[ferds]

Thanks for the great work joneeboi!! also thanks for including some pics of my diyMod in the OP

 

[gueri_fr]

Quote:

Originally Posted by pcyl /img/forum/go_quote.gif i confirm you still get audio out from the ipod female jack

Thanks!

Quote:

Originally Posted by joneeboi You'd have to route wires from the front to the back to the front, which might affect the ultimate fit of your iPod.

You're right. It could be very hard to do.

eric

 

[cfcubed]

Quote:

Originally Posted by joneeboi /img/forum/go_quote.gif That sounds interesting, Fallen. Perhaps I will give my Vitamin Qs a run with the diyMod. I'm pretty sure my BGs are already burned in, and I can't tell the difference from before. <snip>

BTW, my opinion was similar to this one & sort of mysterious given the reviews for the similar 4G iMods (yeah I used 22uf & others 47uf but should be no biggie). Does seem like larger fancy-pants caps may be where the fun is (if you are going as far as the DIYmod anyway).

I've some Sonicaps on the way to try w/my DIYmod someday (part of an order of caps for my Magnavox tube amp restore). Though the DC lineout bit still has me wary. I may consider subbing some sort of direct lineout connector on the top of my 3G (like an extra 1/8" stereo jack) for the cap/resistor packages there now & using that (disabling the dock connector lineout).

 

[joneeboi]

Perhaps we can set up some kind of database that catalogs the different sounds of the different boutique caps everyone's trying out. Once I get my co-op job, I may have to consider some sort of docking station that easily swaps out caps so I can find the best fit. V-Caps are tempting, starting at $46/cap, but I'll probably try out the cheaper options first. What do we have so far? Auricaps, Black Gates, Sonicaps, V-Caps, Obbligattos. I have some Solens and Vitamin Qs that I have to try, so we have quite a few flavours so far. Commence in-depth sound descriptions! We're treading on very thin ice at this point, so we ought to exercise utmost discretion in what we say.

That said, I'll start with my sound description. I'm pairing my 22uF BGed diyMod 4G with my PIMETA (AD8610/AD8620, 2N5087/2N5088 Sijosae discrete L/R buffers and BUF634 in GND, generic 1.0uF C4 box caps), and I'm loving the bass I'm getting. I'm sure most of it is coming from the PIMETA since I used to listen with the Millett MAX, and the bass is much more tangible crossing over to the PIMETA. There is also a bass rolloff near the bottom frequencies, but I think that's coming from the SR60s, as well. BGs are well burnt in, and I didn't notice the earthquake like others have. Then again, that's probably since I've been tweaking my system like mad lately. I haven't been impressed so far with the BGs, as it didn't do so great in the MAX. Granted, I didn't get the NX like tomb and pabbi and others did, but they're still BGs, and they didn't knock my socks off. The downside of the internal BG method is that I can't do a before/after comparison unless I go with ruZZ.il's method, which I didn't this go around. I really don't know what I'm hearing, except that I really enjoy my diyMod+PIMETA+SR60s setup. The difference went unnoticed with me, which is really the reason for which everyone is reading this comparison. I can't offer that kind of insight, so I can only say that I'm so addicted to the setup that I actually decided to turn it from my at-home-next-to-my-laptop rig to my at-school-next-to-my-laptop rig. I'm working on the external diyMod DAC/amp which I'm tentatively calling the Dogger DAC, and I've received permission from Tangent to implement the PIMETA design so long as I don't call it a PIMETA. I'm in love with the AD8610/AD8620 combo since I got the AD8620 from souperman. I tried the AD8610 with the OPA2107, JRC4556, OPA2134, none of which I enjoyed as much as the AD8620. I lost out on a chance to pick up some OPA627s, but it seems those don't measure as well as the AD8610/AD8620. Since BUF634s are out, I'll probably implement the same Sijosae discrete buffer design I'm currently using which will save money and time, but I can't imagine finishing before BUF634s come into production. Not to mention there's that bit about National's new buffer and other DIP8 drop-in buffer packages. This extended discourse is just a long-winded way of saying I'm in love with my diyMod+PIMETA+SR60 setup, and I'll be hard-pressed to release the ninja-tight, kung fu grip I have on said setup.

 

[ruZZ.il]

It'll be hard having different opinions by different people, but may prove as a 'general direction' kind of guide. talking about differences, I found the 8610/20 in my pimeta very detailed, just a little cold for me. I've got double stacked 634s L/R and a single on the G, so maybe the buffs kill some bass.. they're supposedly not that great compared to the discrete. I took 2 0.22 and implemented a variable bass boost in the op-amps feedback just like in the M^3 that adds some THUMP

much happier with my PIMETA since.. but to be honest, I find the mini^3 aqs satisfying and half the size.. <shrugs>
Your dacamp sounds like it'll be killer, the PIMETA is a great platform since its really so flexible (3 channel, class a optional, buffer optional, op-amp rolling friendly, good stuff). you found your dac chip yet? I need to check into that thread

I'm fidgeting with the alien lately.. pity it has no I2S in.
Any chance it'll be mosltly SMD, or is that being selfish?

 

[joneeboi]

I'm going to try to keep it all SMD, and if I find room leftover for through-hole parts, I can accomodate that too. I'll make some tweaks for personal use, though I imagine people may want in on it after I flesh it out a bit more. I've never done this kind of thing before, so everything really is still up in the air. I made some progress last night, but it'll be at least a couple months before I can really hammer anything out. My respect for circuit designers is growing every day

. I'm going with the Wolfson WM8740, the mighty chip in the (older) Opus DACs, though I don't think they're in season at Mouser. My hopes are that they will be by the time I get into prototyping, but that's still a fairy tale at this time.

That's a really interesting idea with the bass boost on the PIMETA. I've read about it, but I don't think my PIMETA necessarily needs it, what with my listening tastes. I thought about putting in the PPAS since PPA > PIMETA though by how much, I'm not sure, and the PPAS is already so crazy tiny. It has the additional advantage of optional bass boost, as well. I'm going to go work out, and then we'll see what kind of work I can put into the DAC/amp. I can assure you, however, that it's no Pico/Predator. Off to the gym!

 

[iQEM]

yay, ipod touch had out with 32gb capacity now...i've heard that ipod touch & iphone are using wolfson dac as well, is it worth to mod em ?

 

[wgr73]

They may be kind of tough to get open? I know that the iphone uses a different pinout in the dock too. If you decide to do it, definitely post your results/pics!

 

[iQEM]

nope, just asking...they both too expensive for me to buy...

maybe someone here that have try to dissamble em ?

here's the url to dissamble iTouch...
Code:

[left]http://www.cnet.com.au/mp3players/mp3players/0,239036128,339284245-6s,00.htm[/left]

and this one board of iPhone...

 

[Ramblingman]

Hey guys ill be modding my 5.5G ipod pretty soon, just want to make sure i kind of know what im doing...

I just have a few questions about caps... ive been searching but havent been able to get my head around it..

What im confused about is all the different values that people are using?

In the first post it seems that if you are going to go with the BG caps the values to look for are 22 or 47uF at 6.3VDC but then when some people build their docks they use like 4.7 or 2.2uF with 100 or 250VDC ratings.

Im just wondering how all these different ratings can work in the same application?

Do caps have like a broad range of successful operation or are they using these big caps and bypassing them somewhere where im not seeing?

And what about the voltage, is that their MAX handling voltage but they will work fine with the ipods very low voltage?


Anyway i've tried to get my head around it myself through searching but havent been able to do it yet

If anyone can please help this noob get an understanding for caps that would be much appreciated!

Im really looking forward to this mod!

 

[joneeboi]

Caps can vary in capacitance in this application, though I'm not sure how low the values can go. The voltage rating for the capacitors means how big a voltage they can take before exploding. The voltage coming out of the DAC measures from 1.5VDC to the 2.5VDC. I've measured 1.5VDC but I've seen some datasheets say 2VDC. Either way, I haven't seen many caps below 6.3V, so almost any cap will work. The BGs we've used measure from 22uF up to 100uF, but the datasheet says 1uF can be used. They get smaller, but depending on the amp you're using, you may not want to use them. Basically, the 100VDC and 250VDC ratings are supreme overkill, but that theoretically can add the sound. *shrug* Moral, almost any capacitance and voltage can be used, so long as the voltage is above 2.5VDC and capacitance, *shrug*

 

[no_eye_dear]

The thing to remember when picking your cap is that it forms a high-pass filter with the resistor to ground. Lookup RC circuit here:
High-pass filter - Wikipedia, the free encyclopedia
If you are using the Wolfson schematic then you could get away with 1uf unless you are using it through a quallity set of speakers (via an amp of course). If the corner frequency of the filter is too high then you may start to get phase distortion on sub-base frequencies.

Thanks to everyone here on the forum I've completed 2 4G's using solid silver teflon direct to the docking station and then converted the dock with nice caps and RCA's on the back. I did two in case 1 accidentally damaged something but they are both perfect

I installed Rockbox on them both as well so I can listen to my FLAC files.

This is a serious bit of kit that fits in neatly with my home brew dual mono T-amp

In fact... now I have one for sale if anyone is interested

U da man joneeboi

 

[no_eye_dear]

The thing to remember when picking your cap is that it forms a high-pass filter with the resistor to ground. Lookup RC circuit here:
High-pass filter - Wikipedia, the free encyclopedia
If you are using the Wolfson schematic then you could get away with 1uf unless you are using it through a quallity set of speakers (via an amp of course). If the corner frequency of the filter is too high then you may start to get phase distortion on sub-base frequencies.

Thanks to everyone here on the forum I've completed 2 4G's using solid silver teflon direct to the docking station and then converted the dock with nice caps and RCA's on the back. I did two in case 1 accidentally damaged something but they are both perfect

I installed Rockbox on them both as well so I can listen to my FLAC files.

This is a serious bit of kit that fits in neatly with my home brew dual mono T-amp

In fact... now I have one for sale if anyone is interested

U da man joneeboi

 

[Ramblingman]

Awesome! Thanks for that post joneeboi, it has helped me SOOOOOOOOOOOO much!

Another thing i think i read but cant seem to find anywhere, i could just be tripping..

was that the ideal uF value would be 1uF for every 100ohm input impedance on the connecting amp?

Anyway thanks again! Ill post pics of my yMod as soon as i get it done.. which will probably be early next week

 

[ruZZ.il]

capacitance using the equation: 1/(2*pi*R*C) to caculate the low freqquency cutoff. The cap works as a high pass filter (more on that here) Basically, its 2 plates that are very close to each other, and when a charge accumulates on one plate, it repels the charge on the other (like how magnets push each other away when orientated right, kinda). but once there's no more charge to push away, it stops.. so basically, it wont respond to a constant charge on one plate after a very short time, but will respond to a changing one. The main purpose that we use them for is to block whats called "Direct Current", which is basically the constant flow of electrons in one direction that would ruin things like headphones. this DC is a result of constand voltages that signals oscillate around in the reproduction of the analog signal from the digital data, bla bla bla..

Back to the equation
R- Resistance of the load. In our case, an amplifier, whos load on a circuit is equal to a resistive load of anywhere between around 10,000 and 100,000 Ohms.
C- The capacitance of the capacitor. A value that indicates how much charge can accumulate one one plate before it stops accumulating more.
So, for example, a 50kOhm load with a capacitor of 1uF would give us a cut-off frequency (the frequency where the signal is attenuated by 3db (basically means only half the power of the signal goes through, as the frequency gets lower, less and less of it gets through. 0hz (dc) wont go through at all) of:
Fc=1/(2*pi*R*C)=1/(2*pi*50000*0.000001)=~3.2Hz.
(Hz- oscillations per second)
so with a common amp, a 1uF cap would give a cutoff frequency of 3.2Hz which is well below what we can hear anyway. we chose such low values cause the cap will continue to effect frequencies above that, to a lesser degree as they're higher... and for flexability.
a 47uF cap would give a cutoff frequency of about 0.5Hz for the same load.. overkill, yes, but we use them cause its effective and cheap cause of the type of cap it is. some of the lowe values, like 1uf, can get really expensive.
Bottom line:
I broad range of caps is good for us, anything above 1uF will have favorable functionality for a broad range of amps.. and all caps behave a little differently, and sound a little different, and here the fun starts.. pick your cap and see how it works, enjoy the music!

P.S Picking the 'right' cap isn't always easy, either go with the flow or browse the forums.. too much to talk about here. Forum user dsavitsk shared his valuable experience here which is worth a go over, imho.

hope this helps more than it confuses....