Clipped audio at -4db?

Please could someone help me understand what’s happened here?

A while back I got my mate to record a vinyl record. I’m not sure what software he used, but we made sure the recording level didn’t peak above 0db.

Now I’ve just looked at the waveform in Audacity, it looks like all the peaks were clipped around -4db, even though (we thought) we were leaving ourselves a bit of headroom.

AFAIR this transfer was made using an ION USB turntable (not known for quality, I know) which doesn’t have a volume, as my first thought is maybe the turntable output was too high?

I’ve shown two levels of zoom below. Thoughts???

That’s the symptom of someone using the analog pathway and the computer Mic-In on a laptop instead of Stereo Line-In (which most laptops don’t have) or the much better USB pathway. Even more evidence for this process is the two blue waves, upper and lower are exactly the same. Mic-In on most laptops is mono – same thing left and right – not stereo.

So next time you transfer the record, use the USB system or the analog system with a good analog to digital converter like the UCA202 (cassette for example in the picture).

http://kozco.com/tech/audacity/pix/UCA202.jpg

Koz

I’m 99% sure it was a USB connection out of the turntable not phono leads (it was a USB turntable), and it was going to a desktop PC not laptop.

But I get your point, and I hadn’t noticed the L & R being identical. It could’ve been the software used or soundcard driver at fault I suppose.

My MacBook Pro will have stereo input won’t it? I might dig my turntable out tomorrow and re-rip it.

That UCA202 device is 48khz. Elsewhere (on this forum, I think) I’ve read it’s crazy recording vinyl at that rate, and should be 96khz, then downsampled for mp3/CD. Any thoughts on that?

I doubt that you have read that on this forum without it being strongly challenged. 44100 or 48000 Hz sample rate are perfectly adequate for recording vinyl and in some ways preferable to higher sample rates.

That UCA202 device is 48khz.

I don’t think that’s correct. I think it will cheerfully run at either 44100, or 48000. If I get a second later I can check it.

But no, it’s a safe bet that it won’t run at stratospheric sample rates.

44100 is the native sample rate of Music CD and 48000 is the sample rate of non-compressed digital television. They’re not too shabby. You are correct, though, that you want to approach any compressed format, audio or video, with the highest possible quality show. The goal of an MP3 compressor is to preserve the quality of the original show – or whatever is presented to it.

Koz

My MacBook Pro will have stereo input won’t it?

Yes, is it’s one of the older ones.

For any line-level device, it’s a direct shot.

Thin circle and two black arrows.


The newer MBPs don’t have it and you should check. Some MBPs have one connection which switches in System Preferences.

However, you can’t plug a classic turntable directly into a Stereo Line-In. You need a Photo Preamp to take the intentional RIAA music distortion out before you listen to it. You could correct this in post production, but it’s not recommended.

UFO-202. Phono Preamplifier
http://www.sweetwater.com/store/detail/UFO202

Koz

Yes, it is one of the older MacBook Pros. :slight_smile:

So I’ve done a re-recording with my own equipment, and the waveforms are now in proper stereo and not clipped. :slight_smile:

However I seem to be getting a lot of surface noise. I’ve tried different records, and there’s little difference. I wonder if I’m doing something wrong or if my equipment’s just not up to it? I hear people doing transfers (admittedly with swanky 1210s) on YouTube and it doesn’t sound as noisy as this.

My lineage is: Mitsubishi DP-51 direct drive turntable > Cambridge Audio P25 amp > Macbook Pro.

Attached is a zipped montage of the 4 main ‘silent’ parts of the record (beginning/end, side 1 / 2). The crackle I can get round with ClickRepair, but the other noise I’m not so sure about. There’s such difference between them too, even though they were all recorded at the same input level!

Can I solve this with EQing? Or use noise removal to get rid of that faint hum?
the_sound_of_silence.zip (982 KB)

When was the last time you lubricated and serviced the turntable? Do you have it sitting on top of something that makes noises? If you’re on Windows, are you recording only from the turntable and not also from the built-in microphone?

It goes away when you lift the arm? It’s noise coming up through the base or the motor assembly or the actual turntable spindle itself running on fifteen-year old oil/sludge in the pivot well.

Koz

I’ve never serviced the turntable I bought it 2nd hand from a vinyl nut a couple of years ago. Yes, the hum goes away when you lift the arm (I’ve got it earthed/grounded to the amp, very noticable when it’s not). It’s sitting on an old empty wooden sideboard which in itself is pretty silent.

I’m not on Windows, I’m on older MacBook Pro running 10.6.8.

Will investigate this pivot well you speak of.

Consult the documentation. My older Empire turntable has provision to lift the table itself and inspect/add oil to the well revealed underneath. I’m trying to remember if my Techniques turntables would come apart and I think they did. The electronics were underneath.

Can you, as an experiment, play a record by hand? Don’t power the turntable. Put the needle on a record and push it around with your finger. That may tell you if the motor is making the noises.

Also, if it comes apart, you may find something dragging underneath.

It appears the turntable is ca: 1980, so finding documentation may be an adventure.

Koz

Hey, that’s a good idea to power by hand. I tried it, and yes, the hum disappeared.

Attached is a motor driven and hand powered montage of the same section of vinyl. Koz, could it still be the pivot well causing a hum, or does my experiment mean it must be the motor?

Even if I fix the hum, I’ll still left with surface noise in the second part of the clip, is anyone able to help me EQ that?
I tried noise removal but it affects the main audio to much.
the_intense_humming_of_evil.zip (952 KB)