I don't think the speed stability of the Magnetophon K series could be taken
for granted, anyway. The BBC acquired a pair of K7s in the late 'forties to
play European tapes for the Third Programme, and there was a row about a
broadcast of Dalibor which went out a few per cent sharp. This led, we are
told (in Pawley), to the installation of frequency monitoring and speed
correction facilities for recording channels - but a BBC greybeard told me
once that the adjustment of pinch pressure on those Magnetophons was
critical and could easily throw the speed the wrong way on its own. Either
way, it wasn't something to set your watch by...
----- Original Message -----
From: "Shai Drori" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, November 05, 2009 5:40 AM
Subject: Re: [ARSCLIST] power line frequency
> You're correct. Jack had magnetofons. They used synchronous motors but had
> a huge blower on the capstan motor to stabilize speed and cool the
> spooling motors. A very interesting design.
>
> Richard L. Hess wrote:
>> At 02:08 AM 2009-11-04, Shai Drori wrote:
>>> The solution is very simple. The capstan of the Tonschreiber did not run
>>> off the incoming AC but had an oscillator and amplifier as a servo. It
>>> could run at any speed from I think 9 to 130 cm/sec.
>>
>> Hello, Shai,
>>
>> That is true, but I don't think Jack Mullin's machines were the
>> Tonschreiber model and were lacking the oscillator and amplifier, but
>> also, I do not believe them to be true Hysteresis-Synchronous motors,
>> either.
>>
>> The point here is that if Tonschreibers were used (or the circuitry
>> associated with them was put into a studio recorder) then George's
>> discussion of mains frequency would need another footnote.
>>
>> Cheers,
>>
>> Richard
>>
>> Richard L. Hess email: [log in to unmask]
>> Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
>> Detailed contact information: http://www.richardhess.com/tape/contact.htm
>> Quality tape transfers -- even from hard-to-play tapes.
>
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