I thought this would be of interest to some ….
BBQ..
BBQ..
Play QS sound source with handmade QS/SQ three Band Full Logic Quadraphonic Decoder
- Thread starter bigbillquad
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That is cool BBQ. National kid is a member here but doesn't seem to post very often anymore.
The flashing array lights are mesmerizing...
Perhaps it's because he has been very busy building this device!
Perhaps it's because he has been very busy building this device!
Reading the text that goes to the video, he says display on left shows SQ decoding & the right one shows QS decoding. That means for what ever 2 ch source it's plugged into it is simultaneously decoding SQ & QS. I don't think that has ever been done before.
Fully analog!!
Soundfield
1K Club - QQ Shooting Star
He's been making these hugely complicated decoders for years. They are all based on large numbers of op amps but as I find his circuit diagrams very difficult to follow I've never really been able to fathom how his various logic and steering mechanisms work. I don't know if he's ever demonstrated any of them to anyone so I've no idea how they actually sound - would love to hear some of them in action though!
A shootout would be great!
I think Onkyo was supposed to have a receiver that detected "which quad system " was playing . This was a mid 70's device , touted as one could stack any type quad lp and play them through as the unit would detect what quad was what. (or so it would seem).
My memory is there was a reciever that would automatically switch over to CD-4 when appropriate and otherwise play whatever matrix decode was selected.
Soundfield
1K Club - QQ Shooting Star
Yes, I think there were a couple of those - I think the logic was that you could stack your stereo and CD-4 LPs on an autochanger (shock, horror!) and the system who switch to quad playback whenever the 30KHz carrier was detected. It would have taken some very, very sophisticated analysis to determined what system a matrix record had been encoded with however!!
National Kid's decoder above seems to be decoding the input in both SQ and SQ simultaneously in parallel decoding chains- what on earth the point of that would be I cannot fathom.
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I think the point of National Kid's setup is to visually determine which method a recording is encoded in without having to A-B test or guess by ear. Some early records didn't have the encoder marked on the disc or jacket, others were possibly incorrectly marked (think Japanese DSOTM) and in Japan there were other proprietary formats that claimed to be conforming to RM but maybe weren't. If one of his models like that was offered to me, I'd be a fool to say no. Besides, the lights are cool. Bling times 4?
Soundfield
1K Club - QQ Shooting Star
Maybe, but I'm not sure how you could come to any conclusion - If you look at the display in the YouTube clip can you tell whether the source is QS or SQ? - I certainly can't (and he's already told us its QS)!!
What is rather strange is that the two displays don't lend themselves to comparision anyway since they are different (he says SQ on the left and QS on the right) - the SQ display will always look 'better' as its got more pretty LEDs!
not sure why that would be or what purpose they really serve (you are right though - they look cool!)
national-kid
Active Member
Thank you for your interest. This decoder performs full logic decoding of QS and SQ simultaneously. The display on the panel shows the sound source direction detection result in those (direction emphasis) full logic processing.
Next is the matter of discrimination between stereo, QS and SQ.
I determine whether the sound source is stereo, QS or SQ based on the panel display, Lissajous waveform, and playback sound.
Sound sources that have a small number of instruments and do not sound at the same time can be identified by the panel display alone. However, if the rear channel is a sound source with only reverberation, it is very difficult to determine whether it is stereo, QS or SQ.
Next is the matter of discrimination between stereo, QS and SQ.
I determine whether the sound source is stereo, QS or SQ based on the panel display, Lissajous waveform, and playback sound.
Sound sources that have a small number of instruments and do not sound at the same time can be identified by the panel display alone. However, if the rear channel is a sound source with only reverberation, it is very difficult to determine whether it is stereo, QS or SQ.
Soundfield
1K Club - QQ Shooting Star
Nice to hear from you again on this forum.
Can I ask why the display on the right (the QS display) does not have LEDs to show CF or CB directions but the SQ display does?
national-kid
Active Member
In the case of SQ, when there is a sound source in the front center or rear center, the direction cannot be determined only by the front left / right volume ratio and rear left / right volume ratio. Therefore, the direction is discriminated taking into account the volume ratio of the front and rear.
Incidentally, in the case of QS, when there is a sound source at the dead center (directly above), the direction cannot be determined only by the volume ratio of the front left and rear right, and the volume ratio of the front right and rear left. However, there is no problem because the dead center (directly above) does not require the direction emphasis logic to work.
Soundfield
1K Club - QQ Shooting Star
Really?
national-kid
Active Member
Yes, that's right.
For example, when there is a sound source in the front center, the left front volume is the same as the right front volume.
At that time, the volume ratio is 1 regardless of the volume. （The volume ratio is 1 with or without sound）
So, even if there is a sound source ahead, it cannot be detected.
Audionics Space and Image Composer was a similar process.
http://www.pacair.com/audionics/Composer/Schematics/index.htm
Soundfield
1K Club - QQ Shooting Star
For in phase signals, surely the fact that the "volume ratio" is 1 tells you that the source is central?
national-kid
Active Member
Please forgive duplicate posts.
If the left and right volumes are the same, the volume ratio is 1 even when the volume is very low. Therefore, it cannot be determined that there is a sound source in the front center. Can only know if there is a sound on the right or a sound on the left.
To compensate for the lack of information, the volume ratio of the sum of the left and right signals and the difference between the left and right signals is obtained. Based on this, it is determined whether the sound is forward or backward.
By the way, in the circuit, A / B calculation is log (A) -log (B).
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