The Pros and Cons of Recording and Mixing via Analog versus Digital
This article has been revised and updated from an editorial counterpoint which appeared in Pro Sound News, January 1997. Here's a refreshing alternative perspective to what's going on in the studio scene for everyone from musicians to owners of project studios to large studios.
Analog vs. Digital - The Good, the Bad, and the Ugly
Doing analog audio in the sixties and seventies was hell. Most of us would like to throw our bias oscillators in the garbage. Analog requires constant vigilance to sound good. In addition, you can't copy an analog tape. The second generation just falls apart; it's a pale replica of the first. If analog's so bad, what's the problem with digital recordings? Can't we give them the warmth of analog if we use vintage tube mikes and analog processors? There must be something to that argument, or the whole industry wouldn't be doing the retro-tube trip. But I wonder if we're all doing it for the wrong reasons. Please remember that there's good tube equipment out there, and a lot of bad. There's also good digital equipment and an awful lot of bad. Much tube equipment is overly warm, fuzzy, noisy, unclear and undefined. Only the best-designed tube equipment has quiet, clear sound, tight (defined bass), is transparent and dimensional, yet still warm without being artificial or muddy. Similarly, some of the cheap digital audio equipment is edgy or hard-sounding, dimensionless, and unclear. Only the very best digital audio equipment (and it's getting better every day) can lay claim to good soundstage width and depth, purity of tone without an artificial edge, and transparency.
Bad Digital versus Good Digital
Many people have argued that digital audio recording is more accurate than analog, saying the accuracy of digital is why we're noticing hardness and edginess in our recordings, and have regressed to tube and vintage microphones. That's only a half-truth. Let's distinguish between bad digital and good digital equipment design. Bad digital sounds bad because it is bad. Bad digital equipment has distortions that innately increase edginess and hardness. Edgy sound can be caused by many factors: sharp filters, poor conversion technology, low resolution (short wordlength), poor analog stages, jitter, improper dither, clock leakage in analog stages due to bad circuit board design and many others. Placing sensitive A/D and D/A converters inside the same chassis with motors and spinning heads is also a dangerous practice. It takes a superior power supply and shielding design to make an integrated digital tape recorder that sounds good.
A lot has changed since I first wrote this article in 1997. Coincident with the demise of the tape-based multitrack and 2-track have come better converters and higher sample rates. "Bad Digital" has largely gone away and been replaced with ranges from "just acceptable" to "very good". There was a time when I could attribute the edgy-sounding, dimensionless mixes that I received to the poor converters in the MTRs (multitrack recorders), but now we see losses in a matter of degree. Nowadays many MTRs record at 48 kHz and above and wordlengths of 24 bits. The DAWs record at 24-bit fixed, and mix at 32 to 64-bit float. The sonic performance of the lower-cost MTRs may not equal that of high-class separate converters, but by 2005 or so I could finally say that even an MTR in the $2000 range using internal converters performs pretty well. Everything has (thankfully) come up several notches over 1997-performance and down in price! Now when I get dimensionless, distorted or gritty mixes I usually attribute them to operator abuse of digital technology, overuse of low-resolution plugins and processing and overuse of cheap samples or synthetic instruments, for example, digital drumsets instead of the real thing. The A/D converter still contributes a bit to the sound quality, let's say 10%, even less if you work at 96 kHz, where even a mediocre converter sounds better.
Through loving care and a number of proprietary processes in the mastering stage, I can bring these mixes up to a much better quality level. It is possible to give the sound greater apparent transparency, more spaciousness, increased purity of tone, improved dynamics and transient response (where these changes are esthetically appropriate). A mastering engineer who has made and heard the best recordings can do a lot for weak mixes. But let's not forget the sound that can come from analog tapes mixed through analog consoles, and from widetrack analog masters. After reading this article, I think you'll reconsider the analog alternative.
Bandaids Instead of Cures
Bad digital benefits from the use of tube mikes and preamps because their warmth and noise help cover up the hardness of the rest of the signal chain. Use of warm-sounding mikes and preamps can become a fuzzy blanket that hides the potential resolution of the system, but it is not a cure, it is a bandaid. Even good digital benefits from proper choice of microphones and preamps (including well-designed tube equipment). Digital recording is considered to be "accurate," but each of its specs must be considered carefully. Consider its linear frequency response. With bad digital technology, linearity of frequency response can turn from virtue into a defect. We can no longer tolerate the distortion and brightness of some solid-state equipment (including poor A/D converters, microphones and audio consoles) because digital recording doesn't compress (mellow out) high frequencies as does low speed (15 IPS) analog tape. To summarize: digital recording can sound edgy for two reasons. One is linear frequency response, which reveals non-linearities in the rest of the chain. The other is built-in distortions in the A/D/A conversion process.
The Virtues of Analog Recording
Listening to a first generation 30 IPS 1/2" tape is like watching a fresh print of Star Trek at the Astor Plaza in New York. I believe that a finely-tuned 30 IPS 1/2" tape recorder is more accurate, better resolved, has better space, depth, purity of tone and transparency than many digital systems available today. Empirical observations have shown that you need a nominal "24-bit" A/D to capture the low-level resolution of 1/2" 30 IPS (if truth be told, the best converters only approach about 19-20 bit resolution in practice). It can also be argued that 1/2" tape has a greater bandwidth than 44.1 KHz or 48 KHz digital audio, requiring even higher sample rates to properly convert to digital. Listening tests corroborate this. 30 IPS analog tape has useable frequency response to beyond 30 KHz and a gentle (gradual) filter rolls off the frequency response. This translates to more open, transparent sound than any 44.1 kHz/16 bit digital recording I've heard. 1/2" 30 IPS analog tape has lots of information, like high resolution 35 mm film. 16-bit 44.1 KHz digital is like low-resolution video. As higher resolution (e.g. 96 Khz/24 bit) digital formats become the standard, maybe then we'll be able to say that digital recording is better than analog. But don't be fooled by the numbers; there's still some "magic" in the coloration of analog tape that we have not yet been able to reproduce in an all-digital recording, especially for popular music forms that often crave the sound of tape saturation. Analog tape has its own problems, but when operated within its linear range, unlike digital recording, it has never been accused of making sound "colder." However, digital recording has finally gotten good enough so that in acoustic music formats like classical and folk, some engineers are preferring digital recording's transparency over analog's warmth.
The Real Cure
If you want to improve the sound of digital recording beyond that of the built-in converters in the multitracks, you will have to spend a small fortune. You can add external A/Ds and D/As which may cost several times the price of the basic machine. To put it in perspective, The entire multitrack digital recorder costs less than a 2-channel A/D converter from the best audio firms! This points out the large economic disparity between "bad" and "good" digital. It's obvious that to have the best digital sound, your project studio can quickly become a high-dollar venture. This is analogous to the art of photography, where a single lens can cost 3 to 4 times that of the camera body.
At first glance it may seem that using a digital console to mix down from MTR can be an advantage, because you are not using the poor D/A converters in the MTR, but now you will have to deal with the long wordlengths produced by the calculations in the digital console, and the digital console has to get its internal extra-long wordlengths down to 24 bit with minimal distortion. Since distortion is cumulative, I suggest you minimize multiple passes through the DSP circuitry in the console or DAW. Numeric precision problems in digital consoles produce problems analogous to noise in analog consoles. However, there is a difference between the type of noise produced in analog consoles and the distortion produced by numeric problems in digital consoles. Noise in analog consoles gradually and gently obscures ambience and low-level material and usually does not add distortion at low levels. Numeric problems in digital consoles can cause several problems. Rounding errors in digital filters act much like analog noise, but at other critical points in the digital mixing process, wholesale wordlength truncations can cause considerable damage, destroying the body and purity of an entire mix, creating edgy sound, which audiophiles often call "digititis." Depending on the quality and internal precision of the digital console and digital processors you choose, and the number of passes through that circuitry, it might have been better to mix down to analog tape through a high-quality analog console.
If you do not use an analog mixing console in conjunction with "old fashioned" analog equalizers and processors--you'll have to take extra pains to keep your digital system from sounding cold. If you can't afford high-quality external A/Ds (and large hard drives), be careful of using too many tube bandaids. Tubes can cover up the evils of the cheap A/D/A's and processors, resulting in a warm, fuzzy sound, but that's preferable to a hard and edgy one. In other words, good digital is expensive and probably the best you can get from bad digital with bandaids is "warm and fuzzy!"
I still suggest trying analog tape! Invest in a great analog recorder. Your first step is to get a good two-track 1/2" machine. After that, consider using wide-track analog multitrack for the main tracks. To get good analog sound that's perhaps better than the most expensive digital, practice your alignment techniques, don't bounce tracks, use wider track widths and higher speeds than you did before.
Cost-wise, analog tape recording has finally exceeded that of even world-class AD/DA converters due to the extreme cost of tape. If you're not doing analog tape, try to get the very best converters and minimize mixdown passes through low-resolution processing and plugins.
Making the Right Trade off Decisions
If you must choose some digital storage and processing, evaluate the tradeoffs carefully. Both analog and "good digital" are clear, detailed, warm, spacious, and transparent. We have to reevaluate the tradeoffs each year. For example, the cost of 2-track, 96/24 digital recorders has plummeted. I recommend the Tascam DVRA1000HD DVD recorder---with or without external converters it has raised the bar in 2-track machines. Study the compromises and look at each situation as a tradeoff: If you have too much "digital", and not enough "analog", your results will not be "fat" or "warm" enough. Or vice-versa! So, the well-balanced "hybrid" approach beckons, perhaps tracking with analog tape and mixing digitally, or vice-versa.
With today's choices, you can offer musicians a real value that sounds great. You can easily assemble an affordable multitrack system that sounds better than the old 44.1/16 systems. Hybrid can sound great! I'm looking forward to seeing your fabulous tapes or files at our mastering house!
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