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Help with optical output to analog conversion

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Help with optical output to analog conversion

Postby mrkniz » Mon Jul 31, 2017 8:08 am

I recently purchased a MOTU 16A interface. It has sixteen 1/4" outputs. These, of course I can connect directly to amplifier(s). But it also has two optical outputs, one for channels 1-8, the other for channels 9-16. I have two questions: 1) Are the optical outputs independent of the analog outputs, or are they merely duplicates? 2) Most important. Assuming they are independent, what do I hook them to to take advantage of the other sixteen channels? I have looked for converters, but can't find anything that will convert eight channels. Since many interfaces have optical outputs, I have to assume that there are components out there for the other end of the cable, but I haven't been able to find any. Please, if someone can help, I'd really appreciate it. Thanks. Ken Zink
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Re: Help with optical output to analog conversion

Postby mdyde » Mon Jul 31, 2017 8:24 am

Hello Ken,

mrkniz wrote:1) Are the optical outputs independent of the analog outputs, or are they merely duplicates?


They're independent, so each 16A can provide 32 channels of audio in total (16 analogue, plus 16 digital via the two 8-channel ADAT outputs).

mrkniz wrote:2) Most important. Assuming they are independent, what do I hook them to to take advantage of the other sixteen channels?


You need one or two 8-channel ADAT DACs. From memory, I believe Behringer make an affordable one (ADA8200?). RME also some (at a higher price-point).
Best regards,
Martin.

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Re: Help with optical output to analog conversion

Postby magnaton » Mon Jul 31, 2017 9:03 am

Here is a link for the Behringer. You'll need an optical cable to connect this ADAT to the MOTU 16A (notice the outputs and optical connections in the back). The only announce might be that you'll have to use XLR cables instead of 1/4" TRS cables used for the 16A.

https://www.sweetwater.com/store/detail/ADA8200
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Re: Help with optical output to analog conversion

Postby johnstump_organist » Mon Jul 31, 2017 11:03 am

I have wondered the same thing. I just found this 8 channel ADAT to analog converter.
https://www.sweetwater.com/store/detail/141
It is the Aphex Model 141 at Sweetwater, in case the link doesn't work.
I don't know about quality though, for 400 USD I don't if the converters would be of the highest quality, although it is not doing anything except the conversion, so maybe it would be good.
John
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Re: Help with optical output to analog conversion

Postby organtechnology » Mon Jul 31, 2017 1:22 pm

johnstump_organist wrote:I have wondered the same thing. I just found this 8 channel ADAT to analog converter.
https://www.sweetwater.com/store/detail/141
It is the Aphex Model 141 at Sweetwater, in case the link doesn't work.
I don't know about quality though, for 400 USD I don't if the converters would be of the highest quality, although it is not doing anything except the conversion, so maybe it would be good.
John


Plus there is a DB25-TRS Tascam Format snake required. ~$100.00
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Re: Help with optical output to analog conversion

Postby IainStinson » Tue Aug 01, 2017 4:19 am

You should probably check that the D2A ADAT device supports the sampling rate range required - some only support 48KHz, some support 44.1KHz, some higher rates. I'm not sure if they switch rates when the host audio system does. I would also think it's important that the quality of the main audio device and the ADAT are similar no point in having high quality for the outputs from the audio unit and low quality from the ADAT.

I shyed away from ADAT output units and bought a second audio unit which supported two devices working with the same instance of the ASIO driver (Focusrite Pro 40 under Windows).

There is full reviews of the Behringer device at SoundOnSound. http://www.soundonsound.com/reviews/behringer-ultragain-ada-8200

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Re: Help with optical output to analog conversion

Postby mrkniz » Tue Aug 01, 2017 8:31 am

To all who have replied to my query:
First, thank you.
I think my problem has been that digital outputs require balanced inputs into the amplifier, and my amplifiers only have RCA inputs. Also, I checked out the MOTU 24Ao, and its outputs are either Phoenix connectors or DB25, and would require adaptor cables that would also only end in balanced connectors (or 1/4" STEREO--and I need 1/4" mono plugs, but they don't seem to exist). Bottom line is that I would have to buy a new amplifier with balanced inputs, and the Emotiva XPA-3 with seven channels costs $2000 (ouch!). Oh, that some company would produce a quality interface with twenty-four (or more) 1/4" outputs with Thunderbolt and AVB connectors, and nothing else!
I like what Iain had to say about shying away from ADAT--it's just not a technology with which I'm comfortable. So, for the time being I'm putting any further purchases on hold. Eventually I might buy a second 16A or an 8a. Right now I'm building new housing for the speakers, then a new console, and then doing some more upgrading of the electronics.
As an aside, this has been my first post in quite a long time, but I do read the forum every day with my morning coffee. What a great group of people!
Thanks again, Ken
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Re: Help with optical output to analog conversion

Postby NickNelson » Tue Aug 01, 2017 9:51 am

mrkniz wrote:I think my problem has been that digital outputs require balanced inputs into the amplifier, and my amplifiers only have RCA inputs.


Hi Ken,

If it's true that all digital converters only provide balanced outputs (which seems surprising to me) this is not an insurmountable problem, though you may need to make up your own interconnects.

I have always found this reference fairly reliable http://www.rane.com/note110.html though a little experimentation is often needed to get the best results.

Nick
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Re: Help with optical output to analog conversion

Postby mrkniz » Tue Aug 01, 2017 10:14 am

Dear Nick:
What a potent website! Thanks very much for telling me about it. Besides all kinds of DIY cable connections, there is also a section about church audio, and my church has had lots of problems in that area. It will take quite a bit of perusing, not to mention sifting through, chewing, and digesting so much information, but it's really going to give me a lot to think about. Thank you very much. Ken
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Re: Help with optical output to analog conversion

Postby organtechnology » Tue Aug 01, 2017 10:39 am

mrkniz wrote:To all who have replied to my query:
First, thank you.
I think my problem has been that digital outputs require balanced inputs into the amplifier, and my amplifiers only have RCA inputs.

Also, I checked out the MOTU 24Ao, and its outputs are either Phoenix connectors or DB25, and would require adaptor cables that would also only end in balanced connectors (or 1/4" STEREO--and I need 1/4" mono plugs, but they don't seem to exist). Bottom line is that I would have to buy a new amplifier with balanced inputs, and the Emotiva XPA-3 with seven channels costs $2000 (ouch!). Oh, that some company would produce a quality interface with twenty-four (or more) 1/4" outputs with Thunderbolt and AVB connectors, and nothing else!


Although there are ways to convert the balanced outputs of a professional or semi-professional audio module to unbalanced, you lose the balanced line noise reduction capability when you do. But it can be done. It is especially easy to wire the 24Ao Phoenix connector to a wire with an RCA plug on the end. Also 1/4" tip-ring (TR) plugs can usually be inserted into tip-ring-sleeve (TRS) jacks with no problems but again you lose the noise reduction of the balanced circuit. The proper way is to go through a Balun (balanced-unbalanced) transformer which is TRS (Gnd, -, +) in and TR (Gnd, + out).

The real conflict here is the collision between the professional audio world and the consumer audio world. The pro audio world uses different connectors, different configurations and different reference levels from the consumer electronics world. Your amp is from the home theater consumer world and the MOTU and the ADAT are from the professional world. But it is possible to purchase the cables you need to get them to work together. CablestoGo.com

I like what Iain had to say about shying away from ADAT--it's just not a technology with which I'm comfortable. So, for the time being I'm putting any further purchases on hold. Eventually I might buy a second 16A or an 8a. Right now I'm building new housing for the speakers, then a new console, and then doing some more upgrading of the electronics.


ADAT is a very old format created for an early 8 channel, 48kHz digital audio tape on a VHS video cartridge. I do not think there are many ADAT machines left but the digital audio format lives on.

As an aside, this has been my first post in quite a long time, but I do read the forum every day with my morning coffee. What a great group of people!
Thanks again, Ken
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Re: Help with optical output to analog conversion

Postby organtechnology » Tue Aug 01, 2017 10:46 am

Thank You Nick!!

Thomas

NickNelson wrote:
mrkniz wrote:I think my problem has been that digital outputs require balanced inputs into the amplifier, and my amplifiers only have RCA inputs.


Hi Ken,

If it's true that all digital converters only provide balanced outputs (which seems surprising to me) this is not an insurmountable problem, though you may need to make up your own interconnects.

I have always found this reference fairly reliable http://www.rane.com/note110.html though a little experimentation is often needed to get the best results.

Nick
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Re: Help with optical output to analog conversion

Postby Eric Sagmuller » Tue Aug 01, 2017 12:24 pm

IainStinson wrote:You should probably check that the D2A ADAT device supports the sampling rate range required - some only support 48KHz, some support 44.1KHz, some higher rates. I'm not sure if they switch rates when the host audio system does. I would also think it's important that the quality of the main audio device and the ADAT are similar no point in having high quality for the outputs from the audio unit and low quality from the ADAT.

I shyed away from ADAT output units and bought a second audio unit which supported two devices working with the same instance of the ASIO driver (Focusrite Pro 40 under Windows).

There is full reviews of the Behringer device at SoundOnSound. http://www.soundonsound.com/reviews/behringer-ultragain-ada-8200

Iain


The specs on this unit kind of speak for the Behringer products themselves in general, not that they don't make some decent stuff. With this unit however, I think you get what you pay for, and I'm sure for many it would be good enough.

Eric
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