Background tone generated during recording

[swiftym]

I've just bought an ion USB turntable, using Audacity as the recording software. Trouble is, during recording there's a short background tone that gets generated. I've tried switching the turntable off and recording silence but the tone still gets generated. Looking at the waveform, it seems to be a stepped square wave with a duration of 0.129 seconds and a frequency of once every 32.77 sec.

There's a chance that it could be electrical noise but I would imagine that this wouldn't have such a regular frequency.

Anyone got any ideas?

[steve]

Do you get the same noise if you unplug the USB turntable altogether?
Are you using a laptop?

[swiftym]

Yes, the tone disappears if I unplug the turntable completely, and yes I am using a laptop (Sony VAIO). Could the laptop be the source of the tone?

[steve]

It's more likely that the USB turntable is the source. Not from the turntable itself, but from its USB connection. We have seen a lot of USB turntables with strange problems like this. It seems that many of them are right on the threshold between working perfectly and not working at all. Sometimes all it needs is a little encouragement in the right direction to get it working, such as plugging in via a powered USB hub, not using a USB hub, using a different USB socket on the computer, using a different computer, defragmenting the hard drive, not using a USB mouse, wearing a purple jumper while using it.... sometimes the problems persist.

Fortunately, the problem does not seem to affect the analogue output of the turntable, so the solution which has so far worked in every case is to use the analogue outputs (phono plugs) from the turntable, plug into a phono pre-amp, then into the line input of the computer.

Unfortunately most Windows laptops do not have a line input, just a microphone input (and often not particularly high quality), which then often requires two extra bits of hardware in the chain - a phono pre-amp, and an external USB audio interface. While this is not particularly expensive (both of these devices can be bought new for around £20 GBP / $40 US each), it is an expense that you were not anticipating, and it has made the whole setup a lot less convenient. This set-up does work very well though.

What I'm going to suggest (and kozikowski will probably shout at me for being such a heathen), is a very cheap option which may work. (Disclaimer: entirely at your own risk, blah blah blah...) My suggestion is to try plugging your turntable analogue outputs directly into the microphone socket of your laptop and recording with Audacity that way. You will need a suitable lead, probably something like this http://cpc.farnell.com/AV07614/audio-vi ... ded-650023

Note, that the recording will sound horribly scratchy and tinny because you have not used a phono pre-amp. One of the things that pre-amps do is to apply Equalization to the signal that boosts the bass and reduces the trebble. This Equalization (on modern records) follows standards called RIAA. Luckily, Audacity has an Equalizer built in, with presets for RIAA equalization, so in theory at least, you should be able to apply RIAA equalization to the recording after you have recorded it, and make it sound as it should.

I would expect that using a phono pre-amp and an external sound card would give better results, but this is a very cheap alternative and I would be very interested to hear how well it works. (you may even have a suitable lead already if you own a Walkman or an i-Pod).

[swiftym]

Thanks for that. I've eliminated the tone by simply changing the USB socket into which the turntable is plugged, although I can't say for sure that the purple jumper didn't help!

Cheers.

[waxcylinder]

Unfortunately most Windows laptops do not have a line input, just a microphone input (and often not particularly high quality), which then often requires two extra bits of hardware in the chain - a phono pre-amp, and an external USB audio interface. While this is not particularly expensive (both of these devices can be bought new for around £20 GBP / $40 US each), it is an expense that you were not anticipating, and it has made the whole setup a lot less convenient. This set-up does work very well though.

But that's all the ION device is: a turntable, connected to pre-amp, comnnected to a Soundcard, delivering its output via USB. It's just all contained in one box, rather than separates. I'm at a loss to explain why so many of them seem to give problems (judging by the postings on this forum). When I ran an ION iTTUSB it had no real electrical/connectivity problems - I was rather impressed with the quality of the electronics. I only abandoned the ION in the end as it gave me too much wow&flutter on some recordings, due to the very lightweight platter, I suspect.

Swifty: glad you got yours working. Another tip for you: some people recording with laptops find that the mains power supply can induce noise in the recording - and this can be circumvented by switching to battery power while doing the recording.

WC

[steve]

But that's all the ION device is: a turntable, connected to pre-amp, comnnected to a Soundcard, delivering its output via USB. It's just all contained in one box, rather than separates

Absolutely - but how many stability problems have we seen on this forum with standalone Audio>USB devices? I can't recall any. The only thing that I can put it down to is the quality of the circuits/components that are used.

although I can't say for sure that the purple jumper didn't help!

What purple jumper was that? Doh ! The one you were wearing !

[waxcylinder]

Absolutely - but how many stability problems have we seen on this forum with standalone Audio>USB devices? I can't recall any. The only thing that I can put it down to is the quality of the circuits/components that are used.

Or possibly it could be down to the proximity of the TT motor magnet to the circuitry ?

WC