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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 11:58:24 +1000

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (168 lines)


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

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