I've got what may or may not be a bizarre problem - perhaps someone will be able to straighten this out for me.
I decided to upgrade my acceptable-ish sounding yet vinyl-chewing Optimus LAB-1100 (AT-PL50 clone) to something a little nicer, and at 250 US the Audio Technica AT-PL120 came highly recommended as one of the better options for a new deck without paying a huge sum. I replaced the stock ATP-2XN with a M97xE, and I purchased a cheap Behringer USB audio interface after seeing it bundled on the LPGear site with their PL120's to rip some of my rarer vinyl that hasn't seen a CD release.
Today I decided to test out the USB interface, and for some reason, whenever the stylus is in contact with a piece of vinyl - even with the motor off - I get audible white noise, heavy by a few dB on the right channel, roughly in the -58 to -45 dB range. This does not have a perceptible increase at all with the motor spinning (aside from surface noise, of course.) And as soon as the stylus is removed from the record surface, the noise disappears. Could this be an issue with the cartridge/stylus? I know the S/N ratio for the turntable is published as "<50dB", however I have not only read in several places that the actual noise floor of this deck is supposedly a fair bit lower than that, but also - correct me if I'm wrong - the noise should primarily be created by motor rumble, should it not?
Anyone have any ideas?
Thanks in advance.
I just tried hooking it up to my old turntable, and while it still produced some audible noise, it was more in the -60 to -55 dB range, much more quiet and acceptable.
I then tried removing and reinserting the stylus into the Shure, and oddly enough the white noise dropped a few dB. I just received a second headshell in the mail today, so I'm going to try mounting the AT on that one and see if it is as noisy as the Shure.
Well, the AT cartridge doesn't seem to give any different results than the Shure. Grr.
I'm noticing that, despite the fact that this turntable has (reasonably) damped feet, the amount of white noise produced seems to be related to external vibration - bouncing up and down on my knees even six feet away from the turntable seems to increase the dB meter dramatically - but aren't vibrations supposed to cause rumble/low frequency noise, rather than white noise?
I'm kinda wondering if you have some sort of circuit continuity issue - eg, that maybe the wiring in/around the tonearm gets dangerously close to coming apart. The resulting resistange spike might explain what you are seeing.
Hm, could very well be. The thing that I don't get, though, is if that's the case, why do I only get noise when the stylus is on the record? It's not as if this turntable mutes the output when the motor's not running or anything, either. I've tested recording myself cleaning the stylus with the included brush, and it is definitely producing output. So what in the heck is going on?
it's a long shot but it could be vibrations that are suitibly damped when the stylus is not in contact with anything but becomes apparent when the stylus is in contat with something. try placeint a rubber mat under the deck or temporarily placeing the deck on your mattress.
EDIT: removed quote, it was unnecessary
A very weird problem!
...heavy by a few dB on the right channel, roughly in the -58 to -45 dB range.
Try reversing the connections at the preamp input. If the noise remains worse in the right channel, then the noise is coming from the preamp. I'm thinking maybe
some low-level, low-frequency, noise/vibration is "triggering" noise in the Behringer preamp????.
On my lunch break I unhooked the deck from my amp and tossed it on the bed in the spare room, so when I get home I'll check out the vibration possibility.
As far as the preamp noise issue, I've tried both the preamp in the Behringer box and the preamp in my turntable with the Behringer set to line level input. Oddly enough, despite having a bit different volume and 'signature' (due to the difference in preamp) the noise was still present. I will, however check to see if the fact that it's louder on one side has anything to do with the preamp. I should probably also try bypassing the Behringer interface altogether as well, but before I do that I'll need to purchase an RCA-to-miniplug adapter, as my other two seem to have walked off on their own.
I'll post again tonight once I've tested the mattress theory.
I'm about ready to give up
I've tried hooking up my deck via miniplug into my sound card, and I get very similar results (perhaps a few dB less noise - that's all.) I just don't see how the needle being in the groove, even when the deck is turned off and the cartridge output being sent directly to an external preamp, would cause such a high level of noise even after I've dampened any vibrations it might be experiencing by putting it onto a mattress.
Is there anything else anyone can think of trying?
Ok, after a bit more fiddling, it appears it might be entirely caused by external vibration, but that vibration seems almost impossible to dampen. I placed the deck on a couple of pillows to see what the noise output level would be, and it showed a significant drop. It seems even the act of lightly brushing a finger along the side of the deck causes a large increase in noise. I'm thinking either my apartment has a lot of low-level vibration or this deck is a gigantic piece of resonating crap.
I'm not sure what would work best to attempt to dampen it - a rubber mat seems like it might be too insignificant to make a difference. Anyone have any suggestions?
It is perfectly normal to get a strong signal in the output when the needle rests on a surface and you move around. I learned never to record my vinyls on tape while listening to another CD, because the sound of the CD, played back into the speakers, was audible in the recording of the vinyl !
But the white noise seems strange. Usually external vibrations come very muffled because of the RIAA adaptation (bass +20 dB, treble -20 dB).
Stupid question, but, is the ground wire of the turntable correctly connected on the ground plug of the amplifier near the phono input ? That makes a lot of difference in background noise.
Unfortunately my turntable is one of those units where they decided to forego the ground wire in favor of some sort of other method of grounding the unit that doesn't work quite as well. I have it plugged into a home theater power conditioner so hopefully there shouldn't be a huge amount of electrical noise, at least. Also, I'm definitely not getting hum at any audible volume so I'm thinking the grounding is probably a non-issue.
I'll see if I can record a sample of the noise I've been experiencing later today and I'll post it for anyone who wants to take a listen.
Thanks very much everyone for the help so far!