Transformer ok for power amp??

[6502dude]

I picked up a 35-0-35 280VA transfomer last weekend with thought of using this to build a power amp.

Is current capacity not adequate for a 2 channel amp?

Please excuse question from newbie if not within scope of this fourm.

[richie00boy]

It's just about OK for an 8 ohm load. You should be able to get about 70-90 watts RMS into 8 ohms per channel.

[6502dude]

Thanks for info.

I can likely get another one of these xformers cheap (used - @ about $16USD) and was thinking of hooking the two up in parallel for extra current capacity.

I have a pile of 2N3773s that I salvaged a few years ago that I wish to use as well.

Cheers

[Giaime]

Well... you 2N3773 looks good, it is a new 200°C max transistor, 160V 150W. I guess you can do dual mono with the 2 transformers (or just build 2 monoblocks ) and get an hundred of watts per channel... maybe with that high voltage and not so high power rating you need to parallel the output transistors...

Just my 0.02

(eheh... I know how a diy-maniac feels when he has stuff for cheap... )

[richie00boy]

Yes, I would go for the dual mono rather than parallel. Although as I said one will be OK for use with 2 channels as long as you aren't into cranking it up all the time and your speakers are an easy load.

[AndrewT]

Hi,
the 2n3773 is a robust 150w transistor, well suited to quasi topology.
Temp rating is Tjmax=150degC.
It has very good current handling at medium voltages, the knee in the SOA curve is at 100v making it better than many 250v & 350v transistors. Power rails of +-50v to +-70v are usable even though it is a 140v device.
Keep them cool if you do push the voltage envelope.
Single pairs work into 8r and medium 8z.
Twin pairs for 4r and medium 4z and difficult 6z.
I second the dual mono route for the transformers.
As a monoblock you should achieve 120w into 8r on 55v rails.

[6502dude]

Thanks for all the great feedback.

I picked up 2nd transformer this morning and am now leaning toward dual mono block design for power amp.

I don't really need a another power amp.

I have a Bryston 4B for living room audio system, a pair of Crown DC300A Series II in my listening room - running bridged mono, and a pair of Crown D150As stored in thier boxes for last 5 years.

However, I have always wanted to build my own power amp. I'm sure it will sound the better than the others :-)

[Giaime]

Yeah, it will sound better, because it's your own

I would do a dual mono, quasi complementary, +-55VDC rails, paralleling 2 transistors per side (you'll need 8 of them for the whole thing) for difficult loads.

Good luck!