kevin gilmore

I doubt that I ever did a ss dynafet. I will look. the latest dynahi and dynalo are both super symmetry, not sure which versions are the lil-knight versions current versions would use either the that340 parts, or a matched quad of linear systems fets

more than just an equalizer, there are 3 companders/expanders in there. so something like a stax ed1 plus a dbx3 (or possibly 3 band equalizer each feeding a compander/expander) for those not familiar with dbx... this thing http://www.ebay.com/itm/DBX-3BX-3-Band-Dynamic-Range-Expander-PARTS-OR-RESTORATION-ONLY-/202076549539?hash=item2f0cb371a3:g:T1IAAOSwm9tZ2pji one of the pictures over there shows the bias board partially populated, so the bias might be as low as 600v, who knows

The volume pots are likely to be linear instead of log because one pot spins the other direction due to the gears 2 active bandpass filters per channel and 3 compand/expand per channel. Lots and lots of signal thru those electrolytics. So maybe an attempt at a near field equalizer? $4k euros for this. very sad

find a gerber that works, gc-prevue or something similar l7815/l7915 are voltage regulators, not transistors

I would expect that to be normal. no way it can work without the servo

Check stax mafia boards thread

here is 2 of them t2parts3cgseditV2.xls t2parts3as.xlsx

messing with the gain probably not a great idea, decrease the resistance of the tail resistors in the front end, or increase the value of the feedback resistors. both will require readjustment of offset and gain

what you are essentially doing is changing the gain on the output tube by a small amount. Something like .1db or so. larger changes in the resistance would change the gain even more. The rest of the circuit will compensate to keep the overall gain the same, so there may be other slight differences. For this circuit the diode is just taking .7v from the voltage from plate thru the resistor to the grid. transformer circuits where the plate will swing negative with respect to ground will definitely respond differently to the diode

I will think about it a while, but it does not make sense. The plate is always going to be a higher voltage than G2/G3, hundreds of volts of AC swing on the plate.

in a push pull circuit with a transformer output, this will keep G3 from going negative. for the electrostatic circuit pretty sure it does absolutely nothing

so what is the diode supposed to do. not much of an extra voltage drop.

i'm not sure if you are the first person to build that particular board or not, but the version 9 board with the to92 worked correctly, and the version you built has just the to92 changed to smt. I would use a scope and signal generator to make sure its working right. Also it has a low impedance input, so anything over a 10k pot is going to cause trouble.

way back when, there were +/-15v regulators just for the opamp. but some of the -15v regulators had issues then, and the voltage ended up -20 or more. this version absolutely requires opa445. if you can get the thing adjusted to 2mv and its completely stable, the opamp is not really required.

measure the voltages on the opamp socket before you stick the opamp in. or possibly the opamp is dead.

that was actually the enamel failure. completely different thing. And those were 6.3V transformers with one of the primaries wired as a secondary

Mikhail called that problem "Acetate Failure" Every singlepower extreme, and many of the others had diode bridge and pass transistor burning

so much can go wrong when you are working on something 20+ years old. So many obsolete parts... The people that know what they are doing probably won't touch stuff they do not own, and people willing to modify your stuff probably are the people you don't want touching it.

I did wonder where they got those emblems. The stands would be the cheapest way possible. That transformer box has got to be stupid expensive. At least some of the smaller 9 pin dual triode tubes have a shield that you can tie to ground to prevent crosstalk. not enough pins on an octal to do that.

one other thing about that single input tube, both channels inside the same tube definitely reduce the channel separation. and those monster stax transformers are obviously stax stickers attached to something custom.

Definitely unbalanced input only so middle tube is phase splitter and the other tube is a driver.likely just a push pull amp with a really big output transformer

why do the 2 pictures not match, specifically the input attenuator hanging out the bottom (or top) and the rotary switch? definitely gotta love the Mikhail capacitor mounting technique.

try this, there should be over 300 files, had to remove a couple of confidential ones see updated links on page 5

no idea what the name is

you can calculate and adjust what trigger voltage you want. all 4 inputs (or 2 if you depopulate) are measured against ground. so any 1 or more of the inputs triggers the relays. power supply ground is signal ground and has to be connected.