17 Oct
2024
17 Oct
'24
7:37 a.m.
On 16 October 2024 13:23:44 UTC, Fons Adriaensen <fons(a)linuxaudio.org> wrote:
But now the smooth saturation is almost transformed
into
hard clipping. The sharp bend in the curve occurs when the
signal amplitude is higher than the bias amplitude.
The only effect that remains in a complete simulation is
the result of the EQ applied to the signal to be recorded.
Higher frequencies have a 'self erasure' effect (which is
nicely reproduced by the simulation) and so need to be
amplified. The net result is that they will saturate at
a lower input level.
How much EQ is required depends mainly on tape speed, higher
speeds need less. At the most popular 'pro' speed (381 mm/s)
this would be something around 10 dB at 10 kHz. At the higher
(762 mm/s) speed typically used for 'master tapes' it's just
a few dB.
So what does effectively remain of the 'smooth saturation
and compression' that is claimed to give tape recording its
magical 'warm' character ? Is it just a myth ?
IMO you've nailed it.
The non-mythical aspect is, as you mentioned, the EQ boost, its impact on saturation, and
the *almost* (but not quite) hard clipping. Depending on the tape setup being
used/emulated, the net effect can be anything from mildly noticeable to completely
imperceptible.
Any effect beyond that is indeed a myth.
Is that effect worth the hassle of using tape, or accurate tape emulation? Almost never.
As you point out, there are often simpler ways, today, to achieve the same effect.
(Plus, great-sounding records have been made without tape or accurate emulation since the
1980s. Tracy Chapman's 1987 debut album, recorded on a Mitsubishi 850[1], is a prime
example.)
I also simulated the green curve directly without
going
through the complicated full simulation, and honestly,
to me that sounds just the same. And unless you really
use very high levels (much more than would actually be
used) the net effect is marginal. Maybe the hard clipping
can be useful when applied to individual tracks (e.g.
drums or bass), but then there are much simpler ways
to do this than 'tape emulation'.
Again, I completely agree.
But I'd add these observations.
Use-case 1.
Many people are stubborn and irrational. Relieving people of any given myth can therefore
be difficult or impossible. Presenting a person with evidence that their belief is
mythical can upset them, and they may respond by dismissing the evidence rather than the
myth! (Historical examples abound: the Oxford Movement - the "Puseyites" -
explicitly advocated "faith over reason",[2] and that attitude is surprisingly
common in all areas of human endeavour, including audio production.)
Pragmatically, then, when a person in the chain (artist, engineer, producer, consumer)
believes tape or tape emulation is worthwhile, it may be simpler to humour them than to
risk the recording (or even marketing) process collapsing against those beliefs. Hence
much of the continuing market for tape and emulators.
(The desire for tape can be due to other factors in addition to "warmth". It can
also come from a desire to avoid post-production. The White Stripes and their fanbase were
an example of this c.2002,[3][4] as were Rage Against The Machine about a decade
earlier.)
Use-case 2.
There are people with access to a PC but without access to tape, who will want to be able
to learn, as closely as possible, how tape sounded. The more accurate your algorithm, the
better it suits this purpose, i.e. as a teaching tool.
Some of those people will end up concluding, as you correctly did, that there are often
simpler ways to achieve equivalent results. But your emulator will have been an important
part of that education.
Conclusion
Thank you for working on this and for sharing your results!
Sam
[1]: https://www.mixonline.com/recording/classic-track-fast-car-tracy-chapman-42…
[2]:
https://www.oxfordbibliographies.com/display/document/obo-9780199799558/obo…
[3]: https://www.newcutstudios.co.uk/cant-ignore-the-elephant-in-the-control-room
[4]: https://www.soundonsound.com/people/liam-watson-toe-rag-studios