Preview Master Recorder for Cutting Lathe

My A80 preview headblock

        The purpose of preview master recorder is to create preview signal to lathe for dynamic groove adjusting if necessary.  There are many kinds of design of "extending" the tape path by various manufactures to have additional playback head installed and sufficient "delay" time.

        The following pictures are collected from web to show different kind of preview design by Nagra, Ampex, Studer, TFK, Scully and MCI.  They are very rare in the market.

Preview master recorder當年有它的目的, 在正式刻片前提供一組preview signal給刻片機系統做"反應". 對於一般playback/record來說, 可以說沒有此必要.  

粽觀各家preview master recorder的設計, 大部分都是以各樣機構延伸方式, 製造出裝preview playback head的空間, 以及拉出需要的"delay timing", 讓刻片系統來得及反應.

由於盤帶機有不同的帶速, 如果以固定的"delay time"來說, 30ips的preview tape path的長度就必須兩倍於15ips的長度. 所以Studer的preview headblock的設計才會使用這麼多roller. 不同的帶速必須走不同的路徑以維持相同的"delay time".