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:

Proportional Font

LISTSERV Archives

LISTSERV Archives

ARSCLIST Home

ARSCLIST Home

ARSCLIST  September 2008

ARSCLIST September 2008

Subject:

Re: New online publication: Manual of analogue audio restoration techniques, by Peter Copeland

From:

Michael Biel <[log in to unmask]>

Reply-To:

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

Date:

Wed, 17 Sep 2008 13:08:14 -0400

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (110 lines)

George Brock-Nannestad wrote:
> From: Patent Tactics, George Brock-Nannestad
>
> Hi all,
>
> Mike Biel wrote
>
>   
>> ...... I am also glad on pages 88 and 89 he explains the strobe disc as 
>> being the basis of 78.26 and 77.92 (leaving out the asinine contention 
>> from Warren Rex Isom that gear-drive teeth ratios were the original 
>> causal determination.)                           
>>     
>
> [a lot of other comments left out here]
>
> Mike, in what way were Warren Rex Isom's ideas asinine - I always had a good 
> impression of his understanding of the technical matters?
>
> Best wishes,
>
>
> George
>
>
>   
Hi George.

We fought this out several times in the 78-L in past years, and someone 
might be able to come up with my more detailed answers.  The question 
came up as to why 78.26 instead of 78.00.  The answer is the strobe 
disc, of course, which started being used in the mid-20s.  The question 
should really be why *78.anything* instead of 80, 76, 75, or even 77 or 
79.  But somewhere in the pre-strobedisc era 78.00 had been chosen, at 
least for public consumption.  Now that the strobe disc technology was 
available, it had to be 78.26 in the 60 cycle world and 77.92 over in 
your land of 50 cycles.  Fine.  But then in the gala anniversary issue 
of the AES Journal, Isom claimed as the reason 78.26 was SELECTED was 
because that is what results when you reduce a 3600 RPM electric motor 
by a 46 to 1 gear ratio for worm gears.  Of course you could get 80.00 
with a 45 to 1 gear ratio, but he used an excuse that Maxfield and 
Harrison was interested in getting Victor to adopt their electrical 
recording system so they chose 78.26. But they were also courting 
Columbia which used 80. (And he completely overlooks that Victor really 
was recording at 76 and Columbia at 78.)  

There are many problems with his theory that the speed was selected 
because of a gear drive ratio.  The first one is that WE did not supply 
the turntables to the record companies, only the recording head.  They 
were affixed to the turntables used by the recording companies which 
were mainly weight driven.   Another problem with the gear theory is 
that ALL turntable mechanisms at that time, whether using spring, 
weight, or electric motors, were governor controlled.  ALL were designed 
with motors that would drive the turntable faster than needed with the 
speed reduced to the proper one by a governor. Even gear drive tables in 
the 20s had a governor.   When I originally researched this I had over a 
dozen books spread out here with the details of almost every turntable 
mechanism from the era and none fit his description.  A short 
description of the situation can be found in the same AES Journal, pages 
750-51 by James H. Kogen.  Most electric turntables at the time used 
idler wheel drives which did not require an even number in their ratio 
like gears do.  It is possible that the RCA 70 series table would fit 
Isom's worm-gear description, but it was not designed until the mid-30s, 
long after 78.26 was established.   Therefore it was designed to fit a 
previously selected speed, not the reason the speed was selected. 

OK, I hear you asking, what about the sync turntables for motion picture 
sound.  First of all, they were not 78.26.  Secondly, his description of 
how 33 1/3 was selected is bogus.  He talks about minimum groove speed, 
but that was not the total consideration.  Reducing the difference 
between inner and outer groove speed was.  It was vital that there not 
be much noticable difference when the discs were switched.  They could 
have used a faster revolution speed to get higher groove speed at 
smaller diameters, but that would make the outer groove speed that much 
faster and more noticably different.  One of the engineers on the 
project, Stanley Watkins, discusses that the speed was selected after 
they were told what the largest size could be pressed by Victor.  It was 
16 inches.  In Isom's AES article he several times states that the disc 
was 20 inches in size.  That screws up all his calculations in that 
section.  

Likewise his description of how 45 was chosen is wrong.  Once again the 
primary design feature was keeping the inner and outer groove speeds as 
close to each other as possible.  I have the RCA ledger sheets of the 
Madam X project from the early 1940s which show they started with 6 1/2 
inch discs at 40 rpm in 1942 and in June 1943 raised it to 45 RPM for 
7-inch discs.  45 at 7-inch provided the closest match with the proper 
time length with a high inner diameter surface speed that was not much 
different from the groove speed at the outer diameter.  The RCA 
engineers scoffed at the Columbia LP because not only was the inner 
groove speed too slow, the ratio between the outer groove speed and the 
inner groove speed was enormous.  To overcome this there was an attempt 
over at Columbia to have the first LP masters maintain a large inner 
diameter, but these records looked wasteful with all that non-used 
area.  This aesthetic reasons is one of the reasons why the LP label is 
larger than the 78 label, but it really should have been even larger!  
The 45 label had to be the large size it is because of the loss of 
printing area where the hole is.  It had the secondary advantage that it 
kept people from questioning all of the blank space on them.   Columbia 
used a small label on their 7-inch 33s in the early 50s, but kept the 
records from looking too empty by using those larger-than-necessary 
gripping lines outside the label. 

This is going beyond my original statement that strobe discs, not gear 
ratios, was the reason it is 78.26 and 77.92.  But your question 
concerned Isom, and although much of what he wrote is good, this entire 
section on speed is bogus.

Mike Biel   [log in to unmask]

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

October 2020
September 2020
August 2020
July 2020
June 2020
May 2020
April 2020
March 2020
February 2020
January 2020
December 2019
November 2019
October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
April 2019
March 2019
February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
July 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003

ATOM RSS1 RSS2



LISTSERV.LOC.GOV

CataList Email List Search Powered by the LISTSERV Email List Manager