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dingding123

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  1. I think some of the resistors are spec'ed at 2W as per the 21st Century Maida design. Would it be ok if you replace them with SMD parts?
  2. Interesting. What's the function of the Flat jumper?
  3. Another Dynahi lives. Sigh... Heatsinks are never enough.
  4. I always wonder what makes the CFA2 sound so good and makes me choose it over the dynahi every time. Does the magic lie in the current feedback topology or the triple darlington output stage? just an idea - what happens if we parallel two or more sets of the triple darlington output for each CFA2 board? Would it be the more the merrier?
  5. That's about 2.2% lower than the 580V Stax pro bias. The slightly lower bias is unlikely cause harm to the earspeakers. In terms of sound, lower bias voltage would mean that the earspeakers are less sensitive. However at 2.2% lower, I'm not sure how much of a difference you may experience. My experience is that the bias does increase a little after warming up. I assume that your measurement was done at start-up. Perhaps you might wanna measure the bias again say, 30 minutes after turning on.
  6. Thanks @Blueman2 I would definitely consider making a chassis with heatsink sides for future projects, but for now, I have yet to source for an appropriate L-shaped aluminium thermocoupler. The transparent case is meant for prototyping only heh. It's cut to order by a seller in China. Just send them a CAD drawing and they will CNC it for you. I plan to transfer everything into a black chassis after I get a bigger heatsink. Currently it's running at a modest 14mA at 68 deg C.
  7. Another KGSSHV Carbon lives! Thanks to @sorenb @Kerry @simmconn for the help on bias voltage. I used 2 x 120v 0.5W and 2 x 130v 3W in the end. The 0.5w parts work well. Next steps: cable management, re-case, increase heatsink size.
  8. Just curious,has anyone tried using dynahi to drive a srd 7?
  9. Dang it haha! Thanks for pointing it out. I'm planning to swap the zeners to some 0.5W ones, which are the only ones available at my local store. My logic is that 0.5w rating would suffice since the targeted voltage drop (around 100v) multiplied by the current (max 1.3mA -ish) would be around 0.13W. Is my calculations sound? Or did I make a grave mistake here?
  10. Thanks simmconn for the help! With regards to the CCS: The unregulated voltage into the CCS is 601v measured at the anode. Thevoltage drop at the 3k resistor is 3.37v. Not exactly 1.3mA but somewhat close. So I think the CCS is working as designed. With regards to the zener string: The zeners I used are the 3ez series with 5% tolerance. Datasheet here, but they didn't publish the Iz to Vz charts https://www.digchip.com/datasheets/download_datasheet.php?id=60504&part-number=3EZ33D5 Currently the zener inplace are as follows (from left to right, ie, from CCS to
  11. ahhhh I see. One question though. Shouldn't the zener spit out a lower voltage (rather than higher, which is my case) when the current is lower? Anyway, I will replace the zeners with 1.5W ones. Also, it seems tempting to change the 3k resistor to say, 1.6k for 2mA, instead of replacing the zeners. Is there any reason I should't try that?
  12. Hi sorenb, yeah, the zener string is seeing the ground and the 3k resistor is alright, and sees source and gate. Hi Kerry, thanks for the help! The zeners are 3W 5%. What do you mean by that they may have a higher test point? Could it be that the labeled voltage is just a nominal one at a certain factory specified current, and at 1.3mA supplied by the CCS, the zeners would give a higher voltage?
  13. Hi sorenb, thanks for the suggestion. I dont think the CCS was faulty, but I replaced the 10m90s with a new one from Mouser anyway. No change in bias voltage The main GRHV voltages are normal: +396V and -406V. Does the 806k and15k resistors have anything to do with setting the bias voltage?
  14. Hi, I have a question regarding earspeaker bias voltage on kgsshvpssicfetdual2new.zip gerber (pic attached). I understand that the bias voltage circuit is essentially a CCS into a zener string. I am trying to get to say , 500V, for my custom-made ear-speakers. Do I simply change the zener string to a combination that adds up to 500V? Or do I need to change anything else? I tried 3 x 130v + 110v, and even 3 x 110v + 130v. The bias voltage (measured from test point to ground) hovers around 540v. Am I missing out something here? By the way, I am hoping not to use the 580V + t
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