Tech: USB Distorted

Subject: Tech: USB Distorted
From: GUEST,Raggytash
Date: 07 Nov 11 - 05:02 AM

I'm having problems transferring music from a USB turntable through the USB ports on my laptop. The sound is "dirty", that is distorted, I'd run several vinyl LP's with no problem and this suddenly occured, all the latest upgrades have been installed and a new needle put on the turntable, this is definitely a problem with my laptop as I have used the same software on a different laptop with no problem.

Any idea's anyone

Subject: RE: Tech: USB Distorted
From: Paul Burke
Date: 07 Nov 11 - 05:34 AM

The first thing is to try it on another computer. Distortion can be introduced in a number of ways:

(1) At the stylus/ record interface: fluff, groove damage, dirt, jam (once when the Boy was small), damaged stylus, incorrectly installed stylus, incorrect arm balance, mechanical damage to arm etc etc.

(2) In the conversion process from analog to digital. Did you install a new cartridge, with a higher output than the old one? This could saturate the analog to digital converter, though only during loud passages. Is there a level control that could have been inadvertently changed?

(3) In the transmission brocess. USB sound is normally transmitted as Bulk Transfers, which means there is no check for lost data packets. If you are connected via a USB hub with other devices connected, you could be asking too much, especially if it's USB 1 or the device is being treated as USB 2 Full Speed (12Mb/sec rather than USB 2 Hi Speed 480Mb/sec). Have you plugged into a different port this time? Sometimes laptop ports are shared: effectively an internal USB hub.

(4) Within the computer- are many other programs running at the same time, or a lot of hard disk IO going on?

Here's a less- than- helpful Microsoft technical note.

Subject: RE: Tech: USB Distorted
From: JohnInKansas
Date: 07 Nov 11 - 05:38 AM

Are you trying to do "real time" recording at a fairly high quality?

If so, your bit rate may exceed the capability of the USB port.
(A lower bit-density might actually give you a better quality in the recorded file.)

Is the laptop (or the turntable) old enough to be limited to USB1 port rate?

If you have a USB2 port, and the turntable can run at USB2, is there a another USB1 device connected. (Early USB2 ports slow down to USB1 rate if there's even one device connected (not necessarily running) that can't handle USB2. Later ones can adjust the rate so each device gets whatever it can handle.)

USB signals are digital. Do you "digitize" the analog signal from the turntable before it goes to USB at the quality you want? (Assumed if it has a USB output port(?).)

Just some quick-n-dirty thoughts about common USB difficulties. The problem probably is just as likely (or more likely?) to be in the digitizing and end-file format.

John

Subject: RE: Tech: USB Distorted
From: Bernard
Date: 07 Nov 11 - 06:03 AM

My guess is it may be a lot simpler - the sound recording level could just be too high.

Open the audio properties for the 'sound card' that is the USB device, and look at the recording levels. See what happens if you reduce the level during a recording to get an idea of what works and what is too much.

Even though you may think you've not changed anything, changes can sometimes occur when changing something else!

Look at the waveform of the recording - 'clipping' (where the peaks of the sound waves are flat instead of curved or spiky) is a sure sign of over recording.

Subject: RE: Tech: USB Distorted
From: Will Fly
Date: 07 Nov 11 - 06:05 AM

You say you're using a new laptop. Is it worth checking audio output levels from the turntable with audio input levels in the laptop software? There might be some peak setting which are being overloaded somewhere.

Just a thought.

Subject: RE: Tech: USB Distorted
From: Bernard
Date: 07 Nov 11 - 06:56 AM

Snap!

Subject: RE: Tech: USB Distorted
From: Will Fly
Date: 07 Nov 11 - 07:37 AM

Indeed Bernard - two minds with one simultaneous thought! :-)

Subject: RE: Tech: USB Distorted
From: Bernard
Date: 07 Nov 11 - 12:07 PM

Be scared... be very scared!!

Subject: RE: Tech: USB Distorted
From: GUEST,Raggytash
Date: 07 Nov 11 - 02:05 PM

No mention of a new laptop by me !!!

I have tried another laptop with no problems.

Cleaned records with microfibre cloth before playing, replaced needle and cleaned needle on a regular basis when recording, normally twice per side to remove fluff etc.

Recording in real time

No other progammes running

Comments about USB qualities are beyond my comprehension (Bear of very little brain me, still think of electric lights as being "sun in a bottle"

Eventually reduced sound recording levels as suggested by Bernard, unfortunately his good advice came after we found the solution ourselves, spending a weekend of fustration and after both my wife and I had spent hours trying to sort the problem.

Anyway THANK YOU to everybody who tried to help and hpefully if anyone else experiences this we will all have another hint to help them

THanks again

Raggytash

Subject: RE: Tech: USB Distorted
From: GUEST,Arkie
Date: 08 Nov 11 - 10:40 AM

Are we to assume the recording level was set too high?