much less crazy idea

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e96mlo said:
The easiest way is to just look in a catalogue from a local retailer if you don't find a site where you can search on specific parameters. Check out Mr Holton's site. He builds some really high power amps with rails up to +/-90 V. Maybe he uses some suitable transistors.


Actually, I find that in his very high power amps namely the 1kW MOSFET amp, his choice of output devices is poor at best.
Okay, i see your ideas...

About the flyback diodes, I forgot to pick names for them...
I have a bunch of high curent/voltage diodes that I intend to use here, but I still don't know the number... Also, about the pots, when you say use all three legs, are you meaning like a rheostat or something? And I will use a current mirror in there since it seems so great, I do think it would achieve better balance than the other ideas(pots) Also, I had a question about bias of the VAS, wheres it supposed to come from, what controlls it?
OKAY, I've completed the amplifier design except for the fact that
I can't find the right transistors to use for the LTP, mirror, constant current source, VAS, and drivers.. I was originally going to use 2n3906 for the small signal transistors and BD139/140 for the vas and drivers, but it seems that they are two low in BVceo
for my designated rail voltage. So, can anybody help me choose what transistors t use, because I don't know about that many so I'm having trouble picking... Also, whoever reads this, please look at the finished diag. attached and note if you see something else wrong...




  • finished.jpg
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Well, I have yet to decide on how I'll make a pcb, I do have a box of pcb tape stencils that you put on the board before you etch it, they block the etchant wherever you use them, so you use them to make traces and whatnot. I do have a few ideas for a heatsink, it will be very big so they'll run cool. The OT transistors will be mouned onto the pcb as well, to reduce compications.

Do you know of a program where I could enter a diagram and get a pcb printout made right on the computer??? That would sure be useful!

Also, instead of using insanely huge traces on the board for high current lines, I'll use moderate sized ones and cut thick sheetmetal to their shape and solder them onto the traces. That'll give me pretty current handling.

And! Then best part is, I have the perfect rackmount chassis for these amps. It was a 3chassis set from an old airplane landing computer from the 60's, made of a few thousand hand soldered discrete transistors doing a task that could be doneon ic at a 1000th the size and weight and better. Anyhow, back to the point, the thing consists of three 6U rack cases with rollerbars so you can simply (unlock) them by pressing a button and pull them out. After you pull a chassie out, it will rotate around on a wheel with a lock on it, just press a button to unlock and rotate the chassie and then let go of the button to lock it ans start service without removing any screws or anything.

This old computer, as I said, has three chassies, one was the main power supply and control unit for the whole computer. The second down was the computer itself, converting all the signas and doing it's estimating and thinking. Next down, on the very bottom, was the time base and function generator, no different from a modern logic timebase and signal gen, except that it would emit about 100 different arbitrary signals at once or compare them for you at will, instead of only about 4 or 5 of the modern generator!

I plan to use the power supply chassie again as the front end and control/protection of the amplifiers. The transformer I'm gonna use is a 5KVA line transformer rated at 110 or 220 volts out/in with 2 seperate coils in each side. I'll simply wire the two primarys in series and feed them 110 volts, and then, do the same on the secondary and have 55-0-55 volts and a bridge and caps, and servo in case I need to adjust the voltage.

By now you should know that the transformer is way to big for a 6U rack box (it weighs 60 lbs) SO I'll mount it outboard and feed 2
AWG copper bar wire into the control unit where it will be rectified, filtered, regulated, and sent to the amplifiers and auxillary circuits.

In each the top chassie, I'll have a pair of my amplifers posted on this thread to run my main stereo speakers up to about 500 watts. Then there will be auxillary amps in the bottom chassie, 2 for the surround speakers rated at 60watts each, one for the sub, rated at 350watts and
one for the center channel, rated at 50 watts.
All connected with theri respective umbilical cords to the main control chassie where they can leach their power and get a signal to amplify.

The control unit will have BAL/UNBAL intput and output line level channels and a selector for everything. It will also employ a RIAA
preamp for my turntable and have sound impairment and measurment connections to monitor waveforms on my scope and analyzers.

I expect the unit, when completed, to weigh about 150lbs alltogether, so I'm gonna need a serious rack to stick it in.
And have to run a dedicated 30 amp line right from the fuse panel to my amp rack alone!:eek: But it will make an impressive system indeed, although, I doubt the neighbors will agree if I start wrecking their low end electronics wil sonic waves from mine:D

Anyhow, that's the idea for the finised project, and I have everything I need for parts except for a handfull of transistors and resistors, and the schoolyear is just up, so I have no excuse not to finish this thing by the end of the year!

Also, we just moved to Saskatchewan from BC here in Canada.
I haven't unpacked all my gear yet so I can't take photos for everybody to get the idea of what this will look like just yet. But I will somtime in August.

So, keep posted, but if you don't, you'll know when I get this thing working, trust me, you'll know! You, and about a few thousand other people!
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