oh, jesus, you're right! gahh... they're in the VIDEO path.
just for shits and giggles, i have 5 components per channel in the audio path of my little prototype stereo amp. it's +1/-1.5 dB from 40Hz to 20KHz. .5 watts clean. i don't know how much distortion it has... it's certainly low enough so that the sound is really enjoyable, but i know there must be a lot of bizzare artifacts that i can't measure with my fuzz-specialized collection of test gear. 8^)
the signal path is input transformer (50 ohms)->damping resistor->tube(class AB)->LED (cathode bias)->output transformer (center-tapped custom) with 8 and 16 ohm output taps. the power supply consists of a toroidal transformer->full wave rectifier->filter cap. there are independent power supplies for each channel. the inputs are balanced (RCAs for convenience, but floating grounds) and the outputs are classic brass thumbnuts. they're pretty clear in the picture. the schematic, verbally, is this: input transformer has centertap grounded on secondary with damping resistor across outer windings. outer windings feed two grids on 6021W. the cathodes are shorted and go to ground through an ultra-bright blue LED for biasing. plates are connected to output transformer's primary outer windings, and center tap is connected to HV power supply's output. hum is canceled. no preamp tubes means no intermodulation between output and input power supplies! full balancing means you can strap this baby easily for more power. low output wattage and voltage means you can re-record directly off the outputs when connected to a speaker load, preserving the bizzare reactive load's interaction with the transformer! unique shit going on here... i can think of lots of fun applications for adding harmonics to bass and vocals using mild distortion, and what's really fun is you can hear exactly when it's getting sweet through the speaker coming from the amp, before you capture the signal back to your recorder. think about this... at .5 watts max, if you push the output to .7 watts for added harmonic distortion, an 8 ohm load will result in a 2.3V RMS audio signal isolated electrically on the output, which is well within the range of most consoles using a 20dB pad on the input! remember, 1V RMS is 0 dBV!
i'm pretty excited about making a commercial product out of this thing. it's got some little issues right now, but i think they're mostly solvable. there's some hum from the toroidal transformers coupling directly to the output transformers, and a bit more hum from the input transformers being trapped physically between the toroidal power transformers, but all in all, it's not that noisy for how convenient and small it is. it would make a really fun headphone amp i think, and a great mixing amp to keep you from turning up too loud... and at maximum power, it would tell you quickly if you had something out of whack balance-wise, or too dynamic in the mix... the offensive item would distort and stick out like a sore thumb! 8^)
