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  • Interests
    IC Design, Servo motors, control systems
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  • Headphones
    HD 600, SR-009
  • Headphone Amps
  • Other Audio Gear
    Etymotic ER4S

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kh90123's Achievements

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  1. I have some GRLV to let go, PM me and Sorenb to inform.
  2. I missed the group buy to get the amp boards for the KGSSHV Carbon, does anyone has any spare amp boards available?
  3. I missed the GB for the KGSSHV carbon boards, does anyone has spare amp boards to spare?
  4. Actually I had one problem. I heard distortion coming out of it, then I bypass the volume pot and the distortion went away. Seems like I might have a lemon volume pot. I will be getting a DAC with pre-amp out soon, and in the future I will go pot-less build, can keep cost lower by not needing any volume pot. Perhaps it has got to do with how I wired up the pot. I am currently using SE input instead of balanced in. The pot I have was sold to me by someone, and from the way the resistance sweeps it really doesn't look like a log pot, it's a linear pot... The 009 is rather revealing...it occurs to me that so many recordings has rather audible background hiss. And it also occurs to me that musicians also makes quite a bit of mistakes in recordings.
  5. I waited 4 years for this. Completed the HV last year but waited another year before getting the can. Heartfelt thanks to Kevin Gilmore, Spritzer (Birgir), Lil Knight, Victor Chew, Kerry, RiStaR, and the rest of Stax mafias. Thanks to KG for his design and guidance, Spritzer for helping me behind, Lil Knight for providing me the boards a long time ago, Kerry, RiStaR for their answers to my questions, and finally to local DIYers Mr. Victor Chew, thank you for teaching me, what you have taught me not only benefited me in making the amp, but also helped me in my job. Next I will try to build the HV Carbon. I have had caps and ICs exploding on me before when building the HV. But this time, I plugged the 009 into the HV, and it exploded.... Into some amazing music.
  6. Could anyone recommend a source for TDK 4CP-601 quad pot? Or Alpha quad pots? Or any other good quad pots recommendation? I only know that Justin carries the RK50, the last time I asked him.
  7. It's done. No music to be listened yet. Getting the SR-009 in 25 days, counting down. My biggest mistake in audio was to sell the SR-007 Mk1 that I had some time ago. I think I also used to have a SRM-T1 modded by Birgir. Unfortunately, there is like 2 unused switches at the back of the chassis to cover up some holes, and also 2 unused input jacks that were supposed to be RCA inputs. I chose to use XLR to RCA adapter instead. The big white switch at the back is also a 5A circuit breaker. 3 fuses for 100V, 115V and 230V mains voltage. Cable management still needs improvement. The Toroidy transformer is although pretty, too huge. Next time I won't get the stainless steel casing. No more explosion, no more arky sparky, bias is stable before the ballast resistor, at a voltage of 588V, offset and balance are all within 0.5V. I let it run for hours, then adjust offset and balance, then I put in the servo. Heartfelt thanks to Kevin, Victor, Birgir, Calvin, Kerry, and all those who aren't here but have helped me along the way. Kevin for his wisdom, Victor for his know-how, and Birgir for his support. It's has not been easy but lately things have gone very smooth after I learned a lot of skills and tricks from Victor. He helped me rebuild the PSU board, and along with that I learnt many things accumulated from his years of experience doing DIY. For eg, I learned to use screws with spring washers on heatsinks, then later I changed from zinc plated screws to stainless steel screws, along with ribbed washers. Zinc plated screws will stain and rust in a few years in this hot and humid tropical weather. This build was at first to be all IXYS 01N100D parts, then it went to having Toshiba 2sc4686a and IXYS CCS. Then after some mistakes and the traces were damaged on the amp board, it went from IXYS CCS to the Sanyo 2sa1968. At first I have like a few 1968. Now I have quite a few dozens lying around to build some stuff, after I got them for cheap from local sources. The end of one build will be the start of another. It's been fun, building my first amp, and my first DIY project. Out of nowhere, I suddenly found myself having quite some tubes, so maybe I will build a Megatron.
  8. No, I didn't mean for the misunderstanding. For the -ve rail I know it's set by the voltage divider between R16, R15, and R30. Since I started replacing parts on the board, the through hole contacts have been damaged, especially on those snap in caps. My current board was working fine until I started putting it into the chassis, where a few parts were damaged because the filtering caps lost proper contact. I will be building a new board. The current board is not safe to continue working on it. Thanks for all the advice.
  9. I replaced them and found that all of them were working. I suspect it's one of the 5 transistors, either the 2sa1486 or the ksc5026m. Getting help from someone to work on this.
  10. After I replaced the 10m90s, the -ve rail now drifts to -550V instead of staying at -500V. What else could be broken?
  11. I need some help. My power board was working fine but after putting it into the chassis, I heard a spark, and then now the -ve rail is -640V. I dare not let it on for more than a few seconds, but the value seems to go higher and higher. I checked the diodes, and they are not shorted. What could have gone bad? Edit: I measure the output from the diode bridge and it's 640V, so it seems something in between has broken and shorting it to output. Ok found out that the 10m90s is fried.
  12. It's coming...Just finished drilling some screw holes just now. Steel is much harder than I expected. Since I bought a RCA to XLR adapter, I am probably not gonna put in the RCA inputs. Amp boards are working, but I have yet adjusted the offsets without the servo on. From what I have done with the servo enabled, it seems that both L and R channel settle to a 0.3V offset. The amp supports 100V, 115V, and 230V mains voltage, which can be switched by the rotary switch at the back. There's also a series overload sensing circuit breaker at the back, which also acts like a switch. I prefer having green ring on the power switch. But for now I will settle with blue. Surprisingly these come with built in resistors. Maybe if I break it I will go buy the green one.
  13. Do you mean I should disable the servo when adjusting the offset?
  14. Are the high wattage resistors supposed to get pretty hot? I use an infrared thermometer and it's showing one of the 240kohm resistor at close to 80 Celcius. Also, the 2sa1486 and the KSC5026M gets pretty warm too, in the range of 60-70+ Celcius. My ambient is very high though, at about 30 Celcius. That's about 50C delta. And I haven't even connected the amp boards to the power board yet. I measure 2.5mV of AC noise on the -500V output, and 0mV of on the +500V output, is it supposed to have a bit of AC noise? The caps should filter them isn't it. After swapping a 150V zener to 130V, my bias now stabilizes at 577V, not bad at all. It was 598V, -20, should be about 578V.
  15. How do I match the IXTP01N100D? I am only using it as the current source. Do I need to like apply some 24V across the drain and source, put for eg a 1kohm resistor on drain, and 0V to gate, then measure the current?
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