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      07-06-2014, 04:42 PM   #1
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optical input to dsp question

I want to run airplay into a Helix DSP, utilizing the airport express optical out capability to the optical input of the Helix. This should give a great quality signal and really allow some good a/b testing against the hifi head unit with usb input source.

My question is how will the volume be controlled with the optical input? Will the airplay source (ipad/iphone etc) work to control the volume with the optical out or does that only work with analog audio out of the airport. If this doesn't work I fear I will need extra hardware like the helix remote or wire up some home made volume potentiometer.
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      07-06-2014, 05:13 PM   #2
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I thought u were using air enabler, not AEx
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      07-06-2014, 07:39 PM   #3
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Quote:
Originally Posted by taibanl
I thought u were using air enabler, not AEx
Changed my mind to get the optical out without worrying about a usb to optical converter.
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      07-06-2014, 08:35 PM   #4
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Volume is controlled digitally, by the source i-device.
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      07-07-2014, 02:43 AM   #5
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Quote:
Originally Posted by cdgatti
Quote:
Originally Posted by taibanl
I thought u were using air enabler, not AEx
Changed my mind to get the optical out without worrying about a usb to optical converter.
IMHO. much more straightforward than a power supply hack. Usb to optical is just converting the form of the signal, not the substance.
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      07-07-2014, 05:19 AM   #6
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thanks Kai and Tai. I thought that's how it might be controlled by the i-device, just like when using it in the house. That will be ok for devices under my control, but if someone else airplays to the system, I will just have to ask them to turn their volume down before sending the signal and then turn it up slowly! So as not to cause damage. On the TP link vs AE question, yea I know and keep going back and forth. I see pros and cons for both.
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      07-07-2014, 05:40 AM   #7
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It will not work. Airport express has too much jitter. Your songs will stutter and skip. I tried it with a Cambridge Audio Dac Magic and it was annoying as shit. I ended up using 3.5mm to RCA into a line driver into my amp. Better bet is to use an Apple TV. There's less jitter. Also, volume control over airplay is via source (phone/iPad).
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      07-07-2014, 06:28 AM   #8
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Quote:
Originally Posted by mathematics View Post
It will not work. Airport express has too much jitter. Your songs will stutter and skip. I tried it with a Cambridge Audio Dac Magic and it was annoying as shit. I ended up using 3.5mm to RCA into a line driver into my amp. Better bet is to use an Apple TV. There's less jitter. Also, volume control over airplay is via source (phone/iPad).
Not my experience, so don't say it won't work!
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      07-07-2014, 09:48 AM   #9
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Quote:
Originally Posted by kaigoss69
Quote:
Originally Posted by mathematics View Post
It will not work. Airport express has too much jitter. Your songs will stutter and skip. I tried it with a Cambridge Audio Dac Magic and it was annoying as shit. I ended up using 3.5mm to RCA into a line driver into my amp. Better bet is to use an Apple TV. There's less jitter. Also, volume control over airplay is via source (phone/iPad).
Not my experience, so don't say it won't work!
You have optical working perfectly normally out of an airport express? You must be the only person on the internet that doesn't have jitter issues.
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      07-07-2014, 12:04 PM   #10
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Quote:
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You have optical working perfectly normally out of an airport express? You must be the only person on the internet that doesn't have jitter issues.
Does the TP link have the same jitter issues?
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      07-07-2014, 12:07 PM   #11
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Quote:
Originally Posted by cdgatti
Quote:
Originally Posted by mathematics View Post
You have optical working perfectly normally out of an airport express? You must be the only person on the internet that doesn't have jitter issues.
Does the TP link have the same jitter issues?
Airport Express is the only device I know of with jitter issues severe enough to actually affect how the DAC syncs to the clock signal. I tried 3 of them and if you search google, you'll see a ton of people with the same issues no matter what DAC is used
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      07-07-2014, 01:54 PM   #12
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math you think even optical out of the AE to the helix will have jitter?
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      07-07-2014, 02:19 PM   #13
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Quote:
Originally Posted by cdgatti
math you think even optical out of the AE to the helix will have jitter?
It's a problem with the airport hardware. Only cheap ass DAC's can keep clock sync, and the helix does NOT use a cheap DAC. If you already have an airport then try it. If not, I'd use an Apple TV because that actually works (although you'd still need a wireless network for Apple TV to connect for airplay).
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      07-07-2014, 02:27 PM   #14
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Quote:
Originally Posted by cdgatti
thanks Kai and Tai. I thought that's how it might be controlled by the i-device, just like when using it in the house. That will be ok for devices under my control, but if someone else airplays to the system, I will just have to ask them to turn their volume down before sending the signal and then turn it up slowly! So as not to cause damage. On the TP link vs AE question, yea I know and keep going back and forth. I see pros and cons for both.
You are aware that the air enabler volume is user adjustable, right?
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      07-07-2014, 02:29 PM   #15
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Quote:
Originally Posted by mathematics
Quote:
Originally Posted by cdgatti
math you think even optical out of the AE to the helix will have jitter?
It's a problem with the airport hardware. Only cheap ass DAC's can keep clock sync, and the helix does NOT use a cheap DAC. If you already have an airport then try it. If not, I'd use an Apple TV because that actually works (although you'd still need a wireless network for Apple TV to connect for airplay).
Sounds like use of synchronous dac when you should be using asynchronous (or vice versa)
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      07-07-2014, 02:52 PM   #16
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Quote:
Originally Posted by taibanl
Quote:
Originally Posted by mathematics
Quote:
Originally Posted by cdgatti
math you think even optical out of the AE to the helix will have jitter?
It's a problem with the airport hardware. Only cheap ass DAC's can keep clock sync, and the helix does NOT use a cheap DAC. If you already have an airport then try it. If not, I'd use an Apple TV because that actually works (although you'd still need a wireless network for Apple TV to connect for airplay).
Sounds like use of synchronous dac when you should be using asynchronous (or vice versa)
You cannot have an asynchronous clock via toslink. That's only possible via USB.
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      07-07-2014, 05:25 PM   #17
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Quote:
Originally Posted by taibanl
Quote:
Originally Posted by cdgatti
thanks Kai and Tai. I thought that's how it might be controlled by the i-device, just like when using it in the house. That will be ok for devices under my control, but if someone else airplays to the system, I will just have to ask them to turn their volume down before sending the signal and then turn it up slowly! So as not to cause damage. On the TP link vs AE question, yea I know and keep going back and forth. I see pros and cons for both.
You are aware that the air enabler volume is user adjustable, right?
Tai do you mean volume is controlled somewhere else other than the iPhone/ipad source?
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      07-07-2014, 11:25 PM   #18
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Quote:
Originally Posted by cdgatti
Quote:
Originally Posted by taibanl
Quote:
Originally Posted by cdgatti
thanks Kai and Tai. I thought that's how it might be controlled by the i-device, just like when using it in the house. That will be ok for devices under my control, but if someone else airplays to the system, I will just have to ask them to turn their volume down before sending the signal and then turn it up slowly! So as not to cause damage. On the TP link vs AE question, yea I know and keep going back and forth. I see pros and cons for both.
You are aware that the air enabler volume is user adjustable, right?
Tai do you mean volume is controlled somewhere else other than the iPhone/ipad source?
Correct. There is a default 70% volume but its changeable via a very simple telnet command
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