Hence, possibly, the Play Trim knob on NAD decks which put a variably 
vicious lift in the top octave to improve replay on Dolby cassettes?

----- Original Message ----- 
From: "Richard L. Hess" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, January 14, 2011 5:00 PM
Subject: Re: [ARSCLIST] Association for Recorded Sound Discussion List 
<[log in to unmask]>


> Hello, Goran,
>
> A friend of mine (who would rather not be dragged into more conversations 
> about this) who worked in the Ampex Standard Tape Lab, and who is not part 
> of this list, reported to me that no one could explain why, but some 
> cassettes that were recorded would lose high frequencies if stored for 
> about a year. The loss was substantial. While Don no longer has any notes 
> on this, I have generally found his memory and knowledge to be reliable. 
> His recollection is that the 15 kHz loss was in the neighbourhood of 10 dB 
> in the worst examples.
>
> I have grilled him on this, and he is convinced that it happened and it 
> was not due to external magnetic fields.
>
> One theory that was proposed at the time was magnetostriction due to the 
> relatively small radii of the guides in the cassettes.
>
> He used Dragons and other top-end cassette machines in the lab. He was 
> responsible for a while for manufacturing Ampex standard "test" 
> [calibration] tapes for audio and video.
>
> Cheers,
>
> Richard
>
> On 2011-01-14 11:43 AM, Goran Finnberg wrote:
>> None of the high speed duplicated cassettes I still have, several 100, 
>> and
>> none of my approx 60 BASF, Nakamichi and RCA test cassette tapes show any
>> change in level or frequency response either objectively or subjectively 
>> IF
>> the azimuth is very carefully adjusted on my Dragon, 582 or 682 Nakamichi
>> decks.
>
> -- 
> Richard L. Hess                   email: [log in to unmask]
> Aurora, Ontario, Canada           (905) 713 6733     1-877-TAPE-FIX
> http://www.richardhess.com/tape/contact.htm
> Quality tape transfers -- even from hard-to-play tapes.