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DASH operation

A post by David Mellor
Tuesday February 01, 2000
A description of the operation of DASH (digital audio stationary head) multitrack recorders.
DASH operation

The first thing you are likely to want to do with your new DASH machine is of course to make a recording with it, but it would be advisable to read the manual before pressing record and play. Some of the differences between digital and analog recording stem from the fact that the heads are not in the same order. On an analog recorder we are used to having three heads: erase, record and play. DASH doesn't need an erase head because the tape is always recorded to a set level of magnetism which overwrites any previous recordings without further intervention. So the first head that the tape should come across should be the record head. Right?

Wrong. The first head is a playback head, which on an basic DASH machine is followed a record head only. If this seems incorrect, you have to remember that while analog processes take place virtually instantaneously, digital operations take a little time. So if you imagine analog overdubbing where the sync playback signal comes from the record head itself, you can see why this won't work in the digital domain. There will be a slight delay while the playback signal is processed, and another delay while the record signal is processed and put onto tape. 105 milliseconds in fact, which corresponds to about 75 mm of tape. To perform synchronous overdubs there has to be a playback head upstream of the record head otherwise the multitrack recording process as we know it just won’t work. For most purposes two heads are enough, and a third head is available as an option if you need it, and you'll need it if you want to have confidence monitoring. (There are no combined record/playback heads, by the way, all are fixed function).

On any digital recording medium the tape has to be formatted to be used. On DAT the formatting is carried out during recording, but on DASH it is often better to do it in advance. The machine can format while recording - in Advance Record mode - but this is best done in situations where you will be recording the whole of the tape without stopping. If you wish, you can ‘pre format’ a tape but this obviously takes time. You can take comfort from the fact that it can be done in one quarter of real time, and the machine will lay down timecode simultaneously.

Since there are different ways to format a tape and make recordings, the 3342S has three different recording modes: Advance, Insert and Assemble. Advance mode is as explained above. Insert is for when you have recorded or formatted the full duration of the material and you want to go back and re-record some sections. Assemble is when you want to put the tape on, record a bit, play it back, record a bit more etc, as would typically happen in classical sessions.

A post by David Mellor
Tuesday February 01, 2000 ARCHIVE
David Mellor has been creating music and recording in professional and home studios for more than 30 years. This website is all about learning how to improve and have more fun with music and recording. If you enjoy creating music and recording it, then you're definitely in the right place :-)
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