The Apple diyMod: My Take on the Famous iMod [56k killer] Featuring 3G, 4G, 5G and nano 1G! - Page 122

As you mentioned, almost any cap will work, but different kinds of ratings for those capacitors will affect the sound differently. The diyMod output coupling capacitor and the input impedance, sometimes input resistance, of your amplifier form a high pass filter, which means that high frequency signals, eg. cymbals crashing, pass through without being disturbed, but lower frequency signals are muted, where the cutoff begins and the how much it attenuates the signal depends on the characteristics of the filter. If you have a deep desire to learn more about filters, Google it or check out pages like All About Circuits : Free Electric Circuits Textbooks. I'll try to keep it to the basics.

The -3dB frequency can be found using the equation that you've likely seen before, f=1/(2*pi*R*C). This frequency is the lowest audible frequency allowed by the filter, so it would behoove you to make it lower than 20Hz, the lowest audible frequency for most humans. R and C are the variables in the equation, where, for our purposes, R is the input impedance of your amplifier and C is the capacitance of the diyMod's output capacitor. Basically, the higher R and C are, the more bass information you will get. This fact explains why with the 47uF Black Gate capacitor, assuming you're using the same amplifier, you will get more bass than with the 22uF capacitor.

To find your amp's input impedance, there are several ways of going about it. First, you can measure it with meters and resistors, but what you can also do is search for it on the internet. What kind of amp are you using? If it's a commercial product, that information is usually listed online. What amp are you using?

What you also have to consider is the quality of the capacitor. You're usually looking for ESR, or equivalent resistance, and you want this number to be low. This is because capacitors pass AC current, and the low the resistance, the easier the signal passes through. This also entails considering the type of dielectric used in the capacitor, be it film, polypropylene, ceramic, tantalum. Typically the film types are better for sound, but they don't have a lot of capacitance for their size compared to electrolytics. Electrolytics are supposed to be much slower in sound than the films, but they have lots of capacitance and lower your filter's -3db frequency.

What you need to decide on is a capacitor line and a capacitance value, not necessarily in that order. Some choose the Black Gates and pick the capacitance and some pick the amount of capacitance and see which brand and series has the best sound. The voltage rating doesn't matter so much.

Best of luck.

To find the input impedance, hook up a signal generator and potentiometer in series with the amplifier input. Short circuit the potentiometer, measure the voltage of the input signal, then turn up the resistance of the potentiometer until the voltage after the pot is half the voltage of the input signal. If you don't have a signal generator, you can just get a relatively large capacitor and assume the input impedance is 10k. That way you can safely assume the filter corner frequency won't be a problem, even if the input impedance ends up being 10k. 47uF will be more than sufficient for almost all intents and purposes.

The iQube input impedance is 10k. I can't access the Little Dot website at work (shows up as a malicious website), and the iBasso D10 doesn't have any info on its website.

That's quite an impressive stack you've got, EFN. I have a similar one in my workshop, but they're all broken.

EFN:

Most of those logic boards either don't have line out pads anymore or don't turn on anymore. The closest thing I have to a frankenPod is a 4G click wheel half-converted to a 4G photo. I never completed it because there were so many little things I had to buy that I didn't feel like continuing. You can call it lazy, but I just didn't have the money at the time. And now, well, I just don't have the desire.

dazzer:

You are correct, sir. That's pretty much the de facto way of doing the diyMod 5G. I believe that's what the iMod does as well, but I'never having seen the inside of an iMod, I'm only speculating. One warning I'll give you is to leave in those little capacitors and the dock inductors and solder to those things instead of to just those pads. As I mentioned to EFN, I have many a logic board unable to produce sound anymore because I lifted the audio pads. Leave the L's and C's in and you'll protect your diyMod without even the need for glue or epoxy. There's no need to go through the process of procuring a new logic board. It causes too much pain to the heart.

The "either / or" situation between the headphone jack and dock is merely illusory in that the iMod 4G was set up this way. That's one way of doing it, but you can choose whatever way you want with the diyMod. You know, I'm going to insert that into my signature since I'm repeating it so much. I hope people get the point. Nothing against you, dazzer, but I just get that question a lot. =T

Ya, no worries, man. Sorry, that's what I meant, solder straight from the Z caps to L2 and L3. I've soldered straight to the DAC pins before. It's not the best, it's not the worst thing. Depending on your experience, it can be pretty hard. I had some 7 strand teflon SPC, and I got rid of the other 5 strands and soldered the other two strands to the pins. It's not fun, so use this method only if need be.

Have you checked out the first post? A lot of this information is there (and more, actually).

I haven't encountered that much of a difference between the two. I think the 4G is a bit more bass-heavy with the 5.5G being more detailed, but it's been so long since I've compared the two that it's hard to say anymore. I don't ever remember it being that bad though. How long have you been listening to your 5.5G?