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Continuing With A Couple Of Classicals

15 Jun

Here are two previously unreleased (blog-wise) classical albums, being somewhat different in style and mix. The “Stokowski” is a QSd2 decode, whilst the “Georg Muffat” is an SQd2 decode

 

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More What’s,Whys And Wherefores of Decoding, And Three QS “Test” Releases

9 May

Since closing both blogs last year, I’ve spent some time doing some improvement work on all of the matrix decode process’s, one ending up quite a major upgrade and the others a small, but essential, alteration.

At around the time of the blogs closure, Owen made an off-the-cuff remark that it was a shame i hadn’t spent as much time on QS as I had done on SQ. He was correct, of course, my personal dislike of QS, and my preference for SQ, showed in my work and the number of releases (especially in the early days). So began my final work on the decoding process’s for the DY/EV-4, QS & SQ matrices.

The upgrade to the QS process (QS2d) is quite marked, ending up nothing like earlier, or other, versions. I “believe” that finally a QS decode can now hold it’s head up against that of an SQ (SQd2) decode in terms of separation, image stability and low level detail.

Those eagle-eyed amongst you may have noticed the upgrade to the SQ decoding process. The upgrade is solely devoted to solving a previously unknown error in the decoding process in decoders based on the official CBS/Sony specs.

I will admit that there is the possibility that many may not notice much of a difference between an SQd1 and SQd2 decode of the same album, it’s partly down to whether you listen, or you . But the improvement is there, none the less, solidifying the overall image like never before.

As mentioned, this upgrade corrects an error in the original decoding mathematics as developed by Ben Bauer, and is inherent in all “official” decoders (be it discreet or based on the Motorola chip set) that introduces a phase error of around 25 degrees on the rear right during the decode process.

If the mathematics of the whole decoding process are checked, all appears correct, but as any engineer who has been in the electronics field for long enough will attest, there are times that unpredictable things happen when it comes to the practicalities of a working model.

My work, and conclusions, were checked not only by using my decoding processes but by the decoded output from a Tate decoder, which showed exactly the same error.

The answer to the question “Why didn’t they see the issue at the time” is simply that they just didn’t have the tools we have today. Many of the tools we take for granted now could probably never even be imagined of back then.

At last SQ is capable of delivering the kind of performance that Ben Baur knew it was capable of, delivering a phase accurate representation of the original master.

Having been able to overcome this long standing issue, I believe that the best, and only worth-while (to date), SQ decoder (The Tate) can be improved by modifying it so it can comply with the above (new) standard, which would not only deliver a better decode, but the logic section should be able to operate more efficiently, or as it was meant too, producing better image stability with less pumping artefacts, etc.

DY/EV-4 decoding has also been tweaked, although it’s impossible to make major in-roads when it come to decoding these two pre-phase matrices, simply because they are just too darned basic.

As a demonstration of QSd2 I’m making available the following three albums, which luckily have two different types of mixes. These are the “Four To The Wall” type that gives an artificial presentation much loved by the majority of quadraholics, and the “Live In The Studio” mix, more often than not, used by jazz labels which attempts to create how things were in the studio when the album was recorded live.

QSd2

Due to an issue with DTS and Dolby Digital audio, this is now reissued

The Importance Of Accurate Decoding: QS

26 Jul

As a further extension of my look into the matrix systems, i thought it might be helpful, for those not aware of their inner workings, to show the importance of accurately decoding these AM sources, and what happens when it’s not done correctly.

To reduce the mathematical load on you all,  i’ll not go too deeply into those inner workings, but i must state that i will be using the terms Fc (Front Centre) and Rc (Rear Centre) which are not part of any quadraphonic system but will be used to (hopefully) help show how this area is affected in the encode/decode process.

QS

The most popular, and successful, of the three Japanese matrix systems that were based on the RM standard, is one of the simpler PAM systems: (j = +-90 degrees)

Lt = (0.924 Lf + 0.383 Rf) + (0.924 Lb j + 0.383 Rb j)

Rt = (0.383 Lf + 0.924 Rf) + (0.383 Lb -j + 0.924 Rb -j)

Above is the QS encode equation, from which the encoder used to create the stereo compatible signal is based on. The way this system works means that each of the stereo channels contains an amount of all four channels.

The Front Channels do not have any adjustment to their phase, only having the Left and Right ‘blended’ to a predetermined amount (which is actually THE MATRIX). The effect on the Fc is that it remains in phase with the front left and right channels.

The Rear channels are similarly blended, but only after having ther phase shifted by +-90 degrees. It is this phase shifting that finally allowed four channels to be encoded and decoded without the severe limitations that crippled the  previous two AM systems. The effect on the Rc is that, because rear left is shifted 90 degrees and rear right is shifted -90 degrees, the “imaginary” point Rc is actually 180 degrees out of phase with Fc.

The “blending” is not just figures plucked out of thin air, but are the result of a great deal of work by the systems designers and is the heart of the whole matrix. The phase shifting is purely a means to an end, nothing more.

There’s one small point that needs to be mentioned here, and that is mono compatibility. I’ve read a few times now that SQ isn’t mono compatible but QS is. That is pure poppycock!

Any matrix system that uses +-90 on the rears, as both QS and SQ do, can never be mono compatible. Why? Quite simply, when the two channels are summed together to create a mono signal, any information that has been panned to be in, or around, the Rc area is cancelled out. It’s basic maths and 100% pure fact.

So, hopefully that gives something of a slight overview of what is actually on each of the channels when playing a QS record, but what about decoding?

This is where it can get very mathy, i’m afraid, so what we’ll look at is what we get out of a basic decode and a none accurate decode. The non-accurate version is just an idea because there are so many ways to do it wrong, but only one way to do it right.

So, if a particular decoder is fitted with some form of Separation Enhancement circuitry then it needs to be fed with four accurately decoded signals. What is to be expected from an accurate QS decoder is:

Front Left’ = Front L + j Rear L + j Rear R

Front Right’ = Front R = -j Rear R + -j Rear L

Rear Left’ = Rear L + -j Front L + -j Front R

Rear Right’ = Rear R + j Front R + j Front L

OK, how many thought that all you got was the main (wanted) channel? Afraid not. This is what you get when the decoder is mathematically correct, which is rather like the dodo, not seen in these times.

So, lets look at a perfectly normal output from a decoder that doesn’t follow the QS rulebook:

Front Left’ = Front L + <>Front R + j <>Rear Left + j <>Rear R

Front Right’ = Front R + <>Front L + -j <>Rear R + -j <>Rear L

Rear Left’ = Rear L + <>Rear R + -j <>Front L + -j <>Front R

Rear Right’ = Rear R + <>Rear L + j <>Front R + j <>Front L

The above assumes the correct usage of +-90 phase shifting. If that is not correct then the picture gets very messy. The use of <> indicates a variable level, which is hard to work out due to the non-correct method of decoding. Also not shown is the effect (even on the Front channels) of phase shifting caused by the mutual and un-mutual phase addition/cancellation.

Feed the above into some form of Separation Expansion circuitry and you get poorly focused imagery that wanders with movement of the head, amongst other things. Unfortunately, this is quite common.

I understand that most would just shrug their shoulders and say that it doesn’t mean anything to them, so you will be able to actually hear the difference later.

Burt Bacharach – Live In Japan

13 Jul

As stated in the previous posting, i’m releasing this album as a QS decode, even though i suspect it was encoded in RM, but as little to nothing is known of the encode parameters of it, QS is the only way of decoding i have at hand.

Ponta Murakami – Introducing “Ponta” Murakami

12 Jul

A quick return to QS for the first of two releases. This album may not be known to many, it’s not listed on Mark Anderson’s Quad discography, but the band’s sound is slightly reminiscent of ‘Brand X’ and has a nice, open, and discreet mix.

Synergy – Electronic Realizations For Rock Orchestra

6 Jul

Decoded using a 24/96 High Definition copy of the original master tape.

There is no QS encoded stereo track on this release, but it is available here

This is the last of the QS encoded albums

Experience Ovation 4 Channel Quadraphonic Sound

29 Jun

Link

 

 

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