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Author Topic: Analog tape flutter  (Read 2038 times)

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Offline splumer

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Analog tape flutter
« on: August 22, 2013, 10:21:49 AM »
Digging around in my garage I found a box of cassette masters from when I recorded with a Sony WM-D3. They sound pretty good, all things considered, and many of them have not circulated, so I'm in the process of transferring them for eventual upload.

The problem is this: one of the tapes, a C-100, has some flutter on side 2. It's bad enough to be annoying. Is there a way to reduce or eliminate it during playback, or maybe something in Adobe Audition (CS6) that would correct it? I'm using a Tascam CD-A700 to my PMD660 for the transfer.
"God love you, Dr. Dre, you’ve made some amazing music and some forward steps in the digital era, but that sound is fake. "
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Offline Gutbucket

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Re: Analog tape flutter
« Reply #1 on: August 22, 2013, 11:51:16 AM »
For referenece, the gold standard for doing this is the Plangnet Process, for which tapes must be shipped to England with work billed by the minute- http://www.plangentprocesses.com/

In the DIY realm, there is Celemony Capstan- http://www.celemony.com/cms/index.php?id=capstan.  Very costly to purchase, but you might check out the 30 day free trial which appears to allow full functinality including saving of the corrected files.
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations > virtual teleportation time-machine experience

Offline splumer

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Re: Analog tape flutter
« Reply #2 on: August 22, 2013, 12:00:51 PM »
For referenece, the gold standard for doing this is the Plangnet Process, for which tapes must be shipped to England with work billed by the minute- http://www.plangentprocesses.com/

In the DIY realm, there is Celemony Capstan- http://www.celemony.com/cms/index.php?id=capstan.  Very costly to purchase, but you might check out the 30 day free trial which appears to allow full functinality including saving of the corrected files.

"The Capstan demo version offers all the same functions as the product itself except that it will not allow you to save or export your work."

It was just an ekoostik Hookah show, not the Dead from Athens in '68. I appreciate it, but I was looking for something a little more affordable.
"God love you, Dr. Dre, you’ve made some amazing music and some forward steps in the digital era, but that sound is fake. "
 - Dave Schools

Offline Gutbucket

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Re: Analog tape flutter
« Reply #3 on: August 22, 2013, 12:13:40 PM »
Oops, my bad.  I found that file save info on their Melodyne trial download page, I now see it's disabled on the Capstan trial.  I was hoping that might be an option to check it out on this material.

I'm mostly just noting the wow&flutter correction solutions I'm aware of, both which work very well from the samples I've heard but are unfortunatley well out of taper reach costwise.  I'd love to hear of an inexpensive solution or tecnnique someone may be aware of.
volition > vibrations > voltages > numeric values | numeric values > voltages > vibrations > virtual teleportation time-machine experience

Offline DSatz

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Re: Analog tape flutter
« Reply #4 on: August 25, 2013, 09:35:26 AM »
Plangent can do amazing things--I've heard it used--but in addition to the high cost, it requires special playback equipment. It works on the assumption that the (high-frequency, usually between 60 and 100 kHz) bias oscillator in the original recorder had a steady frequency, at least on a short- to medium-term basis. To use the Plangent system you have to make a digital transfer from the original recording that includes the high-frequency bias. The system then reclocks the transferred recording so as to keep the bias signal at a steady frequency, which straightens out the audio signal almost as a side effect.

However, the remnant of such a high-frequency signal is always very weak at best, and is subject to a greater likelihood of further erasure simply because the wavelengths are so short, especially on slow-speed tape recordings. Plus nearly all analog tape recorders are designed to filter out the bias signal during playback. So Jamie Howarth (inventor of the process) has a set of decks of various kinds in which he's bypassed the filtering and/or tweaked the response so that it peaks in the bias frequency range. And of course he has to transfer the recordings at high sampling rates and/or do tricks such as playing back 15 ips tapes at 7-1/2 or 3-3/4 ips and then correcting the equalization.

In any case he then has to do a damned lot of numeric processing per minute or hour of recorded sound. It's definitely not a real-time process, even with plenty of computing power on hand.

This also tends to fix up the problem of recordings in which the overall speed shifts as the tape tension changes. That's a problem even on many professional recorders; the holdback and takeup tension would vary with the diameter of the tape pack on each reel, so typically the tape would move a little faster toward the beginning of a reel (or side of a cassette) and a little slower toward the end. That works out OK if you always play the same tape back in its entirety on the same deck. But if you cut and splice various takes together to make a master tape, there can be small pitch shifts at the splices.

Interestingly, rather than recovering horrible-sounding material, his system seems to get used most often for improving sound that wasn't at all bad to begin with. Some people seem to respond very strongly to this improvement; I have to admit that I don't hear it myself. Most likely I haven't caught on to the defect in the originals (sometimes a person needs training before something sounds wrong to them, and then they start hearing it everywhere).

I've also heard Capstan demonstrated. It works by analyzing the audio signals themselves, and requires human intervention in case it gets the wrong idea about a signal--left to its own devices, it can work like overzealous AutoTuning and strip the vibrato out of a violin, for example. But if you have (IIRC) $4,000 burning a hole in your pocket, you can buy the software and use it to your heart's content, and I'm sure it will come down in price eventually, especially if some competition emerges.

--best regards
« Last Edit: August 25, 2013, 09:57:51 AM by DSatz »
music > microphones > a recorder of some sort

Offline StarkRavingCalm

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Re: Analog tape flutter
« Reply #5 on: November 20, 2015, 02:45:59 PM »
I have a couple of analog tapes suffering from this.
Capstan has a 5 day rental for $199. A little steep for 2 tapes especially if there is a learning curve.


Is anyone aware of other software which can fix this?

Offline DSatz

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Re: Analog tape flutter
« Reply #6 on: November 21, 2015, 08:40:11 AM »
Unfortunately not (yet). I am considering the rental deal myself for some old recordings that I'd like to recover. They've assured me that you can rent it more than once if you need to.

Note that if you're running Windows 7, it only runs on the 64-bit edition, not the more common 32-bit edition.
music > microphones > a recorder of some sort

Offline StarkRavingCalm

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Re: Analog tape flutter
« Reply #7 on: November 21, 2015, 10:51:21 AM »
Maybe we can figure out a way to split the rental?

Offline bombdiggity

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Re: Analog tape flutter
« Reply #8 on: November 23, 2015, 01:53:26 PM »
I have a friend who bought Capstan.  It's pretty amazing.  His test case was restoring a well known Genesis SBD that had enormous issues.  That fix is posted online now if you go looking.  Not quite perfect but brought from the realm of rubbish to something now listenable.  I've got a before and after sample clip somewhere... 

Too bad it is so expensive. 

One thing to note is that based on how much time he said it took to get up to speed with the program and work through the issues on a severely affected source a 5 day rental may not be enough time to actually get anything done (and he's a very competent experienced editor)...  I think it is going easier now that he knows the processing better. 
Gear:
Audio:
Schoeps MK4V
Nak CM-100/CM-300 w/ CP-1's or CP-4's
SP-CMC-25
>
Oade C mod R-44  OR
Tinybox > Sony PCM-M10 (formerly Roland R-05) 
Video: Varied, with various outboard mics depending on the situation

Offline bombdiggity

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Re: Analog tape flutter
« Reply #9 on: November 24, 2015, 07:04:11 PM »
Here's one before/after sample I ran across in case any are interested before I delete it:

http://we.tl/jgqBxJX3A7

Not perfect and may not be the final result but considering what it started as the difference is clear.  The source would seem irredeemable. 
Gear:
Audio:
Schoeps MK4V
Nak CM-100/CM-300 w/ CP-1's or CP-4's
SP-CMC-25
>
Oade C mod R-44  OR
Tinybox > Sony PCM-M10 (formerly Roland R-05) 
Video: Varied, with various outboard mics depending on the situation

 

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