kevin gilmore

i like this idea.

There must be 20+ original designs. I'm going to give away all the board files, and nothing prevents people from building whatever they want. But a compact monster amp can't be a bad thing. The thing with the 5687's is that they behave very badly if you push them over +/-300. And given the Rp of the tube, the most you can get is 1150 vppss. Since there are no 1kv triodes unless you use really expensive dht's you have to use el34's strapped as triodes.

Perfect. Sometimes the web is not cooperative. Will check the fit later.

actually someone suggested a name over there for another product. But i like that name for this one. http://gilmore.chem....du/megatron.jpg Only the RK27 will fit, both the RK50 and the dact are both much bigger. i'm having trouble finding the datasheet for the quad, so if someone can find it. otherwise the board has to get longer. The pot is at the back near the inputs, and a shaft goes to the front. Same as the T2.

The Quality goes in before the Name Goes On. (i've been waiting 35 years to use that one now that it is no longer trademarked) And you really only have to match pairs.

.15% for a tube amp? Pretty low... (notice the . ) what i may do later is flip around the input stage and put a pot in the middle. Rk50/dact is easy. Board is going to get bigger.

This is absolutely at the T2/BHSE level. Remember that 50% of the output tube heat is filament heat, only 10 watts per tube goes actually goes to make audio. (ONLY) Because of the feedback, the prototype actually does .15% thd, and slew rates of over 100 volts per microsecond. The power supply is the kgsshv power supply at +/-450 volts. Or the simpler one. The auto dc balance requires very stable power supplies, so if you build the simpler one, the output dc will drift over temperature. A triple kgsshv power supply, +300, +/-500 would give this thing even more output swing. I can do that later. I suppose that you can go completely unregulated if you want to do really simple.

board size with the attenuators on board would be 11.5 x 10.4 rotated input section, board is 9 x 9 inches http://gilmore.chem..../beacssmall.jpg total tube power with filaments 180 watts. going to be perfect for winter.

Except that the attenuator is a 6 layer board which would force the rest of It to also be a 6 layer board and that is a bunch more money. Probably enough room to add the mounting holes for a pair of them. The 1u chassis is impossible due to the height of the caps. Maybe if you lay the caps down. Also the electrolytics are too big, And the attenuator is 1 inch thick

The advantages are more gain and one less capacitor. Trust me, you want the feedback, otherwise it sounds like crap. This is the one that will probably make it to production. http://gilmore.chem....rn.edu/beac.jpg Its 10.8 x 9.2 inches 7 x 6.3v filament supplies. I could split out the front end power supply, then you could run +/-500V for the output stage. The nice thing about this one is auto balance output. In fact you could act like that knucklehead in israel, and swap output tubes with the power on. And no nasty silicon to go up in smoke.

Whats also interesting is on this version you can build an unbalanced only one with just a single board. Figure the board and all the parts on it to be a total of $100 (the opamps are $21 each), add transformer, box and input output connectors.

The latest pictures that were acquired prove that the A10 was in fact wired as srpp. Very hard to determine from the low quality layout. Broskie will argue that due to the load, it cannot possibly be srpp. With very little additional work, this is easy to turn into a super B52, with dc coupled outputs. (+/-125 volt power supplies) (needs a servo to be safe) birgir has decided to tackle this piece of shit next. a full channel on one board including power supply. 5.1 x 3.85 inches http://gilmore.chem....du/dorkstar.jpg

paralled, yes. srpp, definitely not. srpp takes the output from the top cathode and is bad when driving electrostatic loads because of the huge change in impedance over frequency. This takes the output from the plate of the bottom tube. So its a tube driven constant current source. Substantial difference. The reason its doubled up is the cathode to filament voltage limits. No other way to do this with a 5687. Unless you are mikhail and can magically have a filament voltage at both ground and -400 volts at the same time...

The input section is the stax srx circuit. Which is easy to model, but is hard to explain. And it works and works well. The output stage is a tube constant current source. It would be easy to do the same thing to the bae, which would result in a total of 8 output tubes. The feedback is important and reduces what would be 3% THD to less than .2% THD. At some point these things start looking like, and are the size of the VTL WOTAN. The power supplies get to be very large.

i would make a new top out of 1/4 material and machine out areas for the heatsinks. the heatsinks are grounded, so this would work great.

why do you need to unsolder the heatsinks? It was designed to be repaired without ever doing that.

We always do the schematics last after the prototype is working. http://gilmore.chem.northwestern.edu/srxa10.pdf more than 1kv peak to peak stator to stator with .6 volt rms input signal.

that was not delrin, it was something else. I have one at home, will look at it later.

And this is the right way to do it. And its constant current, not srpp! http://gilmore.chem.....edu/srxa10.jpg dc coupled input, dc coupled and self balancing output one cap in the signal path. 10db of feedback, 54db gain and a thd of about .2% max at 20khz

Not sure since i've never seen an audio note up close, but the voltages are about half that of electrostatics. Its unlikely to actually be black teflon. I did test black delrin, and it starts conducting at about 200 volts. All of the connex octal sockets are white teflon. Probably for a reason. If its bakelite, then that is a different story. Not sure what the real stax jacks or the amphenol jacks are made of. I can probably test an amphenol jack, but i'm likely not to have the time to do that for a few months.

just have not had the time to test the final version. i can give you the board layout, have a few made and test. Biggest problem is that i'm moving my lab beginning of august, and i'm working 10 hour days in prep. Plus the stax mafia seem to be doing every possible electrostatic tube amp at the moment, all at the same time.

so its been over a month since andy has built an amplifier, and the stax mafia needs to keep the guy busy. So here is the bae. I changed the front end with a current source, and its dc coupled input and dc coupled output. 2 caps in the signal path. http://gilmore.chem....ern.edu/bea.pdf http://gilmore.chem....ern.edu/bea.jpg http://gilmore.chem....du/beapower.jpg The power supply has a + and - 15 supply, because later i will probably add the servo but at the moment with virtually all of the good opto isolator parts no longer in production, the ones i would use are way over priced. And the test version oscillates very nicely at about 2 volts on the output of 2 hz. So that needs more work. Next up what we are now calling the 2B10. only one cap in the signal path. Paralleled 5687's and DC coupled outputs with the above power supply set for +/-300 A total of 8 5687's. 6 seperate filament supplies... I'll also be doing a new version of the kgsshv power supply with the added 60 volt supply to make a high end, and universal power supply.

I have been thinking of adding a resistor string to the -HV line. But really i would like to add yet another power supply, say -30 volts, and do a current source instead. No reason to have more capacitors in the signal path if they are not necessary. Could use the input filament supply doubled and inverted. More on the srx circuit later. Also thinking of adding an opto coupled servo to the output stage. That gives me the excuse to add 2 more power supplies.

updated Megatron schematic. If you manage to figure out what the stax mafia is doing, please let us know. We are having a hard time keeping track of it all

100 ohm 2 to 5 watts