kevin gilmore

I think that is right, but if you have the 100 volt windings, don't hook them to anything.

you can certainly power it up without a load, but make sure the angle brackets are attached otherwise the current source that drives the zener to power the opamp gets very hot very fast.

And then you really abuse them like singlepower does, and they really do burn up.

So both hammond and plitron are worthless... You would think that companies making this stuff for the last 75 years would have a clue.

Schematic updated with note from Inu. I'm using vintage parts, because with the amount of stuff i have in stock, i don't actually see the reason to buy more. Inu's mod increases the open loop gain of the power supply feedback. So the new versions of the op27's must be a different process or gain from the old ones. Completely makes sense. Now i'll spend the rest of the day synthesizing it, trying to find a better op27 model.

+/- 10 volts in any direction is just fine. You can get it to zero but it won't stay there due to the unregulated power supply. Has to work.

First time i've even heard of 8cg7's in an 007t. if the unit really was set up for the 8cg7's then the filaments of 6cg7 would be way high. In any case unless the tubes are competely toast, if they bias right, then they pretty much have to work. In fact if the tubes are toast, they would not bias correctly. offset to make the difference between the tubes zero bias to make the difference between each tube and ground zero.

The specs on the transformer was to deliver 130ma on the high voltage line DC. SumR calculates however they calculate from there. With all the problems i had with plitron, i made sure that he understood the current requirements. 60ma on the 285 volt winding and 60ma on the 75 volt winding. I did actually use the minus transformer for the 60 volts, but switching to the other transformer is definitely an OK idea. As people can attest to that visited CJ, the thing was on all day, and was definitely HOT, but not untouchably hot.

The -500 volt supply should be the current of the +500 supply plus the current of Q26,Q27,Q34 which is about 25ma. On my amp i measured 50ma on the +500 line, and 75 ma on the -500 line. Ultimately the current on the +500 line is controlled by the led's that do the current sources. If the supply is noisy or oscillating, a small cap across R41 (say .1uf) should shut it up. Or you have a bad opamp or a noisy zener on the power lines. Now why the transformer is getting hot, i don't know. The transormers were spec'd at 140ma i think. (have to look when i get home)

I was talking about the 7 pin socket that fit the current circuit board holes. The connex sockets can't do that. tom has sent me some more tubes, one of my tubes definitely has a problem, as tested on my tube tester. I did not test them before i used them however... So when they show up, i'll listen again.

you got 2 of the 3 numbers right...

Nope, not a DAC.

you gotta love engrish translations... http://gilmore.chem.northwestern.edu/dsc_1550.jpg

The wiring diagram is on the schematic. Each of the channels is seperate and has all the wires to run that particular channel. For the one extreme lunatic out there that wanted dual mono power supplies. Ac and dc all on the one connector. Interchangable. Also easier if there is a problem to troubleshoot one channel at at time.

You should be able to cram it into anything with a 14 x 14 x 3 inside dimension, but it will be tight. Bigger would be better. Lots and lots of holes top and bottom. I now know why the srm727 sounds like shit... Whoaboy...

This is not going to be a one time thing like the T2. There will be a call for board sets, and i will (or someone else will) do a board run of that many plus a few spares. Board set should be about $100.

I really want to use 2SA1968LS for the current sources. Then the entire amp would be isolated parts. Way easier. AND 100% head-fi proof. Even trevornetwork could build one and get it to work first time. (complete with plexiglass chassis) With ONsemi recently purchasing sanyo semiconductor, who knows what is going to happen. Not going to make boards that go instantly obsolete. I could use ixys parts instead. I may have to. Plus there are other things throwing monkey wrenches into stuff. If anyone in japan can help... My good friend Jeff who is the supplier of the vehicle necessary to take 400 lbs of aluminum to the polisher... His mother of 90 years passed away last night at 7:40. So i'm going to be another week late on that. Maybe longer. At least 8 of the T2 chassis are fully finished, and the last 4 will be as soon as more top/bottom material shows up. Speaking of which, I ordered a bunch of .25 inch material for the kgsshv chassis. .5 inch material showed up, and the wrong kind of aluminum in addition, so that has to go back and try again. I understand why justin is late on a lot of stuff. And he is doing at least 25 times the stuff per week that i am. I'm off to pick up a very special package from japan courtesy of someone with a heart as big as all of iceland.

as far as i know the 2sk389 is a discontinued part, and while there are places that still have them, i see no reason to layout the board for that part anymore. Its setup for the lsk389 can and the individual fets.

Yep, first thing is hook up the working channel and make sure the output voltage is zero before doing anything else. If it really is zero, and you have some "el-crapo" headphones you don't care about, hook it up and see if it sounds ok. Pull the dead amp board out, and look for pieces of metal, or other things that don't look right. But if its shorting out the power supply completely, most if not all of the output transistors are completely toasted. (or the bias supply transistor, and or pot are trashed)

they lie. they continue to lie. In january they promised me samples. All i get is excuses. They continue to say the j109 does not meet specs. They refuse to tell me which spec it does not meet. There is another reason...

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If you like electrostats, find a pair of beveridge and fix them up. Come with direct drive tube amps running on 5kv. They need a really big room.

disconnect the power supply output to the amp boards, insert new fuse and see if it blows. If it does, its the power supply board (shorted diodes, or shorted caps) or a shorted transformer. If it doesn't blow hook up the boards one at a time.

this just in, birgir likes his new knob. C1 is a silver mica cap in the original. It lowers the differential gain after about 2 hz. Ties in with the differential servo to keep the outputs at the same voltage. i'm sure you could put a 250 volt cap in there. But the original is 500v. If one of the input tubes shorts out, you really could get the better part of 250 volts across that cap.

Sounds like the srx circuit with constant current sources. Done correctly it sure will sound good. But not on a single power supply. You don't want to run 12at7's at 600 volts. Still, its very simple.