kevin gilmore

Making it harder to fix makes repairs a profit center

and those ultra cheap ids connectors for the 2 pin things. I hate those. actually it was pointed out to me that those are not extrusions but just flat pieces with angle brackets. So REALLY cheap.

also notice that the whole case is aluminum extrusions. So new chassis again. at least the tube is much better and lower distortion and wider frequency response than the mosfet as the voltage gain stage. Now the output stage that sucks all the power is completely useless. only one transformer now so there had better be a delay circuit for the high voltage otherwise the tubes are not going to last very long.

definitely moar better.

I can post pics of the original. And the burned circuit boards that resulted from no heatsinks because the bias was 4 diodes and all over the map. This really is the original design. With a real bias generator and a dc servo because you can't get those output caps anymore, and why would you want them anyway.

yes 10ma in the output stage. That's 80% of the tube rating. you can use the other parts, but they are not as temperature stable.

its kind of funny that something that started out as a $200 amp turned into something >$5k

That is right depending on the second stage zeners. If unreg voltage is at least 35 you will be fine

You sure they are 6s4... I will fix schematic later. Hard to tell the difference between 6s4 and 6973

yep, the input fet has been fixed. also, next version of the kgsshvk board has it fixed too. (at least I think its fixed, please check) hv transformer is going to be lower voltages. best idea to have a separate filament transformer and time delay. current power supply board works fine with the resistors adjusted for 400v which means the unregulated voltages should be about 465v. will post newest picture, same name in a few minutes

actually birgir is right, its worse, not better. http://gilmore.chem.northwestern.edu/llmk3.pdf

same power supply, just adjusted for 400v

as far as I know the portable is not an electrostatic amp. I have a great design for a portable electrostatic amp. Every time I try to get someone to build me the switching power supply transformer, they either cannot deliver, or what they deliver is so low in efficiency that it would eat batteries way to fast. What I really want is stacked printed coils on kapton. anyway, the stax mafia does not let grass grow under their feet. http://gilmore.chem.northwestern.edu/kgst.jpg solid state/tube hybrid done right, and actually pretty cheap.

enough people have been asking for this, we finally decided to do it. It was easy from the current layout. Best to stick with +/-400v power supplies http://gilmore.chem.northwestern.edu/kgst.jpg

you know that for a great design, all you need is a voltmeter.

From what I've heard, the current sources for the tubes are the same cascode in the same exact physical place. Meaning the same screws you can't remove from the triple of small heatsinks. So all you have to do is dump the rest of the crap and drop in 4 tubes. Basically the same as the exstata tube version without the bipolar output stage. Very simple circuit. I could draw it up in a few minutes. The only issue is what the tubes are, and what the power supply voltages are. since evidently there are no other heatsinks on the board, likely its not grounded grid design. Probably a couple of hours of board layout max. I could turn something like that around in one day, and get pcbnet.com to deliver boards in 3 days. Its going to sound way better than the mosfet pile of crap. And be pretty much identical to tube based stax product of the middle 1970's. Still going to be built like shit.

LL mark 3 with tubes being shown at RMAF. all the mosfets in the amplifier are gone.

with those size paws, looks like its going to be a fair bit bigger than that.

how big is puppy supposed to get?

admin as in singular.

that schematic is for one channel plus a little bit. so there should be 8 power output cathode resistors total.

this matches the board http://gilmore.chem.northwestern.edu/megatron.pdf

60 seconds to let the tubes fully warm up same as the T2. you really want to do this at these current and voltage levels especially with expensive tubes. Ristar used 1k cathode resistors on the amp board instead of 1.5k resistors. The 10 big ones. Ristar changed the 15 ohm resistors on the power supply to 10 ohm an he left off the 2n3904.

needs t2 style power on delay for the high voltage. Or separate switch, one for filaments, one for high voltage. 150ma on the power supplies. about right with 1k resistors. room heater for sure. 135 watts of high voltage plus about 85 watts of tube filament power. no front end tube distortion, no limited output frequency response due to limited size center tapped inductor core etc... plenty of gain, low distortion. yeah baby.

If the power supply voltages are right and the offsets and balances are in the 10 volt Range you are done. Go and listen to the music. Leave the 15 ohm resistors alone for now, let me know The voltage across them. Leave the current limiters off for now. Will have modification soon. Too many projects reaching completion at the same time