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joehpj

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Everything posted by joehpj

  1. I am not really sure because I haven't try it. :/ Those who tried it reports its a stable and well embedded solution. Also supports DSD.
  2. Chinese made surgical microscope are cheaper ($25K) and quality are average. Surgical loupes are better for this job I believe. Zeiss and Pentax make nice loupes at reasonable prices. ($2K)
  3. I was going to build a balanced isolation transformer. But I had difficult to choose form either EI or toroid. Regardless of price and size, which theoretically will be better (in performance)? I was planning to build around 2KVA. Does anyone have experience?
  4. please, don't waste your time. Feng always concluded in local forums that Chinese should support Chinese made products. He think a gang of American born Chinese hate him and posts on the other place are intentionally to attack him and his brand. And because other products like HE1 are super expansive and SRL is even better so the price tag is soooo reasonable.
  5. I assume you are referring lsk389? And matched p-channel means 2sj74 pair would work if I could find some real ones?
  6. This only shows how irresponsible they are for their products. Flagship every year?
  7. And you'll get two super hot BJT. 18v is way too high.
  8. The price has a simple reason. Fang once said he thought SRL is the best HP system in the world. So he wanted to sell no less than HE1.
  9. It's single ended input. Should be more like the all-triode design.
  10. It's said the SGL amp has single ended input. The XLR jack was internally connected single ended.
  11. link plz. I can read Chinese.
  12. L700 has bright sound character like 009. Nice HP when paired with stax amps. But with KG amps......
  13. PCM1704 was a 24bit dac. But the ENOB was less than AD5791. Why is that different?
  14. Although DF1704 TI paired with PCM1704 has been outdated and surpassed by FPGA based digital filter, PCM1704 is still a very good chip even after over 10 years of production. Sad to be obsoleted. As I know, TI stopped all audio R2R chip production. So we have to look into discrete design or use AD chip sth like Schiit used. Even for AD5791, it is only 20bit so when playing 24bit data, some calculation must have to be done.
  15. Pcm1704 has been NRND for several years. And recently got removed from the website. Audio gd still got some to make new dacs. But I think this is the last batch they could make. Resistors and solder joints exposed in air will be influenced by humidity, oxidation. Some will drift slightly over years. I don't know if every resistors will. Single chip w/ laser trimming would be better solution in terms of stability. IMO. Discrete however provides better flexibility of design. And the overall performance is not only limited by dac module/chip itself.
  16. IMO, if people are asking for precise resistors, and they should go to single chip like 1704 or what schiit uses. All resistors are laser trimmed and packed together to avoid different voltage drift. Discrete design can never reach the level of precision of single chip.
  17. it will lower the average error. Not in extreme cases just like you said.
  18. This module use .5% resistors in parallel to get .25%. So it's not too far from .2% Soekris used. Edit: .1% in parallel to get .05%. Wrong information. My bad. KG said Soekris module used wrong switch and caused some problem. The overall design was flawed. Can't find the comment now. I don't know if this is better. Also, the original OP based buffer of Soekris sounds like shit. A separated buffer was needed.
  19. http://www.audio-gd.com/Pro/diy/DA01/DA01EN.htm a-gd has released their R2R module. NO digital filter included so it seems future promising when better filter is available. Kingwa said if there were enough people want this, he would also do the digital filter module, separate DSD DAC, and also PS for the whole thing. Please notice the last few lines:"The module had the DC offset , customer want to use the couple cap, or the DAC analog filter output had the couple caps or DC serve design. For the balance DAC design, the proper design can remove the DC offset in the analog filter amp output , without couple caps or DC serve design ". KG's unbaltobal seems to be a good chioce for the buffer or with SuSy dynalo to make a wonderful DAC/amp
  20. green ones are prototype. red ones are final product. Just go for the red ones.
  21. The picture is Denafrips DAC-1 PRO link here: https://item.taobao.com/item.htm?spm=a1z10.1-c.w4004-8327544200.2.yvBVss&id=520399273447 I read from a Chinese forum Hibiki sounds like TDA1541 while comparing to DAM1021 sounds like PCM1704. The Hibiki seemed to have some resolution problem.Of course this doesn't really make much sense because DA chip itself often doesn't have strong sound character. Maybe it's implying if the circuit was fine in the design, then maybe digital filter was not that good.
  22. Bias current seems to have positive correlation with temperature. That means this amp may blow itself without adequate heat sink? Also, the performance will be different in winter or summer. Please describe the sound. Anyway, nice job. It's time for some fancy casework.
  23. 5V seems acceptable. I was thinking if someone was bad luck enough to have a bunch of sands far away from average hfe will be a pain to set the mid point. Is it possible to put a svr somewhere to do the trimming job?
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