joneeboi
Headphoneus Supremus
- Joined
- Jul 7, 2006
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Can you a post a picture of your solder joints?
i_djoel2000
Sorry mate, missed your post.
Well it sounds like processing noises, that's what I meant by the OS, but the fact that it only occurs on Rockbox makes we wonder even more
Show us exactly where the wires run buddy
The voltage rating of the capacitor shows the nominal maximum value of DC voltage it can handle. Since we're working with a max 1.5V, you should get something with a rating a bit higher than that. 6.3V is the normal expected rating for this application.
The capacitance you need for the diyMod refers to the high pass filter that forms when you connect your diyMod to your amplifier. When you connect a series capacitor to a parallel resistor to ground (in the amplifier, this resistor is the volume potentiometer), it forms a first order high pass filter, which allows passes mostly high frequencies while attenuating low frequencies from the signal. DC power is, all in all, 0 Hz, a low frequency. Capacitance is the amount of charge that the capacitor can hold, and in our use, you only need a small amount of capacitance in the diyMod. The equation governing the size of capacitor in a high pass filter characteristic is
C = 2*pi/(f*R)
where C is the capacitance in uF
f is the frequency in Hz
and R is the input impedance of the amplifier.
Basically, we want to filer out the DC while passing as much of the audio signal as necessary. Since humans can typically only hear between 20Hz and 20kHz, the highest frequency you want to pass through is 20Hz, which we'll plug into the equation. R is the input resistance of your amplifier, typically 10kOhms up to 50kOhms or 100kOhms. That means that for an amp with 10K input resistance, you need at least 31uF, and for an amp with 100K input resistance, you can get away with around 3.1uF. What amp are you planning on using with your diyMod? Normally, the commercial amps list the input resistance on their tech spec sheets. If it's DIY, it's normally the resistance of the potentiometer.
what do you think the problem is?
Originally Posted by AT0MAC /img/forum/go_quote.gif
If I cant find any 47uf 6.3v Black Gate capacitors, what else can you recommend that are easier to find?
joneeboi said:
Please don't desolder C84/C86/L2/L3. Please.
Besides, if you're talking about those components, then you're not doing the iPod photo. That's the iPod click wheel. Please look here for further guidance.
It seems you lack the understanding of the basic premise of the iMod/diyMod. You replace the series capacitors of the line level output of the Wolfson CODEC found in the more popular iPods. These types of DACs put DC on the electrical output signal, so you need to block the DC from getting to your headphones or speakers. If more than 20mV reaches your dynamic loudspeakers for enough time, they will be destroyed. One way of blocking that DC is by putting a capacitor in series with the signal, or putting it through a high pass filter. The high frequencies are passed through, but the low frequencies (DC is basically a 0 Hz signal) are attenuated. We want a high pass filter that only attenuates subsonic signals (so one can hear all the music), so we set a corner frequency, aka -3dB frequency, to somewhere below 20 Hz.
The iMod/diyMod converts that high pass filter into a higher quality, audiophile-grade filter by replacing the stock capacitors with higher quality ones. Since the signal passes through the capacitor entirely, it can't degrade the signal by much. The iMod turns your headphone jack into a line out, but that's undesirable because you can no longer use your headphone. People have put up with this before, but I think it's silly. The diyMod shows you how to make whatever set up you want, including replicating the iMod. Preferably, you'd convert your dock line out to a diyModded signal, with or without the capacitors already in series. You can put the capacitors into the iPod, such as in the 4G click wheel and 4G photo, or you can put them in a capped line out dock. Since you have the room, you can put the capacitors inside the diyMod. You can make the line out dock the diyModded source, or you can do what the iMod does and convert your headphone jack into the aforementioned source. Your described scenario converts the line out dock into the diyMod signal.