How to cut 12min endless loop cassette down to 9min - UK Vintage Radio Repair and Restoration Discussion Forum

kriminel99 · 27th Oct 2011, 11:05 am

Hi,

I need a 9 min endless loop audio cassette for an exhibition I have coming up.

They don't seem to exist, but I know where to get 12 min endless loop cassettes. I am going to cut a 3 minute section out of the loop, splice it back together and then record on it. It's critical that it's exactly 9 mins, because it's showing alongside a 16mm film ( on a looper) which is 9 mins. I know they will go a little out of synch (it's not lip synch) but I would like to keep them as much in synch as possible.

I know this is relatively simple but I've never done it before and this piece will obviously be looping, so I want to make sure I get it absolutely right and that the splice is strong and clean. So expert advice is much appreciated!

First thing is: can anyone tell me exactly how many seconds per foot of 1/8th inch audio (cassette) film? This information would make the whole procedure a lot easier and less of a mess. I could just physically measure it.

Secondly, I've been advised to use a splicing block for this. The only one I can find on ebay is this. It comes with tape:

http://cgi.ebay.co.uk/ws/eBayISAPI.d...#ht_956wt_1329

Does it seem decent enough for the job?

And lastly, should I find the pre-existing splice and use that to make the new cut, or does it not really matter?

Thanks for your time,

Charlie

Paul Stenning · 27th Oct 2011, 11:32 am

Audio cassette tape runs at 1 7/8" per second. You can't guarantee that a 12 minute loop tape will be exactly 12 minutes, it could be several seconds either way, more likely a bit overlength.

Yes, use a splicing block and splicing tape That one you found should be fine. It looks like it has a 1/8" guide on the back edge so presumably the clamps can be rotated.

You will probably hear the join unless it's perfect (and if this is the first time you've done it it won't be perfect. Ideally do it at the original join though that will probably be perfect and difficult to find so I wouldn't worry too much about it.

I don't know how endless loop cassettes work so don't know how easy it would be to remove 3 minutes of tape and keep the rest working.

Does the recorder/player have variable pitch control, and if so can it be speeded up enough to make 12 minutes of tape run in 9 minutes? If so that may be an easier way of doing this. You'll need some sort of speed tweaking anyway to keep the tape and film roughly in synch.

An easier way of doing the whole job would be to digitise the film, add the soundtrack and play the whole thing on repeat on a DVD player or laptop with a suitable projector. No film and tape to break, get out of synch etc.

richrussell · 27th Oct 2011, 11:33 am

Didn't you post asking for this a day or so ago? And I think all the things you needed to know (tape speed, splicing equipment) were given in that thread?

julie_m · 27th Oct 2011, 1:45 pm

You need to cut the wanted length of tape, because you don't know for certain that it's exactly 12 minutes long.

9 minutes = 540 seconds.
1 second of tape = 47.625 mm. = 0.047625 m.
540 seconds of tape = 25.7175 m.

Leave about 25cm. slack at the centre hub of the spool, as you wind all but another 25cm. of the rest of the tape onto it. Join the ends with a diagonal cut and as little splicing tape as you can get away with (bear in mind the splice is going to be pulled from the centre hub, over the top of the spool and down to the first guide). Then place the spool in the bottom half of the cassette housing, route the tape around the guides and take up the slack by turning the spool. Lastly, fit the top half of the cassette housing.

But to be honest, Paul's right, you'd be much better off doing it digitally -- the easiest way (no computer required, let alone obscure software) is to use an old analogue video camera, and feed its video signal and the wanted audio into a DVD recorder using a phono-SCART adaptor. That way, you can be sure it won't lose sync and there is no splice to break.

Darren-UK · 27th Oct 2011, 2:10 pm

Quote:

Originally Posted by richrussell

Didn't you post asking for this a day or so ago? And I think all the things you needed to know (tape speed, splicing equipment) were given in that thread?

The earlier thread is a 'Looking for' whilst this one is a 'How to'. Nonetheless, as both threads effectively duplicate each other in respect of information given, we've closed the earlier one. We can now concentrate the discussion here without any confusion arising.

ALANS ANITAS · 27th Oct 2011, 6:50 pm

Hi

I feel it very unlikely that the speed of the projector and also that of the tape recorder will be accurate to better than +or - 2%. so even loose synchronisation will be impossible. Almost all 16mm sound projectors use a mechanical governor, which will vary slightly, silent projectors will have variable speed DC motors. Recording tape will stretch slightly.

The Eumig P8 Imperial, 8mm projector which is fairly common, has a synchroniser which regulates the projector speed, using the tape speed as a standard, however you have to use a reel to reel recorder running at 3.75 inches per second.

Regards

ALAN

TIMTAPE · 27th Oct 2011, 9:46 pm

Quote:

Originally Posted by Paul Stenning

An easier way of doing the whole job would be to digitise the film, add the soundtrack and play the whole thing on repeat on a DVD player or laptop with a suitable projector. No film and tape to break, get out of synch etc.

I agree this would be the best way to go.

However digitising the 16mm film is a whole exercise in itself. There's a lot more to it than simply running the film and pointing a camcorder at the projector's screen. There are multiple issues involved.

These days results very close to the original image quality are possible but the transfer would be best left to people with the expertise and the equipment if preserving the original image quality is important.

Tim

julie_m · 27th Oct 2011, 9:59 pm

Slightly mad idea: If the tape is deck is stereo, you could use one channel for mono sound and record the frequency and voltage of the mains (from a step-down transformer, suitably attenuated) on the other. Run the projector motor via a step-up transformer from a power amplifier. With the gain set just right, the original mains as the tape was recorded will be recreated faithfully every time it is played.

TIMTAPE · 28th Oct 2011, 7:40 am

Another slightly less complex way would be to record and play the audio on a digital device. Long term speed stability virtually guaranteed.

27th Oct 2011, 11:05 am	#1
kriminel99 Retired Dormant Member Join Date: Aug 2011 Location: Glasgow Posts: 4	How to cut 12min endless loop cassette down to 9min Hi, I need a 9 min endless loop audio cassette for an exhibition I have coming up. They don't seem to exist, but I know where to get 12 min endless loop cassettes. I am going to cut a 3 minute section out of the loop, splice it back together and then record on it. It's critical that it's exactly 9 mins, because it's showing alongside a 16mm film ( on a looper) which is 9 mins. I know they will go a little out of synch (it's not lip synch) but I would like to keep them as much in synch as possible. I know this is relatively simple but I've never done it before and this piece will obviously be looping, so I want to make sure I get it absolutely right and that the splice is strong and clean. So expert advice is much appreciated! First thing is: can anyone tell me exactly how many seconds per foot of 1/8th inch audio (cassette) film? This information would make the whole procedure a lot easier and less of a mess. I could just physically measure it. Secondly, I've been advised to use a splicing block for this. The only one I can find on ebay is this. It comes with tape: http://cgi.ebay.co.uk/ws/eBayISAPI.d...#ht_956wt_1329 Does it seem decent enough for the job? And lastly, should I find the pre-existing splice and use that to make the new cut, or does it not really matter? Thanks for your time, Charlie

27th Oct 2011, 11:32 am	#2
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,071	Re: How to cut 12min endless loop cassette down to 9min Audio cassette tape runs at 1 7/8" per second. You can't guarantee that a 12 minute loop tape will be exactly 12 minutes, it could be several seconds either way, more likely a bit overlength. Yes, use a splicing block and splicing tape That one you found should be fine. It looks like it has a 1/8" guide on the back edge so presumably the clamps can be rotated. You will probably hear the join unless it's perfect (and if this is the first time you've done it it won't be perfect. Ideally do it at the original join though that will probably be perfect and difficult to find so I wouldn't worry too much about it. I don't know how endless loop cassettes work so don't know how easy it would be to remove 3 minutes of tape and keep the rest working. Does the recorder/player have variable pitch control, and if so can it be speeded up enough to make 12 minutes of tape run in 9 minutes? If so that may be an easier way of doing this. You'll need some sort of speed tweaking anyway to keep the tape and film roughly in synch. An easier way of doing the whole job would be to digitise the film, add the soundtrack and play the whole thing on repeat on a DVD player or laptop with a suitable projector. No film and tape to break, get out of synch etc. __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster

27th Oct 2011, 11:33 am	#3
richrussell Heptode Join Date: Jul 2008 Location: Selby, North Yorkshire, UK. Posts: 979	Re: How to cut 12min endless loop cassette down to 9min Didn't you post asking for this a day or so ago? And I think all the things you needed to know (tape speed, splicing equipment) were given in that thread?

27th Oct 2011, 1:45 pm	#4
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: How to cut 12min endless loop cassette down to 9min You need to cut the wanted length of tape, because you don't know for certain that it's exactly 12 minutes long. 9 minutes = 540 seconds. 1 second of tape = 47.625 mm. = 0.047625 m. 540 seconds of tape = 25.7175 m. Leave about 25cm. slack at the centre hub of the spool, as you wind all but another 25cm. of the rest of the tape onto it. Join the ends with a diagonal cut and as little splicing tape as you can get away with (bear in mind the splice is going to be pulled from the centre hub, over the top of the spool and down to the first guide). Then place the spool in the bottom half of the cassette housing, route the tape around the guides and take up the slack by turning the spool. Lastly, fit the top half of the cassette housing. But to be honest, Paul's right, you'd be much better off doing it digitally -- the easiest way (no computer required, let alone obscure software) is to use an old analogue video camera, and feed its video signal and the wanted audio into a DVD recorder using a phono-SCART adaptor. That way, you can be sure it won't lose sync and there is no splice to break. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

27th Oct 2011, 6:50 pm	#6
ALANS ANITAS Rest in Peace Join Date: Jun 2006 Location: North West Northamptonshire, UK. Posts: 346	Re: How to cut 12min endless loop cassette down to 9min Hi I feel it very unlikely that the speed of the projector and also that of the tape recorder will be accurate to better than +or - 2%. so even loose synchronisation will be impossible. Almost all 16mm sound projectors use a mechanical governor, which will vary slightly, silent projectors will have variable speed DC motors. Recording tape will stretch slightly. The Eumig P8 Imperial, 8mm projector which is fairly common, has a synchroniser which regulates the projector speed, using the tape speed as a standard, however you have to use a reel to reel recorder running at 3.75 inches per second. Regards ALAN

27th Oct 2011, 9:59 pm	#8
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: How to cut 12min endless loop cassette down to 9min Slightly mad idea: If the tape is deck is stereo, you could use one channel for mono sound and record the frequency and voltage of the mains (from a step-down transformer, suitably attenuated) on the other. Run the projector motor via a step-up transformer from a power amplifier. With the gain set just right, the original mains as the tape was recorded will be recreated faithfully every time it is played. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

28th Oct 2011, 7:40 am	#9
TIMTAPE Octode Join Date: Jul 2006 Location: Perth, Western Australia Posts: 1,969	Re: How to cut 12min endless loop cassette down to 9min Another slightly less complex way would be to record and play the audio on a digital device. Long term speed stability virtually guaranteed.