The End of Analogue - Is analogue multitrack recording dead? (part 4)
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 wasnt 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 doesnt 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 doesnt 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).