Laurence Payne wrote:
On Wed, 17 May 2006 10:56:41 +0100, "Dave Plowman (News)"
wrote:

In practice, of course, double speeding a 1 7/8 ips recording may not
result in much deterioration since virtually no real to reel machine was
optimised for this speed - it was simply used for logging purposes.

You're thinking pro. 1 7/8 ips was far from unheard of on domestic
machines.
Indeed. I recorded the audio of the first moon landing by putting a
microphone next to the TV's loudspeaker. Still have the recording, made
on a Geloso tape recorder, single speed 1 7/8 ips.

S.

In article ,
Laurence Payne lpayne1NOSPAM@dslDOTpipexDOTcom wrote:
In practice, of course, double speeding a 1 7/8 ips recording may not
result in much deterioration since virtually no real to reel machine was
optimised for this speed - it was simply used for logging purposes.

You're thinking pro. 1 7/8 ips was far from unheard of on domestic
machines.

I've yet to try one where the HF performance matched that of a good
cassette, though - although this might also be down to the 1/4" tape.

I've got an Akai reel to reel which gives as good an HF response on 3 3/4
ips as 7 1/2, though, on decent tape. But not at 1 7/8ths.

--
*A person who smiles in the face of adversity probably has a scapegoat *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Laurence Payne lpayne1NOSPAM@dslDOTpipexDOTcom wrote:
In practice, of course, double speeding a 1 7/8 ips recording may not
result in much deterioration since virtually no real to reel machine was
optimised for this speed - it was simply used for logging purposes.

You're thinking pro. 1 7/8 ips was far from unheard of on domestic
machines.

But not optimised?

--
*A woman drove me to drink and I didn't have the decency to thank her

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Serge Auckland wrote:
In practice, of course, double speeding a 1 7/8 ips recording may not
result in much deterioration since virtually no real to reel machine
was optimised for this speed - it was simply used for logging
purposes.

You're thinking pro. 1 7/8 ips was far from unheard of on domestic
machines.

Indeed. I recorded the audio of the first moon landing by putting a
microphone next to the TV's loudspeaker. Still have the recording, made
on a Geloso tape recorder, single speed 1 7/8 ips.

As I said used for logging where quality didn't much matter. ;-)
Would you have used 1 7/8ths for recording a prom?

And I operated the Ferrograph which logged NASA in the studio. At 1
7/8ths. Quality didn't much matter though. Still might have some of the
triple play 7" reels used which were disposed of after. No use on pro
machines.

--
*If horrific means to make horrible, does terrific mean to make terrible?

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
Serge Auckland wrote:
In practice, of course, double speeding a 1 7/8 ips recording may not
result in much deterioration since virtually no real to reel machine
was optimised for this speed - it was simply used for logging
purposes.
You're thinking pro. 1 7/8 ips was far from unheard of on domestic
machines.

Indeed. I recorded the audio of the first moon landing by putting a
microphone next to the TV's loudspeaker. Still have the recording, made
on a Geloso tape recorder, single speed 1 7/8 ips.

As I said used for logging where quality didn't much matter. ;-)
Would you have used 1 7/8ths for recording a prom?

As a schoolboy with nothing better, yes. The comment was made more to
illustrate that 40 years ago, there were domestic machines made that ran
at 1 7/8 ips. Geloso had a "hi-fi" machine that ran at a heady 3 3/4
ips. The Grundig, Truvox, Elisabethan machines of the era didn't set
much store by quality, just getting Auntie Mabel's voice back vaguely
recognisably seemed to be enough.

S.

In article ,
Serge Auckland wrote:
Dave Plowman (News) wrote:
In article ,
Serge Auckland wrote:
In practice, of course, double speeding a 1 7/8 ips recording may
not result in much deterioration since virtually no real to reel
machine was optimised for this speed - it was simply used for
logging purposes.
You're thinking pro. 1 7/8 ips was far from unheard of on domestic
machines.

Indeed. I recorded the audio of the first moon landing by putting a
microphone next to the TV's loudspeaker. Still have the recording,
made on a Geloso tape recorder, single speed 1 7/8 ips.

As I said used for logging where quality didn't much matter. ;-) Would
you have used 1 7/8ths for recording a prom?

As a schoolboy with nothing better, yes. The comment was made more to
illustrate that 40 years ago, there were domestic machines made that ran
at 1 7/8 ips

I never said it wasn't. Simply that they weren't optimised for this speed.

--
*You are validating my inherent mistrust of strangers

Dave Plowman London SW
To e-mail, change noise into sound.

In article , Dave Plowman (News)
wrote:
In article , Jim Lesurf
wrote:
The maximum theoretical HF frequency on replay is defined by the
head gap - the smaller the better. Double the speed of the replay
and the wavelength halves - thus removing the final octave. In
theory, at least.

I find the above a bit confused. The wavelength for a given frequency
will be defined by the *recording* speed.


This article explains extinction frequency as regards the replay head,
as well as much else.

http://www.soundonsound.com/sos/1997...ganalogue.html


Thanks for the above. :-) I agree with what it says - and which seems in
accord with my previous understanding. Alas, it does not seem to say
precisely what you wrote (as re-quoted at the top of this reply).

Let me alter what you said to make a more accurate statement according to
my understanding:

"The maximum theoretical HF frequency on replay is defined by the ratio of
the replay speed / head gap size. This is because the highest resolvable
wavelength will be limited by the gap size, and the frequency generated
upon replay by a given wavelength will be proportional to the replay speed.
The smaller the gap the better. Doubling the speed of replay of an existing
recording has no effect whatsoever upon the wavelengths already recorded on
the tape, nor on the effect of the head gap in being able to resolve them,
but *will* double the output frequencies they produce. If there are no
other limits, this means that in principle we can always recover all the
information even when the replay speed does not match the recording speed.
All we are doing by altering the replay speed is trading off between the
signal duration and the bandwidth it occupies during replay."

Thus - if the head gap size is the only factor - changing the replay speed
should not 'remove' any information at all.

The above, of course, ignores all other limitations due, e.g. to the
electronics not having sufficient bandwidth. In practice, if you replay at
high speed, the electronics might not be able to cope with the increased
bandwidth even though the gap is sufficient.

Hope that now makes things clear. :-)

My suspicion is that your original statement is perhaps confusing
wavelength with frequency, and - more significantly in this context -
recording with replay.

IF you were talking about changing the speed *when recording* then I would
agree that the wavelengths on the tape for any given frequency would be
scaled by the chosen recording speed.

If the above is not clear, let me use an example. Let us assume we record
a 10kHz tone onto tape at 7.5ips. The resulting pattern on the tape will
have a wavelength of 7.5E-4 inches. It will have this wavelength regardless
of how quickly or slowly we may then run the tape past a replay head [1].
Indeed, if we did a static measurement with something that displayed the
field pattern it would show this wavelength since it is a pattern in space,
not time.

In a similar way, once we have chosen our replay head, it will have a gap
size that won't alter when we change our mind about the tape speed. If it
can resolve wavelengths of 7.5E-4 inches being run past it at 7.5ips then
it should be able to resolve them at 3.75ips, or some other replay speed.

Sorry if the above is over-long. However I'd thought my previous comments
were clear, but I am now wondering if the point isn't as clear as I'd
assumed.

Slainte,

Jim

[1] I will assume we can ignore special relativity. 8-]

--
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Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Dave Plowman (News) wrote:
In article ,
Serge Auckland wrote:
As I said used for logging where quality didn't much matter. ;-)
Would you have used 1 7/8ths for recording a prom?

And I operated the Ferrograph which logged NASA in the studio. At 1
7/8ths. Quality didn't much matter though. Still might have some of the
triple play 7" reels used which were disposed of after. No use on pro
machines.

I once had a Chilton (remember those?) with 1 7/8 speed.

On Wed, 17 May 2006 15:56:18 +0100, Jim Lesurf
wrote:

In article , Dave Plowman (News)
wrote:
In article , Jim Lesurf
wrote:
The maximum theoretical HF frequency on replay is defined by the
head gap - the smaller the better. Double the speed of the replay
and the wavelength halves - thus removing the final octave. In
theory, at least.

I find the above a bit confused. The wavelength for a given frequency
will be defined by the *recording* speed.


This article explains extinction frequency as regards the replay head,
as well as much else.

http://www.soundonsound.com/sos/1997...ganalogue.html


Thanks for the above. :-) I agree with what it says - and which seems in
accord with my previous understanding. Alas, it does not seem to say
precisely what you wrote (as re-quoted at the top of this reply).

Let me alter what you said to make a more accurate statement according to
my understanding:

"The maximum theoretical HF frequency on replay is defined by the ratio of
the replay speed / head gap size. This is because the highest resolvable
wavelength will be limited by the gap size, and the frequency generated
upon replay by a given wavelength will be proportional to the replay speed.
The smaller the gap the better. Doubling the speed of replay of an existing
recording has no effect whatsoever upon the wavelengths already recorded on
the tape, nor on the effect of the head gap in being able to resolve them,
but *will* double the output frequencies they produce. If there are no
other limits, this means that in principle we can always recover all the
information even when the replay speed does not match the recording speed.
All we are doing by altering the replay speed is trading off between the
signal duration and the bandwidth it occupies during replay."

Thus - if the head gap size is the only factor - changing the replay speed
should not 'remove' any information at all.

The above, of course, ignores all other limitations due, e.g. to the
electronics not having sufficient bandwidth. In practice, if you replay at
high speed, the electronics might not be able to cope with the increased
bandwidth even though the gap is sufficient.

Hope that now makes things clear. :-)

My suspicion is that your original statement is perhaps confusing
wavelength with frequency, and - more significantly in this context -
recording with replay.

IF you were talking about changing the speed *when recording* then I would
agree that the wavelengths on the tape for any given frequency would be
scaled by the chosen recording speed.

If the above is not clear, let me use an example. Let us assume we record
a 10kHz tone onto tape at 7.5ips. The resulting pattern on the tape will
have a wavelength of 7.5E-4 inches. It will have this wavelength regardless
of how quickly or slowly we may then run the tape past a replay head [1].
Indeed, if we did a static measurement with something that displayed the
field pattern it would show this wavelength since it is a pattern in space,
not time.

In a similar way, once we have chosen our replay head, it will have a gap
size that won't alter when we change our mind about the tape speed. If it
can resolve wavelengths of 7.5E-4 inches being run past it at 7.5ips then
it should be able to resolve them at 3.75ips, or some other replay speed.

Sorry if the above is over-long. However I'd thought my previous comments
were clear, but I am now wondering if the point isn't as clear as I'd
assumed.


JIm, as I remember the theory of recording, the gap size is not that
important, because the remanent field in the tape is determined, not
by the entire gap, but the trailing edge of the gap as the tape leaves
the field. So the gap on the record head will typically be quite a bit
wider than the corresponding read head gap.

d

--
Pearce Consulting
http://www.pearce.uk.com

Let me alter what you said to make a more accurate statement according to
my understanding:

"The maximum theoretical HF frequency on replay is defined by the ratio of
the replay speed / head gap size. This is because the highest resolvable
wavelength will be limited by the gap size,

lowest resolvable wavelength


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.livejournal.com/userinfo.bml?user=fleetie