I have a lot of four-, and some eight-, track cassette tapes, recorded in the '80s and '90s, to transfer to the digital realm, in order to clean-up the audio and make new (digital) mixes where warranted. After the matters of locating and securing the right multitrack cassette decks for playback, there is the crucial factor of the tapes' having been recorded with Dolby B, Dolby C, or dbx noise-reduction. Since the noise-reduction algorithms used were "compander" (compression/expander) in nature, simply re-EQing the audio during or after ripping to digital will not compensate for the changes in the characteristics resulting from the NR.

So, my question is: Are there any plug-ins (preferably AU, for my purposes) or software designed for this, or which have features that deal with these old noise-reduction formats?

 

Doesn't the cassette player have a dolby switch?
If not, simplest way with the best results would be to buy one. On ebay, eg.

The best software for tape digitizing I found is a winamp plugin:
http://www.hansvanzutphen.com/tape_restore_live/download/

I wish you success

 

iZotope RX 4 could be a solution for you mate.

 

That winamp plugin is quite nice, and RX4 will help greatly in noise reduction, but if you want to reverse the Dolby C and dbx "encoding" without owning a deck that supports them, you'll have to do more than that.
Dolby C and dbx are both so-called companders, i.e. the signal is eq+compressed during recording and eq+expanded during playback.

You can post-process your audio recorded from tape using Expander, Equalizer and noise reduction plugins, and by reading e.g. http://en.wikipedia.org/wiki/Dbx_(noise_reduction) you'll get an idea of what to do. You'll have to adjust the controls very carefully by ear until the tracks sound natural without pumping. Don't expect too great quality, as especially Dolby C and dbx are very sensitive to average-quality tapes, as cassettes usually are.

Note that Celemony Capstan v1.1 is able to eliminate wow & flutter of multitrack recordings by post processing.

But as fraifik already said, while you're on the search for an appropriate playback deck, why not buy one that has these on board already?

 

Thanks (to all) for the responses, but it is because of the difficulty in finding/paying for 4-track playback deck(s) accommodating all three NR configurations and 1⅞, 3¾, and even 7½, ips playback speeds and combinations thereof. I don't even know of a 4-track deck made with all three NRs and high and low tape speeds, though one may have existed. (One Tascam 8-track cassette deck, with dbx, would cover that format.) I neglected to mention that I have some 2-track (stereo) cassettes onto which I'd done bouncing from four tracks; they're recorded with dbx; that model had all three NR settings and high/low speeds – but it was only two-track.

There is also the matter of the bias of tape used (normal, CrO2, metal) and the setting thereof of the deck, which affects the sound. The ideal would be to acquire the exact or approxmate models (same brands) of decks as used for recording (i.e., a Fostex for those tapes recoreded at 3¾ with Dolby C). Given that I might have to settle for one 4-track deck lacking one or two of the three NRs in question, but with capability for high and low tape speeds, software would be the solution to the discrepancy in hardware.

I'm surprised that no one's created software for expressly dealing with this particular analog-to-digital situation.

 

I think that the critical point is to find or to resurrect the decks that have recorded those tapes! Especially for eight tracks recording.. clean well the heads and the capstan and demagnetize them. For four tracks recording you can use a normal stereo deck that usually is equipped with dolby B & C, you can reproduce the four tracks in two times reversing the cassette and aligning them in a daw (it is obvious that you have to reverse two tracks in the daw). IZOTOPE and CAPSTAN should be useful for post processing.

 

This one seems like the best option, for several reasons:
- dbx is the hardest to "manually decode", and the Tascam has it built in
- it has 8 tracks. You should be able to play 4-track tapes on an 8-track machine but not the other way round
- if you're talking about the 238, this is a rather solid machine that doesn't break as fast as some others
- Don't worry about the tape speed, pitching your tracks up or down afterwards can easily be done in software
- bias settings are mainly relevant for the recording process, and you only want to play the tapes, right?
bias variations can easily be handled by equalizing.

Doing Dolby or dbx in software might even today mean that the developer would have to pay license fees to the respective companies for using their algorithms, which is only interesting if there's enough demand.
Multitrack cassette decks and r2r machines are still available for purchase, so why not just use them.

 

Thanks for your reply, as well. I can't discern how many of the respondents have actually operated multitrack cassette decks. For example, using a stereo deck to reproduce four-track recordings as described poses problems of re-alignment, tape-speed (and resultant pitch) inconsistencies, and the time involved to correct those things and whether it will yield acceptable results. That would be but one reason why it's "critical" to have four- (or eight-) track decks, running at the proper speeds, with any/all of the three NR circuits in question.

There's also the mechanical matter of the azimuth and separation of the tape heads. That would be further complicated by using a two-track deck for replicating four-track recordings as described. This is relatively "easy" to correct on a multitrack deck

By the way, I'm on Mac, which is why I mentioned AU (Audio Unit), so the Winamp plug-in, which looks like a good idea, wouldn't help unless/until I'd get a Windows computer to work with.

Thanks again to everyone; I'll try Captain and the Izotope and see what results.

 

Setup Signal Flow Routing…

Press Record in DAW…

Press Play on Tape…

Just an Idea though :D

 

Thanks for your thorough reply. The Tascam 8-track you name, and which is the one I'd used, is high-speed-only, with only dbx. It might tbe the most desirable for high-speed playback, given a software solution to the NR issue, but the azimuth of the head assembly and the distances between the tracks might pose another issue? Would two of the 8-track's heads come in full contact with one track of the 4-track tape?

There were some (just a few) recordings done on normal-bias tape on a deck that accommodated that; the rest were high-bias tape on high-bias decks; some decks (such as the 238) had bias settings for "metal" tape, with which I did use metal tape. It would be good to be able to match the bias of the tape with the bias of the units, if possible.

I'm leery of slowing-down digital recordings from double-speed analog playback. Halving the speed in digital results in messy aliasing and such. I'd capture at high resolution, of course, but slowing things down in digital gets messy.

Overall, what I'm wanting to do is approximately-archival work, so variables in the rendering of the audio, in and between analog and digital realms, should be minimized – but I don't have the money to buy three or four "vintage" multitrack cassette decks. (I would also be facing the considerable expense of an eight-channel Firewire interface.) Aside from the 238, if I could buy one 4-track deck with high and low transport speeds and tackle the NR problem with software, that would be sufficient for me. (In fact, if I could buy any of this stuff at present, that would be really cool.)

 

If the head azimuth is adjusted correctly, it will be both correct for four and for eight tracks.
If not, help yourself with micro-delay plugins like the one from Voxengo.
And yes, most likely each of the four tracks will be covered by two segments of the eight-track head, although honestly some minor head adjustments might be necessary, and you might end up using only the best four tracks.

The only problem I see is that if the 238 can only play back slowspeed-recorded tapes on high speed, you might lose high frequencies, so try to pitch down the 238 as low as possible.

Good luck!

 

Thanks again. The issues you mention are partly why I'd prefer to go with hardware properly configured for the formats of the tapes, in addition to that slowing-down audio in digital gets messy.

Even if software were the panacea, there is the human cost of the time involved to tweak and correct and match-up and so on, and of the learning-curve in mastering the software necessary to compensate for lack of proper hardware – in addition to the selective de-noising and other inevitable digital-realm procedures. This would be involving many hours' worth of multitrack recordings, which would be compounded by each variable introduced. Again, if I could address the campatibility of tape speeds and track quantities with hardware, then deal with NR issues with software, that would suffice, and Capstan and RX4 seem like good things to try, though I won't know until I do. If anyone might have direct experience with transferring multitrack cassette recording and compensating for NR with software, I would appreciate their input.

 

This is why I rarely seek advice in online forums.

 

Don't make it more complicated than it actually is.
Once you have the tools set up, the process is more or less the same for every tape.
You can automate a lot of processing using sox (commandline tool, very HQ and powerful), Adobe Audition etc.
And you have to record all tapes anyway, no matter how you process them later.

2 more things just come into my mind:
1) I'd record all the 4/8 tracks twice, once with and once without noise reduction, because the deck's NR fine-tuning may have drifted over the years
2) If the 238 runs too fast, consider installing a slower, regulated, speed-adjustable capstan motor. It's not *that* difficult and will definitely give you better results for tapes recorded at lower speeds.
And as I said, bias is relevant for recording, not playback.

I wouldn't worry too much, I'd just get the 238 and start transferring the first few tapes. You will face all kinds of problems anyway, and when you're at it, I bet you'll get a totally different view on the subject

 

Thanks again for taking the time to consider this issue, but I cannot discuss this further with anyone who has not actually transferred cassettes to digital with software as an intermediary element for dealing with Dolby B and C and dbx noise reduction.

My intention, from all I have decribed, and all the time I myself have taken to clarify and re-clarify it, should be clearly that I don't want to make it more complicated than it should be. Everything you have suggested is a further real or potential complication of the scenario. Install a different motor in the 238? How hard could that be for someone who's unskilled at electrical engineering? Play-back normal-speed four-track tapes on a high-speed eight-track deck, then expect for things to sound okay slowed to half-speed in the digital realm? Take twice as much time to transfer the tapes – with one pass with NR and one without? Because the NR's fine-tuning might have "drifted," when if it works at all, it would likely be much closer than the un-NR'd transfer, even after fudging with it with software? The idea is to pre-empt "all kinds of" unwarranted problems, not to invite the possibility of more. As I had indicated, my aim is to deal as little as possible more than dealing (via software) with the types of noise reduction not represented by the hardware I could have at my disposal.

 

Well, then good luck finding one.