iTunes/computer feeding an external DAC: The Equalizer - diyAudio
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Old 18th February 2010, 11:12 PM   #1
NV&H is offline NV&H  United States
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Default iTunes/computer feeding an external DAC: The Equalizer

I have an external Musical Fidelity (V-DAC) USB DAC that's fed from a Mac computer via iTunes. I've noticed that the equalizer within iTunes is still functional running this way. I was very surprised by this because I just assumed that the equalizer operated in the analog domain. And I assumed that, for "purity of signal" reasons, this feature would be bypassed when a lossless digital stream is being pulled out.

I don't yet have the speakers to fully evaluate the quality of the equalizer, so, can you share your opinions about any signal degradation caused by the equalizer operating this way?
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Old 18th February 2010, 11:36 PM   #2
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Short answer: iTunes is not a hi-fidelity music player. Unfortunately, there's not a lot of alternatives for Mac - try Play from sbooth.org or Cog - News . They at least should make it clearer what DSP you're running.

Longer answer: You're not pulling a bit-perfect version of the original stream. The equaliser operates in the digital domain using digital filters - Finite Impulse Response filters. Personally, I don't think they're any more evil than passive EQ, but the point does remain that it does change the sound in a real and measurable way.
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Old 18th February 2010, 11:45 PM   #3
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Goto: View - Show Equalizer and uncheck the box in the top left that says 'on'. That should solve your problem =D
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Old 19th February 2010, 02:13 PM   #4
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I know how to turn it on and off. I was wondering if there is any signal degradation caused by iTunes equalizer in the digital domain. My speakers aren't built yet, so I can't really evaluated this myself just yet.

I'll probably have a need for an equalizer in the near future and was deliberating my best path forward: iTunes equalizer or an outboard analog equalizer?
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Old 5th August 2010, 10:54 PM   #5
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Old 5th August 2010, 11:00 PM   #6
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I thought iTunes EQ was IIR? Not matter which is sounds like a consumer toy brought to you by the folks that consider an iPod "Good enough"

If you're after quality I agree with other folks here, iTunes is not the way to go. as for an alternate soultion I'm sure someone has an opinion, I don't because the tools I use aren't designed for domestic listening.
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Old 5th August 2010, 11:55 PM   #7
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I don't know about PCs (where Apple follows the rules and addresses the official Windows calls), but i have no complaints about iTunes on the Mac playing AIFF (everything off, iMac G5 to Edirol Firewire DAC @ 24/192).

I am also playing with PureVinyl (it has a lower price companion PureMusic). Like Amarra it uses iTunes for its UI i believe. I understand that PureVinyl is the reason (competition) that there are now much less stratospheric versions of Amarra (which from the traffic on forums would have everyone running a Mac if they wanted best sound quality).

Back on topic the EQ built into iTunes is not a serious tool. There are Audio Unit (?) plug ins that one should be able to run (possibly in conjunction with HiJack) that give you more serious EQ capability.

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Old 6th August 2010, 01:59 AM   #8
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Quote:
Originally Posted by Diginerd View Post
If you're after quality I agree with other folks here, iTunes is not the way to go.
Hmm.... afaik, iTunes will faithfully create a digital stream from the data file provided you have all the iTunes options turned off. This includes the sound enhancer, cross fade, sound check, and of course the equalizer. If you use an external DAC you have the option of transmitting the data stream via USB, Firewire, Ethernet, or Toslink (depending on the Mac model and DAC). You can even stream it wireless to another room if you want.

The "quality" of the data stream will remain the same "quality" as the source file.
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Old 6th August 2010, 02:36 AM   #9
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You missed leave volume at 100%.

Newer releases of iTunes will do the job, but there are many pitfalls waiting to trip you up. I haven put a bit-analyzer on it recently, but a couple of versions back it was 16 bit output only. It would play 24 bit files, but would truncate the wordlength silently. That's just not a nice thing to do withput dithering the result (it didn't do that either).

Maybe that's fixed now, but having that behavior in the first place points to a lack of attention to details in the engine as opposed to a shiny GUI selling DRM crippled digital files of dubious quality. That's the polite version of my feelings on the subject...

As I said, I'm not advocating any particular other app, just checkout what's available as an alternative.
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Old 6th August 2010, 03:45 AM   #10
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Quote:
Originally Posted by Diginerd View Post
I haven put a bit-analyzer on it recently, but a couple of versions back it was 16 bit output only. It would play 24 bit files, but would truncate the wordlength silently.
Yes, I believe it's still limited to standard CD quality 16 bit/44.1kHz. If you have music at a higher sampling rate than this, no iTunes would probably not be your best choice.

Quote:
Originally Posted by Diginerd View Post
As I said, I'm not advocating any particular other app, just checkout what's available as an alternative.
I agree. I just wanted to point out that you can still have (CD) quality with iTunes, albeit not as good or bad as other alternatives.
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