LISTSERV mailing list manager LISTSERV 16.0

Help for ARSCLIST Archives


ARSCLIST Archives

ARSCLIST Archives


[email protected]


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  April 2012

ARSCLIST April 2012

Subject:

Re: ARSCLIST Digest - 13 Apr 2012 to 14 Apr 2012 (#2012-101)

From:

Shai Drori <[log in to unmask]>

Reply-To:

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

Date:

Sun, 15 Apr 2012 18:51:29 +0200

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (260 lines)

Exactly what I said RE a77. Or was that in a private mail?
Shai

בתאריך 04/15/12 3:49 PM, ציטוט Art Shifrin:
> Hi Gang,
>
> Regarding  "Slow Reel-to-reels" , vari--speed does NOT due the rest.  Heads
> with particularly narrow gaps should be used to read snail-pace tapes.
> Having that extra resource permits
> better extraction of highs than does pedal to the metal eq. adjustments.
>
> JRF has made superb specials for me for my repro-only AG 440.
>
> Best Regards,
> Art (Shiffy) Shifrin
>
>
> On Sun, Apr 15, 2012 at 12:00 AM, ARSCLIST automatic digest system<
> [log in to unmask]>  wrote:
>
>> There are 4 messages totalling 241 lines in this issue.
>>
>> Topics of the day:
>>
>>   1. Slow Reel-to-reels
>>   2. Recording_78rpm_records/analog vs digital eq (3)
>>
>> ----------------------------------------------------------------------
>>
>> Date:    Sat, 14 Apr 2012 10:11:02 +0200
>> From:    Shai Drori<[log in to unmask]>
>> Subject: Re: Slow Reel-to-reels
>>
>> Stock machine goes down to 3.75. Varispeed does the rest. At these
>> speeds I use my ears for eq more than the set standards. The key is the
>> gap of the head.
>> Shai
>>
>> בתאריך 04/13/12 10:14 PM, ציטוט Stephen Bolech:
>>> Shai, did you have it modified to play at those speeds, or do they have
>> that as an option?
>>>
>>> On Apr 13, 2012, at 2:59 PM, Shai Drori wrote:
>>>
>>>> I use the Ampex atr-100
>>>> Shai Drori
>>>>
>>>>
>>>> בתאריך 04/13/12 8:57 PM, ציטוט Stephen Bolech:
>>>>> Hi everyone, I'm hoping some of you could give me recommendations for
>> good options to play back 1 7/8 ips and even the occasional 15/16 tapes.
>>   We have a large oral history collection, and though the majority are at
>> 3.75 ips, there are some at these slower speeds.  What are you guys using
>> for these speeds, and what do you recommend?
>>>>> Thank you,
>>>>> Stephen Bolech
>>>>>
>>>> --
>>>> בברכה,
>>>> שי דרורי
>>>> מומחה לשימור והמרה של אודיו וידאו וסרטים 8-35 ממ.
>> --
>> בברכה,
>> שי דרורי
>> מומחה לשימור והמרה של אודיו וידאו וסרטים 8-35 ממ.
>>
>> ------------------------------
>>
>> Date:    Sat, 14 Apr 2012 10:06:58 +0000
>> From:    Don Cox<[log in to unmask]>
>> Subject: Re: Recording_78rpm_records/analog vs digital eq
>>
>> On 13/04/2012, George Brock-Nannestad wrote:
>>
>>
>>> The so-called Nyquist criterion states that if you want to be able to
>>> reconstruct a signal from a sampled representation of it, you have to
>>> decide the highest frequency you want represented and then you have to
>>> sample at a rate that is at least twice the highest frequency.
>> Note, _at least_. It won't do any harm to go higher.
>>
>>> When
>>> you then reconstruct your signal by providing voltages at the sample
>>> rate according to the table of values that represents the audio
>>> signal, you will have your full bandwidth and dynamic range back,
>>> provided the resolution or bit-depth has been sufficient. It has been
>>> claimed that this stepwise presented waveform makes the signal
>>> unlistenable, but that is not the case, because you invariably smooth
>>> it by filtering, so nothing above your defined highest frequency gets
>>> out in the analog domain again. You will note that you are in full
>>> control: define the maximum frequency and define the resolution. If
>>> they are not sufficient to your purpose, go higher.
>>>
>>> Now, we have a problem with pure sampling of a waveform: if it has a
>>> frequency that is more than half of the sampling rate, that too will
>>> be sampled, but in this case under-sampled, which means that the
>>> result appears to be at a completely different and inharmonic and
>>> jarring frequency, an alias. Once we have adopted a sampling frequency
>>> we must simply ensure that no signal above half the sampling rate is
>>> available for sampling.
>>>
>> It is interesting to see the digital photography community wrestling
>> with these concepts. (Most cameras use optical anti-aliasing filters.)
>>
>>> This is done by filtering, so-called anti-alias filtering. With 44.1
>>> kHz sampling rate, no signal above 22.05 kHz is permissible. On the
>>> other hand, we do want our 20 kHz bandwidth - this is what a young,
>>> pre-earbud ear can mostly hear.
>> There seems to be good evidence that we can hear timing differences on
>> impulse signals corresponding to much higher frequencies than the
>> continuous sine waves normally used for testing hearing.
>>
>>> So, our filter has to go from full
>>> transmission at 20kHz to zero transmission at 22.05 kHz *). No
>>> problem, our telephone engineers have done this kind of exercise for
>>> 90 years. However, such sharp cut-off filters come with some frightful
>>> time delay distortion (phase to some), very audible down to 2 kHz.
>>> That was the situation for about 10 years in CD audio, until someone
>>> came up with the idea to correct the time response in the digital
>>> domain by means of a digital filter. The currency to pay for this is
>>> total delay time, but for something recorded a year ago, some
>>> microseconds do not matter.
>>>
>>> In other words, many of our problems come from the filter. If we
>>> increase the sampling rate we can make use of our more frequent
>>> samples in two ways: we can do a gentler filtering that does not have
>>> the delay effect at low frequencies, or we can increase our highest
>>> frequency. If we do the latter, we shall be able to increase the time
>>> resolution of our digital representation. With 20 kHz the maximum
>>> slope of the waveform is only one quarter of that of an 80 kHz
>>> bandwidth - reachable by a 192 kHz sampling frequency and a gentler
>>> anti-aliasing filter.
>>>
>>> A couple of other items came up while we were at 78rpm reproduction:
>>>
>>> - the reason why we need an elevated bandwidth for recordings on
>>> rough surfaces is because that is where the noise signal is.
>> This is the crucial point.
>>
>>
>>
>>> - one might consider that the pickup would be encountering a
>>> formidable vertical wall when it met a square wave. However, the
>>> recording is usually a velocity recording, that is the square
>>> waveshape is differentiated (1st derivative), which means it turns
>>> into a triangular wave. The problem is that with a high bandwidth, the
>>> corners of this triangular wave (where the square shifts from constant
>>> positive to constant negative and vice versa) are very sharp, and even
>>> that may be difficult to trace. George Alexandrovich made a 7" test
>>> record with a "square wave" - there are virtually no wiggles at the
>>> corners of the triangles. It is for testing pickups, but I have not
>>> dared to use it on anything but the ELP.
>>>
>> Back in the days when The Gramophone carried technical reviews of
>> equipment, under John Borwick especially, oscilloscope traces of pickup
>> cartridges playing "square waves" were shown in all reviews. I assume
>> the actual waveforms on the LP were triangular.
>>
>>
>>> - for the same reason a tick, modelled by a steep rise followed by
>>> steep fall becomes two ticks, one positive and one negative.
>>>
>>> - even if you remove these two peaks and interpolate or draw a
>>> waveform connecting the ends, the low frequency excitation of the
>>> whole cartridge-tonearm system (stylus, cantilever, bearing, cartridge
>>> mass, tonearm mass and resonances) still remains as a low-level thud -
>>> a tail. CEDAR started back in 1988 with a program developed by Peter
>>> Rayner while still at the British Library to remove not only the
>>> ticks, but also the tail.
>>>
>> Regards
>> --
>> Don Cox
>> [log in to unmask]
>>
>> ------------------------------
>>
>> Date:    Sat, 14 Apr 2012 11:01:20 -0400
>> From:    "Richard L. Hess"<[log in to unmask]>
>> Subject: Re: Recording_78rpm_records/analog vs digital eq
>>
>> Hi, Don,
>>
>> In the early 1970s, I recall getting into a long, and semi-heated
>> discussion between two brands of cartridges. My colleague had done scope
>> photos of various cartridges reproducing CBS Labs test records,
>> including square waves. He said one cartridge was better than my
>> favourite because it didn't show the ringing in the square waves. I said
>> I didn't like his cartridge because it sounded dull and lifeless
>> compared to my favourite which sounded more like live music.
>>
>> I also recall, a half decade or more later, a magazine, I think it was
>> AUDIO Magazine, showed scanning electron micrographs  (SEM images) of
>> the grooves of one or more CBS Labs test records and the ringing showed
>> up in the SEM images!
>>
>> Cheers,
>>
>> Richard
>>
>> On 2012-04-14 6:06 AM, Don Cox wrote:
>>> Back in the days when The Gramophone carried technical reviews of
>>> equipment, under John Borwick especially, oscilloscope traces of pickup
>>> cartridges playing "square waves" were shown in all reviews. I assume
>>> the actual waveforms on the LP were triangular.
>> --
>> Richard L. Hess                   email: [log in to unmask]
>> Aurora, Ontario, Canada           (905) 713 6733     1-877-TAPE-FIX
>> http://www.richardhess.com/tape/contact.htm
>> Quality tape transfers -- even from hard-to-play tapes.
>>
>> ------------------------------
>>
>> Date:    Sat, 14 Apr 2012 16:54:15 +0000
>> From:    Don Cox<[log in to unmask]>
>> Subject: Re: Recording_78rpm_records/analog vs digital eq
>>
>> On 14/04/2012, Richard L. Hess wrote:
>>
>>> Hi, Don,
>>>
>>> In the early 1970s, I recall getting into a long, and semi-heated
>>> discussion between two brands of cartridges. My colleague had done
>>> scope photos of various cartridges reproducing CBS Labs test records,
>>> including square waves. He said one cartridge was better than my
>>> favourite because it didn't show the ringing in the square waves. I
>>> said I didn't like his cartridge because it sounded dull and lifeless
>>> compared to my favourite which sounded more like live music.
>>>
>>> I also recall, a half decade or more later, a magazine, I think it was
>>> AUDIO Magazine, showed scanning electron micrographs (SEM images) of
>>> the grooves of one or more CBS Labs test records and the ringing
>>> showed up in the SEM images!
>>>
>> That is funny. Make sure you are testing for what you think you are
>> testing for.  ;-)
>>
>> I would like to see those images.
>>
>>> On 2012-04-14 6:06 AM, Don Cox wrote:
>>>> Back in the days when The Gramophone carried technical reviews of
>>>> equipment, under John Borwick especially, oscilloscope traces of
>>>> pickup cartridges playing "square waves" were shown in all reviews. I
>>>> assume the actual waveforms on the LP were triangular.
>> Regards
>> --
>> Don Cox
>> [log in to unmask]
>>
>> ------------------------------
>>
>> End of ARSCLIST Digest - 13 Apr 2012 to 14 Apr 2012 (#2012-101)
>> ***************************************************************
>>

-- 
בברכה,
שי דרורי
מומחה לשימור והמרה של אודיו וידאו וסרטים 8-35 ממ.

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

March 2024
February 2024
January 2024
December 2023
November 2023
October 2023
September 2023
August 2023
July 2023
June 2023
May 2023
April 2023
March 2023
February 2023
January 2023
December 2022
November 2022
October 2022
September 2022
August 2022
July 2022
June 2022
May 2022
April 2022
March 2022
February 2022
January 2022
December 2021
November 2021
October 2021
September 2021
August 2021
July 2021
June 2021
May 2021
April 2021
March 2021
February 2021
January 2021
December 2020
November 2020
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