DACs with Digital Passthrough / Digital Bypass – getting analog audio out while still passing on the digital signal to a receiver or pre-pro

I love having whole house audio.  I can either play the same source in the living room, kitchen, family room, bedrooms, or I can choose to have one source playing in the living room, another in the kitchen, and yet another in the bedrooms.  This flexibility is built into many receivers and preamp/processors; however with more and more sources being only digital (with no analog out) it’s becoming a bit of a challenge to use those sources in a zone2 or zone3.  The reason why is because normally in a receiver or pre-pro only the main zone (zone1) has a DAC (digital to analog converter) that will process the digital signal.  If you want to use that source for another zone, you need to feed the pre-pro an analog signal.

The Music Hall dac15.2 has S/PDIF out for digital passthrough and is under $300.

This raises an interesting problem and I’ll offer a solution using the AppleTV as an example.  The generation 2 and generation 3 AppleTVs only have an HDMI and toslink out for available ports.  There are no analog out ports whatsoever.  So, if you want to use the AppleTV in a zone2 or zone3, you are out of luck unless your pre-pro has the ability to “copy” the audio signal from zone1 to the other zones. That might be good in the short term, but you cannot watch TV or play a bluray in zone1 while listening to music on the AppleTV in zones 2 or 3!  
In my particular case, I have the HDMI out of the AppleTV going to my Anthem pre-pro and I have the toslink out going to an old Marantz receiver that I use to power my 4.1 setup in the family room.  If I want to use the AppleTV in any other room for zone 2 or zone 3 application, I’m out of luck.
A very obvious and initial reaction may be to just put a DAC on the toslink connection.  That way you can just get analog audio out and you might think that you are done.  That’s a problem, however as I’ll explain:
  1. Loss of Bass Management: A traditional DAC normally takes the audio and puts it into 2-channel/stereo analog audio out.  If you do this, you will lose the ability to use bass management in most receivers and pre-pros and you will lose the ability to have room correction enabled (if your unit has it).
  2. No Downmix for Multichannel Audio: Most DACs do not process multichannel audio.  So, if the audio source is a TV show in 5.1 or a movie, or whatever, you won’t get the audio properly down mixed for stereo.  That defeats the whole purpose of having the audio in a different zone.
  3. Loss of Room Correction: Most AVR and pre-pros will not apply room correction to an analog signal.  Anthem is one of the few exceptions that will.
These are two real problems, but there is a solution: you need to have a DAC that has what is called “digital passthrough”.  What digital passthrough will do is decode the digital signal to analog audio so that you can play it in a zone2 or zone3 and it will also send that digital signal along untouched to your pre-pro so that you can decode it normally and take advantage of bass management, room correction, and multichannel audio.  
In my setup, here’s how I would setup the DAC with digital passthrough with an AppleTV:
  1. I’d continue to feed the Anthem with HDMI for audio and video from the AppleTV.  Let’s assume I’m using the AUX port for this.
  2. I’d feed the toslink audio out to a DAC with digital bypass
  3. I’d feed the analog audio out into the Anthem’s analog AUX port.  Thus, if I call for zone2 or zone3 to play audio from the AUX port, it will pull the signal from the analog ports.
  4. I’d then feed the digital bypass/digital out from the DAC to the Marantz receiver to have that decode the audio.  This would likewise work if you have a non-HDMI-enabled receiver and needed to use this trick.
So now, you’d have full digital being sent and also full analog simultaneously sent.  Such a solution works well with both a single AVR/pre-pro setup or one where you have multiple units. 
Now the problem: not all DACs have digital passthrough.  So what do you do?  Well, I’ve started a listing here of DACs that do have digital passthrough.  In my particular case, I’m looking for a low-cost solution since I’m only going to be using this for zone2 and zone3 applications. 
(If you know of any additional DACs with digital passthrough, please let me know so that I can list them here).
There are two categories of DACs with digital passthrough.  The first is what I described above and the second is a DAC that has an HDMI out so the HDMI functions as the digital passthrough.  Right now, this is the short list that I’ve compiled.  I’m looking to get one of the DACs that cost under $600 and do a review on it.  Right now, the Octava, Audiotrak, Matrix, and Cambridge Audio all fit the bill in terms of my goals.
  1. Monoprice 4×2 Matrix HDMI switch with Analog Audio Out (this has an HDMI-only bypass for digital out) $59
  2. Octava 1×1 HDMI Audio Converter (this has an HDMI out connection for bypass and is a great solution for HDMI-enabled systems) $169
  3. Gefen HDMI to HDMI Plus Audio Converter $209
  4. Audiotrak Dr.DAC2 DX Muses $298
  5. Music Hall dac15.2 $299
  6. Matrix Mini-I DAC $355
  7. AMI Musik DDH-1 (Price to be announced but assumed to be around $450)
  8. Cambridge Audio DacMagic Plus $599
  9. Marantz NA7004 $799
  10. Dangerous Music DAC-ST (can be upgraded to 5.1 out) $949
  11. Audiolab M-DAC $950 
  12. Rega DAC (this has both toslink and S/PDIF digital outputs in addition to analog) $995
  13. Bryston BDA-1 $1,995 
  14. NAD M51 Direct Digital DAC (has HDMI passthrough only) $1,995.95
  15. Resonessence Labs Invicta $3,995
Octava HDMI audio converter

Octava HDMI Audio Converter

If you have any more DACs or DAC solutions that will fit the bill, please post a comment so that I can update the list.

I hope that this post and list is helpful to those like me who are looking for solutions like mine!
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  1. I've been making incremental updates to the list. If you have any DACs to add, please post them here so that I can keep this list current and useful for anyone who is interested in a solution like this.

  2. This is a great list- I'm going through this exact process right now to integrate the cool new Chromecast with my 3 zone receiver, thus requiring HDMI->analog conversion for zones 2 and 3. I went w/ the cheapest on your list and suggest that you note to other potential readers that the Monoprice switch/converter sounds terrible. It's distorted and tinny and compressed. In a word, unusable. I've requested an RMA, and am returning it to Monoprice and have ordered the next one on the list – the Octava. This will hopefully work better…

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