kevin gilmore

Before or after spritzer modifies the hell out of it?? A 6s4a is a WAY better tube than any 6fq7/6cg7! not sure about the ecc99

I should also mention that this is a relative thing. many people would be happy with an exstata in stock form. spritzer and i are not in that group of people. Not after listening to the T2, BHSE, BH... whether it is fair to compare an amp that is $500 in parts to an amp that is $4000 in parts is not my problem

OK, lets see if i got this right, since my dsl is down, i think i brought all the right stuff to work. So as spritzer says, before CJ, i built by hand an exstata solid state version. Perfboard version. And it sounded lousy, and it tested lousy. ONE PERCENT thd at reasonable signal levels. Fast forward a bit, i got alex's boards, built them with exactly the same parts as the BOM and guess what, exactly the same performance. synthesized here. http://gilmore.chem.northwestern.edu/exstatas.pdf sure enough slightly more than ONE PERCENT THD (second harmonic, top trace in distortion graph) and third harmonic pretty miserable too. so i started investigating and came up with this. http://gilmore.chem.northwestern.edu/exstatas1.pdf way better, .01% THD. and the sound is night and day better too. but when you clip the thing, it got nasty. SO... http://gilmore.chem.northwestern.edu/exstatas2.pdf but really, the more i play with it, the more it looks like what it actually came from, which still performs almost 5db better. http://gilmore.chem.northwestern.edu/srm313orig.pdf of course with modern day parts you can bump up the srm313 to higher voltage... http://gilmore.chem.northwestern.edu/srm313.pdf and of course you could do the same with the exstata's, but why bother. fact is that the 2sj74 is a lot less trouble than the j271 and you don't have to buy 50 parts to get 4 that work. and guess what the same thing for the exstata tube version. http://gilmore.chem.northwestern.edu/exstatat.pdf and with fixes... http://gilmore.chem.northwestern.edu/exstatat1.pdf fact is that the kgsshv still performs better than all the above and at higher voltages. i'm working on it to make it even better now.

Don't make any mistakes with this amp... Doing so would cause the output transistors to fail, and any modern replacements are going to sound completely different. As i remember there is virtually no short circuit protection on this thing. Should be a great headphone amp, or if you have k-horns... which is what it was designed for.

Yep, that works too... where did you find those white caps ??

some schematics say 230 volts for low bias. Some say 260. the resistor is indeed 5 meg. except for one very old schematic that says its 2 meg. i would go with 5 meg and 250 volts.

Well the power supply was not really designed with low bias in mind. but a rearrangement of the zeners allows for the right low voltage, and extra wire, and probably a little circuit board with 2 resistors and 2 caps needs to be added to the power supply. This is corrected on the kgsshv board and power supply. The alternative is actually quite easy. The 250 volt power supply can be used as the bias and is already very low noise and accessable. As there are two different wires for the two different stax jacks, this is the no modification approach. So you can have one high bias, and one low bias jack at the same time.

You already have 2 stax jacks for that, and you know it. But i will send you one more to replace the defective one plus the 2 knobs and the dact bracket as soon as the stuff shows up. The solid single piece BH is indeed great. I hope to do even better with the solid single piece T2. I think we are both in a race to see who can spend more on massive solid chunks of aluminum.

Not exactly. In fact mikhails amplifier was a fully dc coupled amplifer with a HUGE amount of dc drift over time and temperature. And the drift was not necessarily positive or negative, and it was well over 1 volt or more. So mikhail had to put in an output cap, and since he did not know the direction of the drift, he had to put in 2 caps back to back in series. But then because of the caps he picked, and the time it took them to actually charge up, he biased up the center pin, so that it did not suck so bad (meaning no bass for the first hour or so) and then told people to keep it turned on all the time. Serious clusterfuck, every part of the amp. http://gilmore.chem.northwestern.edu/dinglepower2.jpg

well i have some of the connex teflon ones, but those are very hole size specific and don't match any standard pattern. Also have a couple of the old ceramic ones for the original kgbh, similar to the ones used in your amp...

a stax of staxjacks http://gilmore.chem.northwestern.edu/staxjacks.jpg i wanted to make 40, but friday got in the way... this is enough for a while, the 4 people getting chassis this month, let me know whether you want low bias or high bias jacks. If the material comes in today, i will start on more angle pieces. All of the parts for the 4 are done, so they will ship as soon as the stuff gets back from anodizing.

mikhail used this technique in the squarewave... all poly/teflon caps exhibit some piezo electric effect. and electrolytics just don't belong in the audio chain.

2 inch long #4-40 nylon screw and a few nylon nuts. holds the diodes in place, no chance of a short.

somebody please find me something with heatsinks for the sides. 13 x 13 inch inside dimensions.

Mine already gets 29 mpg on the highway, and 21 in the city. No joke. Beats the crap out of the jaguar which could only do 14 in the city. The C7 with the 440hp direct injection engine should do 35 on the highway. (being 150 lbs lighter, and the efficiencies of direct inject) Maybe even better depending on the aero-dynamics. When i was growing up in high school, one of the people on the block had a very rare XKE with a V12 engine, and 4 x 2 barrel carbs. he was adjusting it weekly. Maybe even more often. Had floating things with ping pong balls in it to do the adjustments. I'm likely to cut up the wood with a diamond saw.

trying to decide which direction to cut the knobs from. paging Dr. Wood... http://gilmore.chem.northwestern.edu/lv1.jpg http://gilmore.chem.northwestern.edu/lv2.jpg http://gilmore.chem.northwestern.edu/lv3.jpg http://gilmore.chem.northwestern.edu/lv4.jpg

I got the michelins at discount tire. I needed to deal with the problem immediately. tire rack is useless. the tires won't fit in the trunk (what trunk) and they won't deliver to anywhere convenient. I'm now good for another 40k miles. By then i will have a C7. (or else) Jaguars are beautiful cars. I owned one. I will never EVER own another one. At least it never left me stranded. But the every single month service repairs were really abnoxious. Got to love the impossible to adjust dual throttle linkage on the V12.

2007 corvette. My daily driver. Including the winter. Which is why i need all season run flats.

Inu has a listenable unit. YEAH. I'll let him describe the sound. In less than 2 weeks he will have the knob and custom piece... Then he will be the first with a finished FINISHED T2 Better than my version of "i've died and gone to heaven" Birgir, stop being a slaggard and get yours done... Just got a raw piece of OUTSTANDING wood from craig in GB... Lets see what kind of knob(s) i can turn this into...

yep, that is what i'm looking for. the other ones make noises as they turn.

So the transformer is going to be 4 inches in diameter. Which means that the inside of the box is going to have to be 13 x 13 inches for a single chassis thing. Heatsinks both sides.

here are some pictures, don't read too much into them. high impedance is 300 ohms, low impedance is 32 ohms, you can figure out which is which. This is before changing the CCS currents http://gilmore.chem.northwestern.edu/dsav1.jpg http://gilmore.chem.northwestern.edu/dsav2.jpg http://gilmore.chem.northwestern.edu/dsav3.jpg http://gilmore.chem.northwestern.edu/dsav4.jpg http://gilmore.chem.northwestern.edu/dsav5.jpg http://gilmore.chem.northwestern.edu/dsav6.jpg http://gilmore.chem.northwestern.edu/dsav7.jpg http://gilmore.chem.northwestern.edu/dsav8.jpg http://gilmore.chem.northwestern.edu/dsav9.jpg http://gilmore.chem.northwestern.edu/dsav10.jpg http://gilmore.chem.northwestern.edu/dsav11.jpg http://gilmore.chem.northwestern.edu/dsav12.jpg more pictures friday or saturday after i change the ccs resistors. thd measurements from above, well over 1%, IM approaching 2%

I think you actually need to measure that resistor. I know what it looks like, but i've been told that it supposed to be brown black violet which would be 100 meg, resulting in a lowering of the bias by about 9%. There is no way you can safely do 300 volt bias when you have the amplifier doing +/- 600 volts. That or someone did the modification wrong. With koss, you can never be sure. Clearly koss has some manufacturing issues.

OK, absolutely positively i should never rely on anyone who thinks they know what they are talking about. The bias on the koss headphones is absolutely close to 600 volts. Here is the proof http://gilmore.chem.northwestern.edu/kesp1.jpg So the tan resistor has absolutely no markings. The 10 meg resistor is in series with the +630 volt power supply (plus or minus a bit, on batteries, about +600) The unknown resistor is to ground in parallel with the cap. You just can't measure that resistor with it in circuit, which is the failings of everyone else. http://gilmore.chem.northwestern.edu/kesp2.jpg and this meter measures to 200 meg. http://gilmore.chem.northwestern.edu/kesp3.jpg Now usually when i see resistors like this, they are 1 gigohm. But even if that resistor is as little as 250 meg ohms, the bias is still (referenced to 600v) a minimum of 575 volts. I could bring the thing to work where i have meters that measure into the gigohms, but there is no reason. THE KOSS ESP950's ARE HIGH BIAS HEADPHONES!