Alternatives to Dolby C?

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WarmJetGuitar

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I never liked the sound of Dolby C noise reduction, neither as a kid copying records from the library or now using my 8-track.
It kills too much treble and room sound IMO.

However when we exceed 8-tracks and copy to another tape we got a choice between two evils: either the slightly too hissy sound of copying to another Fostex quarter inch machine or the AD/DA-conversion of mixing down to the computer and back to the tape machine. At the present moment option two sounds a bit better than the first one but I'd prefer to keep a purely analog chain, at least till final mixdown.

Is it possible to connect another noise reduction unit to my Fostex-machines? Either Dolby A or SR, a DBX unit or a Telcom C4? I don't have any hands on experience with these units but as far as I've read the Dolby C is developed for cassette decks while especially Dolby A, SR and the Telcom C4 are made for professional recording.
Can any of these units be used simply as an effects unit with jacks/phono/XLR being the input or output in order to send a stereo mixdown through them during copying?

Or should I wait for my friend to fix my Tascam 38? Would the double tape width make our second generation tapes sound less noisy?
 
Dolby C does not kill treble or room sound unless the tape machine and tape are misaligned.

Any double ended NR system, including the ones you mentioned, is fussy about tape machine alignment. But that's the trade off that always had to be accepted.

Doubling tape width, or cutting out one tape generation, lowers tape noise by 3db, which isnt much compared to most NR systems. Even the mild Dolby B lowered tape hiss by up to 10db.
 
In my experience all the Dolby systems sound very good when operated with the decoder back to back with the encoder. And I have done just this with all the noise reduction channels in my transfer studio at one time or another, since it's the technique I use to check that they are working to spec.

It's when you introduce tape that things start to change. When you've encountered this loss of treble have you confirmed the record-play response of your Fostex? Not just for frequency response but also for the same level out as went in? All Dolby systems are level-sensitive (unlike dbx, though that is still affected by frequency response). If your output is more than a dB or so lower than the input then you will hear a dullness in the sound. And to complicate things more, the level into the Dolby decoders within your machine is an adjustment within itself.

Have you gone through a complete alignment of your machine per the service manual?

Regards

David Ollard
Thin Brown Line
Multitrack Analog to Digital Transfers - Reel to Reel Tape Transfer - Audio Tape Transfer to Wave Files for Pro Tools and other DAW - Digitize Open Reel Tapes - Thin Brown Line
 
I don’t have any problems with Dolby C or dbx if calibrated properly. In fact I like Dolby C better than pro Dolby A. The R&D that resulted in Dolby C was the foundation for Dolby SR. But Dolby C is more finicky than Dolby B or dbx. C is more complicated with a lot more going on, so it needs to be tight, as David indicated in his reply. I’m sure it tends to drift out of alignment over time on these vintage machines.

But if you really want to try other solutions the answer is yes, you can use other noise reduction types with any deck if you can disable the default NR, which in this case it’s a simple matter of wiring something else into the Fostex. ¼-inch. Is the second deck a half-track or another multitrack? If the former you could try another encode-decode system like dbx Type I for two channels without breaking the bank. I recommend the dbx model 150x, which can simultaneously encode and decode two channels so you can monitor off the repro head while mixing down. The 150x is regularly found at good prices on eBay. I wouldn't spend much over $50.00 for one.

But there’s a catch. If you use any encode-decode NR system you’ll always need it around to play back the encoded tapes. So another option is a single-ended NR system like the Behringer Denoiser.

The word Behringer doesn’t pass through my lips very often with anything good to say, but I’m talking about a specific model made in Germany before they started outsourcing and making cheap crap in China. The Behringer SNR-202, Made in Germany, is one of the best single-ended noise eliminators ever made. With this unit you can bounce your tracks with no NR to your ¼-inch half-track (If that’s what you have) and then bounce back to the multitrack through the SNR-202 to eliminate tape hiss and other noise.

I’ve also used stereo single-ended noise reduction units by Roctron and dbx, but the Behringer unit is by far the best one I’ve owned. The unit was originally released as the Behringer Studio Series, Studio Denoiser MK-III. It was black and red. It was later renamed the SNR-202 Denoiser and looks more like the contemporary silver and black Behringer units. You can find either of these models on ebay from time to time and they are identical on the inside. These are not to be confused with the Chinese made Denoisers that came out later. They don’t compare.

And yes, your 38, if working properly, has better specs all around as Tim pointed out because of greater track width. If the heads are good and you’re only looking at a minor issue with the Tascam 38 I would make that a priority to get up and running.
 
I don't have much to add, except that the internal dolby on the Fostex decks can be shutoff. Also, just a reminder, the Tascam dbx units that usually go w/ the 38 (DX-4D) can be modified to work with other machines. The mod is very very simple to do.
 
Thanks for your advice!

Seems I need to get myself a calibration tape really soon. Am I getting this right: a tape recorded with Dolby NR enabled will only sound proper on the machine used for the recording?

There's quite a few dilemmas here but regardless what I need to get my act together an align the machine properly.

Good to hear that the Tascam 38 is 3 DB less noisy. As long as we keep the input levels high there's no problem with the Fostex, it's for 2nd generation only. Perhaps I should go look for the Behringer unit as well, sounds like a usefull thing to have around.
 
Another machine calibrated in exactly the same way should play it back fine. Hence it's best if the machine is lined up to a common standard to begin with...
 
jpmorris said:
Another machine calibrated in exactly the same way should play it back fine. Hence it's best if the machine is lined up to a common standard to begin with...
Click to expand...

That's true but normally home recordists dont need to play tapes made on another machine, especially when it's an 8 track used in a home studio application. So long as the machine plays back its own recordings fine, that's usually enough. You mixdown the tape to another recorder.

The problem here is that this machine doesnt play back its own recordings well. The only proper solution is service/alignment of the machine to the tape type normally used for recording.

Simply aligning the machine to a standard calibration tape will almost certainly not solve the muddy sound problem. I would first attempt to align the machine to itself so that what goes in is what comes out. That will probably fix the loss of treble/ ambience when Dolby C is switched in. Tape machines are notorious for gradually losing the highs with much use. Even a slight loss of highs without Dolby switched in, gets exaggerated when Dolby is switched in and the result is crap sound. Equally, a change in tape stock can throw the NR tracking out.

Unfortunately the Fostex 1/4" 8 track is IIRC a 2 head machine. That makes aligning to itself very time consuming. You have to keep making little test recordings, rewind the tape to replay and measure the tones, and then back and forth, back and forth, until you eventually hit on the correct record bias and level settings. If that's not enough, you have to do that for each of the 8 channels.

It's a pain to do properly, but once set up properly, Dolby C cuts down a lot of the noise from the narrow tracks - up to 20db. To get the equivalent quietness with no NR you'd probably have to go to 1/4" wide tracks, which for 8 tracks translates to a 2" tape machine! If nothing else, double ended NR, when used correctly saved on a lot of expense both in machine and tape.

Of course many studios had the best of both worlds. Reasonably wide track machines and NR. The result was much cleaner recordings than could be got from either wide tracks or NR on their own.
 
You use a standard calibration tape along with the type of blank tape you’ll be recording with to do a full calibration. You can’t do a full calibration without a prerecorded standard cal tape like those from MRL. This is especially important when calibrating an old deck with Dolby NR that may not have been adjusted for 20+ years.

On another note, remember, unlike a stereo cassette deck with two linked stereo channels of Dolby NR, a Fostex 8-track has eight completely independent Dolby circuits, one for each channel. If they all come back dull sounding it’s probably a combination of issues. Could be bad tape too... our old friend sticky shed will cause dull playback all by itself. A complete mechanical and electrical calibration will fix any issues, given the heads aren’t shot and the tape you're using is good.
 
@WarmJetGuitar:

Best of luck to you, and these guys are giving fantastic advice. I'm fascinated with the technology involved here. I have no personal experience with using analog NR in a open-reel format of recording, though it's amazing what kind if ingenuity is involved in how the system works.
 
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