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aaa

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About aaa

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  • Headphones
    HD-650
  1. for unbalance connection, the only think that you can do to eliminate RFI is to shield the cable. I think the Head-fi guide or somewhere have explained that why you should short the shield to the groud at one end of the cable, whether it's at the source or at the receiving side is really not that important. so just follow loh. As the others have said RFI is not really a problem in most cases unless you have some non FCC compliant cheapo stuff around (like cheap toys with motor). And when RFI does become a problem, so golden rule is to go balanced.
  2. aaa

    Does Koba sell most of the PPA parts?

    FYI Koba currently have some stock of ALPS 27K series 50K stereo Log type potentialmeter. Just perfect for PPA, PiMETA or most other amps. The price I get was $15 each.
  3. aaa

    Emu 0404 modding

    ablaze, Never know that property of BG. IMO, if you are at the stage of cosidering to buy 1000uF caps, and not knowing it's effect, then your question will be valid. But now you have already got the caps and have them soldered on, maybe it should be time you doing some test (of soldering and desoldering) and let other potential modders know the result. BTW you just need to unsolder one of the two legs for each cap, then you can solder a 10-100uF cap on the top side of the PCB.
  4. aaa

    Emu 0404 modding

    When did your get these BGs and how much they cost? Since your used such good parts for mod, I will suggest adding some 0.1uF MKP or MKS bypass caps. They should be much better than the tiny X7R caps EMU used.
  5. sh*t! should have asked around earlier.
  6. huangyong, I'll show it when I take my card out for phase 2 mod, which may take a while. The pad surrounding each TTH hole is very small, and the surrounding plastic melt to form a sticky layer that stay sticky even after cooling down. So it's not really modding friendly. av98m, you are right, the F size (D=10mm H=11.5mm) OS-CON cost $2.50 each. And the killing part is that the stock is extremly in complete, I have been force to use 680uF for places that I'm looking for 100uF.
  7. aaa

    Emu 0404 modding

    The two left most yellow cap should be for bypassing of the voltage supply rails for the op-amp. So you should need 12V cap at minimum. You said that you have replace them with 1000uF caps, and from the photo you are using 8mm dia OS-cons. I don't 1000uF OS-Con for 16V or higher exist, so something must be wrong here. I'm not sure how 0404 regulate it's +-12V supply for op-amp, I will take it as there is a 4.7 ohm resistor before the yellow 10uF caps to filter noise. In that case 10uf should be quite fine. (PPA schematic used only film caps after the resistor) Personally I think 10uF is fine, and more than 100uf is pointless, but there's nothing with using 1000uF either. I don't see that there will be any major problem with changeing it to 1000uF. But there's one potential danger in doing so. that is if I'm right that the caps are for bypassing +-12V supply for op-amp, there's 4.7 ohm resistors before them, and that there's no muting circuit when you turn on the power (as I have seen in 0202 with the huge 1000uF cap). for 1000uF cap takes 100 times longer to be charged to a certain voltage compared to 10uF caps. And because the existence of the 4R7 resistors before it, the current supply to it is limited. So for that few ms that the caps are charging up, the output op-amp will be getting voltage supply that's below its rating. And when this happen the op-amp will not be stable. (this is the main reason that you hear a pop when you turn on some instruments) The worst case will be it outputing huge DC offset (that could be up to rail voltage, who knows?) In the worst case you connect the 0404 to a headphone amp with gain 11, and then to a earphone of Z=16ohm. If you take the DC offset as 1V, the amp make it 11V, and since power=V^2/R, your tiny 16ohm imp earphone will be heated at a power of 7.56Watt, i.e. 7.56mJ per ms, which will burn burn it in just a few ms even if the diaphragm don't break with the loud pop. For 1000uF to be charge to 12V with a 4R7 resistor, it takes 9.4ms (if my maths serve me right), and in that period of time each of the 4R7 resistor will converted 0.144J to heat (the initial peak power is 30.6W!!!), which I'm not sure is safe. Luckily most op-amps are operational from +-5V onward. the popular AD8620 works well down to +-3V (personal experiance), and for it to output DC it may takes much lower voltages. For 5V the time will be 2.5ms, for 3V it will be 1.33ms. So in practice it's quite safe as long as you don't have a killer combi of a low Z phone with a high gain amp that's on when you switch on your computer. well, things will be much easier if you just use 100uF or less... Also can let me know where you get all your OS-CON from?
  8. aaa

    how is E-MU0404

    don't know about 0404, but my 1212M to PPA to HD650 system sound like dead fish (flat, liveless and no energy). The system when using Nomad Jukebox3 's lineout as source was so much better, they are just uncomparable. And I'm not the only one that think this way, my mother shared the same opinion withou any hint.
  9. picture after mod. I screwed up one position, thus the funny flying wire.
  10. parts for mod cost S$33, all for KOBA
  11. Yes the squarish JRC 2068 is the dual opamp. Two are used for DAC and 5 are used for ADC. Each chip serves one channel, one opamp each for the +ve and -ve signal (0202 has balanced output) all technical discussions that has nothing to do with the local context (like where to get modding parts here) pls post at http://www4.head-fi.org/forums/showthread....86&page=1&pp=20
  12. 0202 analog card DAC section, most mods will be here
  13. 1010 digital card part 2
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