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Hi Leif, well you’re right of course, when transmitting, MPX not needed in this instance. I am experimenting using BPP ASIO with my software defined radio (SDR) that uses the FA-66 for transmitting and receiving. When in receive mode, the bandwidth of the spectrum captured is dictated by the sample rate of the FA-66. Larger is usually better in that the spectrum received is displayed on the PC being used by the SDR. For reasons unknown, the FA-66 disables the optical in/out ports using the 192kHz rate. Which leaves the remaining choices of the 48k and 96k rates.
Purely a "nice to have" for compatibility reasons but as you indicated there is no other advantage. Thanks for Replying, keep up the great work!
jay
Hey Leif,
Have you tested one a Creative SoundBlaster Audigy 2 ZS on a scope by any chance? This seems to be the cheapest 192mhz card on the market???
Hi Lee!
Yes I have — this was actually the first card I ever used for MPX output, 4 years ago!
It’s good tilt-wise but the spectrum is not very clean. Also, it’s not actually on the market — afaik they don’t make it anymore. The current generation creative cards all stop at 96k.
Jay, I understand. I recommend using a separate sound card for the SDR instead. 🙂
Best,
///LeifAnyone tried one of these yet – Audiotrak Prodigy HD2
It has very impressive output specs..
http://www.audiotrak.net/products/prodigyhd2/
"The HD2 incorporates many audiophile grade features: a low jitter oscillator, short signal paths, specialised power caps, and a fully differential output stage."
# high quality AKM AK4396 120dB(a) S/N ratio DA converter for extremly high quality 2 channel audio playback via RCA output connectors (5Hz – 40kHz frequency response)
# triple OpAmp design for audio output with three high quality Fairchild NE5532 OpAmps on separate sockets (can be exchanged for tuning & customization)
# fully differential output stageOK so it doesn’t have Digital Input so it would probably be best used for MPX output to a transmiter…
Very cheap on ebay etc, under US$100
This looks like a good card (but you cant tell for sure until you get it onto a scope), I certainly like the optical output which supports 192Khz which will be excelllent for out forthcoming experiments with DMPX.
The main thing that concerns me is the quoted frequency response figures for the analog outputs which is 5hz to 40Khz. This may well give low or even zero tilt (unlikely though) but 40Khz frequency responce is way short of what we need for a linear mpx response, we need ideally 60Khz of analog frequency response.
Even if these figures are a conservative estimate, there may very likely be a roll off before the required 60Khz is reached. If it falls a little short, this can be adjusted for but if it does start to roll off at 40Khz, that’s a big problem.If I decide to get one of these for my DMPX trials, I will thoroughly test the analog too and report back.
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