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Diff: SoundProcessingNotes
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Differences between version 28 and predecessor to the previous major change of SoundProcessingNotes.

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Newer page: version 28 Last edited on Tuesday, February 17, 2004 5:57:32 am by JeffWelty Revert
Older page: version 22 Last edited on Saturday, December 27, 2003 12:37:14 pm by DanielLawson Revert
@@ -5,8 +5,10 @@
  
 I'll add to this wiki as I go, so excuse the journal-like nature. When I've finished I'll tidy it up, or let a WikiGnome do it for me :) 
  
 ''Sorry, this is too longwinded and unwieldly a mess for this gnome to clean up, despite following along with great interest. :)'' --AristotlePagaltzis 
+  
+''It'll be finished soon, and most of it can be condensed down into 'Use decent recording hardware, preamp if possible, gwc will clean your audio nicely, but if you are using 2.6 and an ATAPI CDWriter, use Nero under Windows to burn to CD.'' --DanielLawson  
  
 !! Hardware used: 
  
 I have a Celeron-1300, running Windows 98 (wait a bit...), which has an SB Audidy 2 Platinum eX. As far as I know, there aren't decent drivers for the Audigy under linux, hence staying under Windows 98. That said, I'm not using it very much - it has RCA inputs on its external unit, which means I can plug my turntable directly in. 
@@ -38,11 +40,15 @@
  
 GWC works really well. I followed the suggested notes at the above URL, which I'll summarize here: 
  
 First of all, I amplified the track. GWC seems a bit buggy with this - it won't always amplify correctly. If the waveform doesn't increase in amplitude, it hasn't been amplified. I found if you wait till after processing to amplify, some noise still gets through. 
+  
+(Jeff Welty here - see my comments below about GWC amplify)  
  
 * Run the strong declick tool. The first time I ran this I got about 7000 clicks removed. The second time, about 400, and the third time, about 20. This was 'good' enough, so I moved onto the next step: 
 * Run the decrackle tool. This removed most of the remaining crackle on the recording. 
+(Jeff Welty here -- it's worth a try at skipping this step to see if the denoise tool will clean out the remaining crackle. Avoid decrackling if possible because it attenuates the high frequencies)  
+  
 * Run the denoise tool. Its suggested to use any lead-in you can, but I only lead-out noise available. It seemed to do just as well. I ran it first with the defaults, then used the suggested settings on the url above. It seemed about the same really, although with the speakers I have on this computer it is hard to tell. 
  
 At this point, the tracks were a LOT cleaner and sounded great. 
  
@@ -72,8 +78,12 @@
  
 !! Third Attempt 
  
 After a bit of thought, I realised one thing I might have been doing wrong. The GWC amplify tool didn't seem to work particularly well, and when it did work I think I was using it wrong. It puts up a prompt with 5 entry boxes - Left Channel Stard, End, Right Channel Start, End, and Feather Width (set to 2000, I left it). It stated the the maximum gain without clipping for this track was 25.something, which was a figure I'd seen elsewhere. So I set the 'End' values to 25. Which, in hindsight, probably meant an increasing amplification as the wave progressed, and which would have accounted for the increased noise further on in the CD and the poor noise correction performance - I doubt it can handle fixing an increasing noise source. 
+  
+(Jeff Welty here --  
+Yes, the Left Channel Start value is the amplification to be applied to the start of the selected region in the left channel, and the Left Channel End value is the amplification to be applied to the end of the selected region in the left channel. This allows you to apply fade ins, or fade outs if you desire. The feather width is a little window that "feathers in" the amplification. If there was no feathering, then the amplification could introduce a click into the audio.  
+End Jeff Welty's comment)  
  
 So this time, I used DartPro (couldn't be assed finding another tool to do this, in case it wasn't the problem after all) to increase the gain, and then ran my declick/decrackle/denoise routine over this file. The waveform looked a lot better, and it sounded fine. 
  
 I also discovered that GWC will mark track boundaries just as well as gramofile will, and will export a .toc file for me too. Better and better. I processed both sides, merged the two .toc files (the .toc format allows you to specify a filename and a start/end offset into the file, so you dont actually need to split the original file up :) 
@@ -116,10 +126,14 @@
  
 * A good turntable. Turns out mine wasn't so hot. The stylus is probably the most important bit of this, and I suspect mine has been mistreated. 
 * A decent set of headphones (for monitor purposes). And probably a decent set of speakers to check the full range 
 * A preamp. The output gain from most turntables is low. This is normal. In one of the vinyls I was trying to restore, it was so low the computer wouldn't record anything. A preamp with monitor output, and simple input/output gain controls is probably fine. 
+  
+''Turntable sound output is down around 5mVolts compared to CD output at around 150mVolts. Also the signal needs something called frequency equalisation to restore the output to proper proportions. Disk Smith sells a turntable with inbuilt preamp for $100 that will do the job.'' --Paul Cleary  
  
 You should also make sure your soundcard has a good SNR. The Creative Audigy 2 Platinum Ex has a good one, although it's taken ages for Creative Labs to turn this product into anything more than gamers toy. There's plenty of high-quality professional level cards that will do this very well, and cost less than the Audigy / Extigy (I checked earlier, I cant remember the manufacturer of the cards I was looking at tho, will append later). 
+  
+''I use a cheap $60 Creative soundblaster card for this work and I get very good SNR. The thing to realise is that in all low to med cost soundcards, the audio input part that converts the analog signal to digital is virtually the same. The difference in the cost of the cards is paying for is all the fancy signal manipulation and sounds effects. A person recording from LP to a WAV file just needs the conversion part. I recommend you read Clive Backham's webpages on converting vinyl LPs to CDs ([Google:Clive Backham convert lp cd]). He discusses the whole process from start to finish, including equipment, soundcards and software. I use his Waverepair software for LP to CD conversions but it only works on Windows.'' --Paul Cleary  
  
 It's now Christmas day. I made a few CD copies of what I acheived last night, which sounded at the time like a great improvement. I'm sure it was a great improvement, however its wise to use the correct speed setting when playing back records. I'd been testing the input with a Faith No More LP (45), and forgot to flick the speed setting back down when I started with Music for the Feast of Christmas. 
  
 I'm thinking of stamping a label on the CDs I wrote calling them "Music for the Feast of Christmas, by the Chipmunks of Ely Cathedral"