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Re: Audacity and Media Player on Windows 7 notebooks

Posted: Wed Jul 14, 2010 9:19 am
by R_G_B
Thanks Koz, that explains a lot about sources of noise and clipping that are hard to 'engineer out' of a usb card for $40.

I finally understand why there is no simple fix to make the meter clipping alerts fool-proof. Gale must be saying "at last!". Even View > Clipping will be unreliable if users have mismatched signal levels and sound card hardware enough to cause clipping somewhere below the 0 dB level, before the signal is fed to Audacity. But once understood the most likely causes should be fairly easily avoided by users (don't be tempted to push line level outputs into a mic input, even at 0 on the record level slider, there will probably be unwanted clipping even if there is not gross distortion).

After your lesson, we all want ART USB Dual Pre (or Phono v2) devices with 2 or 3 separate power sources, variable gain, metal case etc for $200 (and an SSD in the computer). Even those sometimes pick up hum from too-close usb hubs or power supplies, but the engineering quality justifies the price.

Then again, people who mainly want to transfer their LPs into MP3 files to play through equipment like a car stereo might hesitate at the cost; and struggle to hear '5 times the sound quality' for their investment.

With the explanations (from you and WC, STF and GA above) of where the problems can arise when using cheaper 'consumer' gear like the iMic, many of the pitfalls can be avoided or at least minimized for those on a stricter budget. Hopefully the much-revised initial post helps them get up to reasonable quality recordings quickly.

A long time ago I gladly paid several $1000 for a Nakamichi 700TT and Phase Linear Autocorrelator chasing quality portable recordings (on cassette tapes). Today with a little caution (and 2 pages of instructions?) anyone can do much better using Audacity, a netbook, an iMic and a memory stick. Better still with more expensive sound cards.

Much obliged, RGB

Re: Audacity and Media Player on Windows 7 notebooks

Posted: Wed Jul 21, 2010 11:55 am
by R_G_B
Intrigued by Kozikowski’s disdain for the humble iMic, I arranged a side-by-side test against the Roland (Cakewalk) UA-1G. If you want (mono) powered mic, non-powered mic and guitar inputs, or (stereo) optical in/out along with your RCA in/out and volume-controlled headphone out with quality 24-bit DACs this might be the USB card for you (reviewed at http://the-gadgeteer.com/2009/07/08/cak ... ce-review/).

The UA-1G also has a physical input level control knob with an LED peak indicator, which should help alert users to avoid clipping through signal-strength mismatch before the digitization step. But it costs 3-4 iMics.

I installed the Win 7 driver and ran the UA-1G in advanced driver mode, with 24-bit selected in Windows record control and DirectSound in Audacity (where it was probably only recorded at 16-bit as PortAudio and Audacity are yet to implement 24-bit recording under Windows (See http://forum.audacityteam.org/viewtopic ... 3&start=40).

Relative to the iMic:
• Electronic noise with no connected signal input is much lower (around -80 dB vs -46 dB).
• Hum from a nearby noisy power supply (iGo juice) is much lower (almost absent).
• The UA-1G is much less microphonic (only detected with mic, not line input levels)
• A noisy signal cable is just as noisy.
• I did not test for HDD and mobile phone noise (I don’t use them).
• In the Sheffield Lab / Thelma Houston recording test the input level adjusted to just avoid peak indications on the UA-1G gave peaks at -10 dBFS in Audacity with the Audacity (= Windows) input slider at 100%.
• When I used effect > normalize to bring the peaks to -1 db, the vinyl noise ended up much louder from the UA-1G than from the iMic.
Vinyl.jpg
Vinyl.jpg (96.74 KiB) Viewed 980 times
• The zoomed waveforms in the music sections were remarkably similar (to my untrained eye).
Loud.jpg
Loud.jpg (94.73 KiB) Viewed 980 times
Quiet.jpg
Quiet.jpg (76.56 KiB) Viewed 980 times
Which one sounded better? You can be the judge. The zipped Audacity project for the UA-1G is at: http://www.sendspace.com/file/btkg80

I may be missing something, but I reckon:
• If you are digitizing LPs for use as MP3 files in a car or other average consumer audio equipment, and you follow the instructions in the much-modified initial post, the iMic gives great bang for the buck.
• The much lower electronic noise and better hum rejection by the UA-1G is going to appeal more to those with low-noise inputs such as studio-quality direct recording from microphones (including guitar pick-ups).
• It may take some tweaking to get the best dynamic range from a particular signal source, based on the different indications from the UA-1G vs Audacity peak / clipping indicators.

Happy digitizing, RGB