How to Improve Audio from Old Re-Recorded Casette Tapes

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djkoz

Well-known member
I need help improving sound quality from cassette tapes.

Before she died 25 years ago my wife recorded several children’s books on cassette tapes for our then very young kids. As a result of moving the tapes were misplaced for a while but have recently been found. I want to transfer the tapes to DVDs which I have done, but the sound quality is poor.

The original tapes were recorded using a small desktop cassette player/recorder with a built-in microphone. Today I recorded the audio from those tapes via the RCA output jacks on the back of a cassette player which were fed into the stereo line input jack on the back of my computer.

However, the quality of the sound is poor. In addition to the motor hum of the original cassette recorder the sound is also a bit muffled. So, my questions:


  1. Is there a better way to transfer the audio from the cassette tapes to the computer? (I first tried feeding the sound from the cassette player into the RCA jacks on my DVX100A and from there using the firewire port to connect the DVX to my computer. However, I could not get the audio to even register on the DVX level meter)


  1. Does Sony Vegas (v Pro 8) have any built-in filters that I can use to eliminate the hum and improve the clarity? (I’ve used Vegas a bit but I am not familiar with more than just the basics of working with sound.)

Thanks for your suggestions.

Dan
 
I've done a fair amount of audio restoration from cassettes.

First I would do a better transfer. It line in on a computer is generally poor quality and noisy. The DVX100 is better but kind of convoluted. Ideally you want to record at at least 44.1/24, the DVX100 will be 48/16, but that should still be OK.

Clean the heads on the cassette, if possible demagnetize them also but that is probably not in the cards. You can clean the heads with 90% (or higher) rubbing alcohol (don't use the 70% - and DON'T use denatured) and some Q-Tips.

Second you probably recorded with some sort of Dolby Noise reduction, playing back with the NR off will make the recording sound dull. It almost certainly was Dolby B (but possibly Dolby C). THere is also usually a choice between "high bias" and "standard bias". You should have chosen whatever the tapes are listed as but there was a way some decks used to detect the type so it may have been set automatically. You should probably try both settings if it's an option and find out what sounds best.

Now if you have great notes on the tapes just do what the notes say but 90% of the time you just have to change settings and find out what sounds best because nobody kept track or remembers what the settings were.

After you have it playing as good as you can. Transfer at 24 bit if possible. Sample rate is not that critical with cassettes since the don't have much high end and what was there probably isn't anymore. The higher bit depth gives you more resolution to work with and that can really help with the processing.

once you have the files in a sound program on a computer you can try to clean them up a bit. Noise reduction plugins may help with the motor noise, they should definitely help with the tape hiss. Rolling off below say 150Hz will probably help. It's not likely that there is much above 10,000Hz and almost certainly nothing you want above 15,000Hz so rolling off the top will clean out a lot of hiss. Whan you have it pretty "clean" then you may want to play with some EQ on the voice. Don't go crazy but a few dB up in the say 1,000 - 3,000 range may help.

The BIG thing is to listen before and after at each stage and ask yourself "Did that make it better, or just different?". It is VERY easy to like a change just because it's different and you don't like how the original is. You can go whole hog on it but the next day you will play it back and ask "What was I thinking???!". Go slow, take small steps and A/B your choices. With a little luck and a bunch of patience you will end up with some very nice memories.
 
I think you are a bit over my head.

The casette player I now have available with RCA output ports is very basic. There are not a lot of adjustments I can make. The recorder with which the tapes were originally made is a very simple (an old) GE home/office tape recorder with a small built in mic. It probably cost $20.

I also was unable to get the audio to register on the DVX when the audio output from the player I borrowed was connected to the RCA input jacks on the DVX. It just did not seem to recognize it.

The DVX manual seems to imply that in order to record audio via the RCA input I also have to supply a video signal. So, on the DVX I connect the input of the RCA audio to the output of the cassette player I am now using and fed in a video feed from my TV. Even with that the only way I could get the audio to register on the DVX meter was to put the DVX into playback mode (i.e. like a VCR) but then, of course, I was not able to record anything.

Unfortunately, since I normally don't have much of a need, my knowledge of sound is very limited.

Thanks for the advice. I wish I were in a better position to use it.

Dan
 
Once you get the audio into Vegas you have the tools to do some clean up, however they do take some know-how on using them. look for the de-noise plug in, in vegas to start
 
By mid late 80's probably even the cheapest recorder had at least Dolby B.

The bad news is that it's not a one button fix to do much with old tapes and they can be a fragile.
You might be better off looking for someone local that could do the transfer. This is the kind of thing I'm often doing as a favor for a friend since few people are ready to spend what it would cost and as long as it's something one can do in quiet patches between paying gigs. It's not super difficult to do a decent job usually, but it does take time and the right tools.

AS to levels, it's hard to say with out seeing the setup but I suspect that it's either that your set up wrong (the RCA ins would only be used in the VCR mode, I suspect), or you may need to pick them as the line ins in a menu somewhere. Or your gain staging is out of whack. The levels on the cassette and the levels on the DVX100 are both going to play in the level you record at, there may even be another setting someplace.

Also a lot depends on what you want to end up with. If the only problem is that it's a little muffled and your getting some motor hum you may just be able to do it with EQ and be happy.


djkoz said:
I think you are a bit over my head.

The casette player I now have available with RCA output ports is very basic. There are not a lot of adjustments I can make. The recorder with which the tapes were originally made is a very simple (an old) GE home/office tape recorder with a small built in mic. It probably cost $20.

I also was unable to get the audio to register on the DVX when the audio output from the player I borrowed was connected to the RCA input jacks on the DVX. It just did not seem to recognize it.

The DVX manual seems to imply that in order to record audio via the RCA input I also have to supply a video signal. So, on the DVX I connect the input of the RCA audio to the output of the cassette player I am now using and fed in a video feed from my TV. Even with that the only way I could get the audio to register on the DVX meter was to put the DVX into playback mode (i.e. like a VCR) but then, of course, I was not able to record anything.

Unfortunately, since I normally don't have much of a need, my knowledge of sound is very limited.

Thanks for the advice. I wish I were in a better position to use it.

Dan
Click to expand...
 
Hey Dan,

I have access to the hardware and software for a good quality restoration. Including a professional cassette tape deck and 24-bit PCI audio interface. Here's what an old commercial (purchased around 1990) cassette tape sounded like running straight to the deck, no processing except to maximize the volume:

http://solitudestudios.com/cassettesample-tubin.mp3

Come to think of it I may have run noise reduction on it. What I'm sure of I never knew that cassette tapes could sound so good until I ran a tape through that deck!

Audio restoration requires the right tools and knowledge. The deck itself and what it's connected to makes a huge difference in the initial sound capture. Just having the ability to set the proper/natural tape speed (pitch control) and a dolby NR selector/decoder/detection is essential. Sony Vegas probably is decent enough but I haven't heard the sources. I'm interested in providing more of these types of services through the studio and we may be able to work something out.

Here's a little audio clean up sample I put up last year to demonstrate some of the things I can do:

http://solitudestudios.com/samples/audiorestore.mp3
 
Noiz2 said:
By mid late 80's probably even the cheapest recorder had at least Dolby B.

The bad news is that it's not a one button fix to do much with old tapes and they can be a fragile.
Click to expand...

When you are running 'old tapes' do you worry about some method of getting 'moisture' out, by 'baking' or the like? And if you 'bake' what do you use?
 
We transfered a few thousand 1/4" tapes and we baked all of them but I haven't done that with cassettes. It may be necessary for some but it's only really a problem for a few brands of tape made in the late 70's and early 80's. THere was a "nonstick" backing that was used that got very sticky with age and moisture. A lot of tapes (that don't have the black coating) don't need baking. We did them all for safety because it was an irreplaceable library of sounds and we were paranoid.

j1clark@ucsd.edu said:
When you are running 'old tapes' do you worry about some method of getting 'moisture' out, by 'baking' or the like? And if you 'bake' what do you use?
Click to expand...
 
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