kevin gilmore

But wait... There should be 499 quotes... 500th episode is this sunday. Evidently there probably are more repeats than i expected.

What i need now is a better lens for taking pictures like this. The various lens distortions really show up, because i can assure you that things are absolutely 90 degrees and flat to less than .0001 inch. Really want a 300mm macro lens that focuses 1:1 at 2 feet or more from the front of the lens. As far as i know, no such item exists. Sure wish nikon would release a new version of the 200mm macro, i don't want to buy a 15 year old lens design. The reason for the longer lens is that it makes it easier to light things. Bocote next week. But i need to find something to coat it with to keep its yellow color, because as it sits in air, it continues to get darker and darker.

http://gilmore.chem.northwestern.edu/andyknobs.jpg

Actually our friendly monk is getting 2 knobs. And they are done too. I have enough depleted uranium to make a knob. And the appropriate carbide bits... Maybe the diamond tools would work better. Going to have to try it sometime. I would probably have to cast a lead container if i wanted to ship it... I can just imagine what would happen if the radiation detectors went off on fedex or UPS. The USPS people are probably too ignorant to notice.

Rumor has it a crazy monk is getting the next knob

I cast them. Learning as i go. The 3rd one came out perfect. The bubbles on the first one really look neat. I have enough material now to spin cast a couple into a mold. Figuring on about 250 grams each before final machining. Power hit trashed one of my two aluminum mounting spindles this morning. No power == no brake. with the feed on, took .125 down to .060 in 3 seconds

The 18k gold one is on the dynahi. Pictures many moons ago, will see if i can find it. Definitely leaving all the woods bare. I think they look better that way. here we go 121.6 grams http://gilmore.chem....du/dynaknob.jpg http://gilmore.chem....u/dynaknob2.jpg http://gilmore.chem....u/dynaknob3.jpg http://gilmore.chem....u/dynaknobj.jpg somewhere i have pictures of the 24k knob, its 151 grams, and i never mounted it on anything. This is years ago when gold was relatively cheap.

So the diamond tools came in today. And i have a chunk of marble and granite to try and turn into knobs. Should be fun. After that i'll go and find some fancy stone. The redheart is shrinking and the cracks probably won't be visible in about 2 weeks. Should be able to make a few aluminum mounts tomorrow. Need to change the title of the thread to just T2 knob turning since i've already done a titanium one, and a 18k gold one. one of these days .9999 fine platinum.

The tube is not pulling current, and you need to look at the cathode voltage to figure out why. Top of the batteries should be +200, you might want to look there too.

Q11,Q12,Q25 or a tube let loose is first best guess. Plate voltage on that tube is likely to be +500

http://gilmore.chem.northwestern.edu/woodies2.jpg The redheart started cracking about an hour after machining, including the original block. So this one needs to dry out a few years. The olivewood also started cracking, but much smaller cracks. And the bocote started out much lighter and is getting darker as it exposes to air. The bocote and the cocobolo should work out great.

Pictures later, the bicote really came out nice, so did the cocobolo. Not really liking the redheart, and the olivewood is so so.

http://gilmore.chem.northwestern.edu/woodies.jpg the bocote looks a bit dark, who knows...

The challenge will be to make the thing as easy as a kgsshv to put together and get to work. Still the voltages are a bit high so i'm going to add foolproof testpoints for adjustments.

bocote, olivewood, cocobolo and redheart on the way. still can't find a piece of snakewood big enough.

I decided to finish off the one with the crack in it, and found out something very interesting. At the same speeds and feedrates that i use for the LV and Rosewood, and with the same carbide tools, the ebony gets stinkin hot. WAY WAY hot. Even with 5 thousandth passes.... Might need some kind of cooling... AH well, on to other hardwoods.

Only the front stator amplifier is shown. The rear stator amplifier is identical to the front and connects to C7. (pdf updated for clarity) R12,13,14 do make sense, its a differential amplifier. But the bias is a bit off and it can clip. It is correct as shown, at least for this version of the amplifier. There is no negative rail. There should be to bias the output stage. More on the darkstar... Input chip is great, i used it on my new preamp. But its bipolar and has significant offset current. I added a servo to drive the vocm pin to make sure the common mode voltage is zero. If ray had a regular pot in there instead of the dact, you would clearly hear woosh as you turn the knob, problems he has had on other stuff in the past. If you run the darkstar unbalanced, output DC may damage your headphones. Nice job ray.

Spritzer as usual is right on the money. From extremely high resolution pictures that were provided to us the following was generated, and has been verified by an owner of the amplifier. This is an early version before the addition of the balanced input. There is one error in the schematic, and the inductor has been measured at 25 millihenrys by an inductance meter of unknown accuracy. http://gilmore.chem....wooaudiowes.pdf And that is the issue with this amp. Replace the pair of inductors with a larger tapped inductor and then the thing turns into push pull and the peak to peak voltages actually are what they should have been in the first place. The power supply is a different issue entirely. And for those that have not seen it... http://gilmore.chem.northwestern.edu/darkstar.pdf The .5 ohm current limit resistor limits the thing to a maximum of 1 ampere... High resolution pictures supplied by our friend skylab...

water and hardige lathes is a really bad combination. i've seen the result and don't want to be blamed for this. Now lots and lots of oil, that would be possible. If i do it completely NC, then that lathe is stainless and designed to take that off white stinking mess that is mostly water. (the rest of it is bacteria)

The high voltage power supply is the kgsshv supply with all the pnp's replaced with 2sa1968's and the 2sc3840 replaced with ksc5026, and the pass fets replaced with the 900 volt versions. (and changes to the zener string and feedback resistors) Eventually due to the march to surface mount, i will be making DPAK to TO220 converter boards so that we can use the 2sa1413, or the ROHM parts in place of the 2sa1486. This will apply to the kgsshv too. The low voltage (well +/-85 is low voltage) is a dynahi supply with upgraded parts. Due to all this stuff, and the heatsinks required its going to be the size of the T2. The only person that really needs this is pabbi1. Practically, voltage swings above the bias voltage may do damage to the heaphones, so really +/-600 volt supplies are sufficient. Yes its a stacked transistor design. No other way to do it with solid state.

So birgir asked for this one, but truth be told, i have been working on it for quite a while, and i have a working prototype. Specs: DC to 200khz +0, -.2 db Slew Rate >350 volts per microsecond Thd < .01% Voltage Peak to Peak, Stator to Stator 2950 http://gilmore.chem....n.edu/togte.pdf This is not for the faint of heart. The amp actually can go higher in voltage by a bit, but anything over +/-750 for the power supply gets to be Very difficult to regulate well. The +/-250 is actually resistor dividers off the +/-750 Its the only push pull fully dc coupled electrostatic amp that i know of Since this schematic i have replaced the 2s3840 with ksc5026 which is a higher voltage transistor and a better match for the 2sa1968.

With the 10k input resistors on the T2, the 22 ohms would have no effect. The 22 ohms should really be 50 ohms to be able to better drive high capacitance interconnect cables.

I'm efficient I had been thinking about how to do this from the very start, so once i got the cardas parts, it was actually pretty easy. The fact that cardas can't even supply a dimensional drawing of what is supposed to be their own part is very sad.

well this should confuse most people http://gilmore.chem....inputboard6.jpg Stuff it with one set of parts and its balanced, and you need 2 boards, stuff it with another set of parts and its unbalanced and you only need 1 board, to keep it the same size, for unbalanced you give up an input. The unbalanced input buffer is an lme49720 dual opamp, or your favorite in a gain of 1 setup. Needs a bit of checking now.

Fine, i'll make a single ended version. I may be able to get both on the same board if i make it a bit bigger. Then you stuff it one way for single ended and another for balanced. The input chip is not compatible with single ended. So there will have to be 2 different single ended front ends.