kevin gilmore

Simulation is a great way to find out if you are in the ballpark or not. If the simulation says it won't work, then it is highly likely that in practice it reallly will NOT work, and sometimes in spectacular ways. But taking a successful simulation, producing a board, and getting the thing to perform as designed is much tougher. Especially with killovolts of AC flying around at frequencies that can sustain a continuous arc.

Yes, and by changing all the operating points, the sweetness of the sound may change. The 50 volts across the 2sk216 and 2sj79 seem to be the magic values where those parts sound the best. Lots and lots of things can be changed or simplified. And i encourage you to build one and test it.

This is not srpp. At least its not driven that way. Its the solid state version of grounded grid. If it was bipolar it would be called a common base amplifier. The capacitance while way higher than a tube would be is still not subject to the miller effect and hence its much easier to drive than you might think. The idea is to keep the sound the same which means keeping the same way the output stage works except with solid state. I likely need to add a gate resistor on the current source to keep it from oscillating. You could use the original current source with 2sc4686's with a bit more base drive current. The normally on part cannot be used as the gain stage because that messes with all the bias stuff elsewhere. The 2sj79 would not be able to drive it.

four per channel... So that's $240 for the output transistors. Going to need bigger heatsinks I wonder how many pieces of justin's new 5 inch heatsink i would have to buy... Nope, not doing this again. NOT doing this again. Someone find me a standard heatsink/chassis assembly that can dump about 150 watts of heat. I might be able to shrink the board to 12 x 12...

here is the first cut on the all sand version. i synthesized it, and everything looks good. The semisouth parts are NOT cheap... http://gilmore.chem.northwestern.edu/t2schemsand.pdf what i would still do is replace all remaining 2sc3675's with 2sc4686a and replace the fet and led's in the batteries with the precision regulator and change R34,R34 as necessary to bring the battery in the range of 640V. And likely make Q23 a darlington out of a pair of 2sc4686a. +250 volt supply modified to make +150v, and cascode with 2sc3840. Overall, less power due to no filaments, but more power in the outputs, making the thing still dish out just about as much heat.

Actually the DAG is from my picture tube days at zenith. Yep, thats the conductive stuff we painted the insides of the bells with. DAG is black. I was thinking about the RED stuff which is definitely a great insulator. Don't remember what we used to call that stuff, although i do remember the slang term.

Excessive amounts of tobacco seem to do way more harm to high voltage electrostatic amps than dust or condensation. Especially when combined with dust, the combo is definitely conductive. Many of the original T2's toasted the power transformers which were way underrated for power. Micromass (now owned by Waters) of the UK continues to sell multi-hundred killobuck instruments and do things with transistors at 5kv that i would not do at 1kv. No conformal coatings, no rtv, no nothing. The stuff manages to live thru its expected lifetime of about 8 years. And in an industrial environment thats full of all sorts of nasties. If it bothers you, buy a can of DAG and paint it on the transistor leads after you solder them in. The stuff is good for about 25kv.

The two of you, and you both know who i'm talking about... Knock it off with sticking chassis in ovens where you cook food. Seriously... There are VOC's... Even in the water based stuff.

titanium screws here UTI-SCREW Inventory-Titanium Screws, Zirconium Screws, C276 Screws, Nickel Alloy Screws tungsten carbide screws are available, and look very cool neither requires any coating of any kind, and don't rust. The servo won't care if its on +/-12 or +/-15.

and the ones you use have fuses that are rated at 250 volts. I'll bet they arc real nice, and might even explode at 500 volts when they pop. The 600 volt fuses are huge.

The kgsshv power supply is NOT current limited. To do that the power supply board would have to be about 1.5 inches bigger in the one direction... Adding 2 x ixys parts and 2 more heatsinks. Making the board this much bigger would guarantee that the thing would never fit in one box. Maybe for a 2 box second version. Still the amount of energy stored in the output caps, subjected to a dead short results in fireworks no matter what you do. But at least the semiconductors would not have popped. I may have come up with an even better solution for the mini heatsinks. have to try it first.

kerry came up with this one... a BHSE with the servo's from a T2. http://gilmore.chem.northwestern.edu/BlueHawaii-T2-Servo-v1-2.zip opens with ltspice.

yeah... please don't do it that way. The alumina insulators really are required. The plastic #6-32's definitely work plenty fine.

I want to make the kgsshv absolutely trivial to build, and want to make sure that people know how to mount the semiconductors. For all the TO220F transistors, a hex head #4-40, a #4 plastic washer, the transistor, a thermal pad, the heatsink, then preferably a belleville washer (which i can't find stock on) and a nut. So for the 2sa1968 version, that leaves only the ixys parts and the low voltage regulators. The small heatsinks are #6-32 tapped. So you have to go with a plastic screw. For the ixys parts, thats the plastic screw, the transistor, the aluminum oxide insulator, and the heatsink For the low voltage regulators, all you need is a screw and a regular thermal pad. The #6-32 lexan screws are pretty strong it seems. unless someone knows where to get the screw tabs that are #6-32 on one end and #4-40 on the other end.

i asked this to marc and craig in PM's, but i might as well ask here. Anyone know the voltage ratings of a TO220F package? Specifically if i put a metal screw in the hole, how many volts does it take for the package to break down between the screw and the collector tab inside. Has to be well into the 1.5 to 2kv range right? I've found some new polycarbonate (lexan actually) screws that seem to be extremely strong, but still metal screws are better.

I think the designs of the servo's are such that the amp reaches and maintains the correct dc voltage very fast, certainly less than 5 minutes. On original BH's, it usually takes about 20 minutes for stability. BHSE is probably a bit quicker at 10 minutes. The tightly regulated power supplies also make a significant difference.

Rule #1 Never mess with high voltage at the end of a day when you are tired. Rule #2 Always remove the lead from the AMP terminal on the DVM as soon as you are done measuring current. Yep, i fried a meter once. It was more than 20 years ago. Half a dozen DVM's around the house, including a couple of $19.95 cheapies makes things a lot easier.

After doing 20 chassis and board sets... cheap really is not in my vocabulary. I very much doubt that even ti khan put $30k pretty much all at once into a multi year project that ended up loosing money For what nelson is doing, these are clearly great devices, regardless of cost. I like the new devices that Dan is using better, they are bipolar obviously, but can't handle the voltages. I definitely want to test at the voltages and currents we need. One of the depletion mode fets as the current source, one of the enhancement mode fets as the grounded grid output amplifier, and then probably a 2sj79 or something similar as the cathode drive should make a great output stage, if it does not oscillate or do stupid things at low currents. The active battery is good as is, and the toshiba part will replace the 2sc3675 with a bit of tweeking, and the ultra stable voltage reference now used in the kgsshv power supply is also a great idea. So it seems that the 2sj79 and 2sk216 will have to stay, as far as i know they are still in production.

I think that those things are going to perform very poorly at 20 ma, but i'm willing to give it a try. Gate capacitance not too bad. Now to find someone with the things in stock. Would be neat to run the things at 100ma, but you will need a fork lift to move the required power supply... Figure about 800 watts with the current sources.

Don't forget the one diode on the power supply board that is backwards, 4 of the diodes, one on each of the supplies is actually a zener and the resistor cross for the servo. also if you get a universal primary transformer, don't wire both the 110vac and 220 vac lines...

solid state front end is definitely doable. Cut the +250 to +100, use 2sa1486 as cascode transistor, cut R6 in half and use everyone's favorite n-channel front end fets. Add zener at junction of R9 and R10. change out the fet and led's in the batteries for the precision regulator and a resistor, remove one adjustment. might have to fiddle a bit with the range on RV1. Neither should make any change in the sound whatsoever. But its not better. There is no suitable 1kv + transistor to replace the output tube. But if anyone knows of anything suitable please let me know. Something that can handle at least 20 watts with 500 volts across it. Cathode of output stage with tubes is possible but then the -500 would have to be -600 or more, then remove Q26,27,28,29 this would likely change the sound a bit. All the output current would have to go thru this tube, and thats a bit much for the kind of tube you would need to use. Still nothing really stands out as any better. Just maybe a slight bit simpler. If you think this thing gets hot, you should have touched the original. No practical way to replace the active batteries with a tube. Gas tubes have too high an impedance.

This is a way better way to explain the tendency to crank the volume. No fatigue of any kind, even at ear bleeding levels. And i can listen for many hours at levels way louder than i should. I've been thinking quite a while on this, what i would do to make anything that would be better than this and i just don't have any ideas. I'm still running on a 2 or 2.5 amp fuse, it has never blown.

craig is alive and well. Inu found a slight tweek thats a good idea... 5pf across the 100k feeedback resistors to kill off slight 650 khz oscillations...

leakage current due to capacitance in the transformer... hook power supply ground to AC neutral thru say a 1K resistor and measure again. leakage current should be no more than about 1 ma.

If this is anything like when Inu got his finished, and decided to play hookey from work at lunchtime... We may not hear from craig for a few hours. And he will have a smile on his face that won't wash off.