Audacity Forum

I am presently attempting to set up my recording layout to transfer my out-of print lps to digital.
My stereo/mixer setup is about 15 feet away from my computer, and I am getting an obnoxious hum - I have been reading the posts about how to reduce the hum, including the link to the MICROHD HD400.

My question, though, is do I really need to eliminate the hum? I feel that I should, but then again, it can only be heard when I turn all the controls (input and speaker levels) to their maximum levels. It registers as about -54 db on the Audacity meters. Is this enough to worry about? or am I just being too picky?

I would eliminate the hum before recording, not try to remove it later. You need to decide if its bothersome to you.

Generally it is not that hard. Use the ground wire on the TT. Make sure the cartridge connections are right. Connect with 3 wire plug all the devices to the same power outlet. A hum eliminator may be needed (as simplest approach) at the pc connections to that sound card. DAK sells one. Amazon should have them too. Tell us your complete set up with all connections including power and signal cables if you still have a problem.

Thanks for your input - my feeling is that it should be eliminated, too - I guess I just needed validation.

I just looked at the DAK item you mentioned - they show it being connected to the speaker out jack on the computer. Since the unit is an isolation transformer, I assume that it would be just as effective when connected to the Line In on the computer?

The hardest part of solving hum problems is determining exactly where the hum is coming from. It is invariably due to grounding (Earthing) problems and is most common with low level signals.

There should usually be an Earth/ground connector on the turntable that can be connected to an Earth/ground point on the mixer. If that is in place and securely connected it may be that all you need to do is connect the turntable, mixer and computer to the same multi-way extension lead so that they have a common Earth. It's worth checking out the simple (and cheapest) solutions first.

If you end up having to spend money, it may be well to consider upgrading the computer sound card.

Actually, the hum/buzz is present even when none of the audio units are powered up except the mixer.

Excellent - you're getting close to tracking down the source of the noise.
If you plug your headphones directly into the mixer, can you hear the hum in your headphones?
If you completely unplug the turntable from the mixer do you still hear the hum?

By the way, where is the "phono (RIAA) pre-amp"? Is it built into the turntable, or in the mixer, or a separate unit between the turntable and the mixer?

molmes wrote:Thanks for your input - my feeling is that it should be eliminated, too - I guess I just needed validation.

I just looked at the DAK item you mentioned - they show it being connected to the speaker out jack on the computer. Since the unit is an isolation transformer, I assume that it would be just as effective when connected to the Line In on the computer?

maybe they have another one
i got one that fit between rca out from my playback
and the input to the computer sound card
basically an isolation transformer (i think)
so no common ground to let hum get created at the input

check out amazon for similar items
and google humbucker humbuster or similar to see if you can find others to choose between

Excellent - you're getting close to tracking down the source of the noise.
If you plug your headphones directly into the mixer, can you hear the hum in your headphones?
If you completely unplug the turntable from the mixer do you still hear the hum?

By the way, where is the "phono (RIAA) pre-amp"? Is it built into the turntable, or in the mixer, or a separate unit between the turntable and the mixer?

I have no headphones - I am hearing the buzz/hum through my computer speakers - I have audacity in monitor mode.

I am running the TT through my AV receiver (Yamaha RX-V1700) and pulling the output off of the CD rec out jacks, which goes to the mixer (Mackie 1202-VLZ Pro). The buzz/hum is present in the computer speakers with absolutely no inputs hooked up to the mixer. There are a couple of peculiar aspects to this - (1) I was gettng the same buzz/hum before I hooked up the mixer in the signal path (the CD rec out going directly to my computer's Line In jack). (2) With all inputs (phono, reel-to-reel deck, and cassette deck) hooked up, I can,of course, mute or un-mute each one - but when I have only the reel-to-reel in the signal path (un-muted), the buzz/hum is of a different "tone" than the others.

By the way, I have a new sound card (Asus Xonar D2X), but I had the buzz/hum even on my old card. I have also replaced (upgraded) my computer's power supply.

Which outputs on the mixer have you got connected to the computer - the RCA "tape outputs" or the 1/4" jack "Main Out" (or some other)?

Do you have a "master" control on the mixer that controls the overall level for the output that you are using? (for example, the "Main Mix" control should be the master for the "Main Out" jack outputs). If you are using an output that has a "master output control", do you still get the buzz if that master is turned all the way down? If you do still get the buzz, does the buzz stop if you physically disconnect the output leads from the mixer?

I believe that I have this solved - I purchased a cheapo Radio Shack Ground Loop Isolator ($17) and hooked it up between the output of the mixer and the Line In on the computer - no buzz/hum! If I crank the Audacity input level slider to max, I can see a little fluttering in the right channel, well below -57db. The pulsations almost look like a data stream or something - funny that it is only in the right channel, though - - - I guess I'll scout around inside the computer box.

My only concern is that the isolator might modify the data stream in some way (like maybe a lower frequency response curve for the transformers - I am going to be digitizing my lps at 32 bit, 96khz, hence the new sound card) - their website doesn't give any specifications or anything. I will e-mail them to see if I can get further information.