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Author Topic: USB/Firewire to Digital Audio w/Analog Monitoring?  (Read 2546 times)

avpman

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USB/Firewire to Digital Audio w/Analog Monitoring?
« on: November 20, 2014, 03:21:37 pm »

Hi,

I'm at a real loss. I know a lot of the focus in this forum is on quality external DACs. But I already have a great Lexicon digital processor to handle that piece of my puzzle. I'm ditching my PC in favor of a MacMini and I need a really good (24/192) USB, or Firewire 800/400 to SPDIF(?) external "card" with a concurrent analog monitor output. Right now I'm using an M-Audio Audiophile 192 http://m-audio.com/products/view/audiophile-192#.VG49u8mTqa8 card inside an old PC. The card gives me great digital output with zero latency analog monitoring.  I need the analog monitor output to work concurrently with the digital output of the card because that signal goes to a whole house audio system which does not require a high end DAC. So to boil it down, I guess what I'm looking for is:

  • External Async USB or 800/400 firewire to digital output with analog monitor. (Async, so the external card will handle the clocking.)
  • Preferably not powered by the USB bus.
  • Highest quality digital output, minimum 24bit/192mhz sampling.
  • Digital output supporting surround-encoded AC-3 and DTS pass-through - if possible.
  • Coax or Toslink digital connection.
  • Concurrent analog L/R monitor output with as close to zero latency relative to the digital output. (I can probably use a headphone monitor output and drop the signal strength down with a resistor voltage divider.)
  • Mac compatible.
  • MIDI can be present but it will not be used.

The analog output doesn't have to be high-end because the whole house audio to which the analog is connected is only used for background sound. But the digital output must be of the highest quality possible. The "close to zero latency" analog monitoring is needed because the Lexiconn digital processor is sometimes on when the analog house audio is on and there's an echo if the latency is high. I found plenty of high end USB -> DAC units, but no USB -> SPDIF with concurrent analog output (which my current M-Audio 192 internal card provides.) I can't say price is no object, but I don't want to cheap-out either.

Any thoughts, suggestions, recommendations, or alternatives would be greatly appreciated!
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mojave

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Re: USB/Firewire to Digital Audio w/Analog Monitoring?
« Reply #1 on: November 20, 2014, 03:31:41 pm »

Cheap option:  The Tascam US-366 meets almosts all of your requirements. It is powered by the USB bus, but that doesn't present any problems in mine.

Expensive, but excellent:  Lynx Hilo

I'm not sure about AC-3 or DTS with either of these. Since you are using digital output, the Tascam will perform probably just as well as the Lynx. The main difference in price is due to the analog output.
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avpman

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Re: USB/Firewire to Digital Audio w/Analog Monitoring?
« Reply #2 on: November 20, 2014, 06:25:59 pm »

Mojave - thanks for your input and taking the time to respond. The Lynx is very nice! But like you said, expensive, $1800 used and $2700 new. I wrote Tascam Pre-Sales and asked a few questions. In their documentation & release notes they say the unit's internal clock couldn't be used with a digital input, and the clock sync would rely on the connected digital device's clock. In my case, that would be the Mac(?) If it get's taxed with other tasks it could potentially create some jitter. Tascam documentation says to set the clock to "automatic" but it's unclear which clock it would pick if the signal were coming from the Mac. There was also no mention anywhere of DTS pass-thru

There's gotta be something out there. My quest continues...
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mojave

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Re: USB/Firewire to Digital Audio w/Analog Monitoring?
« Reply #3 on: November 25, 2014, 08:32:23 am »

Mojave - thanks for your input and taking the time to respond. The Lynx is very nice! But like you said, expensive, $1800 used and $2700 new. I wrote Tascam Pre-Sales and asked a few questions. In their documentation & release notes they say the unit's internal clock couldn't be used with a digital input, and the clock sync would rely on the connected digital device's clock. In my case, that would be the Mac(?) If it get's taxed with other tasks it could potentially create some jitter. Tascam documentation says to set the clock to "automatic" but it's unclear which clock it would pick if the signal were coming from the Mac. There was also no mention anywhere of DTS pass-thru

There's gotta be something out there. My quest continues...
Digital input refers specifically to the optical or coax digital input. In this case the Tascam clock is locked to the internal Mac clock. However, with asynchronous USB the Tascam will reclock the incoming signal and there is no jitter issue.

I own the US-366, but don't really have a way to test the DTS or AC3 output. It also isn't really "pass-thru." Pass thru is when the incoming digital signal (optical or coax) has the DTS and it needs to go through the input and output of the device. In this case, it doesn't always work. In your situation you are using USB for the input and digital for the output. This is different and might work.
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