kevin gilmore

140 pf load. Which is the 120 pf of the O2's and 20pf for the cable.

So i got around to measuring the prototype. It should be mentioned that there is no attenuator of any kind in the prototype, and any standard potentiometer setup will induce an automatic RC filter at the input due to the capacitance of the input fet. So at 400 volts peak to peak, stator to ground, at 20khz the left channel is .12 db down, and the right channel is .14 db down, and both are down about 3db at about 45khz. Measured with a signal generator with a 50 ohm output impedance. Reference 1khz

You know i'm serious. You have seen the basement in my house. The whole setup in a half high rack on wheels should end up weighing about 300 lbs. Probably less. Generators are about 40 lbs, and the amps are about 85. Looking for standards antenna's now... But i'll probably make them, as the new price on those things is silly.

Lets come up with a standardized testing method How many watts at how many feet. I guess you would have to the same thing in free-field which is more like the real world.

Actually this is possible. I have done demo's on this already. 30 mhz at a couple hundred watts into 3 turns of a coil. Stick tube steak in one end, and it cooks as you push it thru. Bump it up to 3kw and you get burning argon gas. And by radiation i mean broadband RF, 1 mhz to say 1ghz. None of the cable companies are advertising anything related to nuclear radiation. More practical is a desktop lindgreen screen room, and i think i know where to get one of those. Now how to convince all the cable manufacturers who obviously don't want their claims actually tested to fork over some demo material.

So for various reasons that i won't exactly go into, i'm about to have a bunch of surplus stuff looking for an application. A bunch of programmed test sources signal generators. computer controllable. All phase coherent to the master reference source. http://www.programmedtest.com/pts500.html 3 x 1 mhz to 500 mhz generators 1 x 1 mhz to 620 mhz generator with dual outputs that can be inter-modulated 3 x 1 mhz to 300 mhz generators one with dual outputs that can be inter-modulated And some CW capable class A RF power amps 2 x 200mhz to 500mhz 50 watts 3 x 10mhz to 200mhz 300 watts As i said, looking for an application. So i contacted craig who is one of the few people that i can think of who can come up with something creative. (knowing full well that he knows where i got the stuff) So we decided on setting up the stuff in tyll's house. (someone tell tyll) Lots of copper screening on the walls, floors and ceiling all soldered together to make a very nice and radiation proof screen room. I mean tyll clearly needs his demo room to be fully shielded anyway so the aliens don't mess with his brain... The idea is to test all the claims of various manufacturers of cables with respect to their supposed ability to remove RF due to (insert techno babble here). All i need now, are some standard antenna's, and a local oscillator/mixer box (actually already have it) and we can bring it down to baseband, and then tyll's audio precision can measure it directly. Probably don't want to be in the same room at the same time if we are running the amps at full blast. So what do people think?

If you put the screws in from opposite sides, you never have to remove the heatsinks to replace the to220 transistors.

i'll give you ancient and fuzzy pictures... I don't even know what i had for a camera back then, but it had to be grim by today's standards. Here are some fresh ones. http://gilmore.chem.northwestern.edu/kgssorig1.jpg http://gilmore.chem.northwestern.edu/kgssorig2.jpg http://gilmore.chem.northwestern.edu/kgssorig3.jpg no compensation caps on the top. And none on the bottom either, but its hard to take that off because the power suppy is screwed to the bottom. Will measure again, probably tomorrow or wednesday.

Actually the gain of the T2 is 1001. 10100/100

The kgss was designed to european inputs which is .6 vrms input which makes 600 vrms output. A gain of 60db. Or a voltage gain of 1000. 3 people in all of the last 10 years said that the gain was too low, and i told them how to get an extra 6db by swapping resistors. One person said the gain was too high as he listens very quietly and i told him how to change the input fet source resistors to reduce the gain 10db. Sounds like your professional source is way high in output voltage, something like 10vrms and even with resistor changes, this would clip the input stage. So an input attenuator is required. With a shunt attenuator, and the attenuation at minimum, and no input load resistors (depends on which of the many versions of circuit board you have) i'm sure its going to oscillate. The 500k resistors on the new kgsshv board take care of that issue. Not sure about the frequency response, i'm going to have to look up my data, i did not have time to do that last night. If the lack of frequency response bothers you, you certainly could build a T2 which is way flat to well over 100khz.

There are 500k resistors to ground on the board, but still a good idea to short the inputs out, or set the pot to zero.

Heat. My 65 inch sharp is about 700 watts... Would expect the 46 to be 200 to 300 watts.

Well... build yourself a HEV90. You know how But first find a stock of the output tubes.

Add 220 volt breaker to mains box. 30 amps should do it. Buy one of the balanced transformers, say 5kw or more. 220 volt primary, 110 volt balanced secondary. If you were in illinois, you would be required to put everything into conduit. Which also includes the donut inside a nema rated box. Keep the donut as far away from the music room as practical, the things buzz and have a gigantic magnetic field. Basements are a great place for these if you have a basement.

DHT's not really suitable for grounded grid applications. That would require 4 seperate and very well isolated filament supplies that bounce up and down and sit at -450V. I do have an all DHT design for an electrostatic amp. No one in their right mind would build it. Its $6k in tubes alone. If you want to build it frank, i will help... I will supply the 250khz floating filament supplies

The psaudio powerplant can in some cases cause more trouble than it fixes. Plus it is limited in power. Would never work on my stack of krell. I did a one inch diameter solid copper ground rod 12 feet long. Beat it into the ground with a 10 lb sledge hammer. Took quite a while. Attached it to a 6 gauge stranded copper wire and ran that into the side of the house next to the media room. Pounded the rest of it in about 6 inches under ground to make sure my quality landscapers did not hit the thing with the lawn mower. Its about one foot from the side of the house. Its stuff like this that has caused me to bust up my left elbow. My new very overpowered snowblower has caused me to bust up my right elbow. Balanced and highly isolated power is the only way to go. Massive donuts for the win.

should have no trouble with that one, 1.5kva. The semisouth parts perform much better at 100ma, but that is clearly silly. I ordered some bimosfets, and igbt's, and some very beefy npn transistors to see if i like any of them. Its very hard to beat out the 6ca7 in that application.

I can't explain it yet either. I am running it at 500 volts with a 1kv supply and 20ma current source. On a decent sized heatsink. The gate current is a factor of 10 more than i expect.

I wanted to be sure i was doing things right, so i brought the test circuit into work where i have more equipment and an easier way to test. The semisouth parts have a significant problem. The massive amount of gate current necessary. Actually measures about 150ma per part, So 300 ma per channel, so to do this an extra 50 volt power supply would be required, spec'd at 1 amp, and referenced to the -500 supply. Plus extra current on the -500 supply. Kind of what you would expect for a jfet. Going to mess with a few of the ixys parts soon.

I don't know how much power your transformer is good for, but the T2 is 200 watts for sure, and the BA has to be at least 100 watts. So you are definitely pushing it. T2 can handle -15% line just fine, but i doubt the BA can.

so i did not have the floating number, then went into messenger, then all of a sudden the floating number appeared... not sure what happened. likely the increased speed is due to the export of the database into a new database which removes all fragmentation. An export and a re-import every 6 months might be a good idea.

Andy finally got his working. A bad Rv1 in one of the batteries. I would imagine listening impressions soon. Andy's first project was rebuilding a ES1, and with a bit of help did so successfully. Andy's second project was the T2. Anyone with the time and perservance should have no trouble with this

There are clearly some things that tubes do way better than transistors. The output tube is one of them. 15 pf input capacitance. Although that really does not matter as much as you might think. An equivalent Rds of about 5k. Also really does not matter except it limits maximum voltage swing. Neither the ixys parts or the semisouth parts are perfect for the job, its the lesser of 2 evils. I plan on trying many semiconductors to see which performs the best. But the ixys parts with the 1500 ns rise times are clearly not what you would want. The slew rate and distortion characteristics are what i'm after. It might be a bit easier to replace just the front end and leave the output tubes. And then you have something similar to the BHSE which is a bunch simpler with a lot less parts. I'm looking at other alternatives and trying to find out where apex gets their complementary 1200 volt fets.

I think that justin really wants a T2. Trouble is, he does not have the 2 weeks of time to build it. Hey mikhail... you wanna help justin out??

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.