Subject:Signal-to-Noise Ratio in Recording from a turntabl

Posted by: deburgess

Date:12/30/2007 5:07:52 AM

I am using an EMU 1212m sound card with balanced inputs to convert vinyl records to a digital WAV format. To connect the balanced inputs on the sound card to the unbalanced output from my Creek Audio-8SE phono pre-amp, I am using an Ebtech Line Level Shifter. With no input to the phono pre-amp, the noise level is about -60dB in the Sound Forge recording software. With the turntable connected, the music peaks are about -18dB. What are some ways I could try to improve my Signal-to-Noise ratio?

Should I reduce my resolution from 24->16 bits with a noise shaper, and then resample the 192 kHz recording to 44.1 kHz with anti-aliasing filtering to remove the high frequency noise contour?

Thank you very much for your advice.

Subject:RE: Signal-to-Noise Ratio in Recording from a

Reply by: musicvid10

Date:12/30/2007 9:24:45 AM

That's probably about the best you're going to get. I'm using less elegant equipment than you and my numbers are (predictably) a bit worse.
The phono preamp is an absolute necessity because of level/curve considerations, and the amount of noise is small compared to noise from the pickup and the vinyl itself. A truer test of the noise floor is to short the inputs. I suspect that -60db may drop even more.
The Ebtech looks like a high-end passive stereo DI Box, and as such won't introduce any measurable noise, but will affect THD by a bit because it uses transformers. It will, however, drop the overall gain by a couple of db. An active DI would only introduce it's own hiss into the mix.
Be sure to use the ground lift to reduce hum, but this won't affect hum being picked up from the phono cartridge. The only other potential help is to plug everything into a good AC EMI/RF line filter, like a Tripplite, and of course use good cables. Oh, and don't set up in a room with flourescent lights, dimmers, tv sets, etc. and make sure all equipment is plugged into the same house circuit. Good basic advice for any recording setup.
Personally, I would try one of the audio restoration plugins to reduce noise in the recording. You should in most cases record at the bit depth/sampling rate that you will use in your final project. 16/44 CD quality has more than enough headroom for vinyl / tape archiving projects unless you're a conservator doing this for a museum vault.

Subject:RE: Signal-to-Noise Ratio in Recording from a turntabl

Reply by: Geoff_Wood

Date:12/30/2007 5:40:22 PM

What's it like without the Ebtech thing, or do you need than fort bal/unbal ? Is it the right way around for what you need ?

Also, I'd be happy with whatever your default recording spec is - it will not change anything significantly given the somewhat limited source quality - and that's what LP is.

However I wouldn't go below 44k1 sample rate, despite the highest frequency (apart from disc noise artifacts) on the LPs is likely to be 15KHz or so.

I don't do anything other than 24 bit, for no particular tangible reason....

geoff

Subject:RE: Signal-to-Noise Ratio in Recording from a

Reply by: musicvid10

Date:12/30/2007 6:01:17 PM

There's certainly nothing wrong with plugging an unbalanced line into a balanced input, it's just that if there is any ground loop there is a chance of picking up additional hum without the lift.

As noted in the specs for his sound card inputs, they will accept either +4dbu balanced or -10dbv unbalanced signals, an option that is pretty much the norm these days unless you are running into a legacy vacuum tube preamp.

As always though, "Individual results may vary." I routinely put a DI (also called a "direct box") in the path when recording or running live sound from any unbalanced analog source, even a keyboard or line-out. This is especially important in live clubs or theaters where mega-buzz from stage dimmer packs is a fact of life.

Subject:RE: Signal-to-Noise Ratio in Recording from a

Reply by: rraud

Date:12/31/2007 9:43:59 AM

If you can, and do not need the headroom, try to get the max peak level around -6dB ....or... as "hot" as possible without clipping. A 16bit file recorded with max program peaks @ -18dBfs is essentially using 13 bits... even if you normalize later on. If you need the headroom, digitize @ 24bit.

Subject:RE: Signal-to-Noise Ratio in Recording from a turntabl

Reply by: PhilBiker

Date:1/7/2008 6:29:25 AM

I am using a very similar set-up.

Why do you have the Ebtech DIs in the chain? The 1212m can accept the line level directly from your phono preamp, using external DI is not giving you any advantage that I can think of. Unless you are using them as a ground lift for your turntable (as the Ebtech "Hum Eliminator" product DIs).

I run my line from the tape-out of my stereo receiver using the built in phono preamp directly into the 1212m L/R inputs. My peaks are at about -10dB give or take. I record at 44.1Khz 24 bit then run the "Restoration" plug-in built in to SoundForge 9, then Normalize. My results are excellent. The noise floor on vinyl is so high that S/N shouldn't be a big concern when transferring to digital. I let CD Architect convert to 16 bit when I author CDs.

Hope this helps!