When cutting a record, which channel has inverted polarity?

[jjgolden]

interesting thread,

We've just always kept everything in the studio pin 2 hot.
As far as I know most modern analog recording gear being made today is all wired pin 2 +.
So we can assume that most music these days is being created with ABS polarity as pin 2+. (except when 25-30+ year old gear is used, then who knows!)


JJG

[jjgolden]

Does anybody know how the pluggins modeled after vintage gear is configured? do they keep a pin 3 unit pin 3+??

JJG

[gold]

It doesn't matter which xlr pin you use as + as long as it's consistent through the system. You can mix and match as long as you flip the pins when necessary. I have found some gear that inverts the output as "normal". Even if the wiring is correct there is no guarantee that all the gear maintains absolute polarity.

[richard-ec2]

the fact is, the absolute polarity of recorded material both on CD and LP is all over the place

We have no idea what was being listened to when it was recorded. If it looks like it's reverse polarity to you but that is what the production team was listening to is it wrong?

With multitrack recording it's really multi mono not stereo. Generally I assume a bass drum hit should make the speaker go out. But who's to say?

What I'm saying is, very commonly, the CD and the LP of the same piece of music have opposite polarity. So even without knowing which is right, you know that one of them is definitely wrong! This really is very common indeed. That's why I say polarity is all over the place.

Just thinking out loud, I would guess that where the CD and LP differ, it's almost always going to be the CD that's right since no polarity inversion takes place in the CD mastering chain.

Going back to LPs, it's beginning to look as if either there's no standard for which channel is inverted or there is a standard but it's not widely known. And yet, cartridge makers seem for the most part to be following a standard - they almost always have the right channel inverted.

[gold]

So even without knowing which is right, you know that one of them is definitely wrong!

I agree with this.

Just thinking out loud, I would guess that where the CD and LP differ, it's almost always going to be the CD that's right since no polarity inversion takes place in the CD mastering chain.

I don't think it's so easy to assume this. Here is one scenario which I could see it happening easily. The record was produced and cut in Europe on a Telefunken with pin2+. The tape is owned by Columbia. They decide to reissue it on CD and play the tape on a pin 3+ machine. Then CD is wrong and the LP is right

Going back to LPs, it's beginning to look as if either there's no standard for which channel is inverted or there is a standard but it's not widely known. And yet, cartridge makers seem for the most part to be following a standard - they almost always have the right channel inverted.

Inverted from what? Just because you get a positive going spike on the left channel doesn't mean it's correct.

[opcode66]

One of the more fascinating puzzlers of late my friends. I like the lively discussion here.

I think I am in 100% agreement with Mr. Gold. And, I stand by the statement that it doesn't really matter in the long run. It is not only arbitraray, but also completely dependant on all parts of the recording, mastering, cutting and playback chain to be in agreement. Sadly, this will never realistically happen.

[Stevie342000]

I agree with both of the last two comments, the problem however arises in recordings made today by sloppy engineers or producers who are not technically developed enough to visual all the issues or to follow set standards or thing because they are in the digital domain there is no issue with polarity for example.

[richard-ec2]

Going back to LPs, it's beginning to look as if either there's no standard for which channel is inverted or there is a standard but it's not widely known. And yet, cartridge makers seem for the most part to be following a standard - they almost always have the right channel inverted.

Inverted from what? Just because you get a positive going spike on the left channel doesn't mean it's correct.

Two answers, one short and one long:

1. From what was on the master tape. I agree that the master tape itself may have the wrong polarity anyway, but I still think the aim of everyone who handles the signal after it leaves the master tape should be to preserve the polarity of the master tape.

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.

[Greg Reierson]

It's a crap shoot. I've seen plenty of cases where the kick drum was positive but the snare was negative. Other cases where a vocal has positive spikes and a horn has negative spikes. Nothing to do with CD vs. vinyl or analog vs. digital. Blame it on mic technique, wiring, lack of standards, lack of skilils, whatever. Maybe they liked the sound better that way.

As an academic issue I'm also curious how the polarithy inversion on the cut works. Shouldn't take too much fuss to figure it out with a cutting system and a scope.

[gold]

1. From what was on the master tape. I agree that the master tape itself may have the wrong polarity anyway, but I still think the aim of everyone who handles the signal after it leaves the master tape should be to preserve the polarity of the master tape.

I agree and try to maintain absolute polarity. As a consumer it would be impossible to determine which is correct without access to the tapes.

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.

If the drums are panned from the drummers perspective should the bass drum make the speaker go in?

[richard-ec2]

If the drums are panned from the drummers perspective should the bass drum make the speaker go in?

LOL - you're right, of course - the issue of polarity in the recording studio opens a far bigger can of worms.

I began by saying I knew of no test record that could be used for checking absolute polarity of an audio cartridge. However, I have heard people say such things exist. I've seen a reference to a very old Denon test record that contains a polarity test - apparently it is a "laterally modulated 500 Hz asymmetric square wave". That sounds quite promising but I've never yet seen a copy of this record on the market.

[markrob]

Hi,

Could it be any of these?


http://www.discogs.com/Various-Testing-Your-Equipment-By-Denon-PCM-Recording-45rpm/release/5451891

http://www.discogs.com/Various-Invitation-To-Denon-PCM-Recording-B-K-Microphone/release/1201887

http://www.discogs.com/No-Artist-Denon-Technical-Test-Record/release/5135198

http://www.discogs.com/Various-Phono-Crosstalk-Canceller-Test-Record/release/3826053

[lucien]

Seems to be Denon XG-7003 pickup test 2.
Pictures in the link below

http://www.canuckaudiomart.com/details/649126779-denon_audio_technical_test_records_xg7002_and_xg7003/images/752371/

[richard-ec2]

Yes, that's the one. Very rarely comes up, though. I only mentioned it because the very fact it exists suggests there must be standard, if only we knew what it was. I think I'll have to try the cartridge manufacturers.

[opcode66]

To my experience and opinion, right seems to be inverted.

[dubcutter89]

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...

2. Should we care?
Yes, if you have a automatic Pitch computer it is a must to at least have same polarity on head and lathe.
No, if you do fixed Pitch and also are not too much worried about this topic at all.

3. What is the answer to the main question?
See 1
If you want to know how Phase and Groove Geometry are coupled it is (at least for the research I've done the last 10+years) like this:
The NAB Standard from 1964 has no info on it. But there is a defacto standard which may have been established by Neumann and is:

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.

Lukas

[dubcutter89]

So (IMO) Left is "inverted"

Defacto Standard means that almost every cut done on a neumann or ortofon system since 1960 is like that.
eventual exceptions: the ones where the studio techs crossed leads before the lathe, made own equipment, didn't care...

Lukas

[Stevie342000]

The 1964 standard for the reference cutting level of 1khz at 7cm/s was established at that point it replaced the previous standard used by RCA et al or inter alia (among others) which was 5.5cm/s. that paper is from 1964 is where you expect to find the information.

Audio Engineering is where the latest developments were published it can be found at American Audio History. A piece of equipment which may be of use was published in Audio magazine in August 1958 page 24 onwards - A Stereo Compatibility Translator - its old school and used a couple of tubes/valves. It has the ability to flick the phase on one channel.

There is much to be found in Audio Magazine from 1957 onwards check out the Goldmark or CBS information published on stereo discs, cutting and matrixing (sum/difference processing) for stereo cutting which is what the above article is about. I may be a little of track here but feel it is relevant. Non the less it is a useful piece of kit for those of us that do not have Neumann cutting systems at least.

So it begs the question when recording is the polarity the issue or is it taken care of in processing? I think it may be in the processing, how you set up your replaying system is something else but that is where the Translator comes back into play as you can use at both ends of the chain when recording and when replaying.

[lucien]

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）。

[opcode66]

Doesn't matter if the polarity of the coil os inverted or the magnet is. The result is the same.

Until we all see a conclusive printed standard in documentation, then this all remains subjective. The other thing is that if the playback end (cartidges) aren't consistent then that sort of makes all of this a mental exercise.