Basic, premium type I and accuracy

Makymak

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#1
Hi all!

Taking seriously my Technics' recording abilities, I started remaking my mixtapes collection. They had been made with a mediocre all-in-one Sony system (NX1) on mostly TDK CDing I when I was at high school (looong time ago!). This debatable cassette is similar (if not same) to AD.

Back to the point. After making a lot of recordings what I have found out is that, regarding Type I, the most accurate recordings were made with the basic ferrics of the known brands eg TDK FE and D, SONY EF and HF, Maxell UR and so on. These recordings are virtually indistinguishable from the source as long as keeping the levels appropriately.

Strange enough, going higher the line and using more advanced tapes (like AD, AR, HF-S, HF-ES, Maxell UDI) the recordings sound more vivid, with more loudness and generally more pleasant (ok, subjective opinion). But more pleasant than the source means NOT accurate recording so it is a bad recording. Shouldn't the premium cassettes offer the most accuracy? Or it is deck depending?

A positive side effect is that I can have great results with cheap tapes (D and UR)! No need to chase premium!

PS. Of course my decks are well serviced and each time they are calibrated to the tape used.
 

J!m

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#2
D tapes are good, but called "D" as it stands for "Dictation", or recording spoken voice. It's a good tape, and my biased preference for a cheapie, but I don't understand why you have rising mid frequencies or whatever is happening with a calibrated deck and proper bias for the tape selected.

That shouldn't be happening.

When I do an SA recording, on an overhauled 122 Mk. III calibrated for the specific tape installed for recording, I get a very good copy coming off CD source. No distinguishable difference off the monitor or tape, and later playback, I can't honestly tell if it is the original CD or the tape. Nando has a TDK SM10 tape I made to test my newly overhauled Sony D5, and he can chime in on the quality of the recording on that (SA tape in a crap shell) tape.

So, something seems off, or the tapes you are using somehow do not calibrate properly, or something. Most decent tapes all reproduce flat with the exception of the extreme upper and lower frequencies. I don't recall any rising or falling in the mids regardless of brand...
 

vince666

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#5
Hi all!

Taking seriously my Technics' recording abilities, I started remaking my mixtapes collection. They had been made with a mediocre all-in-one Sony system (NX1) on mostly TDK CDing I when I was at high school (looong time ago!). This debatable cassette is similar (if not same) to AD.

Back to the point. After making a lot of recordings what I have found out is that, regarding Type I, the most accurate recordings were made with the basic ferrics of the known brands eg TDK FE and D, SONY EF and HF, Maxell UR and so on. These recordings are virtually indistinguishable from the source as long as keeping the levels appropriately.

Strange enough, going higher the line and using more advanced tapes (like AD, AR, HF-S, HF-ES, Maxell UDI) the recordings sound more vivid, with more loudness and generally more pleasant (ok, subjective opinion). But more pleasant than the source means NOT accurate recording so it is a bad recording. Shouldn't the premium cassettes offer the most accuracy? Or it is deck depending?

A positive side effect is that I can have great results with cheap tapes (D and UR)! No need to chase premium!

PS. Of course my decks are well serviced and each time they are calibrated to the tape used.
there are so many tapes which, when properly biased, will still show some boost on the mid-hi and treble on a standard aligned deck.
The "cure" is to adjust REC EQ pre-emphasys, when possible.

about type1, the basic ferrics are generally the ones with standard/flat response while some mid-late 90s basic ferrics and most superferrics from mid 80s and on generally show such boost on the treble side.

regarding type2, tapes like TDK SA and Sony UX, (mid 80s) Denon HD6 and others are the flat standard ones and the fancier models (often dual coated) like Sony UX-S / UX-PRO, TDK SA-X, etc, show some treble boost on standard aligned decks.
Also, when checking many type2 tapes from all the past years, you will see the most variable behaviour of all tape types.
I.e. the metal particle type2 tapes (that's ex, em-x, cd-mh, Denon hd8, etc) would need their own specific REC EQ to really work at best... same goes with oldschoolpure chromes, which need a vastly different REC EQ setting than the typical ferric cobalt type2.

about metals, they tend to be ruler flat on a standard aligned deck when properly biased.
 
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Elite-ist

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#6
@vince666: That's a good explanation. The manufacturer would sometimes display such information on the wrapper to distinguish the tape characteristics from other models within the same tape type.

This is an example of the Sony HF-S compared to the Sony HF:

DSC00660_zps919616bf.jpg

Nando.
 

Makymak

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#7
but called "D" as it stands for "Dictation"
I thought the "D" stands for "Dynamic". There are some lesser tapes in TDK's lineup, like FE, B and T1.

@vince666 that explains a lot. So, the premium ferrics indeed boost some frequencies. But, why? To sound more pleasant? Or to eliminate some losses of the inferior decks?

@Elite-ist I have seen these graphs on a lot of sealed cassettes but I thought they were just for marketing.
 

vince666

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#9
@vince666: That's a good explanation. The manufacturer would sometimes display such information on the wrapper to distinguish the tape characteristics from other models within the same tape type.

This is an example of the Sony HF-S compared to the Sony HF:

View attachment 83123

Nando.
exactly so.
That's just a hint that the tape is intended to be a bit bright on a deck with standard REC EQ arrangements.
Also that bit more sensitivity compared to the HF is how it really is. And HF-ES has still some more sensitivity and treble boost than HF-S.

point is that REC EQ is a recording parameter/variable just as much as the other two (bias and rec gain).
If you keep REC EQ fixed, as is on most cases, you'll end adjusting frequency response by tweaking bias and getting farer from the optimum bias setting if deck's REC EQ setting doesn't just match the tape of choice.

Of course, eliminating one variable (by setting it fixed) from the calibration parameters makes things much easier to handle but compromises are to be expected.
 
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vince666

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#10
@vince666 that explains a lot. So, the premium ferrics indeed boost some frequencies. But, why? To sound more pleasant? Or to eliminate some losses of the inferior decks?
who knows really why?

but Nando's guess makes sense.
the superferrics on boomboxes used to offer a welcome boost.
 

vince666

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#13
That is so true. And most times is unthought.
My idea is that letting the user handle 3 recording parameters (i.e. on manual calibration decks) rather than 2 parameters makes the calibration problem one order or infinite more complex.
And just by having both bias and REC EQ at hand you can easily get confused/indefinite situations, unless you don't perfectly know what you're doing and, at the same time, you are carefully measuring tape's performance with some external device while calibrating (i.e. like I do while checking/aligning/modifying decks), it might easily happen that you get quite a few different calibration settings which are all apparently OK if you simply check the frequency response which will be correct in all of these cases... then, which one to choose?
What really changes?
Examples... you might get a flat response with a lower bias setting but, at the same time, you apply less REC EQ boost... the MOL would be less than the maximum the tape might handle but the SOL would be larger (you trade bass performance in place of treble performance).
Or, you get the optimum bias point and, also, the REC EQ which makes the recording flat in this situation and you will exploit all the MOL of the tape and, if SOL is still sufficient then this might be the best choice... Or, also, you might set some more bias than the optimum and then boosting REC EQ some more to overcome the treble loss and, this time, MOL might be the same as the "optimum" case but treble/SOL would suffer too early.
Let's say that the first case (slight underbias and less REC EQ boost) can be useful if you are recording some music without too heavy bass but with stronger treble than usual... while the second case (optimum bias and suitable REC EQ boost) is generally the best choice for quite all kinds of music... but the third case (overbias with more REC EQ boost) seems a poor choice in general...
Now, if you are simply checking REC/PB response while tweaking both bias and REC EQ you might get on any of the aforementioned cases without realizing which actual one... so, if you go deeper and check also FR at more levels to evaluate SOL and/or you measure MOL then you know which is your actual case...
So, having both bias and REC EQ free to calibrate might bring you into more troubles than not, if you cannot exactly check what's happening about the actual performance.

The easy solution is to set REC EQ fixed (one setting for each tape type, of course) and according to the most standard tapes... so, the bright tapes will be a bit bright and that's it.


The majority of decks are driven by a price point, even back in the day.

Besides the cost to allow three EQ and another three bias settings, you have all that tech time setting it all up.

All that cuts into profits….
A bit of this but, IMO, also a bit of what I described above.
 

J!m

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#14
I think this is exactly why the deck makers (usually) indicated exactly what tapes the deck was factory set-up for. Use those tapes, and you SHOULD get a flat recording.

But there is always tolerance on everything, including lot-to-lot variability on the same tape.

Now add 40 years of "drift" and "tape ageing" to the mix...

I settled on the SA long (long) ago and have not regretted that decision. Poor storage back in the day and I can still play the tapes I made without the knowledge I currently have and enjoy them. Literally mid-80's recordings done sub-optimally are still listenable. New recordings with all my knowledge, experience and equipment to bear, and it is difficult to discern the tape from a CD source. So, I think that's about all one can hope for with a cassette tape- too narrow a tape moving too slowly across the head.

When I was contemplating making a new deck from scratch, I was FOR SURE going to have the double-speed capability. That one mod solves so many problems with the format.
 

vince666

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#19
I think this is exactly why the deck makers (usually) indicated exactly what tapes the deck was factory set-up for. Use those tapes, and you SHOULD get a flat recording.

But there is always tolerance on everything, including lot-to-lot variability on the same tape.

Now add 40 years of "drift" and "tape ageing" to the mix...

I settled on the SA long (long) ago and have not regretted that decision. Poor storage back in the day and I can still play the tapes I made without the knowledge I currently have and enjoy them. Literally mid-80's recordings done sub-optimally are still listenable. New recordings with all my knowledge, experience and equipment to bear, and it is difficult to discern the tape from a CD source. So, I think that's about all one can hope for with a cassette tape- too narrow a tape moving too slowly across the head.

When I was contemplating making a new deck from scratch, I was FOR SURE going to have the double-speed capability. That one mod solves so many problems with the format.
Of course, as you say.
Set/design the deck recording circuit in order to be flat on the standard tapes... after all, if it does exist a standard then it must be taken into consideration.
I also prefer to tweak the rec circuit to tapes like SA (or Sony UX, same situation) , some good basic ferric (Basf FE-I or Sony HF) and a single coated metal (i.e. Sony Metal XR)... this way, the deck will do a perfect job on the standard tapes and the bright tapes will be slightly bright , which is how they were intended to sound, unless I don't have some tweakable REC EQ (as I did on a couple decks here).
Doing the other way around, i.e. by adjusting the circuit to get flat response from the "bright" tape will result on a treble drop on the response of all the standard tapes, which would make them totally unuseable.

A properly made double speed cassette deck would be a game changer, as the performance will grow by a lot.



Vince, when referring to EQ you mean the time constant, right?
wrong. :p

I understand equalizations might be confusing... the time constants (70us , 120us) are related to the playback EQ side, where you have to get a standard PB response at those two time constants (or slightly different values to compensate certain kinds of heads).
The playback head works like an inductor, with a response which is (more or less) always rising with frequency by 6dB per octave so, to get a flat playback response, you have to apply a low pass filter with cut off frequencies set according to the 70 and 120 us time constants.
There is also the 3180 us PB time constant which gives some boost around 50Hz to get flat response on the bass side too.
And this is ONLY the playback side.

On the REC EQ side, the situation is totally different and it doesn't really make sense thinking about time constants.
If you try to record a tape without any REC EQ filters (it happened to me, because of a bad solder joint in the REC EQ filters of one channel) you will get a weird response, made mostly of bass, mids and then the response will abruptly roll-off by a whole lot of dBs on the treble side.
In fact, there isn't such a thing like a "standard REC EQ"... and it's not even needed to be standardized.
The REC EQ is, actually, whatever kind of boosting filter which will provide a proper response on a tape of choice, heads of choice and bias setting of choice... so, it's not uncommon to find totally different REC EQ filter arrangements on different decks, since they would be compensating different kinds of heads, bias setting "strategies" and blank tapes of choice.

For example, on my AIWA AD-F880 where I've put amorphous heads and re-designed the whole REC EQ circuit from scratch, to get a flat response, I need to apply some low shelving boost by a few dBs on the bass and low-mids side together which works on a relatively large frequency range with one (sometimes even two) resonant filter centered somewhere on the extreme treble or even over 20Khz which gives a narrow frequency boost peak which can give a very strong boost (like also 20dB of boost at the extreme treble side)...
The effect of both filters together will flatten the recording on a given tape.
Of course, each tape type must have its own REC EQ filter, in fact, when you switch tape types, you will also automatically switch the REC EQ filters.


Just a small bit of patience... as soon as I will have all the detailed data regarding my own modified AD-F880-MAX nicely arranged on the computer, so that I will add more infos on this thread , this whole matter would be a lot clearer, because I've made quite some heavy work on the REC EQ side, with those 3 switchable settings (3 for each tape type which is a total of 9 different REC EQ filters). ;)

As also put in evidence by Alex in the past, since we are handling more filters together, it's just handy to simulate them with a software like LT Spice... that simulating software was a true lifesaver while doing that work... not sure I could have done it without it.
 
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vince666

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#20
to give you some idea about what I had to do on my AIWA...

I arranged one of the REC EQ filter options for the metal position by applying this REC EQ boost curve (the continuous curve, not the dotted one), where you can see a "bell shaped" filter applied on the infrasonic range which boosts up to 10dB compared to the mids and then a narrower resonant filter around 17-18Khz which applies like 22dB more boost than on the mids... isn't it a weird EQ boost curve?

REF_Sony Esprit IV REC EQ.jpg

well, by applying the above (weird) boost, i.e., on Sony Esprit IV tape (Metal XR is basicly the same stuff) I've got a MOL at 315Hz of about +10.5dB VU (0dB ref = 160 nWb/m) together with this measured REC/PB response (at -20dB in the deck) , which is flat within half dB or so (y-axis division is only 1dB, if it was 5dB it would look ruler flat)... not bad, eh?
But, would you expect to need to apply the above boost to get the below recorded curve at the optimum bias point of this tape, on some nice amorphous heads?
Well, this is just what happened here.

REF_Sony Esprit IV.jpg

and... the same above REC EQ boost curve, but with a slightly different bias and rec gain setting, gave me this REC/PB response on a Sony Metal ES from 1985 , with a MOL at 315 Hz of +13dB VU (!!!) , but this tape is just a monster when the deck is able to push it to the limit... this is totally super metal performance, in fact it's a double coated metal tape.

REF_Sony Metal ES.jpg
 
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