When the conversation comes round to crosstalk, most engineers will recall
an experience when they or the producer decided that one track of the recording
wasn’t really working and it could be dispensed with. The first action
would be to pull the fader down, but the offending instrument, particularly
if it was some kind of percussion, could clearly be heard in the background.
Then it was erased from the tape but the result was no better – it was present
at low level on other tracks. Recorded crosstalk is one of the worst problems
you can get, and if it occurs in the mixer then you need a new mixer which will
make things a bit better. If it occurs on your analogue multitrack then you
need to switch to digital because crosstalk doesn’t happen at all (apart
from a minute amount in the electronics of the machine rather than the digits).
Particularly on narrow gauge multitracks, crosstalk is evident between adjacent
tracks and most noticeable at bass frequencies. It is reduced by noise reduction
but not eliminated.
There is another kind of crosstalk that occurs in the record/playback head
as you are recording. This appears predominantly at high frequencies and, although
it doesn’t affect the recording, it makes life more difficult for you by
changing the frequency balance of the mix as you record. Obviously, recording
a new part, artistically speaking, is all about the interaction between the
instrumentalist and the parts already recorded on the tape. If the previously
recorded tracks sound different to the way they should then this will inevitably
affect the way the musician plays his part to some extent. Another point to
mention is that if you try to bounce a recording onto an adjacent track, this
type of crosstalk may cause howlround in the head itself which manifests itself
as a high frequency tone of tweeter blowing magnitude.
If I may continue with the subject of crosstalk for a moment, anyone who has
used timecode to synchronise a MIDI sequencer to tape will know that this awful
sound tends to leak anywhere and everywhere, so a digital system which is not
susceptible to crosstalk should be of great benefit. Timecode also causes two
way crosstalk problems with the adjacent track, track 7, 15 or 23 depending
on the scale of your facility. The first way is obviously that the timecode
may bleed through to the adjacent track and appear in your mix. The other is
that high level signals, particularly bass, may leak into the timecode and interfere
with synchronisation. If your sequencer grinds to a halt when you try to record
on the penultimate track, this is the cause of the problem.
The other problems caused by using timecode on a multitrack recorder include
the loss of a valuable audio track and the fact that drop outs can cause the
timecode to be intermittent. If you have suffered from intermittent timecode
then you will know how unpleasant it is. One moment you are happily recording
onto your sequencer, then it emits a rapid stutter of metronome clicks and stops.
Since sequencers have, for some unaccountable reason, been designed to respond
only to perfect timecode (or timecode translated into perfect MTC) you have
a problem. The answer to this problem is to buy a synchroniser which will ride
over any bumps in the code until good code emerges once again from the tape.
Now you have the problem that each time you want to stop the tape, the sequencer
carries on for another couple of bars, because the synchroniser thinks it is
compensating for a big drop out! If you record timecode on a digital recorder
as you would on analogue then not only will you be immune to crosstalk problems,
drop outs do not exist (unless the machine is badly out of alignment or the
tape is in an exceptionally bad condition).