Re: [ARSCLIST] (Fwd) [ARSCLIST] Fwd: Recording Speed

[George Brock-Nannestad <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad

Hello,

Doug Pomeroy wrote (I have changed the sentence order to facilitate 
communication) :

> Forgive me, but I do not understand this.  Could you explain it in  
> other words?
> Maybe it's simpler than I think.

> >
> > From: Patent Tactics, George Brock-Nannestad
> >
> 
> <SNIP>
> 
> > In use of the tape
> > as a secondary master, the content could be de-chipmunked by  
> > changing the
> > speed of the tape recorder, and the tape rewound to the calibration  
> > track,
> > which was measured by the counter and would give the rpm of the  
> > original
> > record at the de-chipmunked speed. This way, the actual transfer  
> > rpm is
> > completely immaterial and may be chosen for good tracking--we can  
> > still get
> > at the rpm, just as if we had access to the original record.
> 

----- I shall describe it as a witness would, who observed what I am doing. 
However, it is fairly long, and those who detest long postings had better 
leave now.

On the table we have a turntable with pickup, a record to be transferred, a 
tape recorder (nowadays it would be some digital stuff), and my speed 
calibration disc SC. This disc has been prepared by cementing a straightened-
out paper clip to the label, so that a piece of wire sticks up at the center 
of the SC. This permits you to lift the SC and place it anywhere, even on a 
rotating turntable.

The record to be transferred is placed on the turntable and the SC is put on 
top of it - use either the edges or the wire. Start the turntable and the 
tape recorder and let the pickup play the SC track - 5 seconds is plenty. 
Lift off the pickup, lift off the rotating SC by means of the wire, place the 
pickup on the rotating record to be transferred; a smooth operation that does 
not take long. All the time the turntable rotates and the tape runs. When the 
record has finished you can do two things: either just switch everything off 
or replace the SC and play another 5 seconds at the end. When the tape stops 
it contains the following: ca. 5 seconds of calibration signal followed by 
some noises, followed by the transfer of the record (and then possibly 
another 5 seconds of SC for good measure). 

Now, the calibration signal on the tape is made to express in Hertz 10 times 
the rpm of the record - how this is obtained will be told below. This means 
that if you measure 800 Hz as the frequency of the calibration signal, then 
the turntable made 80 rpm at the transfer. If you fiddle with the speed of 
the tape when playing the transfer until you get a reasonable sound (in tune 
with something, for instance, or in a b key for a brass band), then you have 
interpreted the transfer. If you want to know what rpm the turntable should 
have had to provide this reasonable sound from the original record, you go 
back to the calibration part of the tape and reproduce that with no change of 
speed, i.e. with the speed you fiddled your way to for the transfer, if you 
will get for instance 720 Hz, it would correspond to 72 rpm. Based on the 
tape copy you will in other words be able to specify a speed for a record you 
do not necessarily hold in your hand.

This means that you can do your transfer at e.g. 33 1/3 rpm, which improves 
tracking and is a standard speed obtainable from almost all modern 
turntables. On reproduction of the tape you increase the speed of the tape 
until your SC part of the transfer provides, say, 780 Hz, which will then 
make the sound of the transferred record sound as if it was reproduced at 78 
rpm. There are some de-emphasis issues that we do not need to go into here, 
because they have nothing to do with pitching the record. The whole idea is 
that you have the same change of pitch in the SC signal as you have in the 
record signal, because they were transferred under the same speed conditions.

By making the SC signal having the special relationship to rpm we avoid 
calculations that one would otherwise have to make. It is a signal that will 
provide 600 Hz at 60 rpm, which is 1 revolution per second. This means that 
the groove has to have 600 cycles on one revolution - it could be a locked 
groove! When the turntable speed is increased, the frequency increases in 
proportion. I did toy with the idea of having a special nickel turntable 
platter (in effect a mother) made like a turntable mat with such a locked 
groove at a radius that was outside any record that one might want to 
transfer. Instead of placing and lifting off a calibration record, one would 
simply play the locked groove before (and after) playing the record. Another 
way would be to have a timebase signal derived from the turntable platter and 
record that on the second track of a stereo tape (or a third track when 
recording digitally). I have not myself used anything but my own Speed 
Calibrating Record SC-1. And nickel is not a good turntable mat material, 
because good MC pickups are seriously attracted downwards to this material.

I hope that this has clarified matters.

Kind regards,


George