kevin gilmore

http://gilmore.chem.northwestern.edu/srm323aorig.pdf balanced no problem. But you would have to change out the input pot, or bypass completely.

5. Anonymous but it should be obvious who this person is.

I was wondering about all the flipped parts myself, as i have an identical unit with the same revision of the boards. No flipping on the pins of the regulator. No crossing of the diodes on the input fets either. Clearly the +15 is not being regulated with the regulator wired like that. Measuring that voltage would give you the answer, likely +18 or more and unregulated and filled with hum.

The power transformer has clearly shifted in shipping. This needs to be fixed first. If the bolt is touching the inside of the transformer, all sorts of ground current and vibration is getting into the chassis.

posted on behalf of linear http://gilmore.chem.northwestern.edu/t2schemip.pdf http://gilmore.chem.northwestern.edu/t2schemop.pdf http://gilmore.chem.northwestern.edu/t2schems&b.pdf http://gilmore.chem.northwestern.edu/mjt2a.jpg http://gilmore.chem.northwestern.edu/mjt2b.jpg http://gilmore.chem.northwestern.edu/mjt2c.jpg http://gilmore.chem.northwestern.edu/mjt2d.jpg

if you look at the insides of the original, the 22k resistor was mounted on the backside about .5 inch from the board so that you could put clipleads on it to adjust.

i'm sure inu could translate it. but i know a couple of people at work that can do it too. maybe in the next few days. really, these things are just the srx circuit with an extra tube stage for more gain so that you can have more feedback. 50ca10's are probably impossible to get, as are the sockets, 6ra9's might be easier. Still nothing wrong with 6ca7's. But the resistor plate loads are guaranteed to do the same thing that has happened to a bunch of the es1/es2's when the output tube lets go. So much better idea to replace with current source. Then make sure you have adjustable bias on the output tube. Pretty soon you end up with the modified singlepower schematic. There are errors in the schematics, in the 3rd one, "B" is actually -440 volts. With the 50c10's you can do adjustable self bias without an additional negative power supply.

inu sent me these which are variations on the srx circuit. http://earsp.web.fc2.com/log/stax-r/stax-r-3.pdf warning, the 1150 volt version is only for those that really know what they are doing. And obviously the output caps need to be rated for 1200 or more volts. With respect to high voltage electrolytics, and also mylar caps, a resistor across the cap is pretty much required at all times. Even if you discharge the cap, and then remove the resistor, the capacitor will self charge, usually to very dangerous voltages. The higher the rating on the cap, the worse it gets.

I still listen to 2 cd's, sometimes more every day when i get home. right after i let the dogs out. sometimes with added liquid refreshment.

Depends on which version of the power supply board you have, but 24 volt zeners across the gate to source prevents the pass transistor from blowing up. The fairchild part used in the T2 is way better anyway.FQPF8N80C or FQP8N80C and they are cheap. Probably still out of stock at mouser, so get them at futureelectronics.

In all 3 cases above, its the current source that is the problem. Has to have 1000 volts compliance. This requires stacked pnp's similar to the original circuit. And the capacitor (c1,c2,c3) necessary to stabilize the circuit is going to affect the quality of the current source at higher frequencies. the devil is in the details. Build it and test at appropriate voltages, then let me know. The SiC devices work great on paper. In practice, there are all sorts of other issues because they don't like to work at low currents for example.

Well i'm 30+ lbs LESS buddha than i was when i started this project 19 months ago. You can be pretty sure that if you do a spice analysis, and the results are poor, then if you actually build and test the device, it will be poor or worse. But a good spice result does not necessarily translate to a wonderful sounding amplifier. The ixys10m90s devices sound just fine, but blow up at about 925 volts. Rather consistently. Anything else at 1000 volts does not sound as good. Replacing the 2sc3675's with 2sc4686's does in fact work fine, and sound the same but you have to turn up the bias currents a bit. Same thing with the active batteries. The open loop gain is plenty high already. Anything over 15db of headroom seems to make lots of different amplifiers sound bad. Many of the portable opamp based toys with 50db+ of extra gain are a good example. The slew rate is more than sufficient with a rise time of under a microsecond large signal. Replacing the input tubes is still open to discussion.

My T2 is just about 1 year old now. The hundreds of hours of joy it has given me and will continue to give me in the future is something i will remember forever. I just don't see any way to improve on the design. Maybe ways to make it a bit cheaper and easier to build, but doing anything to increase the slew rate, or further lower the distortion does not seem to be possible.

yup

over the years i have seen bunches of torroid transformers burn up. And not just on audio gear. If we could find a video of them being wound, you would see all the issues that can cause trouble. You spec the transformers as best you can, and hope the manufacturer has a clue. But i know of one well known manufacturer that still to this day has very little clue what they are doing.

i love mine, too bad its not anti-magnetic but is 18k gold http://gilmore.chem.northwestern.edu/dsc_0752.jpg

Not a black circuit board. just reflections from the scanner or camera from the solder mask.

center tap on the high voltage windings is optional.

Someone loan this guy a T2. Has more parts than any other headphone amplifier ever. Or a krell master reference amplifier.

already had the charlie parker, its great music.

Singlepower ran dc filament current all over the boards. Trouble was the significant AC content due to the diodes got into just about everything. The diy T2 does absolutely the minimum amount of filament on the board for this reason.

more fine work by kerry http://gilmore.chem.northwestern.edu/BlueHawaii-AB-T2-Servo-v1-0.zip

First time (well at least so far) that the snow plow has not sent my mailbox into oblivion in 15 years. Sure toasted a few others however. They must have been going at least 30 mph down the street. I have the mailbox on an old single piece of a truck spring, so you whack the thing and it just springs back. Whenever i hear the snow plow barrel down the street, i'm out there 5 minutes later to clean the slush off the end of the driveway before it turns into one solid chunk of ice. The new snowblower i have has this extra feature that turns ice and wet mush into water which it throws out of the way at least 40 feet. Absolutely no problems getting to work and back with the vette the last 2 days.

No... No... Grande Champaigne... The good stuff. Delamain cognac, the 60 year old stuff. Glad my roof is steep enough that the snow does not stick. No way i'm getting up 3 stories...

updated spreadsheet. if there are any other errors let me know. fqpf8n80c... lots in stock at future electronics. If you want to be fancy about it, on the small heatsinks, remove the pins, use them upside down, thread the area on the other side where the pins used to be, and then drill and tap a new #4-40 hole for the transistor. Use ceramic insulator, bushing and stainless screw.