Magnetic Tape Edit - "Butt-Jointed"?

[Whoops]

Hi,
I'm doing tape loops for my Copicat delay unit.

The instructions say the tape loop should be 570mm and "Butt-Jointed", could you please let me know what "Butt-Jointed" in this context means?
Is it a type of edit , tape cut?

I normally cut the tape for these loops Diagonally...

Thanks

 

[soapfoot]

It means a straight vertical splice--no angle

 

[Whoops]

It means a straight vertical splice--no angle

Thank you so much, so that means there's no crossfade in the Edit? is that it?

Strange I would think it would be better to have a crossfade

 

[abbey road d enfer]

The instructions say the tape loop should be 570mm and "Butt-Jointed"

It's rather strange.  I've always made tape loops with diagonal joints.
I wonder why they would recommend right-angle joints...?
There's a subject for experiments.
Indeed, the effects of a splice are much less critical for an echo loop than for an edit in a mix, but what would be the advantages?
I guess it's too late for asking Watkins.

 

[Whoops]

It's rather strange.  I've always made tape loops with diagonal joints.

Same with me

I wonder why they would recommend right-angle joints...?
There's a subject for experiments.
Indeed, the effects of a splice are much less critical for an echo loop than for an edit in a mix, but what would be the advantages?

The way I see it is that with a right-angle joint you can have a click/pop in every loop rotation...

 

[radardoug]

Just do a standard 45 degree splice, I dont think they knew what they were doing.

 

[Gold]

If I had to guess I’d say it was so if all you had was a butter knife and scotch tape you could still use your tape echo.

 

[Tubetec]

I think the butt splice might be slightly more resilient if possibly more audible ,thats probably the main reason they reccomend it.
The main thing I found to cause noise is use of a razor blade thats not properly demagnetised , that will leave a permanent noise on the tape near the cut .
MkI and MkII copicats dont have any erase head so there is a permanent magnet in the take up arm which scrubs the sound . Again a tape path with even small amounts of magnetism can cause clicks and pops so degauss regularly. I found the magnet in my MkII very weak and didnt completely erase , it left a partial ghost echo on the tape next time it came around , sometimes that works quite nicely , other times you want better erasure. I mounted a small flat N'dym magnet on a screw adjuster , now I can dial in the amount of erase I want .

 

[JohnRoberts]

I expect the butt slice will cause a briefer but louder perturbation, but I prefer diagonal splice.

Caveat, I haven't spliced magnetic tape since the 50s.... and back then I didn't do many.

JR 

 

[soapfoot]

I suspect John is correct.

Also, it's probably not really correct to call it a "crossfade" in this instance, as signal is being recorded onto an already-spliced tape (as opposed to editing two pieces of prerecorded tape together)

Assuming a perfect joint, it should theoretically be able to record exactly like any other piece of tape.

 

[JohnRoberts]

I suspect John is correct.

Also, it's probably not really correct to call it a "crossfade" in this instance, as signal is being recorded onto an already-spliced tape (as opposed to editing two pieces of prerecorded tape together)

Assuming a perfect joint, it should theoretically be able to record exactly like any other piece of tape.

With a diagonal splice the tape head will read the sum of both pre-recorded tape segments creating a smooth transition. Razor blade splices were used mainly to slice and dice pre-recorded music performances to rearrange them.

For today's TMI back in the 70s I worked at a company that made electronic pitch shifting gadgets to allow blind listeners to speed up prerecorded talking book cassettes and hear them with the pitch restored back to normal.

A much more expensive high quality competing technology was rotating head machines, mechanically similar to video recorders the, tape would wrap around a rotating multi-head assembly that spins and can generate a relative tape speed that is faster/slower than absolute tape speed for faster playback with pitch shift restored down to normal. The magnetic signal from the tape would seamlessly overlap into adjacent heads with longer wavelength, lower frequency signal splicing together smoothly. 

It was hard to mimic electronically what the mechanical rotating heads could do (decades ago).

JR

 

[soapfoot]

Yes!

I was attempting to clarify that, in a tape echo (the OP’s application), we’re not splicing two pieces of prerecorded tape together (therefore a diagonal splice does not produce a crossfade in this application).

The rotating drum head machine you describe was called the Eltro, and it was a fascinating piece of engineering!

 

[Tubetec]

Im not trying to argue that for most purposes a diagonal splice will be more appropriate .
In some cases a diagonal cut just isnt appropriate like for instance if you wanted to edit parts on 2 inch tape , likewise editing a stereo recording at the start and finish where theres silence youd mostly go with diagonal, If you were editing the music itself Id say straight cut is most appropriate . As I said previously the quality of the result you get in any case is down to technique and materials ( good hands, good sticky tape ,good block ,good blade).

What Ive personally found with the copicat is diagonal splices tend to open up after a while , the capstan has a very narrow diameter so the tape has to go around a tight radius and the entire tape loop remains under tension at all times .

I did quite a bit of 1/4 inch tape editing back in the mid 90's , mostly adding lead-in and lead-out sections in green and red respectively , but also some musical edits . Im not really sure how the rotary head digital machines come into the discussion about tape editing , as far as I know formats like that arent editable . Just as an example an ADAT tape uses the rotary head type set up , I never heard of anyone trying to cut or splice those. The Sony Dash multitrack recorders had stationary heads, I never worked with those machines but again I never heard of anyone trying to edit the tapes either. 

Anyway just my thrupence worth , we wont fall out over it 
I might dig out my copy of 'Sound Recording Practice' later and see what the APRS had to say on the matter .

 

[abbey road d enfer]

The rotating drum head machine you describe was called the Eltro, and it was a fascinating piece of engineering!

I remeber seeing a film, maybe it was Zappa's 200 motels, where they were having a big laugh with this machine.

 

[JohnRoberts]

https://valhalladsp.com/2010/05/04/pitch-shifters-pre-digital/

JR

 

[Whoops]

What Ive personally found with the copicat is diagonal splices tend to open up after a while , the capstan has a very narrow diameter so the tape has to go around a tight radius and the entire tape loop remains under tension at all times .

I always did my copicat tape loops with a diagonal cut and never had noise or pop in the spliced area.
I remember a copicat from a friend was making that noise, I don't remember how his loop was cut.

I can try both also a see if it matters, if not I will continuing using the diagonal cut.

right now I have another problem, I had some hum in the copicat, so I replace all the original lytic caps with new caps.
Now the Hum is worse... Go figure

Hum is stronger at 100hz but also has 50hz and harmonics.

 

[Tubetec]

Interesting historical about the rotary head machines .
A device called the Tempophon springs to mind .
https://wikidelia.net/wiki/Tempophon
Seems to have used the rotary head principle to manipulate pitch , I wonder if theres any sound clips of it .

Yeah hum is very common in the Copicat , you probably have multiple sources like motor , power transformer and residual hum in the supply all mixing in,  adding and subtracting .
On my MkII I replaced some unscreened very highZ wiring with screened and got a beneficial improvement . I also made it full wave rectification on the HT supply which again helped quieten things a bit more. The synchronous AC motor was a big cause of interference ,it was only after I converted that to a much smaller DC speed controlled motor that I got good noise performance. 

 

[Whoops]

Yeah hum is very common in the Copicat , you probably have multiple sources like motor , power transformer and residual hum in the supply all mixing in,  adding and subtracting .
On my MkII I replaced some unscreened very highZ wiring with screened and got a beneficial improvement . I also made it full wave rectification on the HT supply which again helped quieten things a bit more. The synchronous AC motor was a big cause of interference ,it was only after I converted that to a much smaller DC speed controlled motor that I got good noise performance.

I have 2 units, both solid state.
One is MKIV and the other is IC-300.

The PSU seems a bit crude also on these units I think it could be improved a bit, I will check if I did something wrong on the re-cap, or if I messed the position of any wires, if I can't find it I will do a thread with the problem.

Thank you all for you insights

 

[Tubetec]

Its a quirky box of tricks the Copicat .
I think even Old Man Watkins himself acknowleged it was an engineering accident it actually worked .

 

[Whoops]

Its a quirky box of tricks the Copicat .
I think even Old Man Watkins himself acknowleged it was an engineering accident it actually worked .

Yes, it's pretty simple and crude, but it works.
On the MKIV unit I redid all the wiring locations.In stock form the Output cable and the footswitch cable that has the wet signal leave the unit together with the Mains Cable, probably separating them from the Mains cable will reduce some hum induction. I have a broken jockey arm on that one and I will do a replacement in the 3D printer, after that I will test if changing the wires location  improved the noise figures.

On the IC-300, re-cap done and hum got worse...
Thats pretty strange