kevin gilmore

clever huh? first time i have seen this. what it really is, is some local feedback around the current mirror. the lower impedance load forces the current source to supply more current to the drive of the output transistors. all those output transistors in parallel really form an extremely stiff drive current without global feedback. in single ended form, perfect for low impedance ribbons. and 30v/10a switchers are cheap. lot of heat however, 1.5 amp bias current. (total) i have a single ended gain stage to go with it. basically half of the balanced version with a cfa capable input section. input section can have local feedback as shown. or remove that resistor. updated to current version pioneera09pre.pdf

Saw some talk about this and decided to make a new version. use either the tube unbal/bal to bal board, or the solid state version result is about 125 watts rms into 8 ohms at thd of .005% will definitely drive 4 ohms with suitably large power supplies. transistors are standard pinout, so pick your favorite output transistors. the to220 transistors are mje15034/mje15035 perfect for so many things, including esl boost transformers. pioneera09.pdf

you should see some of the chinese cfa3 ripoffs for around $1600. one in particular is fairly decent, the rest are trash. just wait till the chinese start selling the D&G clones. running with multiple >1kv power supplies. what could possibly go wrong.

being retired means i get to do what i want to do and when. so the new thing based on the pioneer a09 (no not the a9) is also zero feedback, 120 watts into 8 ohms, damping factor of 100 and a thd about .001%. the absolute perfect thing to drive your lundhal electrostatic transformers. basically the exactly same ubal/bal to bal board in the cfa3, and then the high power buffers. pair of 30v 20 amp switching power supplies.

i am retired now, 7+ years. And loving it. Due to arthritis issues i am no longer working on any more equipment. including my own. going to pay a couple of high-school kids to stuff and solder boards and chassis etc for new projects.

has to be one of the ones that can be set to 12v like this Amazon.com: FARSENSE USB C to DC Adapter,Barrel PD Trigger Cable(3.3ft) with 10 Connector Tips,USB to DC Power Cable can Switch Voltage by Pressing The Key,Support LED Display Voltage : Electronics

at the moment, do what i did 30 years ago. srm212 plus 12v 7ah gel cell. its portable. kinda portable. or buy 4 x apex opamps and run them class C with the dc to dc converters. i wish i had a better solution. getting all those transistors to touch the heatsink at the same time is not easy. even the koss box requires a decent size battery. (6 x D cell)

no, omega-els has the hvrv-hansen portable. and the power supply blew up. so he is using outboard dc/dc converters to power the no longer really portable thing.

i looked at the ltspice file for a bit. best guess is that there is something wrong with the jfet model that causes issues. replace the fets with bipolar and see if it works right. the reason all the darlington transistors are on the heatsink is so they can thermally track. effects thd. another thing that really effects the thd is the power supply rails. anything under +/-20v is too low and causes much higher distortion. +/-30v is the sweet spot. and once you do that, you end up with an amplifier that is a lot more than 5 watts. in your second schematic, you have taken out the low impedance load on the output of the current mirrors. lots more voltage gain resulting in required high amounts of feedback. definitely not the original design goals. if you want lots of open loop gain, probably best to pick a different design. as far as the bias servo, would have to see thd with and without it.

assuming the parts are stn9360 and matching npn are 600v parts the front end limits to +/-600v. with cascodes you can get to +/-900. anything over +/-600v will damage the headphones.

that is a dual voltage output, single ended flyback supply. can't change the positive voltage without changing the negative. so you really need 2 x single output units. and then you might be stuck with +/-380. which should work.

so my version has an amplifier power of around 20 watts. the hvrv version seems to be half of that. may be the reason why there were a couple of comments about the sound vs the original to126 version.

those modules do work, i have a few. the diodes on the back run stupid hot. never tested for hours and hours. there was a company in poland i think building an electrostatic amp with 4 of these. first version with no fans. second version with fans. both versions burn up in a couple of months.

the dexu parts are providing the isolation. this works. extra parts, maybe the same performance.

those are not isolated. at least they sure look non isolated. how you put them in series with common power supply input.