[QuadList] Ampex AST heads and CMC DPT heads--what's different?

[Ted Langdell]

Hey Tim,

Ditto what Don said. (Thanks!)  I'd be curious to know what differences 
—if any—one would be able to observe in the signal, both visually and  
with test gear.

Since Sony was a third party in the "follow the track with a  
vertically moveable head" game, how does Sony's Dynamic Tracking head  
differ, and are there differences with other 1" recorder maker's ways  
of doing the same thing... IE Hitachi, NEC, etc.

Ted.

Must be lack of sleep, but this discussion has me thinking that the  
concept behind DPT might help some drivers with their parallel parking!

Ted


On May 8, 2010, at 1:00 AM, Tim Stoffel wrote:

> On Fri, 2010-05-07 at 20:56 -0700, Ted Langdell wrote:
>> Yes... AST was an Ampex trademark, and DPT "Dynamic Parallell
>> Tracking" was apparently a TM of CMC.
>>
>>
>> I'm just curious to know what's different... and the story behind it.
>>
>>
>> Ted
>>
>   An AST head has a single, planar bimorph crystal with the head tip
> glued to the end of it. When the head tip moves up and down with the
> bimorph, it describe a (small arc), with the angle of the head tip
> contacting the tape changing as the head moves.
>   CMC determined that the aforementioned angle change hurt the
> performance of the head. So, they added a cantilever to the bimorph
> crystal that actually carries the head tip. Now, when the bimorph  
> moves
> up or down, the cantilever adjusts in such a way as to keep the head  
> tip
> perpendicular to the tape.
>    In general, AST and DPT heads are interchangeable. However, some
> machines required that some pots in the AST servo be preset to a  
> certain
> value before changing head types, to get the servo 'close enough' to  
> be
> stable for alignment.
>
> Tim Stoffel
>
>
> _______________________________________________
> Please trim posts to relevant info when replying!
> Send QuadList list posts to QuadList at quadvideotapegroup.com
> Your subscribe, unsubscribe and digest options are here:
> http://mail.quadvideotapegroup.com/mailman/listinfo/quadlist_quadvideotapegroup.com

Ted Langdell
Secretary