|
Post by dalethorn on Jun 2, 2012 3:47:58 GMT
|
|
|
Post by dalethorn on Jun 2, 2012 18:04:09 GMT
The light on the front switches sometimes from 44 to 48 khz when playing different 320 kbps CBR MP3's. I didn't know that when a 96 khz FLAC is converted to MP3 that it retains the original khz rating. Is there any point to that?
It also seems in some respects that increasing the resolution of playback with commercial recordings is like going to a low-budget fashion shoot with a gigapixel camera, so the makeup on the model's face doesn't look like a nice highlight as much as it looks like raw paint and powder.
|
|
|
Post by dalethorn on Jun 3, 2012 1:48:08 GMT
What's very peculiar with this iPhone digital output is that the EQ settings are still active in the iPhone4s. The phone is connected to the iStreamer DAC via USB and the iStreamer is reporting a 44 khz signal on the front panel. The iStreamer is connected via its output to the O2 headphone amp which is feeding the Shure 1840 headphone. I don't see how the tone controls/EQ settings could be active from the iPhone through the iStreamer DAC to the headphone amp when the iPhone is supposed to be providing a digital signal only to the iStreamer.
|
|
|
Post by dalethorn on Jun 3, 2012 17:07:22 GMT
I did several lengthy google searches for digital eq, ipod eq, ipod digital eq etc., and all I find are vague claims - not a single one by Apple or on an Apple forum. In fact, the only definitive statement was made on a Wadia forum. It would seem from the google results that this is a "delete and do not discuss" verboten topic from Apple's point of view.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 3, 2012 20:22:25 GMT
When a 96/24 or 192/24 bit signal is encoded to MP3, which allows a maximum samplerate of 48kHz, it does not retain the higher samplerate but is converted to 48kHz (easiest to do divide by 2 or 4) and the least significant 8 bits are 'thrown' away effectively. That converted signal is encoded. a CD will be encoded to 44.1 khz sample rate. So when you have 320kb/s MP3's it can be 44.1kHz or 48kHz depending on what format the source was.
So max samplerate 48kHz max bitrate 320kb/s.
Maximum 'standard' bitrate is 320kb/s but can be set (in LAME) to 640kb/s. These files can't be played back by most players so is rather pointless. Just like MP3-HD can not be played back 'lossless' by many players but only the embedded low res 'standard' MP3 stream in the same signal (when set to hybrid mode) can be heard.
|
|
|
Post by dalethorn on Jun 3, 2012 20:36:17 GMT
I am finding out that the reason we've had such a limited number of i-device DAC's is not because of the hardware or even Apple's I/O software, it's because the digital data coming from the dock connector is highly customized by Apple. I doubt that there is any significant encryption in that data because that would put too much of a burden on the Apple mobile processor.
|
|
|
Post by dalethorn on Jun 3, 2012 20:48:56 GMT
I do find that the 320k MP3's I rip from CD's or convert from WAV and FLAC files sound as good on the ipod/iphone playing through the digital port through the DAC to the headphone amp as they sound on my desktop soundcard with its own DAC and amp hardware. While I could get a good DAC and headphone amp for the desktop for perhaps $1000 to $1500 USD, all I would accomplish for most tracks is to improve the audibility of certain details AND distortions in the recordings. I remember very well chasing the perfectionist sound thing with vinyl LP's and finally gave up when every tick and pop became a symphony of its own. So I'd give the istreamer a recommendation for marginal improvement.
|
|
joethearachnid
Been here a while!
Old head on young shoulders.
Posts: 380
|
Post by joethearachnid on Jun 3, 2012 21:52:10 GMT
What's very peculiar with this iPhone digital output is that the EQ settings are still active in the iPhone4s. The phone is connected to the iStreamer DAC via USB and the iStreamer is reporting a 44 khz signal on the front panel. The iStreamer is connected via its output to the O2 headphone amp which is feeding the Shure 1840 headphone. I don't see how the tone controls/EQ settings could be active from the iPhone through the iStreamer DAC to the headphone amp when the iPhone is supposed to be providing a digital signal only to the iStreamer. I would assume that EQ is done in the digital domain and the data path for the music is such that the EQ settings are fed into the digital output. I don't see why this should be a problem, since simply setting the iPhone EQ to flat would negate any possible signal degradation. If I recall correctly, the digital decoding is done by a very specific chip that Apple keeps tight control of, rather than any software decoding. Any company that wants to make iDevice digital devices faces a long and arduous vetting process (I seem to remember that this was why the CLAS took so long to come out). Big companies like Sony or JVC etc. can be processed quite easily, but smaller independent companies (like most hi-end audio companies) will have greater problems. Any company that attempts to bypass this will face legal action and a full sanction from Apple. Hopefully there will be a break at some point and Chinese manufacturers that don't care will start making cheap iDevice digital transports such that Apple can't stop them and the situation will become more sensible, but for now everybody has to stick with the steps to Apple's paranoia dance. -JoetheArachnid
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jun 3, 2012 22:05:30 GMT
Silly question, shouldn't this thread be under "computer audio" or "other devices" as it isn't a headphone amp?
|
|
joethearachnid
Been here a while!
Old head on young shoulders.
Posts: 380
|
Post by joethearachnid on Jun 3, 2012 22:48:30 GMT
That's a good point. Moderator powers GO!
-JoetheArachnid
|
|
|
Post by dalethorn on Jun 4, 2012 1:40:39 GMT
I had it under headphone amps because 1) I inserted it between my iphone and headphone amp, and 2) Because it doesn't make sense as a computer accessory, since a computer should have a better music server than an i-device and the iStreamer is strictly for i-devices.
|
|
joethearachnid
Been here a while!
Old head on young shoulders.
Posts: 380
|
Post by joethearachnid on Jun 4, 2012 10:49:10 GMT
Actually you're right again. It's neither a headphone amplifier nor a DAC designed to be connected to a computer, so it should go in 'other equipment'. Sorry about all the thread shifting. -JoetheArachnid
|
|