JediJoker
2K Club - QQ Super Nova
I want to be able to listen to vintage quadraphonic sources with all the benefits of my Marantz SR6014's room correction. Obviously, the 7.1 analog inputs are pass-through only, as the receiver would cost far more if implementing eight channels of ADC. It would be possible to use the MiniDSP DDRC-88A with the -88BM plugin added as a middleman, but that would mean setting up a whole new room correction profile on a separate piece of hardware rather than using what my receiver already has built-in. Plus, I'd be paying for double the channels of ADC that I actually need, and eight superfluous channels of DAC.
The device I have in mind would have at least two sets of 4 x RCA analog inputs (FL/FR/SL/SR) for quadraphonic line sources, internally switched in the analog domain so as to need only four channels of ADC, and a single HDMI output sending the four channels within a 7.1 LPCM stream (correctly assigned). It would only need to output a full screen black (or, heck, a static or moving logo) video signal accompanying the audio to meet HDMI specifications. Considering the less than stellar signal-to-noise ratio and frequency response found on consumer quadraphonic tapes and vinyl, basic 16-bit/48kHz ADCs would suffice. The anti-aliasing filters could start as low as 16kHz, allowing for a gentle slope to -96dB at 24kHz for zero aliasing and minimal phase shift artifacts in the audible band. Up the sampling frequency to 96kHz and one could achieve even better phase coherence.
Seems like a relatively simple device, no? I am not technically apt or electrically knowledgable enough to actually implement my ideas, but intuitively, they seem trivial. I think the most complicated circuits would be the filters and HDMI components. I know I'm not the only one who would find such a device useful, especially as fewer and fewer receivers include multichannel analog inputs of any kind.
The device I have in mind would have at least two sets of 4 x RCA analog inputs (FL/FR/SL/SR) for quadraphonic line sources, internally switched in the analog domain so as to need only four channels of ADC, and a single HDMI output sending the four channels within a 7.1 LPCM stream (correctly assigned). It would only need to output a full screen black (or, heck, a static or moving logo) video signal accompanying the audio to meet HDMI specifications. Considering the less than stellar signal-to-noise ratio and frequency response found on consumer quadraphonic tapes and vinyl, basic 16-bit/48kHz ADCs would suffice. The anti-aliasing filters could start as low as 16kHz, allowing for a gentle slope to -96dB at 24kHz for zero aliasing and minimal phase shift artifacts in the audible band. Up the sampling frequency to 96kHz and one could achieve even better phase coherence.
Seems like a relatively simple device, no? I am not technically apt or electrically knowledgable enough to actually implement my ideas, but intuitively, they seem trivial. I think the most complicated circuits would be the filters and HDMI components. I know I'm not the only one who would find such a device useful, especially as fewer and fewer receivers include multichannel analog inputs of any kind.