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wrenchone 3rd July 2012 03:40 AM

Das ist aber Schade...
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Attached is a high voltage "Schade" type SE amp that should exploit the HV capability of the ST STW7NB80 800V mosfet. These were an Electronic Goldmine special for quite some time, and I bought my share, intending to use some of them in a quasi-resonant flyback power supply operating off of doubled 115V mains. Some will indeed go there, others will go linear in this app.
The output transformer I'm using is the UBT-1, as I snagged a pair at a discount on E-pay.

I'll probably also try the Semisouth 085 in the output position with a circuit like this some time down the line, as the follower in front of the output stage would allow operation without having to worry about the 085's scandalous gate leakage current.

The heat sink is almost ready to mount the amp modules and output fets. If I get to it tonight, I plan to make up some output/power/feedback cables for the two amp modules. First step would be to power up the amps with bench supplies to check out bias stability and square wave response. I plan to run the amp using a largish 115-230V step-up transformer with a choke input filter. Said choke should be on its way soon from Angela Instruments.

I'll be looking at another variant of this circuit for a low voltage app without an output transformer, but that's just another thing on top of the already teetering pile of projects.

wrenchone 5th July 2012 06:20 AM

I spent a while tonight making up cables and power supply leads (serenaded by enough firecrackers for WWIII), so this amp will soon be ready to slap down on the heat sink for a first power-up with bench supplies. I'll run it open loop at first, but if it's anything like the "SiC Puppy", a little feedback around the output transformer will be beneficial in cleaning up the square wave response. I may have some preliminary sound out of this thing by the close of the weekend.

Melon Head 5th July 2012 10:08 AM

looks interesting

Nelson Pass 5th July 2012 07:47 PM

I have a design called Shadenfreund.


Michael Rothacher 5th July 2012 07:53 PM

It works best when other designs aren't.

wrenchone 5th July 2012 09:23 PM

Of course you could also use as an amp name the peculiarly German term (why do they have a word for it?) "Schadenfreude" - it's happy when other amps burn up, and its distortion figure goes down as a consequence...

Nelson Pass 5th July 2012 10:47 PM

I considered it, but I wanted a name which implied

plays well with others


wrenchone 5th July 2012 11:15 PM

There's such a thing as being too nice - a little nasty leavens the loaf....

wrenchone 8th October 2012 03:22 AM

This guy is still sitting in the basement waiting to be powered up - I think it might be next in line if I can bring it up with a combination of electrophoresis supply and bench supply - stay tuned...

wrenchone 25th November 2012 04:46 AM

Update - I'm bringing this beast to work with me tomorrow (heat sink plus dangling components). It'll get some burn-in with bench supplies while I unravel the cantankerous mysteries of a self-oscillating buck regulator.

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