first: i'm quite a newbie to diy-audio, but i'm very interested in higher-end portable (...and transportable in bags!) headphone listening.
lately the possibilities of portable listening have expanded greatly, now with the ppa amp, and now lately also with battery powered dacs. but the lack of a battery powered, quite high-end battery powered source is very irritating (imo). some pcdps have opt. outs, but the jitter that is introduced makes them very hard to use as nice transports. the headphones are there aswell.
so my question is. how hard would it be to make a battery powered source (f.i. using this battery board: http://www.tangentsoft.net/audio/ppa/bb/) consisting of:
- hard drive
- some sort of buffer
- some kind of controller that could play wav, and some lossless compression formats (like flac)
- presicion clock to reduce (eliminate?) jitter (like the lc audio xo3 clock, or some other diy-clock). how power hungry are these clocks, btw? are there possible to drive of batteries?
- the battery life wouldn't have to be very long, something around 10-12 hours would be sufficient.
- the user interface *don't* have to be fancy, just a usb2 of firewire interface, and the hd pops up as a usual hard drive in the pc, so you can drag&drop files to the player.
would something like this be possible to do?! imagine a portable device consisting of this source, the aos' dac and a ppa... portable musical bliss...
some links:
www.head-fi.org
www.headwize.com
elvencraft.com/ppa/
tangentsoft.net/audio/ppa
lately the possibilities of portable listening have expanded greatly, now with the ppa amp, and now lately also with battery powered dacs. but the lack of a battery powered, quite high-end battery powered source is very irritating (imo). some pcdps have opt. outs, but the jitter that is introduced makes them very hard to use as nice transports. the headphones are there aswell.
so my question is. how hard would it be to make a battery powered source (f.i. using this battery board: http://www.tangentsoft.net/audio/ppa/bb/) consisting of:
- hard drive
- some sort of buffer
- some kind of controller that could play wav, and some lossless compression formats (like flac)
- presicion clock to reduce (eliminate?) jitter (like the lc audio xo3 clock, or some other diy-clock). how power hungry are these clocks, btw? are there possible to drive of batteries?
- the battery life wouldn't have to be very long, something around 10-12 hours would be sufficient.
- the user interface *don't* have to be fancy, just a usb2 of firewire interface, and the hd pops up as a usual hard drive in the pc, so you can drag&drop files to the player.
would something like this be possible to do?! imagine a portable device consisting of this source, the aos' dac and a ppa... portable musical bliss...
some links:
www.head-fi.org
www.headwize.com
elvencraft.com/ppa/
tangentsoft.net/audio/ppa
this seems perfectly doable. What you will need to do is find a decoder chip out there to decode the formats you wish to decode. Then from there it should be relatively simple if you know your stuff. You will have a hard disk and a microcontroller, USB, USB 2.0 or 1394 interface (1394 and USB 2.0 will be much more difficult than just regular USB, The regular USB interface has many controller chips out there, but look around anyways) Anyways you'll have the hard disk, microcontroller, display, controls, the decoder, a DAC, and a head phone drive circuit. Also probably some sort of charging circuit. Ideally you would implement some sort of lithium ion charger to gain the battery life you seak, also in the interest of size and battery life you will want to use a notebook hard disk.
make sense?
well anyways here is some food for thought. Is a portable MP3 player. Much of it will apply to what you are doing, but i imagine bandwidth issues will become a problem with wav files being streamed instead of mp3's
http://www.myplace.nu/mp3/index2.htm
there are many other decoder chips other than the VS1001 used in this project. This particular one has a built in DAC which obviously wont be what youre looking for.
make sense?
well anyways here is some food for thought. Is a portable MP3 player. Much of it will apply to what you are doing, but i imagine bandwidth issues will become a problem with wav files being streamed instead of mp3's
http://www.myplace.nu/mp3/index2.htm
there are many other decoder chips other than the VS1001 used in this project. This particular one has a built in DAC which obviously wont be what youre looking for.
Why not just get an iPod?
Rompurs are we'll see new lower priced units next week @ MacWorld Expo.
dave
An externally hosted image should be here but it was not working when we last tested it.
Rompurs are we'll see new lower priced units next week @ MacWorld Expo.
dave
additional rumor is that apple is entering the flash player market as well.
i'd say if you're going to go the non-diy route, look into alternatives to the iPod. not to bash it, but i haven't been able to find any S/N specs on it, whereas (some) other HD players publish theirs. (most notably, Creative's Nomad Jukebox 3 specs 98dB SNR from their lineout, with THD at 0.1%)
i currently own an unopened iPod, a xmas present, which i'm trying to decide whether to exchange for the JB3.
a few months ago i saw someone posting some progress on designing just the project you're asking about, over on the DIY forums at headwize.com. i can't seem to find them now, but if you search around you might have luck.
i'd say if you're going to go the non-diy route, look into alternatives to the iPod. not to bash it, but i haven't been able to find any S/N specs on it, whereas (some) other HD players publish theirs. (most notably, Creative's Nomad Jukebox 3 specs 98dB SNR from their lineout, with THD at 0.1%)
i currently own an unopened iPod, a xmas present, which i'm trying to decide whether to exchange for the JB3.
a few months ago i saw someone posting some progress on designing just the project you're asking about, over on the DIY forums at headwize.com. i can't seem to find them now, but if you search around you might have luck.
while the ipod and creative zen are very nice products I dont think they are quite what he is looking for. They are meant to play mp3s at a respectable sound quality. They arent what i would call a high definition source.
http://www.modeemi.fi/~vesas/iPod_Audio.pdf
thats a punch of tests on the ipods audio output.
http://www.audiosense.org/results/portable/iPod Mp3.htm
more tests
Creative claims the following for the Zen
Signal to Noise Ratio: up to 98dB
Channel Separation: up to 75dB
Frequency Response: 20Hz - 20kHz
Harmonic Distortion Output: <0.1%
in a test they found the following
RMAA Tests
Tested chain: Creative Zen hp out - ESI Waveterminal line-in
Operating mode: 16-bit, 44 kHz
Test Test Signal Creative Zen WAV Creative Zen MP3
Frequency response (40 Hz - 15 kHz), dB +0.00, -0.00 +0.05, -0.23 +0.18, -0.63
Noise level, dB (A) -97.8 -92.1 -92.1
Dynamic range, dB (A) 95.5 89.6 89.4
THD, % 0.0003 0.0047 0.0048
Intermodulation distortions, % 0.0057 0.014 0.015
Crosstalk, dB -92.0 -87.3 -85.2
that table can be better seen towards the bottom of this page.
http://www.digit-life.com/articles2/creative-zen/
Perhaps moding a zen or ipod would be a better idea? That way you dont have to design a new interface and write all that assemble code and so on...
this is off a another forum
"The rest of the device [iPod] uses a dedicated MP3 decoder and controller chip from PortalPlayer, a Wolfson Microelectronics Ltd. stereo digital-to-analog converter, a flash memory chip from Sharp Electronics Corp., a Texas Instruments 1394 firewire interface controller, and a power management and battery charging IC from Linear Technologies Inc."
perhaps there are some I2C lines in there that can be tapped...hmmmm
http://www.modeemi.fi/~vesas/iPod_Audio.pdf
thats a punch of tests on the ipods audio output.
http://www.audiosense.org/results/portable/iPod Mp3.htm
more tests
Creative claims the following for the Zen
Signal to Noise Ratio: up to 98dB
Channel Separation: up to 75dB
Frequency Response: 20Hz - 20kHz
Harmonic Distortion Output: <0.1%
in a test they found the following
RMAA Tests
Tested chain: Creative Zen hp out - ESI Waveterminal line-in
Operating mode: 16-bit, 44 kHz
Test Test Signal Creative Zen WAV Creative Zen MP3
Frequency response (40 Hz - 15 kHz), dB +0.00, -0.00 +0.05, -0.23 +0.18, -0.63
Noise level, dB (A) -97.8 -92.1 -92.1
Dynamic range, dB (A) 95.5 89.6 89.4
THD, % 0.0003 0.0047 0.0048
Intermodulation distortions, % 0.0057 0.014 0.015
Crosstalk, dB -92.0 -87.3 -85.2
that table can be better seen towards the bottom of this page.
http://www.digit-life.com/articles2/creative-zen/
Perhaps moding a zen or ipod would be a better idea? That way you dont have to design a new interface and write all that assemble code and so on...
this is off a another forum
"The rest of the device [iPod] uses a dedicated MP3 decoder and controller chip from PortalPlayer, a Wolfson Microelectronics Ltd. stereo digital-to-analog converter, a flash memory chip from Sharp Electronics Corp., a Texas Instruments 1394 firewire interface controller, and a power management and battery charging IC from Linear Technologies Inc."
perhaps there are some I2C lines in there that can be tapped...hmmmm
the ipod uses a Wolfson Microelectronics WM8731
http://www.wolfsonmicro.com/products/digital_audio/codecs/WM8731/
http://www.wolfsonmicro.com/products/digital_audio/codecs/WM8731/
Benjlv said:
The iPod can play full resolution CD tracks as AIFFs. If used as such it can outperform many a CD player (some costing much more than the iPod) -- a large part of the performance is that it is streamed off HD.
As such Stereophile gave it runner up in Digital product of the year, the Editors Choice award, and the Budget Product (?).
that's good information, thanks Benjlv!
i found the review of the jukebox 3 here.
it seems to performs a little better than the 'zen' on their tests. unfortunately they didn't test the Line Out, which i expect would measure better than the headphone out.
the other unfortunate thing is, the same 'rightmark' tests done on the iPod used MP3 format instead of WAV (as was apparently used on the JB3), so it's impossible to compare. the MP3 results were pretty poor compared to the WAV ones.
---
dave - i don't know if creative's player can play AIFF files. i know it can play uncompressed WAV files though. i agree with you, i'd prefer to avoid mp3's altogether. 40GB (or 60!) is enough space not to need compression.
i found the review of the jukebox 3 here.
it seems to performs a little better than the 'zen' on their tests. unfortunately they didn't test the Line Out, which i expect would measure better than the headphone out.
the other unfortunate thing is, the same 'rightmark' tests done on the iPod used MP3 format instead of WAV (as was apparently used on the JB3), so it's impossible to compare. the MP3 results were pretty poor compared to the WAV ones.
---
dave - i don't know if creative's player can play AIFF files. i know it can play uncompressed WAV files though. i agree with you, i'd prefer to avoid mp3's altogether. 40GB (or 60!) is enough space not to need compression.
in that case i would look at modifying this project
http://www.myplace.nu/mp3/index2.htm
I would ask in the forum on that site to see if the micro controller can handle the bandwidth of a wav file. If it can then all you will need to do is change the software to recognize wav files and to interface with a different decoder....so on so forth. not simple...but doable.
anyways good luck...i hope this idea goes places.
http://www.myplace.nu/mp3/index2.htm
I would ask in the forum on that site to see if the micro controller can handle the bandwidth of a wav file. If it can then all you will need to do is change the software to recognize wav files and to interface with a different decoder....so on so forth. not simple...but doable.
anyways good luck...i hope this idea goes places.
Benjlv: another awesome link. i think i'll bookmark that one.
in terms of players on the market, i have learned that the iRiver iHP-120 has an optical line-out. (and optical line-in, pretty neat.) so i guess it could be used with external DAC and amp. i'm actually starting to consider this one for myself as opposed to the iPod. it's gotten excellent reviews as to sound quality (incl. really flat frequency response, low distortion), and the next version (iHP-140) is coming out, with 40gb capacity.
in terms of players on the market, i have learned that the iRiver iHP-120 has an optical line-out. (and optical line-in, pretty neat.) so i guess it could be used with external DAC and amp. i'm actually starting to consider this one for myself as opposed to the iPod. it's gotten excellent reviews as to sound quality (incl. really flat frequency response, low distortion), and the next version (iHP-140) is coming out, with 40gb capacity.
Hi All
I recently got an iHP-120 and have been doing some tests on it. I bought mine mainly for listening, but also to use as a portable digital _recorder_ with an external micpre and ADC. Here is what I found.
1. it plays and records uncompressed WAV files at 44 or 48kHz 16 bit, as well as MP3 at 64 to 320k.
2. when recording a wav file from the optical in, the file comes out as an exact digital copy of the input. No AGC, digital recording level, etc. Good
3. when playing files to the optical out, again, the output is bit-for-bit the same as the file. Volume control and EQ settings have no effect on it. Good But if you turn on the SRS sound enhancement it goes a bit funny.
4. The quality of the optical signal seems to be ok, but if you hate jitter you'll probably want to reclock it anyway. I think pretty much all optical receivers introduce jitter of their own.
5. The builtin headphone amp actually sounds all right
and the quality with 256k MP3 is good enough for everyday listening.
6. The user interface is pretty fiddly to work, all the buttons are multifunction, e.g. half the time I end up turning it to FM radio mode when I meant to turn it off.
7. It also has analog line ins/outs. The line in can be configured as a mic in. I never measured THD and SNR for the line in, and I only listened to the line out. It sounds good with just a little hiss and no audible tones like some soundcards have.
So I would give it 4 smilies out of 5 overall. It would have been 5 except for the user interface.
I recently got an iHP-120 and have been doing some tests on it. I bought mine mainly for listening, but also to use as a portable digital _recorder_ with an external micpre and ADC. Here is what I found.
1. it plays and records uncompressed WAV files at 44 or 48kHz 16 bit, as well as MP3 at 64 to 320k.
2. when recording a wav file from the optical in, the file comes out as an exact digital copy of the input. No AGC, digital recording level, etc. Good
3. when playing files to the optical out, again, the output is bit-for-bit the same as the file. Volume control and EQ settings have no effect on it. Good
But if you turn on the SRS sound enhancement it goes a bit funny.4. The quality of the optical signal seems to be ok, but if you hate jitter you'll probably want to reclock it anyway. I think pretty much all optical receivers introduce jitter of their own.
5. The builtin headphone amp actually sounds all right
and the quality with 256k MP3 is good enough for everyday listening.6. The user interface is pretty fiddly to work, all the buttons are multifunction, e.g. half the time I end up turning it to FM radio mode when I meant to turn it off.
7. It also has analog line ins/outs. The line in can be configured as a mic in. I never measured THD and SNR for the line in, and I only listened to the line out. It sounds good with just a little hiss and no audible tones like some soundcards have.
So I would give it 4 smilies out of 5 overall. It would have been 5 except for the user interface.
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