Re: [ARSCLIST] cassette crackle

[Michael Biel <mbiel@xxxxxxxxx>]

Mike Hirst wrote: 
> In future, is there anything that I can do at playback, to reduce or 
> eliminate the problem - maybe a playback deck with a narrower head, or 
> some other solution? 
Most of what I will say here concerns open-reel tape because cassettes 
are so damn small and some of these problems concern mainly older and 
wider tapes.  But I'll get to cassettes in the end.

I know that this is controversal because of the effect on the bass when 
playing a tape back with a head that has a narrower track than the tape 
had been recorded with.  But using a head with a narrower track can 
overcome a lot of problems on old tapes. 

Some of you other old-times might remember the "Head Track Selector" 
that Revere/Wollensak had on their early quarter-track stereo 
playback/mono record machines.  My first machine 48 years ago was an 
ill-fated Wollensak T-1616, and I later used a T-1515-4.  The selector 
allowed you to move the stereo heads down slightly to center on 
half-track stereo tapes and miss playing part of the guard band with the 
lower track.  Remember that the guard-band on half-track stereo is wider 
than for dual-track mono.  Half of that guard band is in the area where 
the lower track is on four-track stereo.  If you play a half-track 
stereo tape with a four-track stereo head, the right channel will be 
lower in level and noisier because of this unless you drop the head 
lower.  The mechanism then allows you to move the heads further down to 
be able to record and play on the lower track three with the upper head 
gap so you could record four separate mono tracks. 

That's how you were SUPPOSED to use this device.  But I found it had two 
other benefits.  I occasionally came across tapes that had been re-used 
on machines with narrower tracks than it had originally been recorded 
on.  For example, a full track tape might later be used on a half track 
machine, or a half-track tape might be later used on a quarter-track 
machine.  Although the person doing the  new recording might not have 
noticed it,  the original recording might not have been erased by the 
next machine in the guard band area.  By moving the head down to this 
guard band area,  I could recover the older recording.  I found a 
master-dub of the Fred Allen Portrait In Sound broadcast this way.

The other benefit concerned old warped tapes, especially full-track, and 
this is where the controversy comes in.  On many old tapes, especially 
acetate, what had been a razor-edge straight recording from the original 
full track head has now become a curvy-wiggle shaped line.  If you play 
this tape back on a real full track head the high frequencies will drift 
in and out because they will not be totally in azimuith allignment and 
some frequencies will be nulled out when a positive and negative portion 
of the same wave hits the head at the same time.  I found that if I used 
the Wollensak instead of a full track machine, I could move the head 
track selector up and down to find a place where there was no tape 
warpage and none of waves would be nulled.   And as for those who will 
yell HEAD BUMP, I say that sometimes the increased bass sounds good on 
the old tapes, and it can be EQed out if you insist.  

I have seen some people suggest using a four channel quad head to play 
back full track tapes and select one AND ONLY ONE of the tracks to use.  
NEVER mix two tracks together when playing a full track tape.  That also 
goes for cassettes.  Never mix the two stereo tracks together when 
playing a cassette recorded on a mono machine. 

My suggestion is to have a machine set up for just playback with a head 
that can be moved every which way.  I remember machines made for playing 
tapes in disc mastering labs that had a large knob to set azimuith 
instead of using a dinky little screwdriver that would eventually louse 
up the little azimuith screw.  Add to that another knob to set the 
height.  Have adjustable tape guides and adjustable pressure pads for 
the guides and possibly even the head.  Removable, of course.  And have 
the guides be rotating if possible to avoid any non-moving surface to 
contact the tape to reduce shedding, either sticky or powdery.   When I 
was in Moscow in 1995, Alexander Tikhonov took me to a studio that did 
the restoration work for Radio Moscow.  He had a special russian-made 
machine (I don't think it was the Hungarian machines that were almost 
exclusively used in the Radio Moscow studios, but I would have to check 
my videotape) that was designed for restoration playing.  I don't think 
it was a modified or one-off machine.  No recording electronics or 
heads, of course.  (95% of us have no need to record tape anyway.)   It 
had maybe a dozen different interchangable head blocks for all sorts of 
different formats with all sorts of different dials on them for 
adjustments.  Never seen a machine more versatile.   Studer make one 
like this?? 

A last note about cassettes.  The narrow tape does not give some of the 
problems that wider open reel tape has, but controlling the head 
location is also a problem.  The cassette shell adds a whole-nuther set 
of variables.  Nobody has ever made an open reel player for .150 tape, 
have they?  Oh, that little Nagra.  What was its tape width?  .125 or 
.150?  But that thing would probably cost as much as a luxury car now if 
you could find it.  Maybe some of you who have worked more with 
cassettes than I have (I HATE them) can recommend machines that have 
more sturdy and accessable adjustments than the usual crap, and some 
that retract the pressure pad. 

Mike Biel   mbiel@xxxxxxxxx