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ARSCLIST  February 2013

ARSCLIST February 2013

Subject:

Re: Mono but Out-of-Phase

From:

Michael Biel <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Wed, 6 Feb 2013 13:58:26 -0700

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (87 lines)

I KNEW that Clark would come in with The Wood Effect!!!  Of course that
is "absolute phase" whereas this problem is with "relative phase"
between channels. BUT there is something to consider that one of these
two mono signals is recorded out of absolute phase!  So while it is
obvious that one of these two channels needs to be reversed -- or
eliminated -- which one??

I have a feeling that all these answers have confused some of the
newbies who have never used a double-quarter inch patchboard -- what Lou
called a dual pole.  This used a pair of tip-sleeve plugs on one plastic
base where the two tips were the balanced-circuit conductors and the
sleeves were ganged together.  There was an edge with ridges on each
plastic block which told the operator which tip was which.  I always
taught that the RIDGES GO TO THE RIGHT.  (Both could go to the left but
it was better to have every operator do it the same way.)  A stereo
signal required two patch cords -- one for each channel.  So if you have
one cord with one end reversed, the two channels would be out of
relative phase.

So, now, years later, which was the one that was out-of-phase???  Clark
could tell you but my ears never heard the wood effect, but I always
heard when stereo was out-of-relative-phase. The original questioner
says that the only problem is with these mono recordings -- the stereo
recordings might also be out-of-phase.  He also said that the playback
machine he is using has the heads properly aligned, but it is necessary
to have the heads aligned to the RECORDINGS. If the recording machine
was mis-aligned, you align to IT.  

But finally, mono recordings were not supposed to be recorded to two
tracks of a stereo recorder in the first place.  If you are sure that
the recording really is mono, only ONE of these two tracks should be
copied.  NEVER SUM TWO MONO TRACKS TOGETHER EVEN IF IN PHASE AND IN
ALIGNMENT.  NEVER.  ALWAYS KEEP THEM SEPARATE -- AND IT IS BETTER TO
ONLY COPY ONE OF THEM IN THE FIRST PLACE.  

Mike Biel [log in to unmask]     


-------- Original Message --------
Subject: Re: [ARSCLIST] Mono but Out-of-Phase
From: robert wasserman <[log in to unmask]>
Date: Wed, February 06, 2013 2:51 pm
To: [log in to unmask]

Though our engineers we good at keeping our old equipment running, in my
college radio days, they were not around during most shows and we were
on our own doing recording, etc, would not be surprised if an out of
phase cable somewhere. Is it possible someone was trying to make fake
stereo? I have some cassettes labelled Stereo that were fake from Mono
reissues that sounded terrible when played back in summed Mono

> Date: Wed, 6 Feb 2013 09:24:24 -0800
> From: [log in to unmask]
> Subject: Re: [ARSCLIST] Mono but Out-of-Phase
> To: [log in to unmask]
> 
> All the other answers are wrong! Joking, of course, but... It was from a student radio station? In the 70s it is likely they had dual pole patch bays and plugged one in upside down, or something like that. Or they had instructors who were less detail oriented...
> 
> I would assume that you are playing back on a familiar tape deck, so no need to test its polarity.
> 
> KPFA had those dual patch bays in the 70s...
> 
> L
> 
> Sent from Lou Judson's iPad 2
> Mobile 415-271-8070
> 
> 
> On Feb 6, 2013, at 6:55 AM, Henry Borchers <[log in to unmask]> wrote:
> 
> > Hi all,
> > 
> > I've got a question for you that has been a real head scratcher for me and I hope there is someone here who might be able to shed some light on it.
> > 
> > I've been digitizing a number of amateur recordings from a student radio station from the 1970s recorded on 1/4" reel tape and a number of these recordings from this collection seems to be mono and have no stereo field but the left and right channels have opposing polarity. It is easy to just digitize both channels and play them on stereo headphones but since they are 180 degrees out of phase, they cancel each other out when summed together with a mono speaker.
> > 
> > I understand the physics of canceling waves (and I know how deal with this) but my question is this. Does anybody know how an amateur reel-to-reel recording could have gotten this way?
> > 
> > --
> > Henry Borchers
> > Broadcast Media Digitization Librarian
> > University of Maryland
> > B0221D McKeldin Library
> > College Park, MD 20742
> > (301) 405-0725
> >

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