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ARSCLIST  July 2019

ARSCLIST July 2019

Subject:

Re: Reel-to-Reel tape problem

From:

Tim Gillett <[log in to unmask]>

Reply-To:

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

Date:

Sat, 13 Jul 2019 21:57:27 +1000

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (278 lines)



Jamie, there may be hum or some other objective speed reference on the
tape but that it was due to airborne induction into the record head
seems unlikely. For good reason we carefully shielded tape heads when
used for playback, but not for record. For it to induce a signal
directly into the record head and useably onto the tape, the magnetic
field would have to be very strong. But I guess stranger things have
happened.

Tim.
----- Original Message -----
From: "Association for Recorded Sound Discussion List"
<[log in to unmask]>
To:<[log in to unmask]>
Cc:
Sent:Sat, 13 Jul 2019 02:19:40 -0400
Subject:Re: [ARSCLIST] Reel-to-Reel tape problem

The head shielding was not so great and they might pick up airborne
hum or RF, pretty much everything does.

Please pardon the mispellings and occassional insane word
substitution I'm on an iPhone

> On Jul 13, 2019, at 01:57, Corey Bailey <[log in to unmask]>
wrote:
>
> Quite possibly there is very little or no hum on the recording if
it was made on a portable recorder because they used batteries and had
a DC motor. I actually had one of these in the middle 1960's and,
IIRC, it used "C" cells. It also had an adapter to be used in the
cigarette lighter of your car where I used this particular recorder.
The recorder (made in Japan) used 3" reels and was 1/2Tr. mono
allowing the tape to be recorded in both directions. I permanently
mounted leader to the take-up reel to facilitate loading & threading
so, I would carry pre-leadered spare reels. I used the recorder as a
dictation machine to record the posted information for new
construction. I would transcribe the tapes using a Roberts deck for
playback, listening with headphones. I remember my voice being off
pitch at the beginning and end of the tapes because the Roberts was a
constant speed deck. I remember that my voice sounded most normal in
the middle of the tape when playing back on the Roberts which, may be
a clue for locating the most accurate pitch.
>
> Cheers!
>
> Corey
>
> Corey Bailey Audio Engineering
> www.baileyzone.net
>
>> On 7/12/2019 9:06 PM, Jamie Howarth wrote:
>> If there’s hum in the recording or if you like send me a 192/24
sample right from the playback and I’ll see if we can make a quick
utility for you.
>>
>> Jamie Howarth
>> Plangent Processes
>>
>> Please pardon the mispellings and occassional insane word
substitution I'm on an iPhone
>>
>>> On Jul 12, 2019, at 21:58, Tim Gillett
<[log in to unmask]> wrote:
>>>
>>>
>>> I'm not familiar with the "gliding stretch" of Adobe Audition but
if
>>> it allows you to set (by ear or even better by a reference on the
tape
>>> such as hum) a start speed and end speed then assuming a linear
>>> increase in speed between those two end points, I guess it would
>>> replicate the original recorded speed. I'd first make the
assumption
>>> that the original recorded speed didn't deviate due to slippage,
>>> battery fade etc. Only if the speed was obviously inconsistent
after
>>> the initial correction of start and end points would I attempt
further
>>> corrections.
>>>
>>> It wasn't just cheap/battery powered machines which used the rim
>>> drive system. On the Continent from the mid 1950's,
>>> Philips, Grundig and perhaps others used rim drive in mains
powered
>>> dictation machines with essentially constant speed AC drive
motors.
>>> Grundig tended to use their own proprietary tape cassette, and
non
>>> standard reels, but the Philips models I'm familiar with used two
3"
>>> standard 1/4" reels inside a clear "cassette". The larger inner
hub
>>> size was used. These machines come up on Ebay. Many were
>>> valve(tube) based machine. Philips continued the rim drive
principle
>>> though to a 1/8" tape in another type of cassette, and then on to
the
>>> tiny "mini cassette", also rim drive.
>>>
>>> https://obsoletemedia.org/el-3581/
>>>
>>> Tim
>>>
>>> ----- Original Message -----
>>> From:
>>> "Association for Recorded Sound Discussion List"
>>> <[log in to unmask]>
>>>
>>> To:
>>> <[log in to unmask]>
>>> Cc:
>>>
>>> Sent:
>>> Fri, 12 Jul 2019 16:41:07 -0400
>>> Subject:
>>> Re: [ARSCLIST] Reel-to-Reel tape problem
>>>
>>> Hello, J.D.,
>>>
>>> I tried thinking this problem through a while ago and it hurt my
>>> brain.
>>> You've heard from three experts who all said basically the same
>>> thing--with which I concur.
>>>
>>> What I thought I would add is a little thought experiment.
>>>
>>> These machines did not have a capstan and they pulled the tape by
a
>>> motor attached to the takeup reel. For some reason it has been
>>> referred
>>> to as "rim drive" perhaps because the motor often contacted a
rubber
>>> surface on the rim of the reel table to provide a "gearing" ratio
>>> from
>>> the motor to the reel table, rather than being directly attached
to
>>> the
>>> spindle.
>>>
>>> So, let's assume that we have a constant speed motor that can
deliver
>>>
>>> infinite torque (bear with my and hold your "tsk tsks"). If that
were
>>>
>>> the case, you could calculate the actual speed by knowing the
radius
>>> of
>>> the tape pack at time of recording, the speed of the motor and
pi. As
>>>
>>> the takeup reel filled up, the tape speed would increase, so if
>>> you're
>>> listening on a capstan driven machine, the pitch would drop.
Let's
>>> call
>>> this calculation (A).
>>>
>>> BUT, the motor does not have infinite torque. As the radius of
the
>>> takeup reel tape pack increases, the moment arm gets longer
meaning
>>> that
>>> the same amount of holdback tension may cause the motor to slow
down
>>> a
>>> bit as it can't deliver all the torque that would be required. So
>>> this
>>> adjustment factor could be figured out, but the speed at the end
of
>>> the
>>> tape will fall short of what you calculated in (A) above. Let's
call
>>> this adjustment factor (B).
>>>
>>> So, at this point, the speed at any given point is (A) - (B).
>>>
>>> Now, some odd things enter in that will change this. As the (gasp
>>> zinc
>>> carbon flashlight) batteries discharge, the motor will not be
able to
>>>
>>> deliver as much torque as the batteries will deliver less current
and
>>>
>>> their voltage will drop compared with fresh batteries, so we have
a
>>> third factor.
>>>
>>> And if this unknowable was not enough, the holdback tension was
>>> provided
>>> by pressure pads--usually against the heads--so this creates
multiple
>>>
>>> additional factors for affecting speed:
>>> --the calendaring/polish of both tape surfaces will affect the
>>> friction.
>>> --the environmental temperature and humidity will affect the
>>> friction.
>>> --the cleanliness of the guides/heads will affect the friction.
>>>
>>> So, there you have a quick snapshot of the dynamics of this
system
>>> and
>>> why fixing it in post in software is the best alternative.
>>>
>>> I reiterate what Ted Kendall said, "there were myriad reel-drive
>>> Japanese recorders around at the time, all of which were
different
>>> between samples, never mind designs." And I might add, there were
>>> differences with the same recorder based on tape type, climate
>>> conditions, and battery condition. A fair number of these
recordings
>>> originated in Vietnam in my experience, but thankfully a large
number
>>> of
>>> the ones I have received were recorded with capstan machines. the
>>> Craig
>>> 212 was a classic of the era with a capstan.
>>>
>>> Cheers,
>>>
>>> Richard
>>>
>>>> On 2019-07-12 3:53 p.m., Scott Phillips wrote:
>>>> These would have been rim drive recorders, without a capstan
drive
>>> roller. There is no fixed speed, it was determined by reel motor
>>> torque and the diameter of the amount of tape on either reel at
any
>>> moment. Good luck with that, software is about your only
available
>>> practical tool I know of..
>>>>
>>>> Best regards,
>>>>
>>>> Scott Phillips
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Association for Recorded Sound Discussion List
>>> [mailto:[log in to unmask]] On Behalf Of J. D. Mack
>>>> Sent: Friday, July 12, 2019 1:30 PM
>>>> To: [log in to unmask]
>>>> Subject: [ARSCLIST] Reel-to-Reel tape problem
>>>>
>>>> I'm looking for some advice/info. I sometimes transfer
reel-to-reel
>>> tapes to CD or digital files for my customers. Frequently, I
receive 3
>>> inch tapes from the 1960s that start at one speed and gradually
speed
>>> up or slow down substantially as the tape plays. The speed range
is
>>> usually between 1 7/8 and 3 3/4, but never landing on either
speed. I
>>> can correct for this using Adobe Audition's gliding stretch, but
it
>>> takes quite a bit of trial and error. What sort of tape player
would I
>>> need to hunt down to play these tapes correctly without having to
>>> resort to a software solution? My customers never have any idea
what
>>> brand and model was used to make the recordings.
>>> --
>>> Richard L. Hess email: [log in to unmask]
>>> Aurora, Ontario, Canada 647 479 2800
>>> http://www.richardhess.com/tape/contact.htm
>>> Quality tape transfers -- even from hard-to-play tapes.
>>>
>>> -------------------------
>>> Email sent using Optus Webmail

-------------------------
Email sent using Optus Webmail

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