kevin gilmore

The digital attenuator part is similar to, but drives different from AMB's thing. Its still an 8 bit relay thing, with latching relays. I used AMB's calculator for the resistor values. My version drives twice as fast as linuxworks thing. I originally was going to use AMB/Linuxworks thing as is, and give credit but linuxworks turned into such a jerk... And they still have not actually released the thing. Mine may be out before theirs The version with no front panel, i was thinking an ipad app. wifi... infrared? that is SO last century...

Not too many companies want to make EI power supply transformers these days. Actually it seems that these days, no one wants to make anything unless they can make a million of them. And then not even then (semicoductors i like) Torroids are much more efficient and smaller for the same amount of power delivered. Torroids radiate much less magnetic field. Torroids buzz less. (well some of them anyway) It may also have to do with the fact that for power torroid transformers, you can wind the primary on one area of the transformer, and the secondaries on the other side and avoid the hastle with interwinding capacitances and other stuff that seems to get UL in a tizzy. There are some things about the good old days i would rather have back. The fast recovery diodes are at least 10 times (probably more like 25) faster than the old high voltage diodes. Once again, trying to find 1kv to 2kv diodes is getting harder and harder and harder. So i use what i can get my hands on, with lead times of less than a year. The SiC things might be really good. i'll let you know once i get some. Fact is that if you build stuff the good old way with the good old parts, you are nowhere near the ultra low noise levels that i can get now. sucks don't it.

Lil knight among others have asked for an updated dynahi board. Here it is. http://gilmore.chem.northwestern.edu/dynahi8.zip changes, remove 2sk389,2sj109, add lsk389,lsj109 2sk170,2sj74 you can use opa445 instead of op27 and then you don't need the 7815 and 7915. 2sa1349,2sc3381 can be replaced with the single versions. I need to check this a few more times. unbalanced input, balanced output version coming soon.

bom errors fixed except for the transformer description which i will have to dig up.

Just noticed that if you are using the lsk389, you have to solder it in to the bottom of the board... The 2sK170's are fine. I'll fix the board layout quick.

I'm cleaning up the BOM now... I only found one error (C9---C10) If others know of any errors, post/PM/email please. http://gilmore.chem.northwestern.edu/kgsshv.xlsx

i thought we already had the schematic for the sra14s... will look soon.

Its time to get back to work on this, now that the other 2 major projects are completed. I've been told to stay away from OLED's because power supply failures can cause burned up lines. So unless someone has a better idea, i'm going to go with this one. http://www.4dsystems.com.au/prod.php?id=114 I want a touch screen, and i want the embedded proc to be able to do i2s to drive the switching etc. Edit: screw it, i ordered both the oled and lcd versions. Also ordered enough stuff to make the thing programmable from wifi. You could do a version with no touchpanel or knobs at all.

This gets into the discussion of which values of film resistors (varies by manufacturer) is the least inductive. If you are careful, you definitely can get metal film resistors that match the carbon comps. Or buy those non-inductive bulk carbon film on ceramic things which are very temperature stable.

If anyone knows of a portable gps unit that actually displays time in seconds, i would really like to know about it.

Yes i have tried a few versions of that too. That was the one time i got my ass kicked, first time in a while. For some reason getting hit with voltages like that does not have the same effect it used to... I'm going to have to try again.

Yeah team... I'm getting REALLY TIRED of the fake parts... There has to be something we can do about this. Maybe massive group buys directly from the manufacturer. The fake 2sk389's are not a surprise. Hey linear systems, get off your fucking ass and finally release the lsj109's please (after 3+ years) I'll have to clean up the bom one of these days.

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.