Tape Warmth, Sidebands, & Artificial Modulation

[lightandmind]

"It has even been known for engineers to artificially increase the amount of modulation noise by unbalancing one of the rollers, thus creating more stronger sidebands containing a greater range of frequencies"

I caught an article that seemed interesting to me, http://www.record-producer.com/learn.cfm?a=29, and I wondered what your thoughts on the validity of these statements, whether or not anyone has had any luck with a multitrack mod like this, and how one might go about performing it.

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[drumsound]

The site is down, but I don't trust the thing you quoted.

[Mark Alan Miller]

Unbalancing a roller on a tape machine? Like, adjusting the height? That would surely cause transport/tape path problems - and possibly uneven head wear and/or tape damage. Unbalancing as in making it out-of-round would add wow or flutter. So, until that site comes back up and I can read more, I'm with drumsound. I don't buy it.

[I'm Painting Again]

here is the context:

There are many digital simulations of the analog tape sound - hardware units and plug-ins - but most simulate only the distortion characteristics of analog, and sometimes a little of the noise. But analog recording is far more complex than that. For instance, there is modulation noise.

Modulation noise is noise that changes in level as the signal level changes. This is a separate effect to the constant background hiss that is audible in any analog recording. Modulation noise has two main causes...

One is Barkhausen noise which is produced by quantization of the magnetic domains (quickly glossing over a complex technical phenomen in five words...).

The other - more significant - cause of modulation noise is irregularities in the speed of tape travel. These irregularities are themselves caused by eccentricity and roughness in the bearings and other rotating parts, and by the tape scraping against the static parts.

We some times hear of the term 'scrape flutter', which creates modulation noise, and the 'flutter damper roller', which is a component used in better machines to minimize the problem.

If a 1 kHz sine wave tone is recorded onto analog tape, the output will consist of 1 kHz plus two ranges of other frequencies, some strong and consistent, others weaker and ever-changing due to random variations.

These are known in radio as 'sidebands' and the concept has exactly the same meaning here.

Modulation noise, subjectively, causes a 'thickening' of the signal which accounts for the fat sound of analog, compared to the more accurate, but thin sound of digital.

It has even been known for engineers to artificially increase the amount of modulation noise by unbalancing one of the rollers, thus creating more stronger sidebands containing a greater range of frequencies.

Don't try it with your hard disk!

[MoreSpaceEcho]

"more stronger".

[leigh]

FWIW, the link works for me, just needed to fix up the formatting from the OP:

http://www.record-producer.com/learn.cfm?a=29

[I'm Painting Again]

I like how the blurb says how flutter stabilizing devices help fix a problem then go on to say "flutterizing" is what makes it sound even better..

it doesn't seem like this was written by a person who has a grasp of tape recording science..99.9% of us don't really either..

but

it sort of explains why tape is "fat"..though not very well..I guess frequency modulation and the resulting sidebands *could* be considered the main certain je ne sais quoi of analog tape recording..

they could have just wrote:

tape sounds "fat" because it is a device which causes more distortion than any other modern recording device we have..

[fossiltooth]

record-producer.com is one of the worst pro audio websites around.

Please don't link there!

[Mark Alan Miller]

Smacks of.... something. Something not so good.

[Nick Sevilla]

"It has even been known for engineers to artificially increase the amount of modulation noise by unbalancing one of the rollers, thus creating more stronger sidebands containing a greater range of frequencies"

I caught an article that seemed interesting to me, http://www.record-producer.com/learn.cfm?a=29, and I wondered what your thoughts on the validity of these statements, whether or not anyone has had any luck with a multitrack mod like this, and how one might go about performing it.

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I like that the guy who wrote it is "attempting" to explain something, but to me he fails miserably.

Most of the time when I was recording onto tape, we always attempted to avoid hearing those symptoms by servicing a bad tape machine regularly. these symptoms are a BAD thing.

And I think the writer does not yet grasp tape technical terms well yet.

I suggest you go and talk to someone like Studer, they do actually answer the phone over there, and have great technicians that are willing to talk ALL DAY about techie stuff. They'll definitely guide you in the right direction.

Cheers

[lightandmind]

Thanks for reposting the link,
Yeah, looked pretty fishy to me also, heince my posting.
Thanks fellas.

Anyone want to list a few of the many factors that result in the artifacts we find on tape, (vs. sterile digital), and what one might do to exaggerate the differient aspects of these artifacts?

[MoreSpaceEcho]

harmonic distortion.

[I'm Painting Again]

nonharmonic distortion

[Nick Sevilla]

Thanks for reposting the link,
Yeah, looked pretty fishy to me also, heince my posting.
Thanks fellas.

Anyone want to list a few of the many factors that result in the artifacts we find on tape, (vs. sterile digital), and what one might do to exaggerate the differient aspects of these artifacts?

Hi,

It's not only the tape itself, it also is the record amplifiers and repro amplifiers. And also the heads, how wide the gaps are, how wide the channel is on tape, how "strong" your magnetize the tape.

I could go on and on and on... but now I just use digital, and distort the signals in other ways.

Here's one :

Use an tube mic preamplifier, and run it on a tad lower voltage. If you have a genuine Variac, you can power a pair of tube mic preamp channels, and with a meter, reduce the running voltage just a little, like 5 to 20 volts less. this can sometimes do it. Similar to the "brown sound" on EVHs records, but using a mic preamplifier instead of a Marshall head. Same principle anyways. You get a duller, "fatter" wider distortion.

Don't use solid state mic preamps, they wont run well, as you'll have to reduce the voltage a lot less, and the results can be unpredictalbe...ie not good.

Cheers

[msmith]

record-producer.com is one of the worst pro audio websites around.

Please don't link there!

I have to qgree...More half truths than my ex-girlfriend...