kevin gilmore

Hey... they were soft and pliable And yes there is a new stax king of the hill. and about time too. Time for sennheiser to step up to the plate and produce some competition.

I think you are both missing the point, these things really are suitable for RF frequencies only. Unless someone can show me otherwise. DC stability on these devices is going to be absolutely horrible, and drift with temperature is going to be significant. Plus the input impedance is going to be way low too. Going to be great for cell phones and GPS receivers, but not for audio.

Actually i think it is 4 of the chips that are proprietary. Lucky i have 2 trashed scopes with bad tubes for spare parts. And now a 2467B that needs serious work. Nothing in this world lasts forever. All of the magic chips in the latest tektronix and agilent scopes are completely proprietary too. And soldered to the boards, so if you blow the input channel, you get a minimum of a $5k repair bill. At least agilent was smart enough to buy out triquint semiconductor.

The 2465 is an analog scope, and does have a 400 volt rating (20 volts per major division) In fact you can push it more than that in 1 meg input impedance mode by going uncalibrated. (probably not a good idea for most people) The digital scopes like the one i'm being forced to use lately (due to frequency) have a maximum voltage rating of 5 volts per major division. Or 100 volts. But really much less than that because the 50 ohm input impedance can only handle 5 watts peak. Over the years i have stayed away from digital scopes as much as possible. What i need to look at, and the way they work are incompatible. The worst ever are the LeCroy pieces of crap. I have 4 of those. Not even heavy enough to use as door stops. Agilent has a new scope that looks like it can do what i want. Stuffed the way i want it, its $280K... No joke. Given the fact that i spent about $70k on a scope 25 years ago,this is not actually such a bad price. If i could find a real time analog scope with a 1ghz bandwidth i would buy it immediately. Unfortunately, there is not now, and never was such a thing. I'm going to be spending the next couple of weeks fighting a home build 65ghz EPR system and know i'm in for serious amounts of grief.

At the rate things are going, commercial products should be available in about 10 years. But these things along with nanotube transistors are really very low power devices and capable of amplification in the 1ghz to 100ghz region.

If you want interesting and cheap and new... I saw and played with one of these last week. ARM DSO Nano - Pocket-Sized Digital Oscilloscope - eBay (item 200470598507 end time Nov-05-10 09:33:18 PDT) The best real analog scope ever made was the 2465C, recently i saw a couple go for cheap. Once you get into digital scopes, lots of stuff changes, and so does the real resolution which is usually 8 or 9 bits. Also most of the digital scopes have limited voltage ranges. I own both a 2465B, a 2465C, a 7000 series mainframe with plugins, the tektronix battery powered dso and a 5ghz tektronix color dpo, and i like the 2465C the best.

True story... Happened yesterday. About 25 years ago i lived 3 doors down from a guy named andy birnbaum. At the time he was a manufacturers rep for various audio companies. He just stopped by, said hello, wanted to put a sign on my lawn because his wife is running for illinois senate... Said he was the national sales rep for skullcandy. So i showed him the T2. He asked me what i thought of the skullcandy products. So i asked him the simple question if they sounded like the O2mk2/T2. No answer. So he wants to put me in contact with someone higher up in the company. This is going to be one interesting phonecall. I figured i would start out with the simple statment that every single part of your product line sucks. In my listening room at the same time were the hd800's and a couple other high end dynamics. He got to listen to those too...

My god what a pile of stuff. If you keep going at this rate in 20 years your house will look like mine. I'm interested in the brown dog adapters.

I got mine yesterday. They are great.

just tried that. It makes it worse by 2 microvolts. I don't think that kind of thing works for high voltages. Then again, very few nutcases are doing high voltage power supplies with microvolt range noise.

As far as i can tell, this is all for low voltage stuff. The secondary of the high voltage transformer is 1800mH. Can't find the original link.

this is another one of those UL requirements. Neutral needs to stay hooked up at all times. For safety reasons in case someone uses a cheater plug. The hot is switched.

the magic smoke results from the temporary caps shorting out the diode... Then apply power. And the other diodes in the bridge go flying. You would think that 15 amp peak diodes with a transformer that can only supply 250ma would win, but they don't. The cap across the primary doubles the spike noise it turns out. My equipment is evidently better than JC's. The sequerra method of a dual inductor (as in transformer but of only 10mh) with the main current thru the primary, and the secondary added out of phase with a tune cap also has no effect. (besides its way to big) The real life self inductance of the power caps makes any attempts at CRLCRLC pointless. When driven from a stack of mercury batteries (3 x 225v) and no load the circuit noise really is about 1.5 microvolt peak to peak.

mikhail and rudi mount to220's like this, with varying results. mikhail would usually bend the pin into a loop and then solder to what used to be the back of the pin. A lot of his broke off after a while because the overstressed transformer generated enough vibration to crack the pins off. The use of a little piece of perf board might make things more reliable.

Tried a number of the C,RC,LRC,.... Which resulted in magic smoke and parts flying across the room. Inductors are a bad bad thing. By the time you are at microvolt levels nothing works. Now if i wanted to double the size of the power supply, i could bandpass filter the noise peaks, invert with an ultra low noise amplifier, and add it back in to the output signal, canceling out the spikes. At which point you would still have about 1 microvolt of thermal and shot noise. The amplifier has 50 to 60db of power supply rejection anyway. Even if you piled up a large stack of car batteries, the resulting noise would be more than 10 microvolts.

So i messed with the imaging NMR for about 4 hours on the block of wood. Proton(high band): Absolutely positively NOTHING. 1 hour of scans at minimum stepsize. Carbon(low band): Maybe even the slightest hint of NOTHING. 3 hours of scans at minimum stepsize. If there is any signal, its buried in the mud. Maybe a few days of scans might generate something. But i really can't do that. Except maybe over christmas or new years. Will try ultrasound on monday. My opinion is that if there was a way to see inside the wood, someone would have already found it and published it.

I'm pretty sure i'm done with the power supply, schematics and board layout updated. Tests indicate about 12 microvolts of noise at full power. Its when the diodes turn on, and using the 35ns soft recovery diodes, even ceramic caps across them make no difference. Over the range 10C to 50C and under full load the power supply voltage changes only 1.2 volts. Measuring this is not at all easy. So i'll call it a better than -140db power supply and be done with. http://gilmore.chem.northwestern.edu/kgsshvpower3.pdf spacers added to the non-insulated parts, update in a few minutes. http://gilmore.chem.northwestern.edu/kgsshvps7c.jpg also dual cap sizes for spritzer, and heatsinks for luvdunhill

one thing i have yet to try is to just add the capacitor, without cutting the land. The impedance of the reference may already be high enough not to need the resistor.

1/4 watt is plenty. 1/8 watt would work too. You can build the 1/8 watt into a pair of sockets. (i'm behind on this)

http://gilmore.chem.northwestern.edu/woodknob3.jpg Tried to xray the wood block. Full power, 50kv @ 50ma. 5 minute exposure. Absolutely nothing. Not even on the part that is 1 inch thick. I did just get funded for a copper microsource which is about 10 times the bang. Maybe one of these days i will sneak it into the APS... Next up Nmr Imaging. (MRI for the rest of you...)

Polishing of the 8 chassis is done, parts will be here monday. Then 4 of them will go for anodizing.

ultrasound huh? I very much doubt it. But i do have access to a newer vintage Siemens unit, will try tomorrow. The stuff is just about as dead as can be, i doubt ultrasound would go thru the wood more than .25 inch. MRI... No way.. But i have a year old bruker imaging system with a 9T magnet, can try that tomorrow too. If it does work, that would be very slick. None of these systems have the resolution that i think would be necessary. At least 100 lines per inch would be needed. I'll walk around tomorrow with my woody and see what i can do.

Yep, that works. Slightly more expensive, but ok. The prices on the cree diodes is just plain silly.

Now i find the stth1512 rectifiers are no longer available in a to220 package, or order time is a year... Need 1200 volt 8 to 15 amp ultra fast rectifiers in a to220 package... In stock...

my xray machines are designed to go ultra small. So even an ic chip is kind of big. i know where to take it to do a standard film xray, will have to try it. Don't think the resolution of film is going to work on this.