kevin gilmore

birgir just sent me this... http://gilmore.chem.northwestern.edu/exstata.bmp i guess that not having a car for 2 weeks forces a person to sit in front of a computer for way too long I assume a rational power supply that does not blow up is comming soon. Or just use the kgsshv supply turned down a bit. Should actually work fine at +/-450

this one looks like fun FOXNews.com - World's Strongest Beer Launches at $762 a Bottle

see our problem is this idiot agency called the fancy candy company who mandates that the output of those little toys is -88dbm. Pretty much useless these days. so its not that the devices are crappy, its that they don't put out enough power. Fortunately there is solutions, and the one like the sony actually does fit into the rf input line and switches itself in and out as necessary. I like my solution better. Its completely portable.

I forgot all about the protection circuit relays on the 717. Yep spritzer is right... What could be happening is that with the cover on, the temperature is going up (normal), and the output dc drift goes out of range and the protection circuit kicks in. So you have to rebalance the differential and set the offset to zero, for each channel.

That part is not so bad. When they give me 4 hours of machine time, i know what to do... I have each and every tool memorized as to position in the tool bin. The really bad part is dealing with the polisher and finisher. The polisher ended up with a huge job, and pushed my stuff off a week or two. So on the current batch i will be lucky to have the chassis finished by the end of next week. probably one more week. I'm sure justin has to deal with this in a massive way. The amp board (of which you need two) is going to be 8.25 x 6.25 The power supply board is going to be 9.3 x 7.7

i'm not going to make 2 runs of boards. will probably change this one to use the 1000 volt fet as the current source, then you can run it on +/-500. Tired of custom chassis work (except for myself) so i'm making this as easy as possible to build.

as soon as you take the cover off, it does not overheat... srm323a2 definitely has current limiting. Q13 (which you can't see the label) and Q14, Q17 (can't see the label) and Q18 set high enough to protect the transistors, but not to kick in otherwise. not the same kind of current limiting as most of the rest of the amps which are current sources.

if someone can build an exstata they will be able to build this... http://gilmore.chem.northwestern.edu/kgsshvhs.bmp slap it in any case you want. power supply this way will be next. perfect for pabbi1's wood boxes.

and just for fun, a srm323 front end and a push pull output section http://gilmore.chem.northwestern.edu/srm323a2.pdf my front end would work in the same way... 2sa1968's a bit expensive, but some people would really like this. +/-450 volt power supplies... pretty close to that magic +/-500...

i just got a copy of the srm323 schematics, and the design is very similar to all the rest, but with the addition of higher voltage power supplies, and 2sa1968's as the current sources. defintely tests even better. My guess is that people would like it very much. At about $600 via ebay (brand new) its definitely in the same range as an exstata by the time you add a case and decent volume knob. http://gilmore.chem.northwestern.edu/srm323a.pdf analysis of srm300 and srm727 coming soon

they don't all suck. this one works great. FM25B - Professional Synthesized FM Stereo Transmitter Kit - Ramsey Electronics and you can add a 1 or 5 watt booster (illegal or course) and transmit a mile or more. Very clean.

its also a jfet. in any case i will try and buy a few and test them. i assume people are using them as current sources, would like to know how they actually perform.

true, but for $10 total more in parts it can be MUCH better.

re: 717, open it up and listen to it, when the sound goes away, look at the led's and see if all of them are lit. If none of them are lit, then you are having a thermal cutout inside the transformer... the srm1mk2 was made between 1985 and 1990. As such its more than 20 years old. More than enough time for the electrolytics to dry up. So people who still have them and don't like the sound should probably change out all the power caps. At this point the 717's are now 10 years old and probably need new caps too.

well there are definitely different kinds of distortion, mainly 2nd harmonic, or mainly 3rd harmonic. and sound signatures are different too. push pull sounds a particular way, whether solid state or tubes. same thing with the various kind of single ended things. There is also soft clipping vs hard clipping. all the stax amps are really singled ended with constant current sources for the solid state amps, and resistors for the tube amps. (the t2 is something else entirely) the exstata output stage is a constant current source. you can add a current source to the exstata gain stage and make it bunches better. The vhv amp i posted a bit ago is the only example of a solid state push pull amp that i know of that actually works. It depends on stacking transistors to meet the necessary voltage requirements, and its performance suffers as a result.

i'm thinking seriously of doing a version of the board with a simplified current source that performs just as good (1000 volt ixys part, thanks marc) and with standup heatsinks. Will make it lots easier and cheaper for people to build it. Power supply will be the same thing. Hopefully will get started on it friday. Will cut the power supply voltages to +/-450 just to make sure the current source has a bit of headroom. if anyone knows of a depletion mode fet that does more than 1000 volts and will run at 1ma, let me know.

There is more than one frank... I have a MIG2 dynamic amp (similar to BH) with 8 x 6c33's 6 filament transformers alone. Consumes about double the power of the T2. Even though i published schematics, no one but me ever built one. I have an all DHT direct coupled electrostatic amp. Its so expensive i can't even afford it. (plus i never finished doing the high frequency isolated filament transformers) $8k for the tubes alone.

i measure with pabbi1 listening levels... http://gilmore.chem.northwestern.edu/srm1mk2.pdf even so we are pretty close. -60db second harmonic is .1% -85db third harmonic is better than .01% i was quoting DC power supply voltages, not AC voltage swing. Ray samuels is the only moron i know that pushes 317HV's to those kind of voltages. Way in excess of their 150 volt ratings. (i think there is a 225 volt version now) And besides which there is no high voltage version of the negative regulator. Now what you could do is run the transformer on 120 vac, and set the jumpers for 100 vac, then use simple zener/fet regulators... That would work great. And the transformer is going to get a bunch warmer.

the SRM monitor is a different schematic... pretty sure... stock exstata +/-300 volts ... 1.0% THD stock srm1-mk2 +/-350 volts... .1% THD stock srm-313 +/-350 volts... .01% THD I would add an auxilliary power supply that is fully regulated. for the srm1-mk2 it would be +350, -350, -370.

now i remember... the srm-1 mk2 is the one before the srm-717... i think they are close, but i would pick the stax unit, then mod the power supply.

don't have the srm-1 schematics at hand at the moment, so i'll speak on the t1,t1s,006t,007t all of which are the same identical design, and are grid drive with the tube as the output stage. If you sub out the tubes with 6s4's things get much better. And if you add a current source instead of the plate resistors, things get better yet. exstata tube hybrid uses 6s4 in grounded grid as gain stage, and solid state output section which is the same as the srm212,313,717. And i assume the srm323. 727 is definitely different. which is better in stock (unmodified form) , srm313 vs exstata solid state... in my opinion, the srm313 is better. clear as mud.

well that depends on which datasheets you look at. most list the 6cg7 at 450 volts, some list 500 volts. on the srm600 the power supply voltages have been lowered to +/-300 volts to accomidate the ecc99 6s4's are rated for vertical flyback use in crt's, and easily run at 1kv.

Of course it does. Lets see, running a 450 volt MAX tube on 700 volts. Does no one ever bother to read the datasheets?

here is another one pointed to me by minivan before at TEN percent distortion. (yep completely open loop, no feedback) http://gilmore.chem.northwestern.edu/vhvtest1.pdf (well some local feedback around the output stage) and after at .01% THD. http://gilmore.chem.northwestern.edu/vhvtest2.pdf with added low impedance input and nelson pass super symmetry who is going to be the first to build it. 6 power supplies. Think T2 power supply only bigger... !!! +/-660 (650) +/-240 (250) +/-87 (90)

reasonable signal levels. 100 volts peak to peak. amp capable of about 600 volts peak to peak. (stator to ground) anything sounds better than a transformer box. unless you like that kind of sound.