kevin gilmore

unlike a lot of amps, the dynahi will work into a dead short if necessary but if you want, build and install the protector board

The failure mode is that the resistors open up, the outputs go to -350V, the resulting bias gets close to 900, and makes the headphones very unhappy.

yep

its supersymmetry, and the 5k resistors are part of the feedback. if you go with fets you can multiply both Rf and Ri by 10 to increase the input impedance. really does not matter for this. definitely does matter for the input impedance for the ubal to bal converter.

try doubling the values of the compensation caps

yep

in balanced mode the gain is Rf/Ri *2 you don't want to change the 5k input resistors, so change the feedback resistors. Unlikely the compensation cap needs to be changed

the pot by the led's is the input section offset pot. was thinking about a different board. you can probably get away with 18ma per output transistor.

when sales of tle ll2t drop to zero. but he is still going to have to do a major redesign to get that to happen

you pull the opamps, and start with all the pots in the center. the pot in the middle of the board, you adjust so that the outputs are centered around zero. Then you adjust each other pot to bring that output to zero. then you put the opamps back in.

now where have I heard that one before?

gfi outlets will not work without a real ground. they work by measuring differential current.

that depends on whether the output is true balanced or ground referenced. true balanced may cause interesting dc level issues releated to common mode.

should work from +/-400 to +/-550

if your water pipes are copper, they are usable as a ground.

reduce the gain of the amplifier by lowering the feedback resistors

for a 10k pot, the series resistors should be 10k, and then calculate the other resistor for the attenuation you need

buy the neutrik xlr-male to xlr-female adapters and pick your attenuation and use either 3 or 4 resistors depending on whether the dac is really balanced or not. http://www.mouser.com/ProductDetail/Neutrik/NA3FM/?qs=sGAEpiMZZMv0W4pxf2HiV9y0EyfHsAgRI%2fcUCPoRaKI%3d

Which is insanely high, but lots of dac's are doing that these days. You need a 10db balanced pad on the input.

icarium has one of my cases

yep that is the one.

suggest you buy the transistor tester meter on ebay, cheap and the best way to test them before you stuff them in the boards and then find out they are not real.

those are vertical mount resistors to keep the board size down

http://gilmore.chem.northwestern.edu/megatron.pdf

actually use a 12V car battery. you will find the shorts very quickly