kevin gilmore

yes it looks real. I have not seen 2sc4686a parts as fake yet. I bought extra parts from many ebay vendors recently and all test ok. 2sa1968 are a different story, most are fake.

lots of 2sc4686a on ebay still for cheap. suggest you buy a bunch.

if you have the latest boards with the zener protection you can replace the 3rd stage bottom and top of the 4th stage with 05n100m (latest on board version) or solder the zeners on the back schematic was never updated I have never actually seen 2sc4686. only 2sc4686a which is a 1200v part

something with a pair of 35V windings would be ideal, 40V windings are going to probably overheat the power supply. And you may have to adjust the bias generator to lower the standing current.

the ref102 WILL NOT WORK it cannot operate in 2 wire mode you cannot use all enhancement mode mosfets it will go boom

you have to replace all 4 zeners. the second stage zeners need to be 33V and the first stage need 40V and the caps need to be voltage upgraded

probably any of the lsk389 would work, but never tried it.

yep 120 ohms or even lower

you change R7/R10 to 350 ohms which will give about +/-33V on the power supply.

default for 500v is the same 5ma. you change the emitter resistors at the bottom of the output stage. and you want a lsk389B. the lsk170B is available from diyaudio.com

phil has sent me his schematics a number of times. He asked me not to publish them, so I did not publish them. He definitely got screwed over by larry numerous times. larry's video game addiction... etc...

I'm waiting for birgir to send me a liquid gold

The on board version can only handle so much power because of the heatsink size. The default is 5ma, which at 450V is 9 watts total for the output stage which is 2.25 watts per output device. The off board version is limited by only 2 things, the size of the heatsink and the maximum amount of power the output devices can handle. So yours is 14ma which is 25 watts per channel. The effect of the higher current is to extend the high frequency response well past 50khz. So the amp will definitely sound different. The choice of resistors will likely not make a change that you can ever hear. Except that a few of the trendy and expensive resistors cannot handle the voltage and cause all sorts of trouble. An lsk389 is going to be better than 2 x 2sk170 from an electrical drift standpoint. Not going to make any difference in the sound. Now the pot makes a big difference. RK50 and P&G are definitely the best of the bunch, rk27 and tkd less so. Mainly in channel to channel matching. dact will do better on matching. digital attenuators are even better.

white delrin. turns out there is a .002 taper in the insides of the neutrik jack. will make a couple out of Teflon anyway

final production stax male jacks http://gilmore.chem.northwestern.edu/staxmale5.jpg in case someone wants to have the Chinese make up a batch cheaper than I can http://gilmore.chem.northwestern.edu/staxplug.pdf

from the left Arizona desert ironwood lignum vitae from craig in the UK new piece of lignum vitae Tasmania blackwood ebony red mallee redheart cocobolo jersulaem olive wood orange pekote

more wood aging over the ventilator at work http://gilmore.chem.northwestern.edu/dsc_0780.jpg steve would be proud

we aim to please!

I have not measured in a while, but the zeners keep it pretty close to 580 +/-5% 600V bias won't hurt the headphones, once in a while you might hear whooshing noises. Also depends on humidity.

using an amplifier that can do 100 volts peak to peak on high efficiency headphones that at most need 2 volts peak to peak is a fair bit of overkill. Its not that you can't do it, but any accident can fry the headphones or blow out your ears.

yep. and I never use pots >25k even if there is no external low pass filter, jfet and tube inputs have a specific capacitance which will form a low pass filter anyway for my system I could use 50 ohms if I wanted to.

the stax mafia believes in continuous improvement I wasn't even going to do this, then it happened anyway. Very minor parts placement issues. silkscreen error fixed http://gilmore.chem.northwestern.edu/boards/kgbhultraminipsV2.zip

our current mini board is for rk27 and tkd pots. if you think about it, the shorter the resitive path, the more mismatching you are going to have. So a bigger pot should always be better.

i'm using 10k quad rk27 for testing the preamp. its ok. if you can find the noble, those are better. minimum order from alpha is 50 pieces i believe

The khozmo is a massive piece of crap. I have 2 on my desk that after repeated tries, cannot be made reliable. wiper made out of material without enough spring and eventually it goes intermittent and noisy. The dact is also a piece of crud. At least it stays reliable for a significant period of time. The rk50, penny&giles, and constant impedance digital attenuators are the only things that work correctly forever.