When cutting a record, which channel has inverted polarity?

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dubcutter89
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Re: When cutting a record, which channel has inverted polari

Post: # 34049Unread post dubcutter89
Fri Mar 06, 2015 11:22 am

What's wrong with mental exercise..?
And that is what it is about - to bring consistency to the playback (and hopefully cutting) side of the game. independant of pick up manufacturer etc.
At least if someone wants to...

And about printed standard: As I've said there is the defacto Neumann version, and I also looked for more "printed info from back when" and found something in the Zuma manual a lot of folks might have on their VMS CD compilation. This refers to JAES standard that I don't have here, but is consistent with previous statement.

Lukas
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Re: When cutting a record, which channel has inverted polari

Post: # 34050Unread post opcode66
Fri Mar 06, 2015 2:02 pm

dubcutter89 wrote:What's wrong with mental exercise..?
And that is what it is about - to bring consistency to the playback (and hopefully cutting) side of the game. independant of pick up manufacturer etc.
At least if someone wants to...
I did not say there was anything wrong with mental exercises. I do them all the time. What I was implying is that if a standard doesn't exist by now, it would be entirely difficult to get universal adoption or implementation of a that new standard. The industry is fragmented these days. And, who would govern the new standard and encourage or require cutters to adopt it? Lastly, how would you inform the entire community? I would say maybe 50% of professional cutters read this board. So, how is the new standard to be disseminated? Certainly not here.

Again, I ask, what good is a standard on the recording end if there is no matching standard in the playback end? That defeats the purpose. It is the equivalent of saying let's change the RIAA eq curve universally on the cutting side, and it doesn't matter if playback phono pre-amps dont have a consistent inverse RIAA.

Last point, have you ever tried inverting polarity in one or two speakers? But, as a blind test. A friend will either wire normal or invert one or two speakers. They wont tell you what they've done. You must listen to music and tones to determine which speaker is inverted, or if both are, or neither. Maybe 2 or 3 people out of 100 could get this right. Maybe 1 out of 100 would be right consistently.
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richard-ec2
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Re: When cutting a record, which channel has inverted polari

Post: # 34088Unread post richard-ec2
Tue Mar 10, 2015 9:38 am

dubcutter89 wrote:A lot has been already posted but maybe this clears some things...

1. There is NO channel inverted in records!
And I highly not recommend to try this by flipping the Drive +- leads on your Neumann cutting system unless you want to spend $$$ for cutter repair...
There is a standard in grooves which is basically: mono (mid) is lateral excursion, stereo difference (side) is vertical excursion.
If you use a Neumann it might be a reversed coil, but thats not out of phase. It is the way it should be
On a Westrex both coils are the same, but the magnetic flux is opposite.
Lateral/Vertical Cutters do it Mid/Side...
I still maintain that one channel is inverted when cutting and that the cartridge has one channel inverted in order to restore correct phase.

Here is a link to a very simple illustration of how it works. Please note how the two channels have opposite polarity. They HAVE to because otherwise you wouldn't be able to play a mono record with a stereo cartridge - the two signals would cancel each other out.

http://www.vinylrecorder.com/stereo.html

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Re: When cutting a record, which channel has inverted polari

Post: # 34089Unread post richard-ec2
Tue Mar 10, 2015 10:07 am

lucien wrote:Concerning cartridges, there is a paragraph with a few lines about polarity in Japanese here :
http://www7a.biglobe.ne.jp/~yosh/cartridge.htm
カートリッジに関する規格

カートリッジの端子は色分け又は記号で示されている(リード線の色もこれに準じる)。
赤→Rh(Rホット)→R+
白→Lh(Lホット)→L+
緑→Re(Rアース)→RG(R-)
青→Le(Lアース)→LG(L-)
ピンの出し方は様々:1979年のJISの解説文では針を下にしてピン側から見た時Rチャンネルが右、Lチャンネルが左を推奨しているがSMEタイプのシェルにつなげるとリード線が左右交差してしまう。同じメーカーでも一貫性がありません。JIS C5503(1979)ではカートリッジの極性について<針先が水平方向に駆動されたとき同相であって、しかも針先がレコードの外周方向に動いたとき、正の電圧が発生する端子をプラス(+)とする>と定め、さらに<極性はディスクリート4チャンネルステレオレコード再生用ピックアップの場合に必要であるが、一般のステレオ用ピックアップもこの規格に準ずることが望ましい>と解説しています。モノラルには言及していないことと下線部分が意味深です。多重マイクや周辺機器の接続関係で一部もしくは全部逆相になっていることは十分ありえる:絶対極性などはオーディオマニアの夢想! IECでもステレオレコードのチャンネル間の位相(channel phasing)だけ定義し絶対極性には触れていません。「溝の外壁に右チャンネル、内壁に左チャンネルを記録し、モノラル盤のように針が水平運動をする時は左右同相in-phaseになるようにする。ピックアップ側もそれに沿ったものとする」と述べられているだけです。スピーカ及びチャンネルの左右は聞く側から見ての位置です。注:1987年版IEC98では従来のchannel phasingの記述に加えて新たにchannel polarityの項目8.2.4があり『2チャンネル再生装置で針先が外側方向に動いた時、左右スピーカに音源と同様の増圧を生ずべし』とあり、JISと同内容の記述です。外側方向〈→R)に針先が動き始める時、正の電圧が生じスピーカにも正の電圧が供給され、スピーカ振動板が前に出る(圧力も正=密)、ということらしい〈下図参照)。
Hey, Lucien, that's wonderful ! That's the first positive lead we've had! (Forgive the pun.)

Here's a very bad translation but it does appear to confirm that if you shove the needle sideways towards the rim of the record, you should get a positive signal in both channels. So that means the right channel is inverted. (It also means the illustration I linked to in my previous post is back to front, assuming it's supposed to be a front view of the cartridge.)
Cartridge terminals (lead wire colors and their equivalents) shown in color or symbol.
Red → Rh (Hot R) → R +
White → Lh (L hot) → L +
Green → Re (R Earth) RG (r-)
Blue Le (L Earth) → LG (l-)
A variety of pin: connect the R channel will have preferred left right and left channel when seen from the side pins JIS 1979 commentary sentence with the needle under the SME type shell and would cross left leads. The same manufacturer is not consistent. JIS C5503 (1979) on the cartridge polar < to plus (+) and in phase when the needle was driven in the horizontal direction, and moved to the circumference of the record needle, positive voltage will occur to jack > and provided a further < polarity discrete 4-channel stereo record for playing pick up if needed , but in General for stereo pickup is equivalent to this standard is desirable > And commentary. Not to mention Mono and underlined deep meaning. Some in relation to connect multiple microphones and peripherals or likely enough that all reverse-phase: absolute polarity, audiophiles and Lee thought! Absolute polarity is not touched, IEC and defined only the phase of the channel between stereo records (channel phasing). "To make and record Groove wall, wall to left channel to right channel, Mono machines needle to horizontal motion when it comes to the left and right in-phase-phase. And also picked up along "and is only mentioned. Left and right speaker and channels are seen from the listening position. Note: in the 1987 version IEC98 in addition to the description of the traditional channel phasing and new channel polarity item 9.2.4 ": 2 channel playback device needle moved outward to the left and right speaker sound and is necessary as well as increased pressure would arise, and is describing the same as JIS, and. Outward q → R) to speaker vibration plate ago you leave, when you begin to move the needle, positive voltage is fed positive voltage to rise loudspeaker (pressure is positive = dense), that seems to be that the q as shown below).
I'm going to see if I can find those standards that the Japanese writer refers to, for final confirmation.

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dubcutter89
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Re: When cutting a record, which channel has inverted polari

Post: # 34090Unread post dubcutter89
Tue Mar 10, 2015 10:33 am

I know what you mean.
But what I wanted to say is that it is not important how a cutter/pickup internaly works (unless you want to design/build one..), what is important is how the channels are arranged into the groove on the record! There is a definition, and that's it. (btw, in 1964 NAB Standard there is no "inverted" in the whole text...)

A real mono pickup works different than a stereo one. Some cutters also work different or for example the decca ffss cartridge works in mid side...

Thinking of a black box pickup (and cutter), it is not how they transfer vibration into electricity or vice versa, it is interesting if they do it as the standard groove is specified. I thought this was the main question?

So ignoring inverted polarity, mid side, technology, cutters, or verbal mystery blabla.... Independent of all this you can just drop your needle onto a record and by analysing the output tell how it is wired. (and for example compare it with my previous statement on a 50+year old information)

To me there are no questions, but if you have some please ask.

Lukas
(who in fact doesn't care to much about this at all)
Last edited by dubcutter89 on Tue Mar 10, 2015 10:48 am, edited 1 time in total.
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Re: When cutting a record, which channel has inverted polari

Post: # 34091Unread post markrob
Tue Mar 10, 2015 10:41 am

Hi,

Interesting to see CD-4 playback referenced in the translation. I've been developing a software decoder for CD 4 recordings and I can see that if the absolute polarity of the standard L&R signal ( Lf+Lr and Rf + Rr) were reversed either at the pickup or when cutting, you would have a problem recovering the surround info as they are matrixed with the recovered signals from the FM carriers (Lf-Lr and Rf-Rr). Inverting the polarity of the FM carries would not invert the recovered information and result in decoding errors (front and rear signal would be swapped). I wonder if the advent of the CD-4 format caused this issue to be addressed via a new standard.

Mark

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Re: When cutting a record, which channel has inverted polari

Post: # 34092Unread post richard-ec2
Tue Mar 10, 2015 2:51 pm

I think the definitive answer to this question lies in the standard known as IEC 98, now renumbered IEC 60098, "Analogue audio disk records and reproducing equipment." I can't find any way of reading this online and it's extremely expensive to buy. Can anyone gain access to this standard and say what the answer is?

BTW there is also an AES standard on audio polarity and you can read an extract online but you can't read the whole thing:

http://www.aes.org/tmpFiles/aessc/20150310/aes26-2001-r2011-i.pdf

However from what I've read online it wouldn't help anyway because apparently it says an upward movement of the stylus should produce a positive signal. As anyone can demonstrate, all cartridges have one channel inverted relative to the other so that's simply impossible - you will always get a positive signal in one channel and a negative signal in the other. The only question is, which way around it should be.

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Re: When cutting a record, which channel has inverted polari

Post: # 34093Unread post markrob
Tue Mar 10, 2015 4:10 pm

Hi,

Perhaps I'm missing something here. But since L-R is the vertical component of the stereo signal cut into a groove. If you built a difference amp that produced the L-R signal (simple), then when you drop the needle its vertical motion will yield a leading edge positive voltage if captured on a scope. Left and right are defined by standard and if positive vertical motion (away from the surface of the record) is defined as L-R , then I think you would be able to verify polarity. Does this make sense?

Mark

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Re: When cutting a record, which channel has inverted polari

Post: # 34512Unread post subkontrabob
Sun Apr 12, 2015 9:03 am

Great thread!!!! :D
dubcutter89 wrote: (btw, in 1964 NAB Standard there is no "inverted" in the whole text...)
Well, strictly speaking you are right Lukas, there is no direct mention of this. The question is effectively avoided. There is no reference to the absolute polarity of the channels.
NAB '64 wrote: Stereophonic Groove Characteristics-(45°-45° system)
3.40 Planes of Modulation-It shall be standard that in a 45°-45° stereophonic disc the
groove shall have orthogonal modulation planes inclined at 45° to a radial line on the surface of
the disc and the intersection of the modulation planes shall be normal to said radial lines.
3.45 Channel Orientation--It shall be standard that the outer groove wall of the disc shall
contain the right-hand channel information and the inner wall shall contain the left-hand channel
information.
3.50 Phase-It shall be standard that the phase relationship between channels shall be such
as to result in lateral groove displacement when the stereo recording system is driven with equal
amplitude and in-phase signals
and the groove displacement shall be vertical when the stereophonic
recording system is driven by equal amplitude signals in anti-phase (180").

Channel Phasing-Stereophonic
3.65 Recording: It shall be standard that equal in-phase signals applied to the left and right
channel inputs of a stereo disc recorder result in lateral modulation
of the stereo groove. Conversely,
equal anti-phase signals produce vertical modulation.
3.70 Reproducing: It shall be standard that lateral modulation of a disc groove will produce
equal in-phase voltages
at the output of the turntable and conversely that vertical modulation will
produce equal anti-phase voltages.

Formulating the standard like this effectively forces all manufacturers to incorporate a polarity change of one of the signals somewhere in their device/system. But it specifies neither absolute polarity of the single channels, nor which of the two channels should be inverted. It is left to the cutter and playback cartridge manufacturers to decide which way they want to have it!

The people sitting on the board/attending the meetings that formulated this stuff came from different companies and organizations, and maybe they just could not form a consensus... Or maybe they didn't think it was that important after all....

It's funny that Westrex is not listed as a contributor, although they built the first commercial stereo heads... ?
NAB '64 wrote: The following organizations contributed to the formulation of these standards:
American Broadcasting Company, New York City
Audio Devices, Inc., New York City
, Collins Radio Company, Cedar Rapids, Iowa
Electronic Applications, Inc., Wilton, Conn.
Gates Radio Company, Quincy, Ill.
Gotham Audio Corporation, New York City
ITA Electronics Corporation, Lansdowne, Penna.
Music Makers, Inc., New York City
National Broadcasting Company, New York City
Pickering and Company, Plainview, L.I., New York
Radio Corporation of America, Camden, N. J.
Radio Station WWDC, Washington, D. C.
RCA Victor Record Division, Indianapolis, Ind.
Reeves Soundcraft, Danbury, Conn.
Shure Brothers, Inc., Evanston, Ill.
V-M Corporation, Benton Harbor, Mich.

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Re: When cutting a record, which channel has inverted polari

Post: # 34513Unread post subkontrabob
Sun Apr 12, 2015 9:31 am

markrob wrote:Hi,

Perhaps I'm missing something here. But since L-R is the vertical component of the stereo signal cut into a groove. If you built a difference amp that produced the L-R signal (simple), then when you drop the needle its vertical motion will yield a leading edge positive voltage if captured on a scope. Left and right are defined by standard and if positive vertical motion (away from the surface of the record) is defined as L-R , then I think you would be able to verify polarity. Does this make sense?

Mark
based on Lukas' statement
dubcutter89 wrote: In a lateral (Mono) groove the positive phase of a sinewave should move to the the edge of the record.

everything else (L,R, Dropping Cartridges) is set with this.
downwards movement on the right channel is the positive direction. To keep mono compatibility, the left channel has to be inverted, so that it gives positive voltage when there is upwards movement.

according to this logic, the needle drop should create a negative peak in the R channel, and a positive peak in the L channel.

Hypothetically, it should be possible to get the vertical signal simply by wiring a stereo cartridge straight to a balanced (=differential) preamp like this:

1: gnd L + R
2: R +
3: L +

If the L channel is inverted, the needle drop peak should be negative. If the R channel was inverted, it should be positive.

Does this make any sense?

I would try it out myself, but it seems I have lost my soldering iron :?

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Re: When cutting a record, which channel has inverted polari

Post: # 49100Unread post jesusfwrl
Wed Jan 24, 2018 4:23 pm

richard-ec2 wrote:
2. A positive-going spike is correct if it reflects a pressurisation stroke. Positive equals compression, negative equals decompression. If someone bangs a bass drum, and the skin on the drum initially moves towards you, that initially creates a pressure which should initially show as positive. The positive spike should come out in the consumer's home as a positive movement of the loudspeaker cone towards the listener - so in effect, the cone of the loudspeaker in the consumer's home moves the same in relation to the consumer as the skin of the drum would if he or she had been sitting in front of the drum kit in the studio. I realise that, in practice, life in the recording studio is much more complicated than that, but the convention nevertheless is that positive equals compression and negative equals decompression. So if you compress the needle on a stereo cartridge, you would expect to get a positive spike in both channels. The frustrating thing is that you don't, because one of the channels is inverted in order to reverse the inversion that takes place during cutting. So you can't check the polarity of your playback system unless you know which channel is inverted.
gold wrote:
If the drums are panned from the drummers perspective should the bass drum make the speaker go in?
A question of perspective:
Having spent many years behind the drums as a drummer, for me it kind of sounds too detached when I'm hearing a recording from the perspective from being on the audience side of the drumkit.
As such, several of the recordings I have engineered are presented from the perspective of the drummer.
I do not feel any particular obligation to place a microphone on the audience side of the bass drum, or worse, inside the bass drum. As such, I rarely invert the polarity of microphones at the recording stage.
I just place them where I need them. But then again, I also tend to not use any EQ on individual channels and more often than not I do not actually use a mixing desk. If multiple microphones are needed, they are connected to multiple mic-preamps all going to a summing buss. The stereo output is very often taken directly to a tape machine of verified absolute polarity, without further processing.
I guess you could call me a minimalist.
So, from the drummers perspective a bass drum hit should initially make the woofer cone move away from the listener. Under the right conditions, an inversion is quite audible to me.

There are definite standards for the absolute polarity of disk records and any other recording medium. A lot of the early standards documents were specifying the channel orientation and phasing which is essentially almost the same as specifying absolute polarity, although they did not call it "absolute polarity". The standardisation of absolute polarity using this exact term began by compilation documents by the AES, the EBU and the SMPTE, harvesting he relevant information from other standards, and presenting it in an easily understandable manner. Of these the EBU and SMPTE standards do not cover disk records. Fortunately, the AES26-2001 (r2011) does.

I have written an article you may find interesting on this particular topic which can be found on my blog:
https://agnewanalog.blogspot.com/2018/01/absolute-polarity-for-disk-records.html

There is also a currently available and fairly fresh test record containing an absolute polarity test band, so you can easily confirm your reproduction system polarity.

Funnily, it looks like the actual polarity test band was cut with a system that was inverting polarity (!!!), so my article clears up what you should be seeing when using the test record.

Unfortunately, many manufacturers of reproduction cartridges are unaware that polarity standards exist. Perhaps our kind (people who cut records), should try to engage more often in communication with other species (Cartridge Trolls?).
You never know, we might even be able to learn something from each other.
Eventually, after centuries of evolution in this direction, we could even get to the point where Lathe Trolls and Cartridge Trolls might even start talking to the people who actually listen to their products!
~~~ Precision Mechanical Engineering, Analog Disk Mastering ~~~
Agnew Analog Reference Instruments: http://www.agnewanalog.com

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