November 10, 201114 yr Author If the west coast (usa) stax mafia can do it, you can too. Only 3 projects are planned for 2012. (well maybe 4) Edited November 10, 201114 yr by kevin gilmore
November 10, 201114 yr 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.. That's good to hear. Just for fun I powered up my amp this morning (was cold in our place), and the offset V (O+/gnd) started off around -40V. The balance offset was only around -10V initially. These numbers came way down as the big sinks started to warm up (took a good 5-10 min I'd say). The initial offset really seems to be dictated by the temp of the big sinks at startup.
November 10, 201114 yr I just got a KGSS (not the HV variant) up and running recently. It is based on my own PCB layouts for the amps and the PSU. The first amp board I assembled I fitted with the current sources based on the IXTP01H100D. The temperature drift seemed to be fairly large, so for the second board I went back to the original KGSS configuration using resistors. I expected this to have much less temperature drift and that also seems to be the case. So at the moment I am running both boards with the resistors instead of the current sources for the third stage. Looking at the data sheet for the IXTP01H100D I guess quite a lot of temperature drift is to be expected, since the drain current, for a given VGS, changes a lot from 25 degrees to 100 degrees. I would expect a current source based on the 2SA1968 to be less temperature dependent. Unfortunately I don’t have any 2SA1968, so I am not able to test that at the moment. Has anyone here compared the two solutions and have an opinion on this? My amp PCB is actually prepared for mounting either resistors or a current source, based on the 2SA1968 (which I don’t have!), but not the current source based on the IXTP01H100D (which I have!), so I had to mount it in a less than optimum way. I used 1.2k resistors for the IXYS current sources.
November 10, 201114 yr Author 500 volts at 2ma is 1 watt, and on my board with the on board heatsinks, there is enough heatsink to limit the heat on the part, and therefore the drift. The off board versions should have even more heatsinking. The 10m90s has less voltage swing, but is more stable with respect to temperature.
November 19, 201114 yr Author Great job. Now time to do up some proper wiring assemblys with the wax coated cotton. Khozmo pot, i sure wish i could get one of those where all the positions actually work.
November 19, 201114 yr Looks great! Really looking forward to powering mine up, if only my PEEK screws would show up... Khozmo pot, i sure wish i could get one of those where all the positions actually work. I got a khozmo as well and I checked every position on all four channels with my DMM and they all looked good.
November 19, 201114 yr Thanks guys. I just got the amp running last night, so I've only been able to listen to it for a few hours. I don't know if its just me being biased because I built this thing, but this amp sure kicks the crap out of my little SRM-1 mk2. The bass on my O2's seem to have better control and extension, and I think I'm hearing more detail too. Needless to say, I'm very very happy so far.
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