kevin gilmore

the card edge sockets were .156 spacing on everything I have seen. The connector for the aux input slot is the same thing.

More difference in the tube between 100 and 150v

The VAS and output stage are from the 717. Resistor pullup on the vas stage. The 727 had a current source that replaced the resistors and really was better once you fix the local feedback. I'm sure that the stax mafia can make retrofit current source boards birgir's thoughts on the sound are exactly the same as mine, the high end is rough and screechy also all the extra connections on each of the plugin boards including the servo are going to get noisy over the years. very cheap connectors, not the augat that I use. also kind of wonder if they really are rated for voltage

per channel the -15v current is around 8ma tubes, 6922 and 7308 come to mind. there are also some subminiatures the change in sound with higher voltage is VERY subtle...

raising the plate voltage to 150 puts the tube in a more linear transconducance region. use stn9360 or 2sa1486 and there is plenty of clearance. in other news, going to 24V instead of 15V for the jfet input based versions of everything also makes the front end amplifier slightly more linear

The idea was a 7 pin header with one pin missing, or a single pin header might rethink that originally I was thinking of soldered in right angle pins

actually chinsettawong's hand built things have better looking drivers I just shipped birgir a latest set of kingsound garbage, why he buys this crap, no idea

the opamps are strictly the servo's, not sure there is any reason to change that part of it. the diamond buffers are strictly the output buffers, unity gain, the servo's are on the main board

Put a heatsink on the back of the buffers

the resistors do waste about 15 watts total of heat. so if you really want it completely right, +400 (or 450) -400 (or -450) +100, +6.3 (x 2) and -15 and then if you want the TS version, floating ac filaments for the output tubes. Done right, its a lot bigger than the original.

I can do that so on the t8000, there are places to install jumpers, evidently because stax was not sure of what tubes they would be able to get, and so they setup the jumpers to do things like 12ax7. Problem is that (waiting on final confirmation from birgir) for the 6922, the 2 x 6.3v filaments are wired in series, so not only do each section of the tubes have to be super well matched, but filament current between the 2 tubes also has to be matched, and the common connection (its a voltage gain of 1000 remember) increases cross talk. so 2 x LDO regulators, set at 6.3V each

standalone grhv for 100v and regulated filaments

12 inch and 10 inch drivers? similar to what Wilson does?

they are definitely elna caps, and look to be the exact same physical size as in the t1, so 100uf

I did notice they were 400v caps, but don't remember the value. birgir will know in about a week. The 100v supply wastes about 8 watts. so that really needs to be a separate winding off the transformer.

its clear that more than one person spent a bunch of time on this. 14 different circuit boards, 2 piece custom extrusion for the front, all chassis pieces painted aluminum etc. So a lot of money spent. Too bad the design is 20+ years old. Too bad they refuse to do a regulated power supply. Too bad they won't make it big enough to do 20ma output stage current.

q19 and q21 are in all stax amps. limits the voltage of that particular section, they never trigger, and I eliminated them a long time ago. q27 and q30 are used as temperature matched diodes. same as Q8 which is mounted on the heatsink the 300k resistors result in a voltage gain of 1k (actually a bit more) when combined with r38,r39. carbon does the same thing with lower resistances they use stacked ksa1156, a pair of 400v parts. I use the stn9360 which is a single 600v part. there is no reason to do this in solid state front end amp because the 100v is 15v main power supplys are not regulated. and the servo jumps all over the place when the air conditioning kicks in.

simplified schematic just updated, I got the current sources flipped. when put in the test position, it puts fixed resistors to the plates of the tubes to -15 so then you adjust the main offset and differential. then move back to the on position and further adjust the servo pots. when working right, keeps the outputs to less than 100mv. but range is very tight.

I was listening to it while taking pictures... multitasking absolutely, don't want any metal nuts floating around in bad places 2 of the screws that hold the bottom plate on have very long screws and nuts, both were loose, and one is almost impossible to get to without taking off the front panel.

power jumper block cleaned of all the epoxy j1,j3,j4 for 100v remove all others j2 j3 j5 for 120v remove all others j5,j6 for 240v remove all others and servo board pictures, unnecessarily complex tube rollers are going to have a lot of trouble with this, the servo has a pretty limited range, and the Russian similar's definitely will not work

here you go, a whole bunch of resistors are the wrong values, when I have time Power supplies are 350v t8000schem.PDF

next to the transformer is 7815,7915 which makes +/-15 to the slot and also the servo board filaments are DC HV is unregulated Cap,100 ohm resistor,Cap servo pretty much identical to the T2 servo the 15k resistors are something else

I have your birthday present

2sc6127 for the outputs and the voltage gain stage, resistors, for pull up on the voltage gain stage, darlington output need better picture of servo, so that one later, stacked ksa1156 for the tube drive, the rest of it is a modern 717 with available parts. wiring, 100v J1,J3,J4 120v J2,J3,J5

its birgir's birthday today, the big 35! so... special security screws on the top, 6 sided ultra miniature metric spline, apple tools work power conversion relatively easy once you get rid of the goop