kevin gilmore

kerry's thing cannot do the kind of drilling and tapping necessary. On the other hand, nate has a desktop with DRO. Perfect for using a center drill on all the holes (required) and then drilling the holes. Tapping by hand is absolutely no problem as long as you have a chunk of metal at least 1 inch thick already drilled with the exact body size of the tap. Only way to keep the tap straight. And if you keep the tap straight, you won't snap it. I have a mill at home without a DRO, so i do it the old fashioned way and pay attention to the knobs. The NC machines just make it easy and fast.

Those heatsinks absolutely do have to be NC drilled and NC threaded. At a minimum a desktop manual mill preferably with digital readout. No way to use a hand drill. Its unlikely that the .5 inch spacing is going to line up with the fins, so no way to put nuts on the other side.

the hifi2000 case is instead of justin's heatsinks, not in addition. The 3U case should be big enough for one amplifier mounted to the side of each heatsink and the power supply board on the bottom. Two smaller power transformers or one bigger one. I'll be ordering one of these chassis soon. From birgirs dimensions, everything should just fit. But just barely. Justin's heatsinks would be used for a completely custom case, and this is a whole bunch of work i don't want to get involved in at the moment.

center tap is optional. and i have an even newer and slightly simpler high voltage supply coming soon. less parts, and the battery thing flipped upside down, and reference is now lt1021-10 because in fact it outperforms the lm4040-10 by a major amount. Long story on the lm4040 part...

My boards were 4 oz copper. Lil-knight's boards were 3.5 oz copper. A person here did in fact build the T2 as his first DIY project. And succeeded. But he had help from above. This thing is a whole bunch of work and even more if you are doing your own chassis.

http://gilmore.chem.northwestern.edu/kgsshvpower4.pdf http://gilmore.chem.northwestern.edu/kgsshvps7e.jpg http://gilmore.chem.northwestern.edu/kgsshvps7e.zip current limiters as suggested by doug, place for add on board for doug's regulator chip mounting hole size increased for #6-32 multiple build options including zeners only for simple and cheaper. (well cheap is a relative term) amplifier with on board heatsinks http://gilmore.chem.northwestern.edu/kgsshvampv6.jpg http://gilmore.chem.northwestern.edu/kgsshvampv6.zip amplifier for mounting to wall of the pesante case http://gilmore.chem.northwestern.edu/kgsshvampv7.jpg http://gilmore.chem.northwestern.edu/kgsshvampv7.zip

Power supply board with either simple zener option, or full regulator soon. Includes current limit to prevent the fets from blowing upon application of dead short.

At this point i will use any complementary j-fets that i can find regardless of package. But no match for the n-channel above. This is getting goofy.

A lot less than having to find an original T2 or build one. The sr-009 is just amazing on both the BHSE and the T2. You will see and hear soon enough.

I think you are now in the right place for a few of my new projects A 5uf cap after the 4.7M resistor is a BAD idea for O2's and most of the latest headphones. I'm sure you can find a distributor that will sell you parts and ship them to australia.

well you should use the 2sa1486 instead of the 2sa1413 if you are talking about the power supply. There are much better power supplies now. The 560pf caps are definitely the wrong compensation in the wrong place. Look at the latest kgsshv amplifier schematic here. http://gilmore.chem.northwestern.edu/kgsshvproduction.pdf what you want are the 5pf caps between the (in your version) collector of the 2sc3675 and the base of the 2sc2705.

i cannot figure out why the power supply is blowing up, mine still works great. However a current limit is a good idea and maybe a switch to doug's magic chip depending on price and real availibility.

i think you should handle the programming of this one. Whatever cpu you come up with just make sure it has an i2c output to drive the attenuator. gotta go watch Dr. Who premiere. will fix too small silkscreen tomorrow.

resistive! Nope, will not work behind plexiglass. Lets be serious here... resolution of one pixel. 320 x 240. Not gonna happen behind glass or plexiglass. You find me the apple display and touchscreen as a seperately purchasable item, and we will talk about it. This display and the cpu that drives it is a one piece item that is <$100. NOW MOAR MOAR BETTER. but 6 layers better idea for ground under the smt. http://gilmore.chem.northwestern.edu/attenuatorsmt18net.pdf kerry wanted the 1206 smt resistors in addition, and i found a way to cram those in too. So this should be it.

added resistor pack to increase drive current to relays for 3.3v tested with 3.3 volts drive and 5v and 12v relays tested with 5 volts drive and 5v and 12v relays would definitely work with 24v relays. three versions now due to possible difficulties in getting surface mount resistors all from one manufacturer. 2 different sizes of smt and .4 inch thru hole http://gilmore.chem.northwestern.edu/attenuatorsmt16net.pdf 2 different sizes of thru hole only, .2 and .4 inch on this one, the 2 extra ground layers are probably unnecessary http://gilmore.chem.northwestern.edu/attenuatorsmt17net.pdf edit: middle one probably unnecessary but wait: there is MOAR 3 different sizes of thru hole only, .15, .2 and .4 inch this runs the complete list of thru hole resistors from 6 cents each all the way to $36 each. 32 resistors needed for stereo, 64 for balanced http://gilmore.chem.northwestern.edu/attenuatorsmt18net.pdf actual working touchpanel controling the relays (and yes i know now that one of the buttons is 1 pixel off) had to turn it sideways because if you have a volume control with resolution of 256, then you NEED 256 pixels wide http://gilmore.chem.northwestern.edu/touchpanel2.jpg

The design of the amp, and especially the power supply is for the most neutral sound, and absolutely lowest noise. It should come as no surprise that this amplifier is capable of driving many of the older headphones to levels that exceed their capabilities. This and the T2 are really for the top of the line stax headphones, especially the new generation. 95db spl is already plenty loud.

The bias has to be +580 (for example) referenced to L+ minus L- (or R+ minus R-) So if you make -400 volts zero volts, make +400 volts 800 volts then if the outputs are prefectly matched at 400 volts, then the bias voltage needs to be 980 volts. This has scare people in the past. For 5 pin headphones, you really need L+ and L- and R+ and R- to be within about 20 volts of each other.

success writing 8 bit words to the relays. be careful that there are 2 different kinds of pcf8574 with different addresses i ordered pcf8754 (address 64) but was shipped pcf8574A (address 112 )

The JFW step attenuators i have in all of my NMR's are 50 ohm, and go all the way to about 800mhz. They have the red prp resistors in them and the resistors are about $5 each in massive quantities. Lots of resistors to pick from, anywhere from about 8 cents each to about $20 each.

This should satisfy even the biggest whackjobs out there. Had to add .1 inch so that it is now 2 x 5.1 inches. 3 different resistor sizes including the stupidly priced thru hole resistors on .4 inch centers. Someone please check this one thoroughly for errors. I could probably increase the resistors to .5 inch with no trouble, but they can't be more than .1 inch wide. http://gilmore.chem.northwestern.edu/attenuatorsmt15.pdf If you blow up the pdf to 400% it should display correctly. (well at least on my screen) edit: if you go with the thru hole resistors, and put some of them on the bottom like you would with the smt ones, then you can go to resistors that are up to .150 inch wide.

I could squeeze in thru hole resistors .4 inch holes. The 2 inches would probably stay the same, but it would be about .5 inches wider.

None of the surface mount resistors i can find are less than 10 ohms or more than 1 meg, so this limits the attenuator to a 25k or 50k version.

4PDT relays now discontinued. So the kgitsojc has to have significant changes anyway. If i change the amplifiers to all surface mount only, the board can be a bunch smaller. The L.I.T.E attenuator with the silver resistors is also in the $1400 range.

Conversion to PDF is filled with accuracy errors. Don't know any other way to show 4 or 6 layers. If you have a gerber viewer i can supply the real files.

ok, 2 final versions. 4 layer version with 99.9% controlled impedances http://gilmore.chem.northwestern.edu/attenuatorsmt10.pdf and 6 layer version with 100.0% matched impedances (2 ground planes added) http://gilmore.chem.northwestern.edu/attenuatorsmt11.pdf