Subject:Best Practice for restoring old tapes

Posted by: Jesus Freak

Date:8/24/2007 7:42:38 AM

Hello all,
I am looking for some advice here. I have just been given the task of transferring a bunch (like, 600) of 20-30 year old tapes to digital format. I have 2 questions.

1) Which sounds better to the typical listener, aggressive noise reduction with some odd artifacts or gentle noise reduction leaving significant tape hiss.

2) Has anyone else done something like this, and what processes/filters gave you the best results?

Thanks!

Subject:RE: Best Practice for restoring old tapes

Reply by: rraud

Date:8/24/2007 9:15:43 AM

That may be subjective to the listener. I find the NR flanging artifacts annoying and one must often compromise. Of coarse this depends on the condition of the tape and how well it was recorded in the first place
Two passes of less noise reduction work better than one, creating an updated noise print for the second pass. Also cutting the high frequencies a little and then processing with a HF exciter may also help reduce the tape hiss.
Of course if they are reel-to-reel, they may not even play at all. Often 20-30 yo R-R tapes (particularly Ampex 456) will not play without "baking" them.

Subject:RE: Best Practice for restoring old tapes

Reply by: Jay Z

Date:8/24/2007 9:30:25 AM

I've done a lot (1000's) of restorations of old, analog tapes for numerous studios when I was the field engineer for Ampex/Quantegy out of the Chicago field office before they closed it down in 2000.

Before you start thinking about procesing the tapes for sound quality, you better be thinking about the physical properties of the tapes themselves. Tapes of that age stand a very real possibility of suffering from hydrolysis of the binders, which can cause a problem with sticky shed as you play them back...Depending on how severe the problem is, the sticky tape causes an audible squeel that transfers into the sound path, and in more severe cases, the shed causes stiction to the point of slowing down and stopping the tape in the transport. I've actually seen 2" masters stall and stop on transports with motors big enough for washing machines!

Obviously, anytime you suffer shed, your losing the magnetic particles of the tape, and this affects the high-end rapidly...Think nose dive in the frequency response!

You CAN fix the tapes long enough to make a couple of dubbing passes...This involves a process of heating the tapes in a time and temperature controled environment.

We used humidity and temperature controlled chambers for this in the lab, but in the field we used manually controlled convection ovens to ensure the exact temperatures remained constant for the time involved.

I'm hesitant to give the time/temperature formula out on an open forum as the temerature that is needed is very close to the point that the basefilms and plastic reels can warp...Also, the lengthy time involved and the monitoring requirements are such that, unless you are absolutely sure of what you're doing, you could have disasterous results...ie: destroyed masters.

There are a number of articles available on the net regarding this process, so you should do a search on "Archival Shed Syndrome"...you might find something that I wrote...Or with a bit of luck, you'll be able to find an article done by Cris Stone of The Record Plant who developed a "poor mans method" of doing the process that works extremely well, and costs practically nothing to make and do.

Be very wary of the "audio restoration" companies out there that want to charge you an arm and a leg for "propriatary chemical processes"...they are totally unnecessary, and in many cases what they are doing is nothing more than the baking process I am aluding to.

In any event, once you have the tapes in a playable condition, you should use a high quality deck and audio system properly calibrated and adjusted for FLAT frequency response to dub into your DAW...THEN, you can process and tweak the audio to your hearts content...or better yet, to your ears content....

Cheers and Good Luck!
JRZ

Subject:RE: Best Practice for restoring old tapes

Reply by: jbolley

Date:8/24/2007 12:14:03 PM

I know standard practice for archival is often one 'straight transfer' vault master and one 'cleaned-up' listening copy.
If you do heavy processing please provide an unprocessed archive as well.
The future will thank you.

Jesse

Subject:RE: Best Practice for restoring old tapes

Reply by: Jay Z

Date:8/24/2007 1:15:39 PM

Just a comment onRRaud's statement of "...particularly Ampex 456". That statement is a bit misleading...Every manufacturers tape has the problem...I know, because I have had to deal with all of them...The reason it seems it's more prevelent with Ampex, is because Ampex had 90% of the studio mastering business, and when you have the majority of the tape on the market, the percentage perception gets skewed. Ampex also made tape for other sellers/distributors, so just because it doesn't say Ampex on the box or reel, doesn't mean it isn't an Ampex coated product.

Cheers!
JRZ

Subject:RE: Best Practice for restoring old tapes

Reply by: Jesus Freak

Date:8/27/2007 7:48:01 AM

Thank you all. I really appreciate your sharing your knowledge and time. I have not run into any problems transferring the tapes, but if I do I now have information on what to do!
Anyway, thanks again all... if anyone else has any "words of wisdom" I would love to hear them.

Jamey

Subject:RE: Best Practice for restoring old tapes

Reply by: Phil Sayer

Date:8/30/2007 4:18:53 PM

I agree entirely with the concept of keeping a straight-dub guard (or vault) copy.

If you have SF9.0 try the Izotope mastering plug-ins - I think you'll be pleasantly surprised. If not, it's down to the usual combination of EQ, normalisation, compression, noise-gating and anything else you can throw at the recording... and/or the restoration plug-ins, designed for vinyl restoration, but I've used them to good effect on cassette tape transfers.

Final advice on the subjective issue of aggressive NR versus leaving some hiss... I believe most people are able to "filter out" hiss after a short time - the brain is a wonderful thing... and secondly, resist the temptation to monitor the results at high level, and listen at near-normal level to ascertain the most pleasing effect.

Subject:RE: Best Practice for restoring old tapes

Reply by: Jay Z

Date:8/31/2007 9:58:19 AM

Over the years, I have found that overly aggressive noise reduction just isn't necessary, and the artifacts that are created in the process are more annoying than the noise. Typically, a -10db to -15db maximum reduction is really all that's necessary, and the artifacts generated at those levels are minimal.