[78-L] Fake stereo

[Michael Biel]

Let me explain something about echo/reverb vs. tone controls and comb
filtering.  There is a slight amount of phase shifting whenever tone
controls are used.  ANY tone control.  In electronic terms this phase
shift is a slight delay measured in microseconds.  (This includes
inherent equalization like RIAA, and is why RIAA playback
re-equalization must be done in the analog domain, NOT in the digital
domain.  We had a tutorial about this at ARSC a couple of years ago. 
You cannot feed a flat LP audio into your computer and expect any but
the very expensive programs to put in the RIAA equalization.)  It is
also why the Vinylphools do not have variable tone controls in their
systems.  Changing the tone can affect the "soundstage" of 2 or 3-mic
stereo like Mercury Living Presence, Decca/London blue-backs, or RCA
Living Stereo which depends on phase relationships.  Overdub or
multitrack stereo are not affected as much, but these guys hate that
stuff anyway.


So, when comb filtering is done, unless it is done so the left and right
channel filters match exactly in a mirror image to each other, you
cannot re-combine the two channels without having some phase
cancellation.  That would be the "pingy" effect you mention, I think. 
I've never heard that word used except in ping-pong which is wide motion
between channels.

The phase-delay of comb filtering is NOT the same as echo or reverb. 
This is delaying the sound to the point that you can hear the delay. 
Tone controls do not delay the sound that much.  Echo is where the
distinct delays are discretely heard, like in tape-delay.  Reverb is
where the repetition delays are so dense that they are not discretely
heard.  Much of what RCA Victor used on pop records was echo, hence the
Harry Belefonte Quartette.  They also tended to roll off the bass on the
left and roll it up on the right along with a roll-off of the highs. 
Capitol Dupohonic tended to do more comb filtering and reverb.  I
wouldn't be surprised if they might sometimes have used the underground
natural chambers by the Capitol Tower, but otherwise reverb was usually
done with the Neumann Plate or the AKG Springs

Echo or reverb cannot be removed.  Rolling off can usually be undone,
and comb filtering can sometimes be recombined IF done with that in
mind.  Sometimes the engineers DID check the compatibility.

Mike BIel  mbiel at mbiel.com  

-------- Original Message --------
Subject: Re: [78-L] Fake stereo
From: Ryan Wolfe <nextset4 at yahoo.com>
Date: Fri, March 01, 2013 2:38 pm
To: 78-L Mail List <78-l at klickitat.78online.com>

I guess that figures, that Capitol would put their classical stuff
through Duophonic.  Yuck.

It's hard to even reconvert Duophonic back to true mono...you can't fold
it down , the pingy airplane hangar effect remains.


________________________________
 From: Royal Pemberton <ampex354 at gmail.com>
To: 78-L Mail List <78-l at klickitat.78online.com> 
Sent: Friday, March 1, 2013 10:41 AM
Subject: Re: [78-L] Fake stereo
 
AFAIK there are some classical albums which did use that L/R delay, and
they are on Capitol (whether on Capitol or Angel I can't say as what I
heard was from an excerpt on the sampler/promo that first hawked
Duophonic).

On Fri, Mar 1, 2013 at 6:08 PM, Ryan Wolfe <nextset4 at yahoo.com> wrote:

> Somewhere, I read an account by guy charged with what were the first fake
> stereo releases for RCA.
>
> He had Toscanini stuff to to work with and described his laborious and
> time consuming attempts
> manipulating a comb filter to try to take the mono sources and put them
> into a convincing and somewhat varied stereo presentation.
> Then RCA wanted him to do that with all their stuff, which was going to be
> impractical, so he / they opted for something easier.
>
> I've never heard a classical album that took a mono source and put it on
>  a true L / R delay, just the ones that use the bass in one channel  /
> treble in the other approach.  Including things like Toscanini.
>
>
> ________________________________
>  From: Ted Kneebone <tkneebone1 at abe.midco.net>
> To: 78-l <78-l at klickitat.78online.com>
> Sent: Friday, March 1, 2013 8:06 AM
> Subject: [78-L] Fake stereo
>
> I have at least one LP of Glenn Miller done in
> what is called "enhanced" stereo, or something
> like that.  One channel is delayed slightly.  The
> effect is supposed to sound like an echo.  It
> really ruins what was perfectly good mono sound --
> and surely is not stereo.
>    When i play this disc, I listen to only one
> channel.  That's the only way it makes sense.
>    I think they tried this "enhanced" process with
> some of the Toscanini recordings.  If the Miller
> records are a sample, I would not own the Toscanini.
>    Ted
> Ted Kneebone