Transferring Cassettes to PC

[Kerb26]

I’m going to transfer some home recordings from cassettes to PC.

I found a couple of articles from SOS that suggested using 16 bit as this would be sufficient for the dynamic range of cassettes. The articles are quite old, so I wanted to ask if this is still the best approach?

The recordings that I’m transferring are very inconsistent in level which makes it difficult to set the gain properly. Obviously this would be easier in 24 bit, but the file sizes would be bigger.

I’ve also heard some people say that you should use 24 bit if you plan to do any processing, but I’m not sure if that’s correct?

[Tomás Mulcahy]

16 bit is more than sufficient for cassette. Let's prove that with maths. Rule of thumb, each bit improves SNR by 6dB. Absolute best case for cassette with a top notch deck and NR engaged is around 60dB. That's 10 bits. And it's highly unlikely that home recordings will have SNR as good as that. So again, 16 bits is more than enough.

[Hugh Robjohns]

Yes, 16 bits would be sufficient, but you'd be pretty challenged to find a 16 bit converter or interface... they are all 24 bits!

And if your cassette transfer is going into the computer at 24 bits, its a bit pointless reducing to 16 bits, especially since any processing you apply will be done at 32bit floating point or higher.

Yes, the file size will be a bit larger, but that's not going to trouble your computer or its storage media.

[ef37a]

Well Hugh, the Berry UCA 202 is 16 bits and, if the OP does not want to spend out much for a one off job is totally good enough for cassette. I have had 3 and all give a noise floor around -80dB fs, i.e. not quite as good as 16 bit theory.

Then, most DAWs give the choice of 16 or 24 bits? Samplitude certainly does. But yes, better to run at 24 bits and keep levels around -18dBfs. If the chap is concerned about file size, once 'processed' they can easily be 'saved as' 16 bit files.

Dave.

[Kerb26]

And if your cassette transfer is going into the computer at 24 bits, its a bit pointless reducing to 16 bits, especially since any processing you apply will be done at 32bit floating point or higher.

My interface is 24 bit. I assumed it would convert at whatever bit depth I set in my DAW. But it sounds like you’re saying that the interface would capture the audio at its native bit depth (24 bit) then my DAW would reduce it to 16 bit?

If so, presumably this would introduce quantization noise?

[Hugh Robjohns]

My interface is 24 bit.

Yes, most are. You've got to go out of your way to find some old 16 bit nonsense these days...

I assumed it would convert at whatever bit depth I set in my DAW. But it sounds like you’re saying that the interface would capture the audio at its native bit depth (24 bit) then my DAW would reduce it to 16 bit?

Yes.

If so, presumably this would introduce quantization noise?

Only if the wordlength is reduced by truncation rather than dithering.

But this isn't worth worrying about. Just set the level with a generous headroom margin so you don't have to worry about potential clipping. Average around -20dBfs with peaks to -10dBfs is a good target. Record with 24 bits. Once the transfer is complete you can optimise the levels to suit your chosen destination's requirements.

[ef37a]

Actually there was a recent SoS review of a couple of M-Audio interfaces that were 16 bit, budget jobs mind.

The tape noise is going to be way higher than any artifacts.

Dave.

[Kerb26]

Thanks to everyone who commented.

[James Perrett]

Just remember that 16 or 24 bits should be the least of your worries when transferring cassettes. Mechanically aligning the playback machine to match the tape is far more important as, once you've transferred a tape with the wrong alignment, there is no way of retrieving the information that you've lost (apart from transferring again with the correct alignment).

You may also need to think about noise reduction - although I usually transfer without noise reduction and then do the noise reduction subsequently in the appropriate hardware or software so that I can fine tune the levels and eq.

[Tim Gillett]

16 bit is more than sufficient for cassette. Let's prove that with maths. Rule of thumb, each bit improves SNR by 6dB. Absolute best case for cassette with a top notch deck and NR engaged is around 60dB. That's 10 bits. And it's highly unlikely that home recordings will have SNR as good as that. So again, 16 bits is more than enough.

Some cassette decks incorporated DBXII NR which from memory was around 80db S/N requiring more care when setting transfer levels.

[ef37a]

16 bit is more than sufficient for cassette. Let's prove that with maths. Rule of thumb, each bit improves SNR by 6dB. Absolute best case for cassette with a top notch deck and NR engaged is around 60dB. That's 10 bits. And it's highly unlikely that home recordings will have SNR as good as that. So again, 16 bits is more than enough.

Some cassette decks incorporated DBXII NR which from memory was around 80db S/N requiring more care when setting transfer levels.

I agree Tim, I have a Sony Dolby C machine that can copy CD (TDK SA) such that it is hard to tell from the original. However, OP is dubbing "home recordings" it is very unlikely that the dynamic range of the original material is anything like 80dB.

'GIGO'! (wtgr)

Dave.

[Nazard]

Rather surprisingly, some cassette decks were capable of sounding extremely good. For example, I have a Tandberg TCD 440A, which was straight from Tandberg, (then in Leeds), and the SA90/SA90X tapes, still sound terrific.

[Hugh Robjohns]

Yes, it was quite remarkable what they managed to get out of the cassette format, particularly through the 1980s and into the 90s.

[Tomás Mulcahy]

Some cassette decks incorporated DBXII NR which from memory was around 80db S/N requiring more care when setting transfer levels.

Yea, so just do the math. That equates to 13 bits. My Yamaha MT4X running at double speed (which gives a 3dB improvement) and dbx engaged claims 85dB. Still only 14 bits I had so many tapes I decided it was worth my while doing them at 16 bit via a 24 bit converter. YMMV.

On the subject of cassette sound quality, that Yamaha is probably the second best cassette 4 track ever made. Apparently the Marantz was better. The Yammy was definitely a lot better sounding than my Tascam Porta Two. Amazing technology for the time.

I jumped to Cubase VST as soon as I could and never looked back

[Tim Gillett]

Absolute best case for cassette with a top notch deck and NR engaged is around 60dB.

...

... My Yamaha MT4X running at double speed (which gives a 3dB improvement) and dbx engaged claims 85dB...

I said,

Some cassette decks incorporated DBXII NR which from memory was around 80db S/N requiring more care when setting transfer levels.

I did not say, "therefore 16 bits is not sufficient to capture that." Rather, I agreed with you.

[Tomás Mulcahy]

To be clear Tim, one is a standard cassette deck, the other is a double speed four track. It's safe to assume OP is referring to a standard cassette deck, not to a four track.

Regardless, the maths is sound and is all that is required to comprehend the procedure.

[Tim Gillett]

To be clear Tim, one is a standard cassette deck, the other is a double speed four track. It's safe to assume OP is referring to a standard cassette deck, not to a four track.

Tomas, you claimed,

Absolute best case for cassette with a top notch deck and NR engaged is around 60dB.

FYI, a number of standard cassette decks (stereo, 1.875ips) had dbx built in. Teac and Technics ran such models. dbx was not peculiar to double speed and/or four track decks.

Regardless, the maths is sound and (16 bits) is all that is required to comprehend the procedure.

You will notice that I did not say "and therefore 16 bits is inadequate to capture dbx cassette".
Rather I said,

Some cassette decks incorporated DBXII NR which from memory was around 80db S/N ................requiring more care when setting transfer levels.

(my emphasis)

[Hugh Robjohns]

While there is nothing wrong with the sums I'm still struggling to see any practical benefit to recording the cassette transfer at anything less than 24 bit.

Why make the job harder than it needs to be? What realistic benefit is there to transferring at 16 bits? I can't see any.

By all means store the 're-mastered' audio at 16 bits if you want to save some storage space and/or format for CD archive.

But for transferring cassettes with widely varying levels, 24 bits make it so easy to capture the loudest tracks with plenty of headroom, without any compromising the noise floor of quieter tracks. Set once and forget.

And since some re-mastering is inevitable, even if only some realignment and optimisation of levels, the saved interim project will have an even longer wordlength anyway.

[Tomás Mulcahy]

Hugh, I agree. In my case for an archive it represented a 44% saving on storage. YMMV.

Again Tim, the maths trumps everything including pedantry

[BWC]

I don't think it's pedantry, you were off by 20 - 25dB in your, rather assertive, claim. That warrants correction. He never disagreed with the math, or the conclusion that 16b is enough. Both he and Hugh are just saying that while 16b might be sufficient, 24b makes it easy, and there's no good reason to be stingy, and I agree. It's been a very long time since I was worried about conserving data storage space. 44% of? Enough to worry about?

[Tomás Mulcahy]

As I said, I agree with Hugh. Was simply sharing my experience on a particular project. As I said YMMV. It makes no sense to qualify a general statement about average cassette decks to account for uncommon exceptions. OP knows how and why to proceed and can make an informed choice. Let's move on!

[BWC]

It's only because you said, "absolute best case", not "average". But I agree, moving on...

[Tim Gillett]

...The recordings that I’m transferring are very inconsistent in level which makes it difficult to set the gain properly. Obviously this would be easier in 24 bit, but the file sizes would be bigger...

I agree that how to set record levels is not always obvious. If it was, there wouldn't be so many recordings made, even using excellent gear at 24 bits, which are noisy or distorted, but usually distorted! The great thing about transfer of say cassette recordings is there is a limit to how high the level on any cassette recording can be. If we set our DAW record level a few db's above that maximum possible level on any cassette there's normally no need to alter it. James touched on aligning the cassette deck to the signal on each tape. That is the adjustment to be made for best results. It can't be fixed in the DAW, as James mentioned.

[James Perrett]

If file size is an issue then you could use Flac files instead of .wav format files which will give you a 50% reduction in file size. Most of the software that I use can handle Flac files as easily as .wav files (my ancient copy of Adobe Audition is the main exception).

And I'll go along with Tim and repeat my suggestion to check the azimuth - using the correct azimuth for the tape is far more important than whether to use 16 or 24 bits.