8 track looping gaps in audio

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diurnalburdens
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8 track looping gaps in audio

Post by diurnalburdens » Wed Apr 05, 2017 2:34 am

I have a question about 8 track looping (though this probably applies to cassettes too).

I keep getting a short gap in audio when I play back a loop I recorded. At first I thought this was because of the erase head ie the distance between the erase head and the record head, meaning the erase head is blanking a section ready to be recorded onto and when I press stop I'm left with that gap. So I tried to add a switch to cut out the erase head from the circuit but I still get a gap in audio.
Any ideas? Is it just bad splicing on my part?
I'm just wondering how you get a clean loop. I'd prefer to be able to record and loop live, rather than be chopping pre-recorded audio into loops.

I've tried so many things: stopping quickly when recording, switching out the erase head, yanking out the cart whilst recording, holding in play and record and just switching straight to play when I'm done recording. Everytime I still get that little gap in audio.

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Misomusist
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Re: 8 track looping gaps in audio

Post by Misomusist » Wed Apr 05, 2017 3:47 am

How do you know when to stop?

I'm guessing you have a loop of tape, spliced with no leader, so how do you know when the loop ends?

Is it the type of system with a combined playback/record head, or are they separate, can you record and listen to the repro as you go, and just keep going round and round, without the erase head, do you hear any gaps then?
I think trying to quantify music is one of the biggest wastes of time in the world, like discussing your favourite colour or deity or pizza topping. People should realise that and get on with their life.

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Re: 8 track looping gaps in audio

Post by diurnalburdens » Wed Apr 05, 2017 3:59 am

Misomusist wrote:
Wed Apr 05, 2017 3:47 am
How do you know when to stop?

I'm guessing you have a loop of tape, spliced with no leader, so how do you know when the loop ends?

Is it the type of system with a combined playback/record head, or are they separate, can you record and listen to the repro as you go, and just keep going round and round, without the erase head, do you hear any gaps then?
Loop spliced with no leader yes.
I've timed the length of tape so I know how long the loop should be. I just make sure I go over that when recording, so that I'm taking a 6 second snippet (when using the 6sec cart) of a longer bit of audio.

It's a combined rec/play head so no monitoring what's on the tape whilst recording, unfortunately.

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Re: 8 track looping gaps in audio

Post by diurnalburdens » Wed Apr 05, 2017 4:07 am

Someone on another forum is saying that later 8 recorders than mine (Akai CR81d) have a delay/relay between the erase and rec/play head, which makes for seamless drop ins and drop outs.
If that's the case then I'll have to take a look at newer models as I don't have the skills to add a relay circuit.

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Re: 8 track looping gaps in audio

Post by crochambeau » Wed Apr 05, 2017 6:26 am

Does the gap happen at the point you're hitting stop?

I would think turning off the erase function would resolve any drop outs, presuming your splice isn't gapped.

I recall 8 track carts have a metallic leader or some such to actuate head shift, maybe that's playing hell?
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Re: 8 track looping gaps in audio

Post by xdugef » Wed Apr 05, 2017 6:38 am

crochambeau wrote:
Wed Apr 05, 2017 6:26 am

I recall 8 track carts have a metallic leader or some such to actuate head shift, maybe that's playing hell?
A few posts up he says there's no leader.. much like the current state of the union

I guess as a sanity check I'd try recording a continuous tone over a long section of tape.. then make a loop.. also be sure to splice the tape at a diagonal. When you play this back the only variation you should hear is at the exact point of the loop. If you are making a splice at a 90 degree angle then that might also explain the gap you are hearing.

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Re: 8 track looping gaps in audio

Post by diurnalburdens » Wed Apr 05, 2017 7:20 am

crochambeau wrote:
Wed Apr 05, 2017 6:26 am
Does the gap happen at the point you're hitting stop?

I would think turning off the erase function would resolve any drop outs, presuming your splice isn't gapped.
Seems to be at the stopping point yes.
Maybe I got the switch wrong on the erase head, but it seemed to introduce unwanted clicks and pops into the audio. It definitely stopped erasing though as the previous signal was still there.
There was only one wire coming from the erase head to the board, so I used that, naturally....

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Re: 8 track looping gaps in audio

Post by diurnalburdens » Wed Apr 05, 2017 7:26 am

xdugef wrote:
Wed Apr 05, 2017 6:38 am
crochambeau wrote:
Wed Apr 05, 2017 6:26 am

I recall 8 track carts have a metallic leader or some such to actuate head shift, maybe that's playing hell?
A few posts up he says there's no leader.. much like the current state of the union

I guess as a sanity check I'd try recording a continuous tone over a long section of tape.. then make a loop.. also be sure to splice the tape at a diagonal. When you play this back the only variation you should hear is at the exact point of the loop. If you are making a splice at a 90 degree angle then that might also explain the gap you are hearing.
Tried the loop from pre-recorded audio tone and it's continuous.
Splice is 45degree.
I'm convinced it's something to do with the erase head and its distance to the rec/play head. But beyond trying to switch it out again, I'm stumped.
What would explain all the pops and crackles I get when it's switched off?

I'm sure someone on here switched out the erase head on a reel-to-reel at one point. Tim?

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Re: 8 track looping gaps in audio

Post by crochambeau » Wed Apr 05, 2017 8:59 am

A pop sounds like a bias spike of other current shift through the record head winding when you switch out. Resolving that sort of thing might be as easy as employing a "pop free" mod like you'd do on a bypass switch, or it might need something more involved.

If you can do audio on audio you have disengaged the erase head.
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Re: 8 track looping gaps in audio

Post by Misomusist » Wed Apr 05, 2017 9:05 am

Oh it's an 8-track 8 track!

And there's no metallic leader on the tape to make the head jump to the next track?

You don't hear the head clunk or anything?

Like crochambeau says if you can do sound on sound, then the erase is OK, but what happens if you go over 6 seconds? Can you do a pop-free loop, just letting it play and play, does the pop only happen when you turn it off? You said you yanked the cart, and it still happens?
I think trying to quantify music is one of the biggest wastes of time in the world, like discussing your favourite colour or deity or pizza topping. People should realise that and get on with their life.

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Re: 8 track looping gaps in audio

Post by crochambeau » Wed Apr 05, 2017 9:12 am

Misomusist wrote:
Wed Apr 05, 2017 9:05 am
And there's no metallic leader on the tape to make the head jump to the next track?
Cue Adrian in five... four... three...
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Re: 8 track looping gaps in audio

Post by xdugef » Wed Apr 05, 2017 9:44 am

crochambeau wrote:
Wed Apr 05, 2017 9:12 am
Misomusist wrote:
Wed Apr 05, 2017 9:05 am
And there's no metallic leader on the tape to make the head jump to the next track?
Cue Adrian in five... four... three...
Just put a goddamn vactrol in there and call it a day FFS

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Re: 8 track looping gaps in audio

Post by crochambeau » Wed Apr 05, 2017 10:51 am

That would actually possibly work.
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Re: 8 track looping gaps in audio

Post by diurnalburdens » Thu Apr 06, 2017 5:04 am

crochambeau wrote:
Wed Apr 05, 2017 8:59 am
A pop sounds like a bias spike of other current shift through the record head winding when you switch out. Resolving that sort of thing might be as easy as employing a "pop free" mod like you'd do on a bypass switch, or it might need something more involved.

If you can do audio on audio you have disengaged the erase head.
Ideally I'd have a momentary switch in there to just drop out the erase towards the end of the loop recording.
Something is definitely not right when it's switched off though. It's a series if pops, not just when I hit the switch.
Need to try it again.

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