kevin gilmore

I have tried every combination of capacitor of all kinds, and resistor and capacitor of all kinds in parallel with the power diodes with no success. Now if i go back to really lousy diodes and EI transformers, then the caps actually do stuff. But with the fast recovery diodes the last remaining bit of noise is very hard to get rid of. I really like the basaudio thing. Sure wish i had seen it earlier. The T1 current source feeding the gate of T2 makes all the difference. But it also needs the low voltage supply for the opamp, which i did on the T2 with a current source and zener. Will study more tomorrow. Thanks marc. Still i like the hybrid approach that shuts down the current source in the absense of a load. And adding that to the basaudio thing probably turns it into an oscillator like the problems i was having. More to do plenty of extra time now due to this... http://gilmore.chem.northwestern.edu/dsc_1813.jpg

I always thought the idea was to make absolutely the best performing thing possible, then once that is accomplished, find a way to reduce the parts count and price. Reality has no place here. We are nuts by definition. If you are not nuts, then please leave. John Curl class obsession is absolutely required. For the high voltage stuff, everything i'm doing is either 450 volts or 500 volts. Not really interested in anything else. OK, well 250 volts for possibly the next generation T2 in some even bigger chassis. The low voltage stuff is also however important and has different design issues, but really much of the same stuff. For example dynahi/dynafet/B22 class things with +/-30 volt power supplys, and even +/-40 volts for those that desire to some quality to go with their 160 volts peak to peak into lcd2/he6. The most successful stuff so far (i.e. the stuff with the lowest noise, and best regulation) uses depletion mode mosfets as the current sources, and then either series pass or shunt mode pass devices. Until someone can show me some clever way to shut up the power supply diodes. Maybe the SiC things, but i don't have any of those to test. Compared to the unregulated supplies of the past with a few hundred millivolts of ripple, any of this stuff is light years better.

I have the power supply done, no problems, and one channel done, also no problems, i'm using a real lsk389. Doubt that matters. An oscilliscope is your friend. especially if the trouble you are having involves an oscillation of some kind. If there are no parts flying across the room, you have to be pretty close.

The problem with tubes is ... well tubes For a kgsshv supply you would need 4 of them. For a T2 supply you would need 8 of them and still need some solid state stuff. As well as lots of extra floating filament windings to run the heaters.

So i've been playing with the miada thing at 250 volts due to lack of some other parts. Its R1 and D1 that are the problem, the spike noise from the power supply diodes rips right thru and you end up with about 180 microvolts of spike noise. Still way good enough for lots of stuff, but probably noticeable in the ultimate S/N of an electrostatic amplifier.

A maida circuit with a tl783 is possible, ray manages to do the same thing at 600 volts without the front end voltage reducing transistors. I'll try it. But the idea is to use an unregulated voltage of about 625 volts to make sure that there is enough to do the 580v bias. Will order the parts and see what the real performance is. The problem will be voltage drift over temperature as there is no extrememly stable reference.

The universal series/shunt/hybrid regulator board will be posted soon Seriously, some things work out great, some things not so great. The tl431 has too much gain to make it useful. There may be other similar devices out there that work better, but it is unlikely. The idea of an amplifier with all isolated packages sure would make things easier. Don't know of any isolated versions of the 2sj79/2sk216 either. Any current source that references the unregulated input voltage (like the cavalli thing) absolutely guarantees that the spike noise from the diodes rips right thru the current source and the rest of the circuitry. This is why the 10m90s part works so well.

well for one thing, i had already been using that setup for some time, not sure how long. But the 16 bit dacs in the sony (and later the d-ej01 or some such) beat the crap out of the less than 14 bit ipod at the time. Too bad the stax eats so much power, a new version of that setup is something on my todo list. edit: d-ej01 corrected. I still have 2 of them.

The hybrid shutdown part combined with the required caps across the tl431's cause massive oscillations. hundreds of volts. with the shutdown part removed, it works and is about 35 microvolts peak to peak noise. The tl431's really like to oscillate, and once you add enough cap to shut them up, everything slows down.

media players did not exist back then http://gilmore.chem.northwestern.edu/porta.gif date... 2/20/2000 besides which, compressed to hell music from one of the early mp3 players on stax headphones... be serious. to bad sony never actually sold their portable sacd player. I would have bought it. Now back to our regularly scheduled program, food, a bit of rest, now lets see if i can't send some parts flying across the room.

Hey, i used that for years and years. But after 9/11 there was no way in hell they were going to let me on an airplane with that. It was a 12 volt 7 AH gel cell.

OK, so linear's first circuit with the ixys current source devices and the tl431 with a 10uf cap across it actually tests at 20 microvolts peak to peak noise. (10k load) about 4 to 5 times worse than the T2 battery version. With anything less than 10uf it has very nasty startup oscillations. Obviously with the cap across it, it is nowhere near as fast as the T2 battery. Absolutely needs a 24 volt protection diode across it. Going to try the tl431 as the current source next, but anything i have tried like this previously has a lot more noise from the switching of the diodes because of the resistor to the gate.

The current kgsshv power supply is a series pass design. Works just fine from 0 to full load. Alex Cavalli is now famous for making shunt regulators that blow up real good when the load disappears for any reason. In theory shunt regulators can be a bit quieter than series regulators. In practice, once you get into the hundreds of microvolts of noise or less its the power transformer and diodes that are most of the problem, and something not easy to fix. Compared to the hundreds of millivolts of ripple on most power supplies for tube use, we are well into the major tweek realm. I think that added zener diodes across the tl431's and tlv431's are probably necessary for startup and shutdown conditions. It sure would be nice to have 100% isolated packages for the entire designs.

Except for the srm300, none of the other stax electrostatic amps have regulated high voltage power supplies. Just diodes and capacitors.

sure is much simpler. I wonder how stable it is. Will evaluate my model for the tl431 is probably lousy, but load regulation is in the many percent, and the noise is 7 or 8 millivolts. You are relying on the pass fet to stay stable over temperature, and that certainly is not the case. Will play more can host ltspice stuff.

Actually if the batteries are adjusted well, the opamp output voltages are no more than +/- 3 volts. You could certainly turn the other opamp into an inverter and drive the current mirrors that way. A savings of a few parts. edit: if one of the opamps was at the rail, the other opamp would have to be at the other rail. Here is the first cut of the hybrid shunt regulator version of the kgsshv power supply. http://gilmore.chem.northwestern.edu/shuntregver2.pdf Unlike some other shunt regulators however, the current sources shut down if the shunt element pulls too much current, so its safe to power up with no load. edit: silly bench mistake fixed. Actual noise under load about 3.5 microvolts peak to peak.

The common mode servo is Q34,Q35 and Q36. You could replace those, but you would need another opamp to do it. Even though you could get rid of a few parts you still would need an inversion from the one opamp to drive both current mirrors. So you need 2 opamps for that.

Make sure you change out that electrolytic again, and throw the overvoltaged ones in the trash can. To everyone, power up the transformers on the bench to make sure you know how they are wired before you hook them to the boards.

So lets see, about 650 volts on a 450 volt cap. Yep that is probably going to cause it to get stinkin hot... And the regulator circuitry does not care, as it can handle 800 volts easy.

Actually the 2sc2240 would work just fine. But i was simulating absolute worse case. Lets say the current source on the top of the top input tube shorts, then the top tube shorts... Suddenly 250 volts on the cathode. Of course this has not happened yet, and is unlikely to ever happen. But i do wonder what would happen if just the tube shorted. This scenario would blow up the 2sc3381's anyway. And this is why i figured it would be easier to use the 300 volt versions. Which are still dirt cheap.

The simulation shows absolutely no difference between the 4 transistor current mirrors, and the single transistor circuit. Does need to be a 100 volt transistor however. Due to tube shorts, probably should be rated at 300 volts. Whatever the npn equivalent of the mpsa92 should work great.

just bought this, it will be here monday http://www.saeco-usa.com/en/products/household-automatic-machines/1/automatic/0/xelsis-digital-id/311/xelsis-digital-id.html replaces a 15 year old saeco magic deluxe that is finally beginning to show wear.

posted for linear http://gilmore.chem.northwestern.edu/servochange.jpg

So a couple of people have asked for a discussion of the design elements of the T2, and any observations and improvements that are possible. So as not to polute the T2 build thread, which is already seriously poluted, the discussion of T2 design elements, including kerry's dynamic amp should go here. doug wadsworth (wadia) should be stopping by soon Actually, a moderator change the thread title to discussion of the T2, and other circuitry as we see fit including but not limited to my other designs and shunt regulators and stuff like that etc...

Well with a set of linear supplies, it tips the scales at 800 watts of heat. I would say its kinda hot