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JAM-1969-11-17@44=Receiving_Compliments-v2

Messages in this topic: 1
Clitheroe KidDec 19, 2011

Badger Dance,

May I ask you for a technical opinion?

I understand the technical issue involved: thermal effects in the tape recorder's control circuit result in the capstan motor on the tape-drive mechanism 'hunting' for synchronisation, and this can be corrected where the tape has also recorded the 50 Hz 'hum' present on the mains power supply circuit.

My question is this: if the magnetic tape is then copied onto a Transcription Services disc, will correction still be possible?

Or is the 50 Hz mains hum that is present on the original tape recording obliterated by additional 50 Hz mains hum introduced in making the disc recording, if using the standard disc recorders available at the BBC in the 1970s when the Transcription Services recordings which were supplied to the ABC were made.

Stephen Poppitt
Jimmy Clitheroe - The Kid Himself
http://www.JimmyClitheroe.co.uk/

To: just-a-minute@...
From: badger_dance@...
Date: Mon, 5 Dec 2011 18:39:07 -0800
Subject: Re: [just-a-minute] JAM-1969-11-17@44=Receiving_Compliments-v2

Thank you once again for the JAM.

Regarding the synchronisation, consider if this is a function of the computer and the media players that are running at the same time.

I would be surprised if the programmes were now broadcast from tape but a digital source.

The variance in the playback speed is more likely to be the earlier recording/play-back where the speed lock of the capstan motor was 'hunting' around the correct speed lock (thermal effect of the control circuit would be my guess) This would explain the synchronous start, speeding up, then slow down to achieve synchronisation again.

Probably recorded on either a BTR/2s or (at the time a new) B62 tape machine.

It would be possible to correct this variation by digitally fixing the playback speed by synchronisation with the mains 50Hz hum that will present on the tape.

Many old tape machines here: http://www.btinternet.com/~roger.beckwith/bh/tapes/btr2.htm

...or the B62 like this one: http://i.ebayimg.com/00/$%28KGrHqQOKnEE1P2-!LF!BNdtyNh%28EQ~~_12.JPG

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