"Process audio" means perform advanced mathematical processing on data in the digital domain. IOW, advanced digital filtering, sample rate conversion, etc.
I was (am) hoping that with the SoC + DRAM, one may create high-performance portable DAP (like the Head-Direct HiFi Man, etc).
Otherwise, I'm not sure the audio community at large should (will) sink time+effort into YET ANOTHER audio technology ... not when an iPhone + portable D/A can do so well.
Al that said, Wolfson support is a plus ... anyone directly compare Wolfson with RaspFi?
I was (am) hoping that with the SoC + DRAM, one may create high-performance portable DAP (like the Head-Direct HiFi Man, etc).
Otherwise, I'm not sure the audio community at large should (will) sink time+effort into YET ANOTHER audio technology ... not when an iPhone + portable D/A can do so well.
Al that said, Wolfson support is a plus ... anyone directly compare Wolfson with RaspFi?
You are not comparing like with like. If one was after a competitor to the AK100/120 pair, the Raspberry Pi, not least by virtue of its physical layout and size, would be a less than ideal place to start. As has been pointed out, the CPU is limited but with the option of add-on boards anything is possible but it is never going to be a neat sleek package the size an AK, nevermind an ipod or a walkman. It simply does what many other devices do but for a little less money.
in general, yes.
otoh, there are times when it makes sense to process.
my audio stream is spdif out to a dcx-2496 digital crossover. it splits into high/low and then sends spdif out to 2 dacs that go to 2 amps and finally to discrete woofer/tweeters.
the dcx does 'bit math' and clearly changes the data as it processes the audio into high/low bands.
I'm not at all upset about that. and technically, the bits are not longer 'bit perfect' once they go thru a dsp like my digital crossover.
in fact, the audio stream gets upsampled to 96k before it gets passed to the sharc dsp chip in the XO. so there's at least 2 destructive stages in this process.
audio still sounds pretty good to me, even with all this 'stuff' going on.
Real-world audio
For the basic Rasp. Pi, I think the orig. proj. requirements (that's right out of Project Management syllabus), did not contain any real specifics on HIGH-performance audio. It's more for low-cost classroom lab projects, budget kit hobbyists, and (possibly) a philanthropy option for developing nations.
The orig. RP designers may have thought: high-performance audio enthusiasts are going to have resources/funds and they'll likely for SOMETHING ELSE (stuff better suited for audio enthusiasts... no need to repeat that whole laundry list here!).
And that's my point ... if someone can get the basic $35 RP + (external audio periph., e.g., RaspyFi) to sound VERY good, offer ergonomics , be easily upgraded, and in a small/conv. pkg (e.g., Altoids, in true DIY style) ... all the power to them. But given what's there (sub-par SoC/ARM, lack of software/drivers, no DSD)...yada yada ... that's a very tall order.
What about Wolfson's support? Surely if a big-shot audio-chip developer supports it, this Pi thang may be a real deal -- right?
Wolfson is a smart company
So smart that they also know some POLITICS of success .... "hey, we at Wolfson care about classroom/lab audio ... we're with ya, budget audiophiles! ... we support audio w/o borders ... Raspberrys for Rwanda."
And a couple of DIYers might be genuinely confabulated that they can ultimately get their RP project to perform.
10% inspiration, 90% perspiration ... so polemics like moi MAY be deliberately lighting fires ... to get developers/DIYers worked up ... "I'll show that hollowman #$&@ !!!" Bring it on...keep it cheap ... and look at how the real wold does it ...i.e....
Why can't someone offer a DIY/kit version with sexiness and specs of this:
For the basic Rasp. Pi, I think the orig. proj. requirements (that's right out of Project Management syllabus), did not contain any real specifics on HIGH-performance audio. It's more for low-cost classroom lab projects, budget kit hobbyists, and (possibly) a philanthropy option for developing nations.
The orig. RP designers may have thought: high-performance audio enthusiasts are going to have resources/funds and they'll likely for SOMETHING ELSE (stuff better suited for audio enthusiasts... no need to repeat that whole laundry list here!).
And that's my point ... if someone can get the basic $35 RP + (external audio periph., e.g., RaspyFi) to sound VERY good, offer ergonomics , be easily upgraded, and in a small/conv. pkg (e.g., Altoids, in true DIY style) ... all the power to them. But given what's there (sub-par SoC/ARM, lack of software/drivers, no DSD)...yada yada ... that's a very tall order.
What about Wolfson's support? Surely if a big-shot audio-chip developer supports it, this Pi thang may be a real deal -- right?
Wolfson is a smart company
So smart that they also know some POLITICS of success .... "hey, we at Wolfson care about classroom/lab audio ... we're with ya, budget audiophiles! ... we support audio w/o borders ... Raspberrys for Rwanda."And a couple of DIYers might be genuinely confabulated that they can ultimately get their RP project to perform.
10% inspiration, 90% perspiration ... so polemics like moi MAY be deliberately lighting fires ... to get developers/DIYers worked up ... "I'll show that hollowman #$&@ !!!" Bring it on...keep it cheap ... and look at how the real wold does it ...i.e....
Why can't someone offer a DIY/kit version with sexiness and specs of this:
Indeed. The problem is there is so less things to screw up with DAC/AMP, and there are a lot of DIY dacs in nice packages already.
RP got a large community and can be bought for cheap. Passive cooling, low power. And it IS capable of performing one "simple" task - get audio from the net (being it radio or local NAS) and play it via DAC to taste being controlled via Web UI from your phone or tablet. It does not need housing at all for some cases (active speakers, in-wall/ceiling mount - it's fine for that purpose mostly I suppose). There is just no other solution like this for this kind of money. Once upon a time there was a Sqeezebox but it is a different story.
DACs for Detroit
Image: Courtesy cbsdetroit.com
...DACs for Detroit ... Raspberrys for the repo'd ...Pi's for the poor or Pi's for penny-pinchers ... Fi's for the foreclosed ...
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Image: Courtesy cbsdetroit.com
Apple Pi(e)
At-large - Wikipedia, the free encyclopedia
... and to confuse things further, I used it metaphorically (not the strict/legal term above)...
Not just the community (public) ... but manuf's, too. Newark and geeky PayPal group buys have to "compete" with iPads and Cypher Labs. Even competition WITHIN the DIY community ... so the ODAC ...
Every one want's a slice of the ... er ... pi(e) ... and Apple is the most popular...
I don't think you are familiar with the compound word I used earlier ...
At-large - Wikipedia, the free encyclopedia
... and to confuse things further, I used it metaphorically (not the strict/legal term above)...
Not just the community (public) ... but manuf's, too. Newark and geeky PayPal group buys have to "compete" with iPads and Cypher Labs. Even competition WITHIN the DIY community ... so the ODAC ...
Every one want's a slice of the ... er ... pi(e) ... and Apple is the most popular...
Ah I see now. You missed the point. Wolfson board is an addon for RaspyFi, but it is targeted to eduction/fun mostly unlike OP board which is hifi.
The Wolfson/element14 card is add-on for Raspberry Pi (the $35 computer). RaspyFi is audio software (like Foobar or iTunes). HiFiBerry Mini is another audio card (like Wolfson's card).
RaspyFi software can work with these two cards.
I think that's right ...
As far as which of the two audio cards is more "hifi" ... do you/anyone have links pointing to direct comparisons between the two?
BTW .... you're correct about my confusion ... and that was a point I was trying to make .... too many things to keep track of ... everyone who gets excited about new technology wants to start a project web site, blog, etc.
You can pick just about any topic but I'll stay ON-TOPIC and use the add-on RP audio stuff:
raspyfi.com (software)
crazy-audio.com
hifiberry.com (hardware)
sites.google.com/site/picoreplayer (software)
element14.com/community/community/raspberry-pi/raspberry-pi-accessories/wolfson_pi
This DIYAUDIO thread!
etc. etc.
Is the RP device worth this much attn/time/effort/confusion?
Why not devote the same time/attn "perfecting" pre-existing stuff.
Enough editorializing philosophy ... just spreading awareness ... bbbee ... bbbee .... bbbeee ... that's all folks.
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Just to clarify my orig. query in this thread.
First, a bit of pre-text ... kilobuck, high-end digital audio devices -- DCS, Ayre, Meridian, Chord, MSB -- use powerful DSP with custom-written software, to implement filters and processing that are supposed to sound decent. E.g., Minimum Phase filtering, very-high oversampling (Chord), etc.
Admittedly, I don't know much about how suitable SoC/ARM is for audio (or can it be programmed JUST for audio, ditching most of RP's non-audio functions).
I was hoping this could be done because dCs, MSB, etc. cost to prohibitively more ... especially on a plumber's "salary".
I'm gonna assume the answer is "no".
So I guess I'll have to put in some extra hours this season ... X-mas dinners lead to massive cloggings ... and I charge by the hour, 3x on X-mas eve and New Years. Ahh....I can hear that Sony now.
First, a bit of pre-text ... kilobuck, high-end digital audio devices -- DCS, Ayre, Meridian, Chord, MSB -- use powerful DSP with custom-written software, to implement filters and processing that are supposed to sound decent. E.g., Minimum Phase filtering, very-high oversampling (Chord), etc.
Admittedly, I don't know much about how suitable SoC/ARM is for audio (or can it be programmed JUST for audio, ditching most of RP's non-audio functions).
I was hoping this could be done because dCs, MSB, etc. cost to prohibitively more ... especially on a plumber's "salary".
I'm gonna assume the answer is "no".
So I guess I'll have to put in some extra hours this season ... X-mas dinners lead to massive cloggings ... and I charge by the hour, 3x on X-mas eve and New Years. Ahh....I can hear that Sony now.
How do they charge their kilobucks without
It's all snake oil, that's what it is.
Typically they put better components into higher end product in line but best of all it sounds without these patented circuits. I learned that trick tweaking commercial products in the past. Since then I prefer DIY. You get what you pay for at least.
? What for?
It's all snake oil, that's what it is.
Typically they put better components into higher end product in line but best of all it sounds without these patented circuits. I learned that trick tweaking commercial products in the past. Since then I prefer DIY. You get what you pay for at least.
I like the idea of a RPi being a controller for a small integrated DAC. What level of sound quality could we expect from it?
I know it's a subjective question, but there apparently is some hearable difference between a $100 DAC and a $1000 DAC.
When playing FLAC's from its SD, would the hifiberry be comparable to for example a laptop + schiit modi (supposedly good value budget dac)? Would it sound better, or worse? Why? Would it for example benefit from a better power supply, or is this already pretty good? Or does it depend on how the Pi itself is powered?
Sorry if this question's a bit noobish, I'm still looking for a good affordable DAC myself and I have a Pi lying around.
edit: Perhaps I should start off an answer based on my own current understanding of DACs. I think it could be good because there's no USB transport in between, so no need for complex asynchronous reclocking things. I think it could be bad because it shares power and ground with the Pi, and the Pi might pollute that, causing the clocks to be not so nice. Perhaps isolated data channels and a separate power supply might fix that, but I'm not sure about it. Am I right about these things?
I know it's a subjective question, but there apparently is some hearable difference between a $100 DAC and a $1000 DAC.
When playing FLAC's from its SD, would the hifiberry be comparable to for example a laptop + schiit modi (supposedly good value budget dac)? Would it sound better, or worse? Why? Would it for example benefit from a better power supply, or is this already pretty good? Or does it depend on how the Pi itself is powered?
Sorry if this question's a bit noobish, I'm still looking for a good affordable DAC myself and I have a Pi lying around.
edit: Perhaps I should start off an answer based on my own current understanding of DACs. I think it could be good because there's no USB transport in between, so no need for complex asynchronous reclocking things. I think it could be bad because it shares power and ground with the Pi, and the Pi might pollute that, causing the clocks to be not so nice. Perhaps isolated data channels and a separate power supply might fix that, but I'm not sure about it. Am I right about these things?
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I think, it will is more in the $100 range than in the $1000 range, but I'm very happy with the sound quality. THD+N is well below 0.004%.
I did tests with different power supplies. The DAC chip is quite robust against power supply noise. However, I decided to use an ultra-low-noise voltage regulator. The impact of it was measurable. The difference between my worst and best available power supply (a lab power supply and a cheap Nokia charger) was measurable, but very small. Using an another power supply in addition to the Raspberry Pi power supply did not improve the performance. The voltage regulation works very well.
The biggest improvement on the Raspberry Pi side is not the power supply, but the ethernet port. If you can, use wireless networking.
Daniel
P.S. A limited number of the DACs is now in stock
I did tests with different power supplies. The DAC chip is quite robust against power supply noise. However, I decided to use an ultra-low-noise voltage regulator. The impact of it was measurable. The difference between my worst and best available power supply (a lab power supply and a cheap Nokia charger) was measurable, but very small. Using an another power supply in addition to the Raspberry Pi power supply did not improve the performance. The voltage regulation works very well.
The biggest improvement on the Raspberry Pi side is not the power supply, but the ethernet port. If you can, use wireless networking.
Daniel
P.S. A limited number of the DACs is now in stock
@Tinco: There were people accessing the I2S pins on olders boards. I don't have a link available for it. But I would recommend, to sell the old Raspberry and buy a new one. It will be much easier. Also, cables on the I2S lines are not optimal for signal integrity.
@BeaufortRalph: You have to use cables to connect to the I2S input. However I'm not sure, if the Beaglebone Linux kernel already has I2S support. I will look into this and see, if there could be a DAC board similar to this one for BB, but this won't happen in the next months.
@BeaufortRalph: You have to use cables to connect to the I2S input. However I'm not sure, if the Beaglebone Linux kernel already has I2S support. I will look into this and see, if there could be a DAC board similar to this one for BB, but this won't happen in the next months.
Just for info:
From this site: BeagleBone Black: BBB - Building a DAC | element14
The BBB has an on-board I2S interface, which makes interfacing an external DAC easy. The I2S interface is connected from the AM3359 processor to the HDMI chip (TDA19988) but it is not required for HDMI to be used in order to make use of the I2S interface. The I2S interface is brought out to some pins on port P9 (see here for details). It was encouraging that Technoshaman and Donald Miller had some success with the interface, so I wanted to try it out and I got some time today.
Since the interface is capable of 24-bit/192kHz audio, it was worthwhile picking a nice DAC. A good but not over-the-top device seemed to be the Texas Instrument's PCM5101 which is nice because it has reasonable specs and also provides a built-in charge pump so that it can function from a single supply. A headphone amp was connected, and this was ON Semi's NCP2811A. The combination of PCM5101 (actually my prototype used PCM5101A which can also function from 1.8V, but this was not needed) and NCP2811A was chosen so that the entire circuit could operate from the BBB supply if desired, even if it was from a Li-Ion battery that was powering the BBB, and for low noise and distortion. The only problem is that the PCM5101 has quite a high output (clearly a good thing!) but the audio amp minimum recommended gain is 1 and it cannot meet the required output voltage, and it means that it will distort at high volume. So, at a lower volume (and lower SNR) it will be fine, and I prefer this particular amp because of the very low distortion. The ON semi datasheet was sparse though.
From this site: BeagleBone Black: BBB - Building a DAC | element14
The BBB has an on-board I2S interface, which makes interfacing an external DAC easy. The I2S interface is connected from the AM3359 processor to the HDMI chip (TDA19988) but it is not required for HDMI to be used in order to make use of the I2S interface. The I2S interface is brought out to some pins on port P9 (see here for details). It was encouraging that Technoshaman and Donald Miller had some success with the interface, so I wanted to try it out and I got some time today.
Since the interface is capable of 24-bit/192kHz audio, it was worthwhile picking a nice DAC. A good but not over-the-top device seemed to be the Texas Instrument's PCM5101 which is nice because it has reasonable specs and also provides a built-in charge pump so that it can function from a single supply. A headphone amp was connected, and this was ON Semi's NCP2811A. The combination of PCM5101 (actually my prototype used PCM5101A which can also function from 1.8V, but this was not needed) and NCP2811A was chosen so that the entire circuit could operate from the BBB supply if desired, even if it was from a Li-Ion battery that was powering the BBB, and for low noise and distortion. The only problem is that the PCM5101 has quite a high output (clearly a good thing!) but the audio amp minimum recommended gain is 1 and it cannot meet the required output voltage, and it means that it will distort at high volume. So, at a lower volume (and lower SNR) it will be fine, and I prefer this particular amp because of the very low distortion. The ON semi datasheet was sparse though.
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