kevin gilmore

spice models on tubes are notorious for incorrect output voltage swings. With a B+ of 300v, a plate resistor of 2.5k, the maximum voltage the tube can possibly do is 225VPP. And that maximum is theoretical because the tube is going to be hard saturated at the bottom, and the linearity is going to be crap. with a plate resistor of 1.5k its even worse, under 200VPP. Voltage gain this way will be under 2. Its all about the Rp of the tube, in this case spec is 800 ohms, but will quickly rise to 1k+ as soon as you start putting signal thru it.

The lowest plate resistance of all electrostatic amps out there is the hev90 which has a plate resistor (actually 3 in series) with a total resistance of 18.3K and runs on +550 volts. This is the maximum rating for an ecl86. Most of the stax amps have plate resistors in the range of 47k to 60k. birgir pointed me to this http://www.bartola.co.uk/valves/category/valves/dht-valves/ 6P21S would handle at least 600 volts. The emission lab tubes would fit the bill, but with good sockets are over $250 each and you need 4

2.5K for the plate resistors, what is the B++ No way that is going to work. The B++ has to be a minimum of 600v to be able to get enough linear voltage swing out of the output section. 800v or 1kv much better. I think that the 2a3 is not going to like 600v. But you will have to try it. A plate resistor that is a minimum of 25k is reasonable. 211's or 845's would be much more fun.

28-70 f2.8 the lenses make all the difference.

the headphones cannot possibly know whether they are hooked up to a balanced or unbalanced amplifier. Maybe if you want to get fancy and add some extra weight you can use wire with a shield on it and wire the shield to either xlr ground (4 pin) or the 5th wire (5 pin)

all tube supersymmetry electrostatic amp with dc output servo http://gilmore.chem....du/electra3.pdf and the one cap one transformer cascode version http://gilmore.chem.northwestern.edu/electra4.pdf

i figured i would toss these two out for your entertainment http://gilmore.chem....edu/electra.pdf http://gilmore.chem....du/electra2.pdf obviously you have to add adjustable bias for the output tubes.

andy fresh roasts coffee. Then ships me some. Very yummy. Highly addictive.

But the amplifier part is in fact completely dual mono. Was from the start. 2 completely seperate power supply umbilicals. Just in case someone wanted to make dual power supplies. see... i think ahead.

in and done

dual mono for the win. 2 amplifer boards 2 power supply boards 2 transformers monster sized box(s)

yes they replaced them. And charged us double.

2.1v - vbe junction (.7) /180 ohms == 7ma. But the led's actually are more like 1.7 volts due to the drive current. So its about 5.5ma. You can change to a higher voltage led, but the red led's thermally match the output transistors. So you want to cut the 180 ohm resistors to something like 150 or 120 ohms.

or decrease the emitter resistors.

Its the output stage current you want to bump up. You can bump up the 3rd stage a bit, but no reason to go crazy on that one.

retro, i like it. Probably too tough to put the tubes in the same place as the st70.

Done

regular white goo for me. none of that stuff with the silver in it.

Such a simple thing, such a global effect

just think of all the extra picofarads of capacitance the horror, the horror

A person trying to buld a BH is having trouble, because the 2sk389's from ebay are actually npn transistors. It works, but low input impedance. LSK389 are available and should be the only thing you use if you need those. No p-channel fets yet.

waiting on kerry for any final changes to the multiamp board. preamp board is finished.

but it does not cover them very tight. The correct box end wrench should be able to loosen the bolts. But it would take a while. If the bolts are on very tight, it could be a real bear.

Its probably about 2 years ago, but it was on the news. Some person people called a vigilante in new york was going around and removing the boots on booted cars. Without anyone asking, evidently just for fun. Did a couple hundred cars. I don't think he was ever caught. But at about $2k per boot, he ended up costing the city plenty. You can now buy a gasoline powered hand held corrundum bladed saw at home depot for less than $200. The thing is that people who don't know try to attack the lock mechanism, which is highly protected. Cutting the pins with the saw is evidently fast and easy. Wear eye protection, the sparks that fly are probably kind of nasty. I don't think that any of those boots would fit on the monster wheels of my corvette. But i don't park anywhere where i could run into this problem. The last parking ticket i got was at least 25 years ago. A couple of people that had their cars damaged by attempts to boot them evidently sued the citys involved and won. lasers big enough to do this are not portable devices. I would think a portable oxy cutting torch would do it, but may have other problems.

absolutely there is. I've seen it done a few times. There was a guy in new york that had a gasoline powered ceramics saw that would rip thru one of those things in about 30 seconds, leaving no damage to the tire or the rim.