Pre recorded cassette tape degradation

[stevehertz]

I've just done a test recording using a Maxell UDXL II without any Dolby and I'm pretty impressed with the results. I pushed the recording level to peak at +4 on the LED meters and just maybe, in a couple of places that was a tad too much. But anyway the higher frequencies seem less coloured, more accurate and balanced. I don't listen to classical music with very quiet passages so I don't actually need 'silence' when music is not playing. I ask myself, what compromise is better? A raised but hardly ever heard and not bothersome noise floor, or less noise on the very occasions that it matters and a doubtful, varying top end?

It's a pity cassette players didn't have a variable noise gate so that you could set it to eliminate start of tape and between tracks tape noise. But then there are many recordings that start and end very quietly so you'd get annoying cut off effects. But I suppose you could play a blank tape and adjust the gate to just about remove the background noise, then any signal higher than that would pass through. That way, any cut off effects would be down at noise floor level anyway and not too objectionable.

[Restoration73]

It's important to realise that as soon as the audio level is equal to or above the Dolby
mark on the VU, the circuit produces no audio benefits. If you are prepared to use an
audio limiter to ensure the audio is always around +3VU or more Dolby has no effect.
It may be argued this alters the dynamic range,but this is what broadcasters do every day.Apart from that dBx is a great nr system, but totally incompatible with ordinary
decks (or even other decks with a different calibration)

[wd40addict]

I briefly flirted with DBX, thought it was great until I recorded some piano...

[ben]

Bear in mind that that Steely Dan album was released in 1973 or 74 I forget which. So the tape will likely be of a rather dull sounding formulation to begin with, and hi speed duplicated.

I picked up a reissued MCA cassette of this LP on holiday in the USA in the very early 1990s, that sounded extremely dull! So perhaps the masters used to cassette duplication weren't the best. A pity, as SD were famed for their attention to sound quality.

In fact it wasn't till the 1980s that digital loop bins revolutionized the sound quality of prerecorded tapes which by then often used a variant of BASF tape. That said, there are exceptions to the rule.

Yesterday I pulled out another EMI cassette, from the 80s, (Kate Bush) and that tape has degraded, with bad wow and flutter. Had this last year with another EMI album of same type of cassette. And the ones with the yellow shell also slurr. None of these are down to poor shells or tight spools - there's no mechanical binding. It's the actual tape used which has degraded.

For a manufacturer who sold vast amounts of their own 'EMITAPE' , their prerecorded ones from the 80s (unlike the early lime green labels) have aged terribly.

I attach some photos and also some another dud, a Warners US edition tape, I have a number of these all from late 70s and they too show terrible wow, which makes the deck grind to a halt before the tape end.

Fortunately I now own these albums on vinyl or CD.

[Restoration73]

I would have said that wow is a function of a distorted cassette body and/or ineffective lube insert. Some of the EMI "Soundhog" blank tapes were poor. The professional EMI 1/4" tape was excellent and not to be confused with the domestic Emitape.

As for age, I have a test cassette made by Decca for BIB Audio Accessories, circa 1974, excellent recording on a ferric tape, accurate levels, azimuth, and Dolby calibration.

[TIMTAPE]

Originally Posted by ben

... it wasn't till the 1980s that digital loop bins revolutionized the sound quality of prerecorded tapes which by then often used a variant of BASF tape. That said, there are exceptions to the rule...

Yes the big companies' later change to digital masters for high speed cassette duplicating made a big difference. The result was now like someone at home making a direct CD to cassette copy. No extra generational losses. Just the losses in the cassette itself. And the cassette tape was recorded not inside the cassette shell but on a special pro open reel recorder running at a high speed.

From my experience high speed duplicating re real time speed doesnt increase modulation noise. I dont understand why it would.

The basics of high quality high speed analog audio tape duplicating appear to have been worked out by the US Ampex company in the 1950's. The open reel copies Ampex made were sought after by audiophiles in preference to the vinyl releases. If they were full of modulation noise I'd find it it hard to believe these high speed duplicated tapes would have been sought after for their audio quality.

[stevehertz]

I like the originality and vibe of the packaging of pre recorded cassettes. Moving forwards I will evaluate the quality of such cassettes that I have and if 'acceptable' keep them, if not replace them with new type II tapes recorded from CDs. The only problem with the latter being the extra playing time you end up with ie an extra 20 minutes per side to FF through rather than just flipping the cassette and playing the other side. Annoyingly, in general you can't get an album on one side of a C90 to play all the way through, uninterrupted. I may dismantle such tapes and reduce them to about 25 minutes per side to ape the original. There'll be no leader at one end but I don't see that as a problem.

[Ted Kendall]

Originally Posted by TIMTAPE

From my experience high speed duplicating re real time speed doesnt increase modulation noise. I dont understand why it would.

The basics of high quality high speed analog audio tape duplicating appear to have been worked out by the US Ampex company in the 1950's. The open reel copies Ampex made were sought after by audiophiles in preference to the vinyl releases. If they were full of modulation noise I'd find it it hard to believe these high speed duplicated tapes would have been sought after for their audio quality.

The plain fact is that scrape on high speed duplicators translates into modulation noise at baseband. It is plainly audible, as is wow caused by scaled-down flutter.

As for audiophools going after fifty year old catalogue tapes, well, who knows why they latch onto anything? A prominent audio critic in the UK has gone overboard over this and, given what these issues generally sound like, I'm disinclined to believe his judgments on sound quality on anything else. Some pre-recorded tapes can, however, sound pretty good. Leaving aside the current absurdly expensive products from The Tape Project and others, I have some tapes made by King Records in Japan from Decca and Philips masters, and these are very good indeed - stereo balance is right, the signal is not crammed on as it so often was, wow is inaudible and the frequency characteristic sounds right. Unfortunately, they are on Ampex stock, so require careful handling and sometimes baking, but the care that went into their production is obvious and far above the mediocre norm. If they were real-time duplicated I shouldn't be surprised. Mind you, I don't recall having a Japanese vinyl pressing that was anything but near-perfect, either...

As a rule, early American stereo tape issues on two-track are of reasonable quality, although some from smaller concerns suffer from hum and noise, and the miseries of trying to make a staggered-head tape produce stable stereo are best avoided. The attention that went into their production was evidently uneconomic, judging by the fanfare with which Ampex launched high speed duplicated four track issues, majoring on their lower cost. Decca, ever in the vanguard of hi fi, had no truck with open reel issues in the UK, and EMI allowed Steresonic tapes to wither on the vine because the cost of production was ruinous.

Even in period, for which read the 1960s, pre-recorded open reel tapes were generally regarded as inferior to their disc equivalents as a means of domestic music reproduction. An article in Tape Recorder around 1968 (What's wrong with tape records?) provides a snapshot of the prevailing situation. John Crabbe's Hi Fi In The Home pointed out the relative paucity of catalogue and inferior sound quality and came down heavily in favour of disc, despite its own numerous problems. And this from the editor of Tape Recorder!

In 1969, EMI persuaded their ageing duplication rig, first used for tape record production in 1954, to make a final appearance for a range of 3 3/4 ips quarter track stereo issues. It would have been better if they hadn't, and evidently the market agreed.

Incidentally, the Studer A80QC was only ever a playback machine, as far as I know. It was intended as a yardstick for setting up duplicators and for quality control of their output, hence the name. A lot of real-time duplication, in the UK at least, was done on banks of Nakamichis from a digital source.

There was indeed a push to raise cassette quality for the Walkman generation and in response to CD. Hi Fi News gave away a cassette made by Decca and intended to show just how good digital loop bins, 120uS EQ and good Type II stock could make a cassette. And what material did they use to demonstrate ths modern wonder? The slow movement of Mozart's 21st Piano Concerto (as used in Elvira Madigan), featuring Vladimir Ashkenazy with cracked pitch and mod noise you wouldn't believe. The effect was risible.

As I said several posts ago, mass tape duplication at high quality was akin to balancing a cone on its point - theoretically possible, but near impossible in practice. And most concerns doing it didn't even get close. In disc, or CD manufacture come to that, nearly all the audio-critical factors are fixed in a physical original which merely(!) has to be replicated in a moulding process. Tape duplication re-opens Pandora's box and renders the product vunerable to degradation at any point.

[cmjones01]

Originally Posted by stevehertz

I re-recorded on to the original ferro tape from CD using Dolby B. The audible results were still rather poor. Not to mention the poor mechanical aspects of the cheap Ferro cassette. I then made the same recording on to a Maxell UDXL II and the difference was light and day

Something I've only discovered recently, and wish I'd known back in the 1980s, was just how critical the bias adjustment is when recording a cassette. It actually explains a lot of poor-sounding recordings with weak high frequency response, though not wow and flutter of course.

An under-biased recording will generally sound a little too bright, with the high frequencies over-emphasized, and will distort easily at higher levels. An over-biased recording will sound dull, with attenuated high frequencies. This is easy to demonstrate with a 3-head deck with manual bias control. What I've noticed is that the difference between too little bias and too much is very, very small - an eighth of a turn on my Sony deck's bias control can transform recording quality.

Cheap, poorer-quality tapes tend to need less bias. Even the stalwart TDK 'D" and Maxell 'UR' need a little less bias than most decks' standard settings in order to get the best from them, and really grotty tape like that mentioned by the OP probably needs significantly less in order to get decent top-end frequency response. Indeed, my Sony actually has a 'low' bias position on the tape type switch, below the usual Type I/normal, to accommodate such tapes.

The tape manufacturers exploited this sensitivity in order to sell more expensive tapes. Look closely at the specifications of a range of tapes from one manufacturer, for example TDK. Their Type I range included D, AD, AD-X, AR and so on, each more expensive than the next. Each of them has an optimum bias point a little higher than its cheaper cousin. The result is that, on a typical deck with fixed bias, the cheaper tapes sound duller, the more expensive ones sound brighter, 'better'. Yes, of course the more expensive formulations have lower noise, higher maximum recording level and so on, but it's generally possible to get just as good a frequency response on a lower-end tape as on a more expensive one just by setting the bias and recording level correctly. I could have saved a fortune on tape as a teenager and student if only I'd known (and had a 3-head cassette deck...)!

It's an analogue world.

Chris

[stevehertz]

Originally Posted by cmjones01

Something I've only discovered recently, and wish I'd known back in the 1980s, was just how critical the bias adjustment is when recording a cassette. It actually explains a lot of poor-sounding recordings with weak high frequency response, though not wow and flutter of course.

An under-biased recording will generally sound a little too bright, with the high frequencies over-emphasized, and will distort easily at higher levels. An over-biased recording will sound dull, with attenuated high frequencies. This is easy to demonstrate with a 3-head deck with manual bias control. What I've noticed is that the difference between too little bias and too much is very, very small - an eighth of a turn on my Sony deck's bias control can transform recording quality.

Cheap, poorer-quality tapes tend to need less bias. Even the stalwart TDK 'D" and Maxell 'UR' need a little less bias than most decks' standard settings in order to get the best from them, and really grotty tape like that mentioned by the OP probably needs significantly less in order to get decent top-end frequency response. Indeed, my Sony actually has a 'low' bias position on the tape type switch, below the usual Type I/normal, to accommodate such tapes.

The tape manufacturers exploited this sensitivity in order to sell more expensive tapes. Look closely at the specifications of a range of tapes from one manufacturer, for example TDK. Their Type I range included D, AD, AD-X, AR and so on, each more expensive than the next. Each of them has an optimum bias point a little higher than its cheaper cousin. The result is that, on a typical deck with fixed bias, the cheaper tapes sound duller, the more expensive ones sound brighter, 'better'. Yes, of course the more expensive formulations have lower noise, higher maximum recording level and so on, but it's generally possible to get just as good a frequency response on a lower-end tape as on a more expensive one just by setting the bias and recording level correctly. I could have saved a fortune on tape as a teenager and student if only I'd known (and had a 3-head cassette deck...)!

It's an analogue world.

Chris

Yes but achieving the correct bias is another thing. Fortunately a couple of my decks have the ability to test and set bias prior to making a recording. If not, you're stuck unless you re-bias your deck to suit a particular tape and then you're stuck with having to use that tape.

[TIMTAPE]

Originally Posted by Ted Kendall

Incidentally, the Studer A80QC was only ever a playback machine, as far as I know. It was intended as a yardstick for setting up duplicators and for quality control of their output, hence the name. A lot of real-time duplication, in the UK at least, was done on banks of Nakamichis from a digital source.

Yes the A80 QC seems to have been playback only for 1/8" cassette tape 1.875/3.75ips but if the cassettes were duplicated "in shell" why would they need a full sized open reel player designed for 1/8" tape? It makes no sense. Why not just check them as they are "in cassette" on a cassette deck?

And why were the (often) Tapematic automatic tape loading machines also set up for 1/8" cassette width tape on 10.5" reels which amounted to over 20 cassettes worth of programmes recorded serially on each reel? Again it makes no sense unless that is how they were recorded in the first place, serially on large open reels of 1/8" tape.

Edit, just found more info on the Lyrec company. In 1994 they had high speed tape duplicating gear at 128:1 speed. In 1997 they introduced 160:1 speed.

https://museumofmagneticsoundrecordi...rersLyrec.html

[TIMTAPE]

Originally Posted by wd40addict

I briefly flirted with DBX, thought it was great until I recorded some piano...

DBX wasnt perfect but excellent on much material. Its main weakness was tape noise pumping on purely or mainly bass sources, but it had no special problem with piano. Piano tends to reveal wow and flutter.

[Ted Kendall]

In-cassette duplication was never practical for the majors - they continued to use high speed pancakes to the end, and were the customers for the A80QC. The real-time plants catered for small runs and the carriage trade, such as it was, and machines such as the Nakamichi MR-1 allowed off-tape monitoring, rendering separate QC unnecessary.

dbX was a triumph of figures over ears - Dolby A did what could be done and did it reliably and inaudibly when properly lined up, whilst dbX shot for the moon and missed. The essential difference was that Dolby acted in the bands where noise was problematic and went for about 10dB of reduction - these factors ensured that the ear's masking made its operation inaudible. dbX claimed 30dB broadband reduction and used straightforward 2:1 compansion. Not only did noise pump on pianos and bass guitars, but the stereo image went for a walk on the slightest provocation. I have to play it back in the line of duty, obviously, but I don't like it at all.

[TIMTAPE]

In the days when I serviced the Otari 8x in cassette duplicators I had their full service manuals and as I recall the flutter specs translated to normal tape speed were quite respectable. As mentioned the pro duplicators used speeds right up to 160x or 300ips. At what duplicating speeds would the flutter be audibly the worst? Ted do you have the flutter specs to back your claim?

[Ted Kendall]

My observations, not claims, come from long experience of pre-recorded tapes and knowledge in many cases of the equivalent disc issues. Seldom is pitch entirely steady to the extent that it is on a properly centred LP on a good turntable. The playback machines I have used have exhibited no abnormal wow on their own recordings, so the inescapable conclusion is that the wow is on the tape, either from the loop bin or the slaves. Many of the tapes I have tried were still in their shrink wrap when I bought them, so may be reasonably be assumed for these purposes to be more or less as they left the factory. I have found insecure pitch to afflict 1950s EMI issues, both stereo and mono, the 1969 stereo quarter track series and just about any American 4-track issue. I can't speak for Barclay Crocker, having never heard one, but I repeat that the few King Records tapes I have come across have been flawless.

Pitch problems remained on the few cassees I tried in the digital loop bin/type 2/120uS era, as did mod noise. High speed duplication was the only economic approach for mass production of tapes, but it produced audibly inferior results to the equivalent discs. Even in the mid-70s, when record companies were pushing cassette hard in the wake of vinyl pressing problems sparked off by the oil crisis, critics only praised them in terms of lack of clicks and pops, and statements like "as long as the middle range is clear and musical we are satisfied" sound like a distinguished critic warning his public without offending the record company.

If I want commercial material programme, I try to get hold of it on vinyl or unadulterated CD. If needs must, then tape it is.

[Ekcoman]

Some of those old tapes deposit a lot of debris on the tape heads so it maybe necessary to clean after just one side play.

[TIMTAPE]

Thanks Ted,

I guess I was wanting to focus on just the speed error of the HS slave recorders such as from major manufacturers like, as far as I can judge, Electrosound, Lyrec and Gauss.

There seems precious little info on the www re the W &F specs of the HS slaves but I did find a brochure from Electrosound around 1971. They mentioned 0.1% W&F and the use of scrape flutter idlers close to the record heads which they claimed virtually eliminated scrape flutter.

http://lcweb2.loc.gov/master/mbrs/re...und%206000.pdf

Of course with every analog tape stage in production there will be additive speed errors, and of course before digital masters they had to use extra tape generations not least to protect the masters which would (hopefully) never be used in the HS duplication process.
In the days of our fully analog tape talking book productions we only ran the studio recording through the master duplicator once, and then subsequent duplications were made from a sub master or 2nd generation, so the user copies could be 3rd generation - with the inevitable extra W & F, noise distortion etc. But what could we do? Cost/benefit kicked in.

In servicing the in cassette duplicators I always paid extra attention to the master player units to avoid as much as possible damage to the master/sub master recordings by the machine, due to magnetisation, physical tape damage.

The thing is having worked in the service of tape machines most of my life I know that it's the easiest thing for perfectly good duplication/transfer machinery to be not well maintained. I saw it again and again. Still see it. Tape heads and guides not cleaned properly. Then capstan shafts and pinch rollers! Sometimes there was a sizeable piece of cotton from the cleaning cotton bud still wrapped unevenly around the capstan shaft, or caught around the bearing of the pinch roller, causing drag and leading to extra W&F. Sometimes it only came to my attention when the owners reported another problem to me and I had to look at the machine, so it seems they had tolerated the extra W &F or not even noticed it.

The only fair test of any equipment is when it is maintained at its best, but members of the public buying commercial audio and video arent usually in a position to know if that was the case when the product was made.

Tim.