kevin gilmore

yes you definitely need the opamp, otherwise the opto has no drive.

use 2 and make sure the pass transistors have enough heatsink, as in bolted to the main heatsinks

the professional... (picture 9) http://www.head-fi.org/t/798779/sennheiser-he-60-baby-orpheus-w-hev-70-amp-original-box-immaculate the amateur seriously, ray has turned into a real sleezeball...

don't let any of the idiots over there know about this, the first thing that will happen is that someone will plug the tubes into a bhse directly and destroy $2k in tubes and probably trash the rest of the thing. these dht's have virtually identical curves to 6ca7 in triode mode.

i have over 200 op27 in stock. where i got them, no clue. but better than paying for them. finally had to buy opa445 from mouser as i ran out. one chip dead out of the package. have not seen that in a very long time.

you know that its possible that the hifiman amp has output transformers in which case the 300b would actually work as push pull. If so, what is that massive heat sink in the middle for. Still completely stupidass.

SE to balanced is what you probably mean, and you can do that. you can also do SE output, but then why?

Sure. Lower noise

I use 10k pots for everything. makes it simpler

http://gilmore.chem.northwestern.edu/currentamps.jpg

the stax mafia are definitely planning on a multibit dac. Problem is finding switches good enough (and fast enough) to do 24 bits, 1/2 lsb

http://gilmore.chem.northwestern.edu/g9f21766.jpg

https://en.wikipedia.org/wiki/Joe_Alaskey

I got my hands on the old Tektronix all tube curve tracer, the high voltage version goes to 1700 volts. I tested about 50 6ca7 tubes, no 2 indentical. not even close. did the same thing with c2m1000, and to the resolution of the screen, fairly easy to get bunches of matched quads but there is still some variation.

Is that how it works. I've been doing it wrong all these years.

its not like a voltage amp, so a balanced version is still the same output current. other than the cast output circuit i'm unaware of any balanced transconductance amps.

alcohol AND diy, especially electrostatic power amps. at the same time. usually entertaining, and possibly deadly.

overkill? ME? NO, never. the resistors i picked are actually 1.5 inches long, the layout is 1.8 inches. So you can use the concrete resistors. i don't like the sound of protection circuits. So this amp is capable of about 30 amps into .1 ohm. Its just so much simpler this way.

you are buying the 10m90 from mouser right?

susy is low impedance input, so you can't use a 50k pot. 10k pot max!

the attenuator resistors are not actually 10k, they depend on attenuation per switch and total impedance.

partial schematic suitable for checking http://gilmore.chem.northwestern.edu/attenuatorv2.pdf board pictures http://gilmore.chem.northwestern.edu/attenuatorsmtv42flipground7.pdf

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I think it's closer to a 6U as a stereo balanced the board is 4.35 inches high and 11.55 wide the transistors take up a bit of extra space past the board so say 10 inches X 15 inch heatsinks

if people really want, I can probably flip the tubes to the other side to make stuff like this easier.