kevin gilmore

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

max williams should be joining us soon. His entire thing was 3 pages of code. And one entire page of the code is to control the preamp inputs (of which there aren't any in the volume control only version) and to flip the MSB and LSB because he got the bits upside down. How someone else can turn this into 10k+ lines of code, i just cannot fathom Now as to morse code, we can certainly do that as long as you have 2 keys. One for clock and the other for data.

There will be multiple versions of things that can control this, from the simple to the very silly. Pretty sure this is 100% code compatible with the linuxworks stuff should he choose to ever release it. Standalone single chip arduino based thing with rotary optical encoder being worked on soon. 4dsystems thing being worked on also. (see picture previously posted, rest of parts to develop the software inbound) latest version here http://gilmore.chem.northwestern.edu/attenuatorsmt9.pdf all signal traces exactly matched for length and differential time distortion no more than about 50 femtoseconds. (Seriously) And mainly due to the slight differences in the internal ground planes. For the massively insane i have a 6 layer version which is absolutely and perfectly matched for capacitance too. This version should probably be made with multilayer arlon or similar material.

Yep i have one of those. Needed when i changed out my water heater. Not enough whoopie out of a propane torch to sucessfully solder the copper fittings. Almost as good as an oxy/accetyline torch without the required large cylinders. Have a small hydrogen torch for some specialty work

I was commenting on the heat from the power supply. Clearly the current sources and the tubes get hotter at higher voltages. The power supply heatsinks are slightly undersized and might be able to be replaced with the 2.5 inch versions. The current sources have plenty of heatsink. Most of the tube inside the chassis definitely raises the inside temperature a bunch.

Actually in this case if the unregulated primaries are where they should be (about 440 vdc under load) then running the outputs at +/-350 actually causes the pass fet to dissipate more power than if it was running at +/-400. Reason is that most of the power goes into the output tubes which are driven from a constant current source that will change very little between 350 and 400 volts. Suggest you measure the unregulated B+ under load to see if you can swap out the zeners for the higher voltage. Running the power supply unregulated is not really a good thing. BH and BHSE amplifiers were designed to run on +/-400 volts. T2 runs on +/-500 volts. kgsshv can run on 450 volts, or 500 volts.

i'm pretty sure i can do a 1206 inside the 2512 package, will look later. Compensation caps really not necesssary, the uln chips are just transistors anyway, and really don't need them, and for the other chips, its very close to the electrolytic anyway. May be able to add a cap on the bottom.

Ti has a lot to say about this. The dac i'm currently testing has between 30mv and 80mv of dc on each of the outputs depending on temperature. Ti says that the common mode servo needs to be extremely fast. My bench testing completely disagrees with this statement. balanced dynahi and balanced dynafet have a slow common mode servo. Further facts, if you are balanced in ONLY, and balanced out ONLY, then any common mode DC is meaningless anyway. You should further pay attention to things that are bridged amps (like 4 channel B22) and fully differential balanced amps (like B24). dynahi and dynafet orignal versions can be 4 channel, newest ones are differential balanced. The issue is whether or not the input has a common ground or not.

relay pads are 1.2 x 2.2 mm as specified by omron... what size do you want? edit: i'm thinking that programming this is gonna be very easy http://gilmore.chem.northwestern.edu/touchpanel.jpg

yep, on the back. look at the pdf file. updated picture http://gilmore.chem.northwestern.edu/attenuator5.jpg

depends on how good you are and if you buy the tacking glue. I can assemble it. I DON'T really want to assemble it.

Alrighty then, now an even bigger headache http://gilmore.chem.northwestern.edu/attenuator4.jpg just barely room for the 4 mounting holes, unless i make it bigger can't put mounting holes by the digital stuff. No room for on board 3.3V regulator. someone check for accuracy, the individual layers http://gilmore.chem.northwestern.edu/attenuatorsmt5.pdf Board is exactly 5 inches x 2 inches and 124 holes. 50 boards are $11.28 each plus $200 tooling charge from pcbnet.com So about $15.28 plus shipping, someone else should do this so as to avoid the 11% illinois state and local taxes. I could change the digital connector to a 10 pin ribbon with each pin doubled up. I'm pretty sure this will in fact fit into the T2. Need simplified single pot thing like the twisted pear to control it for this application. This exercise is left to the viewer.

pretty good guess. This is exactly 5 inches x 2 inches x 4 layers. not done yet, but the rest should be easy. My eyes hurt. Ground planes both sides. All audio in and out on the one side. http://gilmore.chem.northwestern.edu/attensmt4.jpg

latest http://gilmore.chem.northwestern.edu/attensmt3.jpg now what i could do is have 4 relays in series then flip the other 4 relays to the back of the board. That way the inputs and outputs are on the same side. It would absolutely have to be a 4 layer board. Not such a bad thing.

edit: http://gilmore.chem.northwestern.edu/attensmt2.jpg 5.7 x 2.6 inches, just this part. I would think that very few would be able to hand assemble this.

Yep, down on your side of the pond. 4dsystems lcd touchpanel with cpu http://www.4dsystems.com.au/prod.php?id=148 i have one now, and it works absolutely great. add an arduino and the network stack board and program the thing from an ipod.

Not going to happen. Managed to take .5 inch by getting the relays as close together as possible. All the other relays are the same exact physical size whether they are surface mount or not. Each relay is 20mm width. I doubt i can rotate the relays, but will see. If i rotate the relays, by the time i locate the resistors, there would be virtually no benefit. here you go on the tightest fit i can get. http://gilmore.chem.northwestern.edu/attenuator3.jpg