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8th November 2016
#241
Deleted 691ca21
Guest
Anyone want to attempt a plugin version?
9th November 2016
#242

Quote:
Originally Posted by Giro1991
In your previous post, your first two paragraphs - are they describing specifically the first image alone?

I have been thinking the algebra behind the Stereo Pan Pot and why it works within both S&D circuits.

1.At the output of the 1st S&D transformers:
M = A + B
S = A - B

2.The M input of the 2nd S&D transformer should be connected directly with the M output of the 1st S&D circuit.

3.However both, M and S busses are connected in parallel to the S input of the 2nd S&D transformers through differential attenuators and a polarity switch or an allpass filter shifting phase 180°.

4.The signal at the 2nd S&D input would be:
4.1.Stereo pan-pot pointing North:
+M
+S

4.2.Stereo pan-pot pointing South:
+M
-S (= S signal with phase shifted 180°).

4.3.Stereo pan-pot pointing West:
+M
+M

4.4.Stereo pan-pot pointing East:
+M
-M (= M signal with phase shifted 180°).

5.Thus, the signal at the 2nd S&D output would be:
5.1.North:
(M + S) * (1/2) = A
(M - S) * (1/2) = B

5.2.South:
[M + (-S)] * (1/2) = B
[M - (-S)] * (1/2) = A

5.3.West:
(M + M) * (1/2) = M
(M - M) * (1/2) = 0

5.4.East:
[M + (-M)] * (1/2) = 0
[M - (-M)] * (1/2) = M

Last edited by henry_the_horse; 9th November 2016 at 05:09 AM..
9th November 2016
#243
Gear Nut

Quote:
Originally Posted by henry_the_horse
In your initial explanation you used letters A, B, also connoted in the first image. This was confusing because the first image doen't match with your explanation, just a bad wording.... you've now said you were using A,B terms in general, not specifically figure. 1.

However, the dashed-line in the first image, you label it a differential attenuator. It isn't because the symbol in that image is not the same as the symbol of the real 'differential attenuator', clearly labelled in the official second diagram.
There is a slight difference - they aren't the same. Thus a differential attentuator may well be present but isn't shown.
What is definitely shown is a level adjustment of some sort, preceding the S+D network.

The second image is more clear here on the individual level adjustments in the path, (spreader, fader) as they are labelled clearly.
The first image is more vague, it may be a pan-pot, not necessarily a differential one.

The first image is very misleading as well, i.e. mono into a shuffler.
9th November 2016
#244
Motown legend

Verified Member
Quote:
Originally Posted by Deleted 691ca21
Anyone want to attempt a plugin version?
9th November 2016
#245
Gear Nut

Quote:
Originally Posted by Deleted 691ca21
Anyone want to attempt a plugin version?
This is gearslutz , for gear. (I hope)

There, said it.

Quote:
Originally Posted by Bob Olhsson
The s1? its limited to 90 degrees arc, not a full 360 circle like the Telefunken no idea how it works but the equation I stated above, i'm confident is the one required;

Quote:
Lout = Lcosθ + Rsinθ
Rout = Rcosθ – Lsinθ
where -45° = θ = 45° describes the degree of 'rotation' of the stereo sound image. For θ = 0°, we
have normal stereo, for θ greater than zero, the stereo image is rotated to the left, and for θ less than 0, the
stereo image is rotated to the right, all without any alteration of any sound level whatsoever.
Note the underline.
If this can be extended to 360 operation, not sure. Seeing as the telefunkens have S&D networks inside, perhaps phase reversal is required at some point as per henry's post.

Michael Gerzon too did a paper with methods henry discussed. i.e. cascaded S&D circuits.

I'll see if I can upload that.
9th November 2016
#246
Gear Nut

Perhaps I'm glorifying the 360 dial too much, the effect is probably not far off an automated flanger. But the prospect of hearing what it sounds like is pulling me in... The schematic is there, just need to build one . My lifelong goal? perhaps.

Edit nvm, i've since realised this is a different sort of phasing
9th November 2016
#247
Gear Maniac

Verified Member
Quote:
Originally Posted by Giro1991
Perhaps I'm glorifying the 360 dial too much, the effect is probably not far off an automated flanger. But the prospect of hearing what it sounds like is pulling me in... The schematic is there, just need to build one . My lifelong goal? perhaps.
Automated flanger? What would that have to do with the 360 pan pot?
9th November 2016
#248

Quote:
Originally Posted by lukpac
I think I may have asked this before, but I'm not sure if it was addressed. For *stereo* mixing, would there have been a way to route 1,2,7,8 to both channels (i.e., center)? Recording The Beatles suggests that stereo mixes were for a time made with those channels (prior to the use of 3-6 for mixing), resulting in a straight L-C-R image:

track 1 (channel 1): left
track 2 (channel 2): right
track 3 (channel 7): center
track 4 (channel 8): center

But it doesn't seem like there would have been any way in the desks to accomplish this, specifically, sending 7&8 to both channels. Perhaps there was some sort of external mixing/bridging involved? It's not clear to me how the stereo mixes could have been monitored in that case however.

Or is it likely the 4-track outputs were *always* padded down and sent through 3-6 for stereo mixing?
M.ch.1 = L
M.ch.2 = R
M.ch.7 = L -> S&D -> Spreader -> S&D -> 11.25° L
M.ch.8 = R -> S&D -> Spreader -> S&D -> 11.25° R

After the first S&D signal is
M
S

Spreader works only on S buss.
Maximum (i.e. -12dB) attenuation on the S buss = 1/4 * S

45°/4 = 11.25°
9th November 2016
#249

Quote:
Originally Posted by Giro1991
I'm unsure if the matrix is L,R,L,R in that order around you, or in the same arrangement, oops in all four... or a combination of the two as per dolby.
I suspect the oops, which means... no mono. But so what? Just add a 'pure mono' speaker in the front like Tri-field.

Fantasound as Bob kindly mentions IIRC is simple L, L+R, R. with appropriate pan laws.

Testing any of this with the 360 (dial?) on the REDD will be problematic of course, you need a decoder to test, ahem, the surround function....something best left to a mathematician to design...

< 360 > sound with four points is a possibility (trig has four 'quadrants' all I know), two less so keeping in mind the earlier quote;

Many surround decoders (and panners, i.e. B-pan) exist today but if the REDD did it way back when, then that's something.
The matrix of the REDD.51 Stereo Pan-Pot in the S&D circuit is:
North: A B
West: M Zero
South: B A
East: M Zero
It is a stereo pan pot , not 360°. The control does a 360° turn but the angle is unrelated to the position of the stereo signal since the REDD desk it is not quadrophonic but stereophonic.

The angle between channels is:
90°: when pan-pot is set to 0° (N)
0°: when pan-pot is set to 90°L (W)
90°: when pan-pot is set to 180° (S)
0°: when pan-pot is set to 90°R (E).

The Rotation control in the S1 plugin is a stereo panner, keeping a constant angle between L and R signals. Hence, when set to -45 the R signal is 45° to the L and the L signal is out-of-phase. The Vanderlyn/Clark/Dutton Stereosonic Stereo Pan-Pot does not introduce phase issues. Anytime the angle is wider than 90° there will be out-of-phase cancellation between L and R channels. That is why it is dangerous to set the Spreader to positive values.
10th November 2016
#250

Quote:
Originally Posted by Giro1991
In your initial explanation you used letters A, B, also connoted in the first image. This was confusing because the first image doen't match with your explanation, just a bad wording.... you've now said you were using A,B terms in general, not specifically figure. 1.
Yes, A and B are used for what would be L and R and matches the 1st image.

This symbol means variable attenuator, that is, a fader.
. The diagonal dash line means reversed ganged (= differential attenuator), meaning it is a pan-pot.

After the 1st S&D transformers the busses are:
S = (A + B)/sqrt(2)
D = (A - B)/sqrt(2)
The first image misses the 1/sqrt(2) gain attenuation (= -3dB) of the 1st S&D transformers.
The shuffler is pictured in the D buss only. It does, however lack the phase compensating network on the S buss, and the Mic.faders within the S&D circuit, which are present on the 2nd image.

In this 2nd image, S buss is on the left and D buss on the right. The Mic. faders are pictured after the shuffler, while in a REDD.37 the Mic. faders are after the 1st S&D transformers but before the Spreader and Shuffler.

The 1st image describes the REDD.C37 Shuffler while the 2nd image comes from the Dutton et al. paper, which was just the EMI research on stereosonic circuits and not actually the implementation on the REDD.37 desk. The mono tape machine is not a mistake, since its signal is split between A and B parallel busses, hence becoming stereo when not panned centre.

Last edited by henry_the_horse; 10th November 2016 at 07:29 AM..
10th November 2016
#251
Gear Maniac

Verified Member
Quote:
Originally Posted by henry_the_horse
M.ch.1 = L
M.ch.2 = R
M.ch.7 = L -> S&D -> Spreader -> S&D -> 11.25° L
M.ch.8 = R -> S&D -> Spreader -> S&D -> 11.25° R

After the first S&D signal is
M
S

Spreader works only on S buss.
Maximum (i.e. -12dB) attenuation on the S buss = 1/4 * S

45°/4 = 11.25°
So you're saying they *couldn't* be mixed dead center, correct?
11th November 2016
#252

We had this same conversation 5 years ago.

Yes, the REDD.C37 spreader does not narrow down to mono, just -12dB less on the Difference channel, hence 1/4 gain attenuation.
20 * Log10(1/ 4) = -12 dB
For an original angle of 90° between a stereo pair, the spreader would narrow down to 22.5° between stereo pairs, or 11.25° each channel from the centre. You can use the PAZ Position plugin to check where the Beatles early stereo mixes have the vocals panned. This amount of attenuation was carried over to the TG12345 Mk.I spreader, which can be seen modelled by Waves here:
http://www.waves.com/1lib/pdf/plugins/tg12345.pdf
The stereo image could have been further narrowed due to stereo recording head track cross-talk on the BTR/3 or by the cutting technician when transferring to disc.

Last edited by henry_the_horse; 11th November 2016 at 04:28 AM..
18th December 2016
#253
Gear Nut

See next
9th January 2017
#254
Gear Nut

Hi henry;
Quote:
Originally Posted by henry_the_horse
The 1st image describes the REDD.C37 Shuffler
Are you sure? Because I've since found the origin of the first image to be a study published in a Wireless World article from 1968 and REDD isn't mentioned.

Regardless, the subject of that article is 'inter channel level differences'. This helps explain why a dual mono (not "stereo", tut tut) signal fed to S&D after a pan pot may prove useful after all.

Consider the following;
A mono signal split into two, without level differences in the case if pan pot were to be inactive (at 12oclock), would not be subject to the shuffler as no difference exists because the signals are identical.

If reverse ganger fader is adjusted at all, level differences exist and the shuffler becomes active, BUT in a frequency selective manner in the form of a shelf treble cut in the differential.

Can you (or anyone) confirm that 'reverse ganged fader' is indeed nothing more than a panpot one finds on most analog mixers today?
I realize it can either be linear or constant power, here its probably constant power, cos/sin

Henry describes the REDD.51 below as;
Quote:
Originally Posted by henry_the_horse
The matrix of the REDD.51 Stereo Pan-Pot in the S&D circuit is:
North: A B
West: M Zero
South: B A
East: M Zero
[See #242 for the maths]
Is this the same as the article?

Because outwith width control alongside S&D, there appear to be three other functions mentioned in this thread that are panning related;
• Mono-in reverse ganged pan pot augmented with S&D as per Wireless World level difference article, (where role of phase appears irrelevant)
• The network henry described in above quote, where role of phase does appear to be relevant
• The Telefunken stereo-in pan pot designed for use with stereo pair techniques as seen in post #253 where phase is most definitely relevant

9th January 2017
#255

Quote:
Originally Posted by Giro1991
Hi henry;

Are you sure? Because I've since found the origin of the first image to be a study published in a Wireless World article from 1968 and REDD isn't mentioned.
The flow diagrams come from Harwood's article the description matching the REDD.C37 circuit (i.e. Spreader/Shuffler/Stereo Pan-Pot). Although there is no mention of the REDD division, references number 4 and 5, listed at the end of the article, are research works written or co-written by head of the REDD division, Dutton, Ph.D. Particularly, reference number 4 is the article about the REDD.C37 circuit written by Vanderlyn and Dutton in 1957.

Quote:
Originally Posted by Giro1991
Can you (or anyone) confirm that 'reverse ganged fader' is indeed nothing more than a panpot one finds on most analog mixers today?
I realize it can either be linear or constant power, here its probably constant power, cos/sin
Indeed. Reverse ganged faders is the design of an ordinary pan-pot: the user turns 1 knob but the actual circuit is 2 variable resistors connected to 2 busses. This pan-pot should NOT be confused with the Stereo Pan-Pot of the S&D circuit. A mono pan-pot (i.e. REDD.Z20) was not included in the original design of the REDD desk channels 1, 2, 7 and 8 which feature the S&D circuits. In 1963 EMI Studio No. 1 REDD.37 desk was modified by fitting REDD.Z20 circuits on mic. channels 1, 2, 7 and 8 and this is the current state of this desk, which was owned by Lenny Kravitz. As pointed out by Brian Gibson previously on this same thread, the REDD.Z20 circuit is not a conventional pan-pot rather a constant impedance network.

As for the reverse ganged faders mentioned by Vanderlyn, Dutton & Clark, however this is actually a spreader circuit, it does not mean it is THE spreader featured in the REDD.C37 design. Blumlein did not require differential attenuators for his S&D design, rather an economical fader in the Diff. channel. This design would have guaranteed neither constant gain nor constant power. Since the REDD design complies with the old UK radio constant 200R impedance standard then a constant impedance network may have been used for the spreader within the S&D circuit.

Quote:
Originally Posted by Giro1991
Henry describes the REDD.51 below as;
Is this the same as the article?
It is not the same as Hardwood's 1968 article. The Stereo Pan-Pot is integral with the REDD.C37 Shuffler and Spreader circuits. It is 360 degrees in the control knob turn only, not in the function, which consists in folding one stereo channel over the other and viceversa. Full stereo-to-mono folding is achieved when turning the control to either 90 degrees clockwise or counterclockwise. When turned past 90 degrees in either direction the position of the channels is reversed and the opposite channel begins de-folding from mono until the pan-pot control points towards the operator and the channels are in full stereo again but reversed.

Best regards.

Last edited by henry_the_horse; 10th January 2017 at 12:14 AM..
21st January 2017
#256
Gear Nut

A really good artcle explaining the many areas of stereo imaging, including the stereo in-stereo out pan pot discussed previously in this thread, can be found here under Stereo Rotation: https://www.researchgate.net/publica...forms-a_review

@ Henry

You make it clear that a single fader in the Diff. channel isn't as effective as reverse ganged faders in both the S and D channels. Thanks for that.

Also that, although the 'Harwood inter-level difference shuffler (EQ) is not the same as the 'Stereo Pan Pot' (which BeeGee termed 360 in earlier posts), both do still use ganged faders. More importantly both isolated functions, can co-exist in the same path, in series with the EQ, not necessarily in the REDDs but in general.
I.e. they aren't necessarily dependent on one another, it's more that both require S&D decode/encode.

You say, the sole difference is that the ganged faders required for the Stereo Pan Pot are situated within the S&D matrix, not outwith.

Not wanting to go into specifics about differences between REDDs, more the theory.

I suspect that the Telefunken works on the same principle as the Stereo Pan Pot which I suspected all along.
The primary difference is that the Telefunken can directly accept inputs from microphones arranged in M/S method, if switched to M/S. When XY is selected I'd assume it takes appropriate measures to encode/decode S&D signals there too.
In fact I'm now confident the principle is the same in both.

Thanks for your help once more.

EDIT On a lot of post throughout this thread the term Phase was wrongly used in place of Polarity which caused my initial confusion when I tried to grasp how the hell level changes alone, could alter the relative phase of two parallel signals which would otherwise require shifts in the microsecond range between them to shift the image (which is certainly possible). This is not the function of the Stereo Pan Pot / 360 dial present in channels 1,2,6,7 of the REDD, to be clear.
27th January 2018
#257

Quote:
Originally Posted by Giro1991
@ Henry

[...]

Also that, although the 'Harwood inter-level difference shuffler (EQ) is not the same as the 'Stereo Pan Pot' (which BeeGee termed 360 in earlier posts), both do still use ganged faders. More importantly both isolated functions, can co-exist in the same path, in series with the EQ, not necessarily in the REDDs but in general.
I.e. they aren't necessarily dependent on one another, it's more that both require S&D decode/encode.
You say, the sole difference is that the ganged faders required for the Stereo Pan Pot are situated within the S&D matrix, not outwith.
The Stereo Pan Pot does not use reversed ganged faders. However, the Spreader uses them and is integral with the REDD Stereo Pan Pot hence situated within both M/S matrixes.

Quote:
Originally Posted by Giro1991
I suspect that the Telefunken works on the same principle as the Stereo Pan Pot which I suspected all along.
The primary difference is that the Telefunken can directly accept inputs from microphones arranged in M/S method, if switched to M/S. When XY is selected I'd assume it takes appropriate measures to encode/decode S&D signals there too.
The REDD desk does also accept inputs from a M/S microphone array. You just patch out the 1st M/S matrix while patching in the Spreader, Shuffler, Stereo Pan Pot, and 2nd M/S matrix, allowing decoding back to A/B stereo before going to the Interamps. This allows the EQ section of Mic.ch.1-2 to equalise M and S signals.

Quote:
Originally Posted by Giro1991
EDIT On a lot of post throughout this thread the term Phase was wrongly used in place of Polarity which caused my initial confusion when I tried to grasp how the hell level changes alone, could alter the relative phase of two parallel signals which would otherwise require shifts in the microsecond range between them to shift the image (which is certainly possible). This is not the function of the Stereo Pan Pot / 360 dial present in channels 1,2,6,7 of the REDD, to be clear.
Indeed. The correct term is polarity. The REDD Shuffler does use a phase correction network after the HPF due to the phase delay a filter introduces.
5th May 2019
#258
Here for the gear

As I’m not an engineer, I have done sessions as a studio hack since 1964 . I’m one of those players that never got involved in the recording process, until it was mixdown time. You didn’t have to be an engineer to know which tracks you were on, and what a fader was I played guitar or bass on any given session . Without question the bass is always the one you as a musician want up in the mix , regardless of all else . At the end of the day it’s whomever is paying the bill seems to have the final say . That’s not to say they dictate to the engineer , rather they imply this or that . Back in the 60s-70s there were heads of labels ,and A&R people that actually cared about the music, and the artist would have some say in respect to the mix. One must remember this was all analog, and there were limits of freedom and “ freedom of limits “ ( Beatles ) . One should never underestimate the value of a great demo . I did one session with Hal ,and Joe back in 67/68 ? This some of you may find interesting . Back in those days in LA ( the Wrecking Crew before they had that moniker ) session players of this caliber . Blaine,Osborne ,Kaye, Knechtel, Campbell ,Tedesco etc. did demo sessions between master sessions . If they were working with The Beach Boys or whatever / whomever , they would slide a one or two hour demo session in, usually at Sunset Sound or Gold Star. I was a staff writer for Mercury / AM as was a good friend of mine Asher Benjamin . He was a great pop writer . The way it worked was like this. You would get a monthly stipend ,and were expected to come up with x amount of songs a month . You would record the demos in your apt. on a twin track Sony or if lucky a Revox / Studer . You would take your 7.5 ips tape in whenever you wanted , if the A&R people thought you had something they would flit the bill for a proper demo session, hence all the session players in LA would get paid by the record labels . The rates of course were lower for demo sessions than master sessions . I’ve read quite a few of your articles here . I’ve NEVER heard of a 1/4 inch 30 ips master in my life . I always assumed 15 ips at best. I’ve read that 30 lost something in tonality ,as opposed to 15 being the sweet spot . Then again, I’m NOT an engineeer nor technician . I assume everyone here has read RTB ( Recording The Beatles ) . This book Ryan ,and Kehew are giving away at \$110. with shipping . I tried to get them to let me help publish the book, as I’ve been in the publishing business quite some time . Curvebender is self publishing . I’ve received a few letters from I believe Kehew . He has told me repeatedly to go piss up a rope . I told him several times , you could be millionaires off this book, they don’t care . With that said ,he told me they would be publishing a new edition that will have more details than the first . That’s hard to believe , but he said it, and I’m sure he’s right . If you have NOT got the book, BUY IT ! In closing . The Steve Hoffman Forum . If you want to genuflect , show how obsequious you can be , and be censored by their “ gorts “ by all means get involved . A bunch of wanna bees that dictate what you can say ,and sell. Some of the people on that site are great,and well informed analog record collectors , but the ones running the show are egomaniacal dictators ...
3 weeks ago
#259
Gear Nut

Word
2 weeks ago
#260
Lives for gear

Quote:
Originally Posted by ubemuzk
With that said ,he told me they would be publishing a new edition that will have more details than the first.
Goddang it, now I have to buy another copy. Those clever SOBs...
2 weeks ago
#261
Lives for gear

Quote:
Originally Posted by ubemuzk
I’ve NEVER heard of a 1/4 inch 30 ips master in my life . I always assumed 15 ips at best. I’ve read that 30 lost something in tonality ,as opposed to 15 being the sweet spot . ..
I've about 1/100th of your experience, but I'd never heard of such a thing either.

It certainly did exist of course. Its my understanding that an insignificant number of tracks were recorded and mastered at 30 IPS at the very end of the period of analog dominance. Its major significance is that anti-digital folks like to use it as an example to complain about a 20K or 22K bandwidth: "Well, analog machines running at 30 IPS could reproduce frequencies up to 30k" (or 40k or 60k depending on the writer's imagination).

Loved the rest of the post too.
2 weeks ago
#262
Lives for gear

Verified Member
Quote:
Originally Posted by ubemuzk
I’ve NEVER heard of a 1/4 inch 30 ips master in my life .
I have not only heard of them, but I have made many of them myself!

...Are you perhaps not talking about quarter-inch, but rather quarter-TRACK?
I certainly have NEVER seen any of those recorded at 30ips!
.
1 week ago
#263
Motown legend

Verified Member
The very first Ampex model 200 ran 1/4" at 15 and 30! A few people used it right into the 1970s when most switched to 1/2" two-track. The problem with 30 is that heads optimized for it don't perform well in the low-end running slower speeds.

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