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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

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A Heads Up…..

30 Oct

This is just a mention (for those that don’t keep a weather eye on the blogs) that a planned series of Quadraphonic live recordings have started to be made available over on the SACD-to-DVDA resurected blog.

 

The Importance Of Accurate Decoding: SQ

26 Jul

Lt = Lf + (0.707 -j Lb + 0.707 Rb)

Rt = Rf + (-0.707 Lb + 0.707 j Rb)

It looks so simple, doesn’t it, and yet this frightenly complex little (encode) equation can cause nightmares when it comes to decoding it…, and i speak as one of those who have been affected!

SQ was but just one of Benjamin Bauer’s inventions, and it’s fair to say that it was the more popular of the two competing PAM systems during the 1970’s. But it’s not perfect by any means.

Unfortunately the one point that CBS used in early advertising against the Sansui QS system was also it’s (never mentioned) Achilles Heal, and it wasn’t until a couple of years ago it was finally dealt a blow in the name of depth, separation and imagery.

So, let’s look at what a correctly decoded SQ signal looks like:

Front Left’ = Front Left + 0.707 -j Rear Left + 0.707 Rear Right

Front Right’ = Front Right + -0.707 Rear Left + 0.707 j Rear Right

Rear Left’ = Rear Left* + j Front Left

Rear Right’ = Rear Right* + -j Front Right

* = as part of the decoding process the levels of the rear channels are automatically returned to their ‘pre-encoded’ level

And this is what you get when it’s not decoded correctly: (Assuming correct usage of +-90 degree phase shifting)

Front Left’ = Front Left + 0.707 -j Rear Left + 0.707 Rear Right

Front Right’ = Front Right + -0.707 Rear Left + 0.707 j Rear Right

Rear Left’ = j Front Left + 0.707 Rear Left + 0.707 j Rear Right

Rear Right’ = -j Front Right + j-0.707 Rear Left + 0.707 Rear Right

This is just one of many variations of what has been done, sometimes there’s only one of the phase shifts used, and there’s even been times when there’s been no phase shifting done at all!

The situation above is that the rear channel information is being output from both the fronts and rears, and at the same levels. This causes a somewhat foggy phase mess where sounds may come from the approximate direction it is supposed to come from, but can move from the rears to the fronts, or visa-versa, with the movement of the head of just leaning to the front or back.

I’m sure, buy now, you’ve noticed the elephant in the room. The major drawback to SQ is that the front channels receive no processing at all, so what you hear is the entire four channel encoded stereo information. And it’s this that limits SQ’s ability to produce a clean image with good levels of low level detail and separation.

Every single decoder from the basic 10/40 type to the king of SQ decoders, The Tate, suffer in this respect. There was nothing that could be done about it, so it was NEVER discussed. Even in our technically enlightened times there’s no way of dealing with the problem using hardware.

But, as previously mentioned, a few years ago i stumbled upon a way of dealing with this issue, and although the process is only working at 50% of its capacity, the difference it makes is quite remarkable, allowing SQ decodes to be heard without the limitations that have been accepted as the norm since it was released 47 years ago.

Oh, and the process is called “Phoenix”, and has come into use with all of the other matrix decoding process’s, with differing levels of improvement, to boot.

 

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.

Just what is RM?

13 Jul

One of the more confusing things about the Quadraphonic period in Japan is what is RM and what relationship do the three matrix systems QM, QS and QX have with it.

I’ve searched for as much information regarding this subject as is possible, and all i have come up with is that much information is missing, probably locked away in various vaults that will most likely never see the light of day.

What i have pieced together is:

The format we call RM is in fact a set of specifications laid down by the Japanese authorities as a guide line for any company wishing to produce their own matrix system. In the end three companies took on the work, Toshiba (QM), Sansui (QS) and Nippon-Columbia (QX), all being ‘based’ on the RM standard, but all three different, and therefore incompatible, if the idea of an accurate decode is wanted.

Different labels chose to go with their choice of system and albums were initially released in all three formats. There was also equipment for all three systems available in the market place, but quite quickly Sansui’s QS system won the day and became ‘the’ Japanese home grown matrix system.

What what of RM? There were releases on a few labels that actually state that the RM matrix system was used. Did the Japanese actually create RM encoders before QM, QS or QX came about? That would make sense because to demonstrate the idea of the matrix system that  had been decided upon as the basis of any future quad matrix system, there would need to be demonstration material.

It could be that some labels, eager to get in early, used the RM system for some early releases, before the format war began.

Fast forwarding to today, all of that leaves us in a little quandry, how to get the best out of the Four different matrices used in the early 1970’s. Unfortunately it has been almost impossible to find out exactly how QM, QX and RM worked, so we are left having to decode these albums using QS, which isn’t optimal or ideal if your after as accurate decode as possible.

But, until the day some information becomes available, it’s the bet we can do.

The reason i’m writing this is because of the next release, which i’ve finally given in after a few years holding back, has been decoded using QS. There are a number of Japanese releases that mention that it’s a 4-Channel LP, but say absolutely nothing else, which i’m suspecting could possibly be RM encoded. It’s interesting to note those albums were single inventory and any mention of them being quad was quickly dropped.

Seeing as the label who released this particular album was A&M, who went on to start using QS, you’d have thought that if RM and QS were compatible they’d have made a point by continuing labelling them, instead of removing any mention of them being quad.

I realise this is just my view on a rather complex issue, and there are other views, but all we are left with is an issue with very little to go on.

Ralf Nowy – Lucifer’s Dream – Updated

11 Jun

Have just made available a corrected version of the “Ralf Nowy – Lucifer’s Dream” release, which corrects an issue with the stereo track.

Web Radio Programme Broadcasting Quadraphonic Material

13 Aug

This may be old news to some of you, but there is an interesting radio broadcast on the internet that broadcasts quadraphonic material. The station broadcasts in mp3, so i’m not sure how well it decodes, i’m recording it as i type as a test, but it may be an interesting project for those so equipped

The radio station is here: http://radiomaxmusic.com

The program is broadcast twice on Sundays, at 9am and 9pm USA ET and is called “VINYL RESTING PLACE WITH WILLIE B

He broadcasts mainly in QS, which allows him to use 4-channel tapes he has, just listened to some unreleased quad mixes of ‘Paul Revere and The Raiders”

Hopefully you’ll be able to catch the repeat at 9pm USA ET.

Would be nice to hear of your views etc  🙂

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