kevin gilmore

definitely the t8000 is dc coupled. but it has a servo, so the frequency response low limit is .1hz

twice the impedance at 10k than a cascade current source alone, 20 times better than the t2 current source but by specs, only good to about 930 volts

I will synthesize that and get back to you

you can't, that is the problem. there are other depletion mode ixys parts with 1kv or more, but they are not sharp cutoff and have more capacitance so you have to cascade them.

not enough voltmeters

also notice the same rms voltage as 727 which means +/-350 power supplies

my guess is a single dual triode as the differential amplifier, probably a pnp cascode, pnp current source driving a npn only way to keep it all dc and still get the plate voltage down to something manageable

looking at the pictures, small surface mount transistors on a board that is insulated from the heatsink. so pretty much the couple of pnp and npn surface mount parts that are available plus a tube front end that emulates the t2 with a lot less parts price seems grossly high for that

T2 was the only stax with a servo. both common mode and differential mode. 717 had protection relay circuit if dc was out of spec

jude reviewed the new stax amp, t8000 over there

i suppose that should work. as long as all the parts are rated for the voltages you want to use

a room full of amplifiers?? ask birgir. how about 3600 square feet of amplifiers.

I expect to now be able to spend significant amounts of time on new designs

huh? where you getting the high voltage power supply?

i have turned in my retirement notice, so my file server probably won't be up for more than a couple of weeks, get copies now. i have a complete backup and will be moving to my own domain soon.

that works too. seems like the world stock of 2sc4686a are about to go extinct.

probably a regulated version might be better

yes that is the idea, something with at least 1kv isolation. 12v to 12v, series resistor, tantalum cap, and then a resistor to get to the right led current. but you do need 4 of them per amplifier, but they are cheap any changes to the board will keep all the spacings intact.

I did both ksa5 power supplies. The original is triple pass transistor/zener regulated

here are 3 current sources at 10khz currentsource.PDF

its ac coupled and there is no servo

the closest thing to a perfect current source is a high voltage tube with a cathode resistor, i.e. megatron T2 current source is actually not really very good because the resistor divider for the pnp current source causes a significant change in current for example 700v peak to peak on the plate the current varies from 13.3 to 15.8ma same thing for a cascoded depletion mode is 14.8ma to 14.85ma a better idea would be to replace the stacked pnp and resistor with a very highly isolated dc to dc converter, something good for 2kv of isolation and you would need 4 of them per amplifier.

the copper ground straps are a bit of overkill. definitely make sure all the tab transistors are flat to the heatsink

no, not a modification of the power supply, that current limit is before the regulated cap. talking about adding a to-247 on a heatsink with a single resistor. since these are not sharp cutoff devices, the value of the resistor is unknown, would have to test it with lower voltages say 30v. but about 3 volts across the resistor so about 60 ohms The adapter is added on the + side of the power supply line. If it works which I suspect it will, can add it to a new version of the board, but the board might have to get bigger.

soren came up with this to limit the output current of the hv900 supplies http://www.mouser.com/ds/2/205/DS100183B(IXTA-TP-TH6N100D2)-368848.pdf put one on a heatsink and adjust to limit output current to say 50ma