kevin gilmore

littlefuse dalbani littlediode nikko... all the same company. and yes they sell lots of fakes. 2sa1968 are pnp. but if they test as 30v transistors, they are definitely fakes.

don't know about buying parts in india. parts in usa are around $150.

https://www.head-fi.org/threads/stax-srm-007tii-amp-tube-rolling-bias-adjustment.653258/post-16389801 this person published half the schematic. This schematic is similar to, but not the same as your amp which has dc filaments. you need to replace all the parts including the diodes and capacitors. the other high voltage caps don't look very good either. and likely one or more of the tubes are bad.

modifications would be required to lower the bias to 200v from 560. it is unknown whether the headphones can take the extra voltage swing of this amp. one version of this amp will definitely be analog input only. lithium batteries suck. get used to it.

you want the ground2 file.

cfa2 is balanced out only with a balanced input cfa3 is balanced out regardless of input. also some versions are ZF/SS

not cfa electrostatic.

makes no sense to make this a diy kit. the main board is more than 200 components on both sides of the board. The board house wants about $60 to assemble this board. no one i know can hand stuff that board for $60. The dac board is likely going to use the ess chip which has nda agreements associated with it. So no gerber files or schematics either. Still should be much cheaper than the d10 or kse1500.

doug is tall enough he does not need a ladder.

define similar. shure is 4 x discrete opamps made with 400v complementary bipolar parts. stax d10 is 2 x apex pa443 dual monolithic opamps made with 350v n-channel mosfets. stax d10 uses xmos 208 and ess dac. i don't remember what the shure uses. birgir has pictures of both should he desire to post them. there is a guy in ukraine (i think) that is selling a shure clone for about $800 (no dac)

ULTRA REFERENCE electrostatic headphone amp KGSSHV Carbon for Stax SR-007 SR-009 | eBay they are 1500uf caps as i remember.

the guy in vietnam is using even bigger caps. so no reason why it should not work.

I think that caps that big can be very dangerous. So if you are going to use them, find a way to make sure you can never come in contact with either of the terminals.

musican pegasus is probably in the same range

depends on which version of the pcb.

paradoxper settled on 50k feedback resistors and 4.2k ZF resistors. to increase the gain. both have to match so there is no volume difference between modes

SS mode its 25k (or 50k) /5k as long as there is enough gain in the front end. in ZF mode front end is a voltage to current converter. So 10k in parallel with whatever you pick for the ZF resistor. Much easier to do in spice.

i have the older model, never had any trouble with it

the harder the wood the easier it is to machine it. african blackwood has less issues than ebony.

the lathe is very decent, and capable of cutting screw threads if you ever need that. even though its early 1960's vintage. the other stuff is not capable of anything of high accuracy. at least not without digital readouts. And its heavier than it looks. just the lathe top is probably about 700 lbs

the 47uf caps have to be populated. the 600pf caps are optional, paradoxper decided not to populate them

this is what you want i think. kgdynalobal9 - CADCAM.ZIP

i went back and looked at everything. there is no servo in the amp part itself because its in the front end. the latest file which should be posted somewhere above is cfp3rssfixedsssw also attached here. cfp3rssfixedsssw - CADCAM.ZIP

which ever has the later date. definitely has the latest servo

so the idea is a 10 hour runtime. so a 3 cell lipo battery with 2.8 amp hour batteries is the target. if it has to be a bit bigger then it has to be a bit bigger. the amplifiers are 200 microamps output stage bias with 1.5ma current limit. Could certainly bump up the current limit a bit. the benefit of kerrys power supplies is that they are extremely small, max component height is .3 inch. if we change to a transformer based supply then the transformer is .8 inch. if we use the hvm supply for the bias it is .5 inch high. Smaller is better! For a given chassis size more room for the battery is a good thing. The final product will likely be a single circuit board with the power suppies on one side and the amplifiers on the other. The components with the largest height will be the stax jack and the volume pot.