kevin gilmore

should be final rev's of these two boards unbalanced/balanced to balanced http://gilmore.chem.northwestern.edu/ubaltobald3.zip ss dynalo balanced http://gilmore.chem.northwestern.edu/kgdynalobal5.zip

I have tested it, listened to it, works great. offset is 1.5mv going to swap out the opa445 for op27 and then remove the offset pots. and probably add a pot on the pnp current source to do a final trim. input impedance with the bipolars is 10k. replace them with the jfets and it works better

ball bearing from the back make sure no one pours water over the thing

because tyll's kgss absolutely needed a wood knob, I sent him the one I made out of Arizona desert ironwood. Which left me without one. So I had to make one, and I made another ebony one. black and white ebony and snakewood hopefully tomorrow. http://gilmore.chem.northwestern.edu/knobs5.jpg

http://gilmore.chem.northwestern.edu/ubaltobal1.jpg

the same connectors used in the diy-t2 but less pins. ugly but rated for the voltage and not plastic crap amphenol industrial circular connectors

no idea. probably china too. what evidently happened to wima is that when they switched to china they changed the sizes of most products, making them smaller with different films that are more tightly wound.

there is a thread over at diyaudio saying that since wima has moved production to china, quality has turned to absolute shit. time to buy caps from vishay

nopants you are fucking idiot. birgir and I spend hundreds of hours on this stuff and you make a stupid joke. not funny input board complete and works perfect. thd less than the base of my ancient test gear (<.002% thd, and absolutely flat) picture later.

you forgot to tell us that you let out the magic smoke

balance pot has to be set in the middle or bad things may happen. normally the pots are set to middle out of the box. its usually pretty hard to do diode checks in circuit and get reliable info if all the leds are lit it is working and maybe the one pot is shorted

http://gilmore.chem.northwestern.edu/ubaltobal.jpg rest of the parts on monday

you need a better solder sucker. but what you can do instead is remove the 4 x 2.2k resistors set the pot for maximum resistance to the xlr jacks, and wire a new one that way

the pcb is wrong. but you need to check the pot to be sure the pins on the pot should be ground,out,in

knobs need to be 2 inches or more thick. reason is I have to have something to grab onto reliably to put the insert in. once the insert is in, I can bring it down to about .8 inch deep. machining into the insides of an expensive 2 inch collet chuck might get someone really pissed at me if I make a mistake. I have enough now for about 20 ebony knobs. but none are absolutely black like the few I had made previously. will be getting enough wood to make doug a pair of panels anyway. need to find someone that has been sitting on a piece of pure black ebony for 30 or 40 years.

this is how it should be wired, but the pot is actually not wired like that if the footprint for the alps is correct in their documentation http://gilmore.chem.northwestern.edu/chinesekgss.pdf

the pot is definitely wired wrong. what he probably did is turn the pot into a variable resistance for current output dacs. This would then require all the extra voltage gain. the whole input section needs to be re-wired. will draw up what I think it should be when I get home. the 4 resistors to ground by the xlr input jacks. 2 of them are 49.9k ?? . R40,R47 What are the other 2.R37,R42 the 4 resistors from the pot to the input fets are 2.2k?R9,R10,R11,R12 the 4 resistors on the bottom of the board, what is the value? the schematic I did showed only one channel. If you replace the 154k resistors with 100k, you have to replace a total of 8 resistors, 4 for each channel.

what is the finished size of the side panels if they were flat? going shopping for more ebony. (both kinds)

just got in by accident a piece of ebony 15 inches x 2 inches x .5 inches. probably not long enough for 2 end pieces

sure looks to me that the pot is wired wrong. input goes to the wiper, output goes to the amp... ??

rca and + input of xlr wired in parallel. the switch switches the - input of the xlr to ground for rca. guess they could not buy more stax jacks

needs an ebony knob.

real numbers. (single ended input) measured single stator to ground kgsshv with 450v power supplies and 2 x 100k feedback resistors with 572 millivolts rms input produces 800 volts peak to peak output (not clipping) Chinese kgss with 350v power supplies and 2 x 154k feedback resistors with 320 millivolts rms input produces 700 volts peak to peak output (just barely clipping) so with a 1.5v rms input the pot if it was linear would have to be at 20% or less to avoid clipping. and the matching on the pot is going to be lousy at 20%. if you change the 154k resistors out to 100k resistors, the input at clipping would be at 500 millivolts rms. Which was the original design spec. nothing is wrong with the pot. (other than its a cheap piece of shit and used poorly) you probably need a 10db input pad. and you need to cut the gain by changing the feedback resistors back to the original design spec.

its not the pot, but when you get it and take it apart, take a picture of the bottom of the board.

the gain is way high. I don't know why. The 100k feedback resistors are actually 154k. So its about 3.7db high in gain (unbalanced), 7.4db high (balanced) There are resistors across the pot on the bottom of the board, I never looked into the way they were wired. NO reason why those resistors would be changed, the output bias is normal, so they could be changed back to what they are supposed to be, then readjust the balance. http://gilmore.chem.northwestern.edu/chinesekgss.pdf birgir thinks its a linear pot that was converted to log via the resisistors soldered to it on the bottom.