kevin gilmore Posted November 9, 2011 Author Report Posted November 9, 2011 Actually 1350 ohms for those particular parts would be right on the money.
Horio Posted November 9, 2011 Report Posted November 9, 2011 (edited) Actually 1350 ohms for those particular parts would be right on the money. How important is it to nail the 2mA across the source resistors on the IXTP parts? Edited November 9, 2011 by Horio
blubliss Posted November 9, 2011 Report Posted November 9, 2011 We crossed the 50k resistors and one board is now working. Very close on balance, millivolts, and about 3v on the offset without much work. Now working on the other board which does have some fried parts due to the 1486 being in backwards before, looks like 2 of the 4686 were done in. We left in the 1.2k for now since we didn't have the 1350.
kevin gilmore Posted November 9, 2011 Author Report Posted November 9, 2011 The 2ma is the target number. Anything within 10% is more than enough. The 1.2k should be just fine. If you have lots of heatsinking you can increase the third stage current. Which increases the high end frequency response a bit. I have fixed this board layout and will upload files later.
blubliss Posted November 9, 2011 Report Posted November 9, 2011 Two working boards now! We replaced all the active parts on the 2nd board and there was still a problem. We finally found that the LED, D1, was bad. Later we'll hook up both boards and maybe have a listening test.
Horio Posted November 9, 2011 Report Posted November 9, 2011 Congrats sir! Thanks for doing the "hard work" for the rest of us. Looking forward to your impressions of the sound. Hopefully I'll have mine playing music this weekend.
kevin gilmore Posted November 9, 2011 Author Report Posted November 9, 2011 Remember that O+ and O- are now flipped, so wire accordingly to maintain absolute phase. new board layout has both items fixed.
cobra_kai Posted November 9, 2011 Report Posted November 9, 2011 This problem is not present on the on board heatsink version? I'm guessing not since joamat was able to get it up and running.
wink Posted November 9, 2011 Report Posted November 9, 2011 Is the problem present in the off board versions using the 2SA1968 sand instead of the IXYS devices?
blubliss Posted November 9, 2011 Report Posted November 9, 2011 Kevin figured it out, I was just the guinea pig
wink Posted November 10, 2011 Report Posted November 10, 2011 "Is the problem present in the off board versions using the 2SA1968 sand instead of the IXYS devices? " Obviously, YES..... should follow this thread more closely.
blubliss Posted November 10, 2011 Report Posted November 10, 2011 Listening to music with the 009 and it is quite nice. I know I probably shouldn't use these phones, but... Switched on the T2 for just a minute, swapped back and forth a few times just for giggles. A T2 it is not, but that makes sense. The sound is richer, thicker than the T2, less refinement I would say. Now this could be great for poor recordings and such. The T2 tone with the tubes I am using just seems more right. It's been on for about 45 mins. and the heat is very low, nice, that is a big plus over the T2 (unless you live in Iceland ). Is there any burn-in for this type of amp?
chinsettawong Posted November 10, 2011 Report Posted November 10, 2011 Congratulations, Andy! Wachara C.
cobra_kai Posted November 10, 2011 Report Posted November 10, 2011 Listening to music with the 009 and it is quite nice. I know I probably shouldn't use these phones, but... Switched on the T2 for just a minute, swapped back and forth a few times just for giggles. A T2 it is not, but that makes sense. The sound is richer, thicker than the T2, less refinement I would say. Now this could be great for poor recordings and such. The T2 tone with the tubes I am using just seems more right. It's been on for about 45 mins. and the heat is very low, nice, that is a big plus over the T2 (unless you live in Iceland ). Is there any burn-in for this type of amp? Congrats on the successful power up!
Horio Posted November 10, 2011 Report Posted November 10, 2011 (edited) Andy, how much does the balance/offset float around after initial power up? A few volts? How long does it take to stabilize? Edited November 10, 2011 by Horio
blubliss Posted November 10, 2011 Report Posted November 10, 2011 The voltages change a bit , maybe around 10 volts or so on the balance, possibly more on the offset during warm-up. Just adjust to zero at the start, then after an hour. I readjusted to 0 after an hour plus tonight, will check periodically the next few times I run, then leave it alone. I actually think I may be done adjusting already and everything seems to be under 1 volt.
Horio Posted November 10, 2011 Report Posted November 10, 2011 Yea, my offset seems to be starting off around 10V at initial power up, then it falls within a +/-1V range after about 5-10min. I don't recall what a safe offset "limit" is for stat phones, but I seem to remember 10V not being a big deal (unlike the dynamic world).
johnwmclean Posted November 10, 2011 Report Posted November 10, 2011 Glad to see 2 amps up and running. Congrats guys!
kevin gilmore Posted November 10, 2011 Author Report Posted November 10, 2011 The idea with everything including the very stable power supply is to set the thing once after about an hour of warmup, and likely never touch it again. 10 to 20 volts of offset for electrostatics is nothing. My T2 stays at -13 volts and its just too much work to open it up and adjust it. Has not drifted in 2 years. This amp is no T2. But it is pretty close, and about 15% of the parts cost. A hybrid T2 output stage with a solid state front end is next.
chinsettawong Posted November 10, 2011 Report Posted November 10, 2011 Wow! One project after another. There is no way that I can catch up. Wachara C.
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