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

[RCM]

Originally Posted by CAvanessia

How does this setup differentiate between the caps or is it just some electrical thing we don't have to worry about?

My thoughts exactly-can some of the signal escape the teflon cap and make it through the bigger cap without passing through the teflon cap? Would it not be better to put them in series with the teflon v-cap hooked up between the larger cap and the amp as a sort of staggered filtering system?

Hey-I'm admittedly electrically challenged!

I've got a set of 6.8uf V-caps on the way and was looking to add some teflons to the mix as well...

[joneeboi]

At this point, you start getting deeper into the tweaking bit, balancing between the treble and bass with the quality of brands and combination of cap sizes. Since you're going the route of external casing for the caps, you don't have to worry about real estate. If you do decide to go that route, let us know how it goes.

[joneeboi]

The bigger cap manages the lower frequencies and the smaller ones take care of the higher frequencies.

[Jambo]

Having several caps in parallel for AC coupling is a new one on me. I would have thought that you would introduce more non-linearities than you would remove...

[joneeboi]

What kind of nonlinearities were you referring to, Jambo? It seems to me that it's more of a stability issue than sound. Surely, the sound will be affected and some will describe the sound to have such and such quality, but I mean that the sound would follow the improved technical, specification side of the electronics. I'd imagine it being much like the Driver Number Wars we seem to have between the IEM manufacturers of late. Shure came out with another triple driver, UE released the triple.fi and Westone projected their 3. All the while Etymotic hasn't changed their stance from a single driver philosophy (how long has it been, 15 years?), maintaining that the crossovers in the multi-driver IEMS take away from the sound. Following the analogy, some would say the more paralleled caps, the better; the link up there has a picture of three bypass caps.



It inevitably comes down to your personal design philosophy; do you prefer to delegate work or do you prefer a single task-accomplisher accomplishing tasks? As I mentioned earlier, one argument against paralleling so many caps is the issue of limited space. Since not too much is taking up the ALO VCap dock, vvs_75's Sonicap dock or CAvanessia's BG NX dock, you could experiment with as many bypass caps as you like. I don't think more than two would be necessary as we're only working with a 20Hz-20,000Hz bandwidth, but again, it comes down to personal choice.

I hope I didn't spew too much garbage for those of you actually in the know. =T

[Jambo]

It's an interesting one, I've honestly never come across it before in coupling caps. As you point out though it is common practice in decoupling caps as in your picture.

The non linearities I was referring to.. Well, say for your load 4.7uF gives you your desired frequency response, if an ideal capacitor is assumed then that is all you need.

However, in your decoupling example, smaller caps are paralleled up with the bigger caps as they tend to have lower ESR and ESL and will perform better at higher frequencies. In other words, you're compensating for parasitics. What you're trying to do is compensate for the non linearities of one cap by adding another one. The range of frequencies you want to cope with in decoupling is in theory infinite, and how linearly you do this isn't all that crucial. Unless loading an LDO or something else that can go unstable, pretty much every cap you can add is a bonus.

To apply this to AC coupling, I would say that in order to make that work you would want a very accurate model of the caps that you are using that you could simulate and see what happens. My point is that if you weren't careful about it, you could easily introduce more non-linearity than you already had by adding two different capacitances, ESLs and ESRs, and that this is a problem this time since it is in the signal path.

By all means though, experiment and see what you can hear, and if anyone can experiment with this on an audio analyser I'd be interested in seeing the results. I just know for a fact that this is not common practice and I figure there must be a reason for it.

As you point out, the audio bandwidth is not very big so I really doubt whether any difference would be audible so long as your main cap was of decent quality.

[KoKoKrunch]

Hey thanks for the diagram jonee, I kinda figured out something like that after reading up more, but still needed to confirm!

[powertoold]

Adding a cap probably does produce more non-linearities, but those aberrations could have a smaller standard deviation.

[Jambo]

Something I also meant to mention is that some small caps (eg ceramics with certain dielectrics) have a capacitance that varies with voltage, you really don't want to put them near the signal path.

[Johannes Freed]

Anyone done the 2G Nano yet?