LISTSERV mailing list manager LISTSERV 16.0

Help for ARSCLIST Archives


ARSCLIST Archives

ARSCLIST Archives


ARSCLIST@LISTSERV.LOC.GOV


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Monospaced Font

LISTSERV Archives

LISTSERV Archives

ARSCLIST Home

ARSCLIST Home

ARSCLIST  June 2012

ARSCLIST June 2012

Subject:

Re: multiple copies for surface noise reduction, was Re: audio from pictures

From:

"Warren, Richard" <[log in to unmask]>

Reply-To:

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

Date:

Fri, 22 Jun 2012 15:23:33 +0000

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (1 lines)

Hi Mike and others,

My recollection is that Walter Welch used his two Edison players synchronized but 1/4 revolution apart to play identical records with what was supposed to be an enhancing effect and what was, memory says, certainly an interesting effect. He may well have also played records synchronized exactly.

Best, Richard

-----Original Message-----
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Michael Biel
Sent: Friday, June 22, 2012 11:14 AM
To: [log in to unmask]
Subject: Re: [ARSCLIST] multiple copies for surface noise reduction, was Re: audio from pictures

> I proposed a stack of tables all powered by a single motor for
> playing the discs simultaneously, with use of digital delay lines
> to align the audio from them after transferring.

Doug's idea is not original. There was an acoustical player with about
ten turntables with their own tone arms and horns stacked up on a single
spindle. I think it was illustrated in From Tinfoil to Stereo. The
author of this, Walter Welch came up with a simpler solution to playing
two identical records simultaneously with perfect synchronization. He
rigged up an electric motor on a long shaft which connects to the
spindles of two Edison Diamond Disc machines with their spring motors
disengaged. Multiple film machines are easily synchronized using
three-phase motors locked together, but these are sprocketed and the
films can't slip like tape can. Tapes can be synced using SMPTE time
code, but turntables might not run at exact speeds unless the motors are
also locked.

Mike Biel [log in to unmask]

-------- Original Message --------
Subject: [ARSCLIST] multiple copies for surface noise reduction, was
Re: audio from pictures
From: Doug Pomeroy <[log in to unmask]>
Date: Fri, June 22, 2012 10:30 am
To: [log in to unmask]

>
>> Date: Wed, 20 Jun 2012 10:44:42 +0100
>> From: Ted Kendall <[log in to unmask]>
>> Subject: Re: audio from pictures
>>
>> <<SNIP>>
>>
>> Chris Hicks of Cedar did his doctorate on just this question of
>> multiple
>> copies. When the algorithm could be persuaded to work, the results
>> were
>> much as you would expect - enhancement of the correlated wanted
>> signal
>> and reduction of the random noise. Unfortunately, pulling the
>> recordings
>> into good enough sync for artifacts to be negligible was a
>> frustrating
>> and difficult business, even with recordings made one after the other
>> (by me, as it happens) on the same kit on the same settings on the
>> same
>> afternoon, with meticulous centring. The minute geometrical
>> differences
>> between different laminated pressings were enough to throw things
>> continually out of register. The example produced, however, is a
>> tantalising glimpse of what might one day be possible.
>>
>> Whenever I do a master of the QHCF Decca of "Souvenirs", I use three
>> copies from the shelf - one for the very start, one for most of the
>> side
>> and one for the last few turns where the others are afflicted with
>> "Decca scrunch".

I gave a talk on this subject at the ARSC conference in Nashville in
1997.
Two perfectly synchronized copies would provide a theoretical signal-
to-noise
improvement of 3 dB, four copies an improvement of 6 dB and eight
copies an
improvement of 9 dB. The first problem is finding so many copies in E
condition.

But the bigger problem is how to achieve perfect synchronization.
John S Allen of the Boston Audio Society discusses this matter in an
article he
wrote for the Spring 1990 issue of the ARSC Journal. He says the
accuracy of
sync must be "about ten microseconds (72 degrees of phase shift at 20
kHz)".
No real-world turntable is stable enough to achieve this result on
successive
plays, and I proposed a stack of tables all powered by a single motor
for
playing the discs simultaneously, with use of digital delay lines to
align
the audio from them after transferring.

Discs which are even slightly out-of-round would need to be matched
perfectly
with others of the same shape (not impossible, since these discs reflect
the shape
of the metal stamper used to press them), and digital "azimuth
correcting" software
might be used to help deal with alignment variables such as this.

Doug Pomeroy

Top of Message | Previous Page | Permalink

Advanced Options


Options

Error during command authentication.

Error - unable to initiate communication with LISTSERV (errno=111). The server is probably not started.

Log In

Log In

Get Password

Get Password


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

ATOM RSS1 RSS2



LISTSERV.LOC.GOV

CataList Email List Search Powered by the LISTSERV Email List Manager