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Mono with a stereo stylus
tinpanalley
post Jul 9 2011, 22:08
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I'm not going to buy a mono stylus for my cartridge. I don't even know if they make one. My question however is about the software.

Should I bother setting my software (I have Sound Forge and Audacity) to mono recording? Or should I just record my mono vinyl in stereo and then decide what to do with the 2 channels? There has to be some standard way of recording mono via a stereo stylus.

Thanks for any input!
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mixminus1
post Jul 9 2011, 22:55
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QUOTE (tinpanalley @ Jul 9 2011, 14:08) *
Or should I just record my mono vinyl in stereo and then decide what to do with the 2 channels?

I'd recommend this.

One channel, i.e. side of the groove, may turn out to be cleaner than the other.


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tinpanalley
post Jul 9 2011, 23:02
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Ok, that's what I thought. Then do I double it to both sides? Leave it as just one channel? I'd like to be able to keep it digital and burn to CD as well. I heard mono CDs don't exist. Is that true? I have several mono CDs so how do they burn them then?
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Paul Sanders
post Jul 9 2011, 23:24
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If you plan to declick, record in stereo. Clicks are often much more prominent in one channel than the other, and if you record in mono they are less well detected.


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tinpanalley
post Jul 9 2011, 23:40
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QUOTE (Paul Sanders @ Jul 9 2011, 18:24) *
If you plan to declick, record in stereo. Clicks are often much more prominent in one channel than the other, and if you record in mono they are less well detected.

Thanks! Great point! Will do.
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DonP
post Jul 10 2011, 00:32
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The surface noise is stereo too. If I record a mono record in stereo, the program material is in the middle while noise is distributed across the soundstage. Prob'ly you could use some filter, similar to pro-logic or a reverse karaoke filter, to remove the non-centered signal.
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mixminus1
post Jul 10 2011, 00:32
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QUOTE (tinpanalley @ Jul 9 2011, 15:02) *
Ok, that's what I thought. Then do I double it to both sides?

Yep, that's it, and yes, there is no such thing as a single-channel audio CD - Red Book (standardized) audio CDs have to be 2-channel, 16-bit, 44.1 kHz.


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tinpanalley
post Jul 10 2011, 01:34
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QUOTE (mixminus1 @ Jul 9 2011, 19:32) *
and yes, there is no such thing as a single-channel audio CD - Red Book (standardized) audio CDs have to be 2-channel, 16-bit, 44.1 kHz.

Wow. That's so interesting. So, the double channel doesn't affect volume or resonance? It's exactly the same as a single channel? I'm comparing for example to a film on DVD. If you play it as 2.0 Mono, it sounds hotter than 1.0 Mono but that could be due to the strength of the center speaker.... ok, nevermind, silly point.

This post has been edited by tinpanalley: Jul 10 2011, 01:35
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AndyH-ha
post Jul 10 2011, 01:43
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There is a definite advantage to recording "stereo." It is true that sometimes one channel is better than the other (and this isn't necessarily constant; you may need to pick and choose from each channel, using copy and paste to make one best) but most often you can make use of the fact that you have two, out of phase with each other. Automated declicking works better against both of the channels (rather than first converting to mono, then declicking), as does decrackling (decrackling is more likely to be desirable with the older mono disks than with newer, probably in better condition, LPs).

After declicking, convert to mono. This in itself will remove, or greatly reduce, a large number of clicks . They are partly, or more or less completely, out of phase with each other and cancel. The same is true with a lot of the background broadband noise. Its level will be decreased significantly by converting to mono. All this assumes the phono cartridge is properly aligned to allow it.

I don't know what Sound Forge provides. In CoolEdit/Audition there is a channel mixer that, properly used, gives the net mono in one channel and the removed difference in the other. I find this frequently helpful during the manual declicking stage. Canceled clicks (partially or fully) are in the removed channel and align with their former position in the music. Those that are only partially removed can be seen much easier, telling you where more work needs to be done (if the click isn't completely removed from the music). If you are going to do only manual declicking, this arraignment may be even more helpful.

I use this two channel form for the rest of the processing, right through converting to 16 bit. Then I convert the reject channel to silence and copy-paste the good channel into it. Both channels are now identical, even to the dither. It is ready to write to CD-R and it gives the smallest possible file size when converted to FLAC.
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mixminus1
post Jul 10 2011, 02:32
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QUOTE (tinpanalley @ Jul 9 2011, 17:34) *
I'm comparing for example to a film on DVD. If you play it as 2.0 Mono, it sounds hotter than 1.0 Mono but that could be due to the strength of the center speaker.... ok, nevermind, silly point.

The compressed audio formats that DVD supports (Dolby Digital (AC3) and DTS) can have only one channel.

2.0 Mono is equivalent to a "mono" CD: two channels with the exact same content - the original mono track. As such, they would play out of the front LR speakers in a surround configuration, while 1.0 Mono would only play from the center channel.

Whether or not the 2.0 will sound louder or quieter than the 1.0 in a properly-balanced system will depend on how the 2.0 track was mastered, and also on your room acoustics and speaker placement.


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tinpanalley
post Jul 10 2011, 02:58
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I guess what I'm getting at, and perhaps this is conceptually incorrect, is the question of whether 2 mono channels one on top of the other wouldnt sound louder than just the one channel? because there's two of them I mean. Or does it not work like that?
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tinpanalley
post Jul 10 2011, 05:35
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"converting to 16-bit" - is that the same as saving at 16-bit? Or is it necessary to use the actual bit-depth converter?

Also, with the bit-depth converter in Sound Forge, I have the option to do dither and noise shaping right away. It says, "In general, Highpass Triangular with noise shaping produces the most favorable results." Is that true for our purposes?

It defines Highpass Triangular as:
"Eliminates distortion caused by conversion to a lower bit depth and eliminates noise floor modulation by producing a slightly higher noise level. Noise is shifted to higher frequencies than standard triangular dithering."

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AndyH-ha
post Jul 10 2011, 06:06
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If you play a mono track from the computer it will normally go to both output channels. At any given volume setting, playing two channels is going to be louder than playing only one. However, duplicating the mono track in each of the tracks of a "stereo" file will still put out the same signal to each output channel, therefore it will not be louder: playing a one track file into both channels of a stereo system is the same as playing a two tracks identical file into a stereo system (if all are at the same dBfs value).

It is essentially holy doctrine than any reduction of bit depth should be done with dithering (to avoid quantization distortion). It does avoid quantization distortion that will otherwise be there without the dithering. However, actually being able to hear that distortion from a single bit reduction conversion is difficult, and probably impossible with any real music.

Noise shaping is another perfectionist measure. Dither is added noise. The unavoidable quantization error is additional noise. Noise shaping takes most of that noise out of the audible range. Again, hearing it, noise shaped or not, from a single application, is rather unlikely with music.

Probably any noise dither/shaping option offered is good enough. There are patented formulas and extravagant advertising claims, but probably no positive ABX results for any reasonable approach. If is possible to do something worse if you really try but that isn't likely to be an offered option with any reasonable software package.

You can test, to an extent, by generating silence in 24 bit or floating point, then converting to 16 bit with different dither/noise shaping options. This will show you what gets added to the music.

This post has been edited by AndyH-ha: Jul 10 2011, 06:10
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AndyH-ha
post Jul 10 2011, 06:12
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Also, in the more specific case of an LP or cassette transfer, the broadband background noise provides adequate dither already (as does the noise from most microphone preamps, etc. But, more doesn't hurt in the slightest.
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Martel
post Jul 10 2011, 19:06
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QUOTE (tinpanalley @ Jul 10 2011, 03:58) *
I guess what I'm getting at, and perhaps this is conceptually incorrect, is the question of whether 2 mono channels one on top of the other wouldnt sound louder than just the one channel? because there's two of them I mean. Or does it not work like that?

I would expect the downmixing to work like this: C = (L + R)/2 or C = 0.5*L + 0.5*R
Which means you should get the average volume of both.


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Fedot L
post Jul 10 2011, 21:27
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QUOTE (tinpanalley @ Jul 9 2011, 21:08) *
I'm not going to buy a mono stylus for my cartridge.

There are neither mono nor stereo styli. This depends on if a cartridge is one channel horizontal groove modulation transducer, or two channel 4545 to vertical, groove modulation transducer.
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tinpanalley
post Jul 11 2011, 00:53
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QUOTE (Fedot L @ Jul 10 2011, 16:27) *
There are neither mono nor stereo styli.


Oh, I see... my mistake. Thanks!
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dc2bluelight
post Jul 11 2011, 07:20
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QUOTE (tinpanalley @ Jul 9 2011, 16:08) *
I'm not going to buy a mono stylus for my cartridge. I don't even know if they make one. My question however is about the software.

Should I bother setting my software (I have Sound Forge and Audacity) to mono recording? Or should I just record my mono vinyl in stereo and then decide what to do with the 2 channels? There has to be some standard way of recording mono via a stereo stylus.

Thanks for any input!


hmm- the thread didn't expand, so I'm afraid I repeated a lot of what others have written...sorry, couldn't see how to delete the post, so here it is anyway:

The best way is to record your mono record in stereo, then analyze the two channels. Often you'll find one or the other is "cleaner" in some way, less distortion caused by wear, less noise, etc. There are three ways to compare: !. Left only 2. Right only 3. Left plus Right. Listen to all three, pick the best way. For example, if you find that the Left channel sounds less distorted, just delete the right. If a mono sum sounds best, then do that.

Also, if you do any de-clicking via software, those systems often use a Left minus Right signal on which to base their click detection, so a stereo input signal is important to have, even with a mono record. De-clicking also benefits from additional bandwidth, so if you plan to use one, a higher sample rate is of some benefit.

If you are trying to record 78 RPM records, you have a whole different issue though. The groove is bigger, so you do need a real 78 RPM stylus, the standard stylus will just ride in the bottom of the groove and rattle around in there sounding terrible. 78's also used several different EQ curves (not RIAA), so you need to deal with that.

Here's something about that relating to Audacity: http://forum.audacityteam.org/viewtopic.php?f=39&t=35665

Still record them in stereo, pick the best channel or sum of both.

This post has been edited by dc2bluelight: Jul 11 2011, 07:23
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2Bdecided
post Jul 11 2011, 12:53
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QUOTE (Fedot L @ Jul 10 2011, 21:27) *
QUOTE (tinpanalley @ Jul 9 2011, 21:08) *
I'm not going to buy a mono stylus for my cartridge.

There are neither mono nor stereo styli.
Yes there are. Mono records (from the mono-only era) have larger grooves. Ideal tracking is with a larger stylus. They play OK with a stereo stylus, which is what most people do - but then can sound better when played with a larger mono stylus. Depends on record wear.

Mono records from the stereo era (e.g. re-mastered re-issues, compilations etc) usually have grooves identical in size to those of a normal stereo recording, and would be damaged if played with a "mono" stylus.



You do not record mono records, played in stereo, in mono on a PC - because this will usually only capture the left channel. You, at least, want to be able to sum both channels together to cancel out all the out-of-phase noise. You can't do that if you only have the left channel wink.gif . You can do this electronically before digitising, but (as has been amply commented on) after is better - it leaves far more possibilities for digital restoration.

Cheers,
David.
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tinpanalley
post Jul 11 2011, 17:05
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QUOTE (dc2bluelight @ Jul 11 2011, 02:20) *
If you are trying to record 78 RPM records, you have a whole different issue though. The groove is bigger, so you do need a real 78 RPM stylus, the standard stylus will just ride in the bottom of the groove and rattle around in there sounding terrible. 78's also used several different EQ curves (not RIAA), so you need to deal with that.

Yes, I know, I already have a 78 stylus for my cartridge.

QUOTE (dc2bluelight @ Jul 11 2011, 02:20) *
Still record them in stereo, pick the best channel or sum of both.

The sum of both thing is what I don't understand. I get the idea of taking the best sounding channel, duplicating it to both left and right and then outputting. But I don't get the idea of taking the left and right and somehow getting them to cancel each other's noise. It just doesn't make sense to me. Both sides of the groove are going to have different amounts of wear no matter what. How can their sum actually cancel out noise?
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pdq
post Jul 11 2011, 17:48
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Think of it this way...

A stereo cartridge generates a left signal when the needle moves 45 degrees to vertical in one difection, and a right signal when it moves 45 degrees to vertical in the other direction. Since these motions are perpendicular to each other, there is no interference between them.

If you have the same signal in both channels, they are phased in such a way that the needle moves horizontally, just as it would for a mono record, i.e. push against the needle from one side, and pull equally from the other side.

You don't normall get a purely vertical motion, This would require out-of-phase signal in the left and right channels. When you combine the left and right to mono, vertical motion cancles out. Therefore, any dust or dirt or scratches that produces a vertical motion of the needle cancels at least partially when you mix down to mono.
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2Bdecided
post Jul 12 2011, 10:51
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100% of the wanted signal is horizontal motion.

50% of the unwanted signal is vertical motion, 50% is horizontal motion.

Therefore by throwing away the vertical motion (adding the two channels and dividing by two), you can double the signal to noise ratio (halve the noise).


Actual numbers can be a bit different. The noise isn't perfectly uncorrelated, so the gains aren't as much as you'd expect. But the quantity of noise in vertical domain is sometimes higher than in the horizontal, so the gains are greater than you'd expect.


Lots of supposedly wonderful turntables from the mono era weren't really suitable in the stereo era because they had lots of rumble in the vertical plane which was inaudible in mono, but caused easily audible rumble through stereo speakers.

Cheers,
David.

This post has been edited by 2Bdecided: Jul 12 2011, 10:53
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tinpanalley
post Jul 13 2011, 20:47
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Ok, I'm going to use Audacity to record my mono record in stereo at 32-bit float point.
Then I'm going to listen to both channels to see if the right really is cleaner and whichever is cleaner I'm going to dupe to be on both channels.
Then I'm going to do a click clean up and then I'll finish by saving as 24-bit wav but in stereo instead of converting to mono.

Does that sound ok?
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greynol
post Jul 13 2011, 21:11
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Record at 24-bit, make sure your editing software is processing with at least that much precision and then save the end result in 16 bit (dithered).


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DonP
post Jul 13 2011, 22:06
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QUOTE (tinpanalley @ Jul 13 2011, 15:47) *
Ok, I'm going to use Audacity to record my mono record in stereo at 32-bit float point.
Then I'm going to listen to both channels to see if the right really is cleaner and whichever is cleaner I'm going to dupe to be on both channels.
Then I'm going to do a click clean up and then I'll finish by saving as 24-bit wav but in stereo instead of converting to mono.

Does that sound ok?


Most of the advice has said the noise removal and declicking work better on the stereo signal. So no.


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