What in the heck should I do with these?

[lt_texan]

My trusty BK 200wpc amp blew up years ago. Salvaged:

- Mains transformer 625W (!!!) with 4 x 50VAC secondaries.
- Smoothing caps 4 x 17,000MFD 95v. (Do you think I carefully discharged these?)
- And a high quality huge enclosure with equally impressive heat sinks.

I was thinking a LM3875 chip amp with a ridiculously over spec'd mains transformer, but I think the 50VAC (unloaded) secondaries are too high.

I've never built a solid state power supply, but I would think this would give me a dual mono 2 x +70/-70v dc supply.

Any suggestions?

 

[CanAm Man]

Sounds like you have the start of a Class A amp. I'd recommend you go over to the Pass Labs forum, and ask the same question. I think you'd be a candidate to build the new F5 Turbo.

 

[NissanSR20Man]

Sell them to someone doing a L15-25D build as the 50V secondaries would be perfect

 

[pacificblue]

Buy what you need to build a chip amp, including adequate transformer and caps. Make a listening test to find out whether it can replace that BK amp you are used to. Then decide, whether you sell the BK transformer with the caps or the chip amp. Or both.

 

[pinkmouse]

Yeah, I agree with the other posters, not really suitable for a chip amp. I'd have a look through the SS forum as well, Apex and Ostripper have some nice designs for those rail voltages.

 

[Juergen Knoop]

a single supply chipamp is doable with your transformer and the four electrolytics. Yet I'm not aware of any kit or project here.
Can you do a pcb and build/test a circuit on your own?

 

[lt_texan]

I never ventured over to the Pass Labs forum.

OMG.

I think best for me to inventory the parts for a while. Sit down and cool off.

I'm a tube guy. I'm a tube guy. I'm a tube guy.

Thanks to all for the suggestions.

 

[lt_texan]

Oh damn, just realized, 2 primaries for 120/240V.

So wire the primaries in series with 'merican volts and get 4x24V secondaries. (Secondaries measured 49.5V, so figure designed for 48V.)

Good for +/-30V rails.

Guess I'll head over to Pass Labs Forum

Thanks again!

 

[Speedskater]

Remember that when you rewire the primary like that, it becomes a 312 Watt transformer. As each secondary can only carry the same amount of current, but now it's at half the voltage.

 

[lt_texan]

yikes, didn't think about that. Think more in line that the iron could support the wattage in different configurations.

So, the original design was for the primaries to draw 2.6A each in parallel at 120V.

And secondaries are 4 x 48V at 3.25A = 625

So, it doesn't make sense to think with the primaries in series it will draw 5.2A and the primaries will deliver 24V at 6.5A each.

 

[ChristianThomas]

Tripath TA0102A perhaps. But even there the voltage might be a bit high - prob 56V max. Mind you, you could probably run two stereo amps off that. And for voltage, it's not against the law to take off a few turns either, to get the voltage you need.

 

[woodturner-fran]

I have exacty one of those amps - donated by a friend after it died.

I have it wired up as a pass delite amp, although I'm about to build a LM3875 amp into it. Don't know if those heatsinks at the back would be good enough for an F5, but they'll come very close. If you build an F5 and trim back the bias a tiny bit I'd bet you'd be OK. .

 

[jaycee]

Anything over 30V after rectification is too much for the LM3875/3886 chips. There are STK hybrid modules that will take higher voltages, but they are long out of production and only NOS stock exists.

You are correct you would end up with 70VDC symmetric supplies. That's a lot of juice. You're certainly talking about a discrete solid state amp with that sort of supply.

 

[geraldfryjr]

A bridged chipamp (BTL) could run off of those windings like a BPA200 or BPA300 or some thing if you wanted to go that route.

Just for a thought.

jer

 

[lt_texan]

Thanks guys, but I think best for it to go up for sale.