kevin gilmore

current version of board, luvdunhill wanted heatsinks on the +/-15 to power something http://gilmore.chem.northwestern.edu/kgsshvps7a.jpg will add the crd's once i test that it works as i believe it will.

Decca ribbon tweeters. Element resistance, 25 milliohms. Driver transformer 100:1 .5 inch wide strip of aluminum about 4 inches long. 10 mill thick. Have a pair, have not played with them in quite some time.

That is not oscillation, that is the charge/discharge of the main caps. What you have to do is remove the other traces and expand the green. Also look at the drive voltage on the base of the reg transistor. Sure looks like it works right to me. Fact is this power supply design is at the -100db level for noise/ripple. Not easy to do for high voltages. John curl has enough of a hard time doing that for +/-30v. Also that version of the voltage doubler might be more than 900 volts which is a bit much for the ixys part. This is exactly what i want, a discussion of design by informed people. Doing the circuit boards is the easy part. 2.6K load resistor?? Thats quite high in power...

Yep, works for the BH, but you are wasting a bit of power because the unregulated rail needs to be 600 volts to make the bias source work. Now if you want to get really silly you can replace R1/R28 with a 1ma CRD (in parallel with a 100v zener to protect it on turn on) and get the ripple down into the 50 microvolt range. I have not tried this yet, but i have ordered the diodes.

There is a reason stax always used red led's. led's don't share current well, so putting them in parallel, usually does not work.

Had to be at least 20 takes and a massive edit job. No way even those professionals could do that in one shot.

like this http://gilmore.chem.northwestern.edu/kgsshvpower3.pdf The 4 pass fets are all isolated case... Same thing with the 2sc4686a Sure would be nice to come up with an isolated version of something for the bias supply. It would make assembly idiot proof. You can of course go nuts on the 10 volt reference chip, some of the linear technology chips are 10 times better, and 20 times the cost. Problem is distributor availability on those. The issues with the zeners is absolutely real. This is why the KGBH supply, and the cavalli supplies drift a few percent over temperature. The KGBH supply is still absolutely the best for AC noise rejection, but i want something that is better than a 1% line/load supply.

This is the power supply i'm planning on going with http://gilmore.chem.northwestern.edu/kgsshvps3.jpg it uses the active battery from the T2 as the regulator. And is adjustable for exact voltages. It is the most efficient (least amount of excess heat) of the 3 supplies. (2 watts vs 5 watts vs 9 watts) And it spreads the pass transistor heat on 2 heatsinks. It is almost as good for regulation over temperature as the T2 supply. (.2% vs .05%) and very low in noise. (about 5mv peak to peak for 1% AC input ripple) It should come about the same money. Schematic later.

Some of the solders i use are older than i am. Never had a problem.

The smell of lignum vitae is like no other wood i've run across. Even after aging of 20+ years.

Going green is not necessarily a cheaper route in the long run. Witness the $700 i recently spent on upgrading my kitchen to all LED's... I love the color and intensity of the light. I don't mind the fact that 600 watts of halogen turned into 50 watts of LED (from the heat perspective). I do mind that all the fancy lutron dimmers in the house had to be retrofit with miniature switching supplys to make them work right with the led's. And no matter what they say about the lifetime of these things, they have switchers in them, and a big electrolytic capacitor which is not going to last even 10 years. Yes i will be able to repair them myself, but most other people won't want to mess with them. Same thing with the CCFL bulbs, but they are now so dirt cheap, they are throw away items. Which is a really bad thing because of the mercury they contain.

Well i have to cut it up into a round shape before i stick it into the lathe... Otherwise i waste an entire huge piece of EXPENSIVE wood just for one knob. This way i'll get 4 knobs. And everyone knows what 4 knobs in the hand is worth... holes for the screws will be drilled and tapped. Special screws designed for woods like this.

you might want to consider one of the hybrid units that have a very high efficiency heat pump on the top, and an electric heater for those high usage times. Lots less parts than the tankless types. And completely electric, so no exhaust pipe necessary.

yep, i'm going overboard on this one http://gilmore.chem.northwestern.edu/knob%20assy.pdf I figure about 10 hours of labor on this. The metal stuff will be non-magnetic stainless.

finally back on track after 9 days of stomach flu... http://gilmore.chem.northwestern.edu/woodknob1.jpg 30 minutes on the bandsaw, this stuff is tougher than aluminum. Smells wonderful.

The undersized hawaiian shirt won't?

I used 20 gauge for everything except 18 for the ground. That's the maximum size the amphenol connectors can take.

So here is what i wanted spritzer to do. He came close. Get some of the ultra thin copper tape with stickem on the one side, cut with a sissors to be exactly the width of the card edge land, attach over the card edge land, and make it long enough to go past the length of the socket. Then do the resistors as spritzer has done. That way no pressure on the socket. This just has to be the way to get these things to sound like what people seem to want them to sound like.

Someone needs to get tyll to show up... That would clearly liven up the party. I contacted tyll, we will see.

To manage things the group buy of boards will be a seperate thread. Probably do board runs of 20 sets at a time. You can do a bit of handwaving and say that a bridge circuit built from strictly one kind of part is complementary because when measured across the bridge, the rise and fall times are identical.

yep that is exactly how it works. Such a simple circuit

Birgir finally has his hands on the SRM727, and evidently does not like the thing at all. Extended comments hopefully coming from the big guy soon. Comments on the 300 should also come soon once he can get his fingers inside the chassis to rewire the transformer. I've come to the conclusion that the srm323 is stax's best sounding amp that is still in production.

I can do that. Just great music. And i just got the count basie and the kansas city 7 disc, which is also amazing. (the other 3 were good, but not this good)

Not exactly. Fully complementary: a transistor in the top half of a circuit is matched by a transistor of opposite polarity on the bottom half of the circuit. Slew rates are identical or close to identical in every section of the amplifier. Fully differential: input signals with common mode noise with respect to ground are ignored. Special care for electrostatic amps, for which the outputs both go up and down with respect to ground for common mode noise, but the bias would therefore change for signicant amounts of dc at both inputs. Symmetry: Everything is active in both directions. The result of fully complementary. Tubes can be fully differential, lots of circuits exist. Tubes can never be complementary as there is no such thing as a p-channel tube. The output circuit of a circlotron can be considered as fully symmetric, but the drive circuit is anything but. Dynalo, dynahi,dynafet,b22 and B24 are all fully complementary, fully differential and fully symmetric. Lots of power amps over the years are the same. Very very few dynamic headphone amps do this. Mainly due to cost issues. The electrostatic circuit above is all of the right things. But the required super-symmetry causes the input impedance to be way low. Plus a huge amount of parts, lots and lots of heatsinks and board area. kgss, kgsshv, kgbh, T2 and every other stax amp are balanced and have differential inputs, but are not symmetric and definitely not complementary either. One of the results is that power supply noise and drift are now a significant issue.

i posted this a while back. http://gilmore.chem.northwestern.edu/vhvtest2.pdf someone build it and let me know how well it works.