Radio 3: pre-echo on Liszt loud piano parts

[hooty2]

Writing as it happens:)... Radio 3 building a library/Liszt piano sonata in b minor.
The reviewer commented on a recording from the 70's.. the unfortunate hiss but ..."the annoying pre-echo as the loudest parts are played"

anyone know what this about?

[The Elf]

It's another of those vagaries of tape. When tape was wound on a spool the very loud parts of a recording would bleed onto the tape it was wound against - and often to the layer of tape underneath that too. You can hear the effect of this as the loudest sounds often being faintly heard just before they should arrive.

You can hear this effect on many old recordings. The one I recall most is on Genesis's 'Chamber of 32 Doors', where you can hear the song start twice before it actually comes in!

Tape - I'll dance on its grave...

[ef37a]

I am sure The Doc will give us the precise SP but I understand this is why it was BBC practice to store tapes 'tail out'. This meant they had to be rewound before playback and that reduced print through.

Terrible stuff tape, almost as bad as those flat, black things!

Dave.

[hooty2]

cheers folks... education education education

[Sam Spoons]

I assume the print through would be onto the tape either side of the loud signal not just the wrap underneath? If so you would get both a pre and post echo. Storing tail out would not have solved the issue as the 'sandwich' of plastic film base and oxide means that the oxide layer in a wound tape is separated by a base layer on both sides.

[Wonks]

I assume the print through would be onto the tape either side of the loud signal not just the wrap underneath? If so you would get both a pre and post echo. Storing tail out would not have solved the issue as the 'sandwich' of plastic film base and oxide means that the oxide layer in a wound tape is separated by a base layer on both sides.

There are two types of print-through, one is heat-induced and one magnetic.

If the spool is kept wound in the same position as heat print-through occurs, then the print-through remains. Keeping it stored in a different orientation e.g. fully wound, then the print-through areas no longer correspond, and over time the thermal print-through is supposed to fade.

Won’t do anything for magnetic print-through though.

[forumuser840717]

Apart from other benefits of winding though the tape before playing, storing tail out means that the heaviest print though occurs as post-echo rather than pre-echo so it's masked by the programme.

For geeky interest, there's a bit of info about it in this AES Tech Bulletin

I once came across a Studer A80 which had been modified to run leader tape along with the recording tape, in an attempt to reduce print through by adding a 'spacer layer' to the tape pack. It did work and reduced the print through but wasn't the most practical idea. Not least because the double thickness tape made for odd handling characteristics which used to freak out the transport on many other machines it was put on and the advantages of the lower print through paled into insignificance as someone had to hand re-spool the tape from the floor after the transport on other machines dumped it all when the tension sensors went nuts in fast wind. Assuming they didn't just shred the tape.

[Hugh Robjohns]

Storing tail out would not have solved the issue as the 'sandwich' of plastic film base and oxide means that the oxide layer in a wound tape is separated by a base layer on both sides.

The AES tech bulletin gives chapter and verse, but storing tail out means the tape must be rewound before playing, and the act of rewinding actually helps to diminish the print through by 3dB or so. Weird but true!

[Wonks]

Possibly some static electricity effect, or magnetic separation effect, generated by the much higher tape layer parting speed when running in rewind as opposed to normal forward play speed?

[MOF]

Possibly some static electricity effect, or magnetic separation effect, generated by the much higher tape layer parting speed when running in rewind as opposed to normal forward play speed?

??????? The previous replies are correct Wonks. Apart from ‘static electricity’ nothing else makes sense.
You’re in danger of creating mistakes on the internet.

[Wonks]

I see what you did there.

[MOF]

I see what you did there

[Tim Gillett]

A good way to deal with print through was to anticipate it at the record stage. The thickest open reel tape (Standard Play) and somewhat dynamically compressed signal helped. So Dolby A, DBX or a decent soft knee compressor/ limiter helped the recorded signal itself, even studio or venue ambience, to mask print through. Cassettes with their often Quadruple Play tape stock were also very vulnerable to later print through. In our audio book productions we had massive print through problems even with recordings only a year old. Because our recordings were very long we had to use the thinner Long Play tapes with greater print through. It's worst on very dynamic programme including unaccompanied voice. Print through only got worse with time and heat so minimizing the likelihood it would be heard many years later was really a long term strategy.

[ken long]

The AES tech bulletin gives chapter and verse, but storing tail out means the tape must be rewound before playing, and the act of rewinding actually helps to diminish the print through by 3dB or so. Weird but true!

On top of all the reasons already given, it's also good practice to have the original spool be the take up so that you get a tighter and even pack at the end of playback.

[Exalted Wombat]

Pre-echo can happen on vinyl too, when the grooves are cut too close. (Of course, an LP may also inherit print-through from a preceding tape generation.)

The compulsion to worship vinyl can spawn comments like "I find this to be a charming artifact of lp playback."

https://forums.stevehoffman.tv/threads/ ... lp.229120/

[BJG145]

Liszt's wrists were exceedingly supple
Especially after he'd had a couple

- ECB

[Tim Gillett]

Pre-echo can happen on vinyl too, when the grooves are cut too close. (Of course, an LP may also inherit print-through from a preceding tape generation.)

Yes and common practice with disc cutting tape masters was to splice plastic leader tape hard up against the start of the programme, meaning any echo pre that splice point had to originate from the cut disc.

[James Perrett]

Yes and common practice with disc cutting tape masters was to splice plastic leader tape hard up against the start of the programme, meaning any echo pre that splice point had to originate from the cut disc.

That practice is now causing real problems if stripy leader tape was used. The stripes attach themselves to the magnetic coating and peel it off the backing - no matter how carefully you try to pull the layers apart.

[Hugh Robjohns]

I didn't know that!

I've always used solid colour and clear leaders, but more through luck and availability than anything else.

The Beeb standard was yellow between items on a tape (eg, separate inserts on a news programme reel), red at the end, and often blue at the front of stereo programmes, and green for mono. I can't remember what we used white for... but most edit rooms only had yellow and red in stock anyway, so it was yellow at the front and between items, and red at the end.

Not all leader tapes were made equal -- they often had radically different coefficients of friction compared to the recording tape itself (usually much higher!), and that sometimes caused problems with the machine's speed changing slightly as the leader ran through, resulting in a slur to the start or end of a recorded piece!

I also remember scraping off the red and yellow colour on leaders sometimes to leave a transparent section about two-inches long to trigger the optical end-of-tape sensor and activate the stop button -- an important function in a busy self-op news programme to prevent the tape running on into the next item!

In the commercial world various manufacturers used different colours to differentiate tape types. One standard was white for standard-play, green for long-play and blue for double-play. Again, red always signified the end.

[forumuser840717]

That's been a problem for years. It's particularly annoying when the stripy leader is used between tracks!

Some tapes and some leader tapes are more prone to it than others and it's really important to check for stripy leaders before baking tapes as that can make adhesion considerably worse (though, in very rare cases, it can also cause it to release).

Similarly, some will release with various solvents ranging from water to different strengths of alcohols or even acetone, while some tapes are destroyed by the solvents so experimentation and note keeping are important.

[Tim Gillett]

Yes and common practice with disc cutting tape masters was to splice plastic leader tape hard up against the start of the programme, meaning any echo pre that splice point had to originate from the cut disc.

That practice is now causing real problems if stripy leader tape was used. The stripes attach themselves to the magnetic coating and peel it off the backing - no matter how carefully you try to pull the layers apart.

In my experience and reading of the relevent digitisation manuals and guides I've not come across this. Does it occur independently of the tape type and condition of the binder layer?

[James Perrett]

In my experience and reading of the relevent digitisation manuals and guides I've not come across this. Does it occur independently of the tape type and condition of the binder layer?

I first encountered it with old Ampex tapes but have also had problems with 3M 256 and also BASF which were in otherwise good condition and not baked. It sounds like Forumuser 840717 has more experience than I do - I've never tried using any solvents to reduce the adhesion to the ink in the leader.

[Tim Gillett]

Thanks and yes good to hear more details from 840717. Tim.

[James Perrett]

Just had another delivery of tapes to transfer - and all the quarter inch tapes have stripy leader everywhere! I think they're all 3M 256 although some of them are in Ampex boxes (but look too dark for Ampex).

[Tim Gillett]

That could be interesting. I've not come across this problem with sticking stripy leader and am not sure what it even looks like. Any chance of a photo or link to one?

Interestingly on the AES list of 3M tapes manufactured, I couldnt find 256 mentioned at all.
https://www.aes.org/aeshc/docs/3mtape/aorprod-cust.pdf

[James Perrett]

Interestingly on the AES list of 3M tapes manufactured, I couldnt find 256 mentioned at all.
https://www.aes.org/aeshc/docs/3mtape/aorprod-cust.pdf

I've just checked the box and it says the tape was made in the UK so maybe the AES list only deals with US made tapes.

[Kwackman]

Interestingly on the AES list of 3M tapes manufactured, I couldnt find 256 mentioned at all.

I think, with absolutely no certainty (!), that this was made for the BBC?
Hopefully someone can confirm, or prove me wrong. Again

[Hugh Robjohns]

Interestingly on the AES list of 3M tapes manufactured, I couldnt find 256 mentioned at all.

Comes across more as accusative and disparaging than interesting...

However, I can easily prove both James and Kwackman absolutely correct.

3M 'Scotch' type-256 wasn't made -- or, AFAIK, made available -- in America and so, probably not surprisingly, it doesn't appear to exist in the American listings.

However, there was a 3M tape factory just north of Swansea in South Wales in a place called Gorseinon that made recording tape for the BBC, amongst others. As it happens, I actually visited that factory in 1981 while at university as Chief Engineer of the university radio station, in a successful attempt to blag a couple of cartons of recording tape for our four studio Revox A77s! I'm afraid I cant remember the tape type I acquired, but it was in orange boxes.

Back in the 70s and 80s the BBC went through many hundreds of thousands of 10.5-inch reels of quarter-inch recording tape every year, so most UK and European tape manufacturers were only too happy to make tape to the BBC's fastidious specifications.

The Beeb needed copious quantities of new tape stock that could be sourced from multiple suppliers but that would work consistently on every machine, everywhere across the entire corporation without the need to continually realign studio tape machines for different types or batches of tape -- something that was obviously impractical on many levels.

Naturally, the BBC's tape spec wasn't entirely bespoke; it was based closely on an existing high quality formulation that several manufacturers either made already or had something very close to and could tweak their formulations a little bit to match.

In reality, of course there were very small differences in the tape formulations from different manufacturers, and possibly between different batches, and so slightly different optimal bias requirements. Consequently, the HF response, in particular, could change slightly and some particularly fussy radio Studio Managers and TV sound supervisors and dubbing mixers expressed preferences for one brand over others... but the differences were always pretty minimal and most never noticed!

Anyway, amongst the various formats and formulations being made at the UK 3M factory in the mid-80s was definitely one called 3M-256, and that version complied with the BBC's then new 'type-200' specification for quarter-inch tape. Here's an image of the box to prove its existence and remove any doubt.

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Zonal 675 was another type-200 compatible brand, as was Agfa PEM468. There may have been others, but those are the only ones I can remember.

However, I do remember that the type-200 spec came into BBC service in the mid-80s because I spent weeks of work in 1984 or 85 with my engineering colleagues realigning shed loads of tape recorders all across BBCTV and BBC Radio in a very short timespan to facilitate the changeover from the prevailing type-102 tape alignment (if memory serves).

The type-200 spec was introduced to take advantage of the improved characteristics of the newer tape formulations that were appearing in the previous years. One of the most significant improvements was in the higher peak flux capability -- the BBC type-200 spec alignment set peak level (PPM6) to 1000nWb/m.

Type-200 tape remained in use across the BBC right up until tape was phased out as a primary recording medium around late 90s.

Not all of the Beeb's legacy tape machine inventory could be persuaded to run with 1000nWb/m, of course, and many of the older models had to be retired at that time. For comparison, the previous BBC type-102 tape formulation used an alignment of 640nWb/m for peak level (and the type-100 before that was 400nWb/m).

You can read more about the beeb's development of recording tape here:

http://www.orbem.co.uk/tapes/media.htm

[Kwackman]

However, I can easily prove both James and Kwackman correct.

That's going onto my C.V.

Zonal 675 was another type-200 compatible brand

I remember that tape, big purple dots on the front of the box.
I can't remember much technical stuff I learnt, but can remember the colour of the box.

[Hugh Robjohns]

I remember that tape, big purple dots on the front of the box.

It was rather distinctive.

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