformer has option for 110/220V you could connect primaries in series and effectively reduce secondary voltage in half. Mini A would be tempting then. Too bad Grey's not around. __________________ 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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20th August 2002, 01:25 AM	#2
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	The rails will be too high for a Class A Power Amp given a 4 ohm load and the VA rating of the transformer. Your really limitted to a class AB power amp of about 40W/channel into an 8ohm load, a line level circuit (perhaps a preamp) or a (possibly Class A) headphone amp.

20th August 2002, 01:40 AM	#4
transducer diyAudio Member Join Date: Mar 2002 Location: Toronto, Canada	Audiofreak, So the VA rating is too low for a class A amp using these rail voltages? (by the way, I estimate around 29VDC) This tranny actually came out of a preamp that I had done years ago, based on Corey Greenbergs buffered preamp. Variac, I had thought of a gainclone, I actually have 7 LM3886's lying around, had also thought of a paralleled bridged configuration for 200W but the tranny is too small. Would this tranny be fine for a pair of gainclones using the 3886? I guess my overall power would be lower than full potential. RonS

20th August 2002, 01:47 AM	#6
transducer diyAudio Member Join Date: Mar 2002 Location: Toronto, Canada	Unfortunately there is only one set of primaries for 117VAC RonS

20th August 2002, 01:58 AM	#7
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	Loaded voltage will be about +/-25V i suspect which leaves +/-20V swing assuming you use LM3886's. Now, the transformer is good for about 4.5Amps rms output which equates to 50W max rms per channel into 4ohms or about 40W rms average into 4ohms assuming a normal stereo musical signal. This drops to 20W rms per channel into 4ohms if the input signal is mono.

20th August 2002, 02:19 AM	#8
Nelson Pass The one and only Join Date: Mar 2001	How about a nice pair of Zen channels? You should be able to put two 10 watt originals on that sink, or better yet, a pair of 10 watt channels with the Zen Variations 2 circuit and a little value adjustment. One secondary per channel, isolated as with the Zen Lite.

20th August 2002, 02:22 AM	#9
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	Now that is a good idea!!!

20th August 2002, 02:37 AM	#10
transducer diyAudio Member Join Date: Mar 2002 Location: Toronto, Canada	Hi Nelson, Wow, an answer from the man himself, and to my first ever question on this forum! I'm interested in the Zen variation 2, but I cringe at the thought of that big ol cap on the output My source is single ended, so I can't do anything there. Any other thoughts? Cheers, RonS

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