OK this is the boring long explanation, if you want, just skip down to "###########"
I'm digitising my old vinyls, so I can stick play them in the car. I've been using "audacity" to clean them up, but I had heaps of trouble with a Dylan song, (Dark Eyes), his harmonica seems to be a similar frequency to the clicks, so they don't show up.
I found Google play only wanted $2.19 for it, so I lashed out and got their remastered copy. Just out of interest I thought I'd compare waveforms, to see what the difference was between clicks and no clicks.
To my surprise, I find a bigger difference than I expected. My recording has left and right channel out of phase, their remastered effort has both channels in phase, and to me they look identical.
###########
So question is, should left and right channels be out of phase?
Has the google play recording cheated, and are using the same channel for both?
Have I wired up my stereo wrong?
Just checked some CD ripped files and they have both channels in phase.
Thinking about the Dylan track, it's mainly him, harmonica, guitar and voice, so there's not going to be much difference between channels.
Looks like I have to check my wiring.
Phase reversal doesn't happen that often in unbalanced systems, look for any floating or balanced connections (XLR's and 6.5 balanced connections).
Stereo separation may NOT be high with early recordings, live recordings the only thing that may be stereo is the crowd between tracks and reverb / delays on the vocals.
Or it could be, these so called quality 320bit MP3 files are really nothing more than mono recordings
Select to expand quoteGizmo said..
Phase reversal doesn't happen that often in unbalanced systems, look for any floating or balanced connections (XLR's and 6.5 balanced connections).
Stereo separation may NOT be high with early recordings, live recordings the only thing that may be stereo is the crowd between tracks and reverb / delays on the vocals.
Yes that's what I was thinking, I'm fairly sure all the wires I connected were center active and screen ground. But some of those were to plugs on long extension cords. One of them is probably on the wrong pin.
Just have to figure out if it's between turntable and amp, or amp and computer.
Guess I check tape wave forms.
Select to expand quotemyusernam said...
its bob dylan so it's going to sound pretty awful!
SACRILEGE!
Select to expand quoteGizmo said..
If you going into the computer on a 3.5 plug start there....
yeah on unbalanced stereo circuits, if the long terminal (ground / shield / common) is open, it can sound out-of-phase, and you may have some extra buzz/hum
Funny how now were the now in the new high tech age we have to get less fidelity sound &lower resolution tv . Than previous editions
Your vinyl is correct I think .
apparently with vinyl, a single needle couldn't reproduce stereo out-of-phase signals, and these had to be filtered out prior to pressing the master, so i guess in that way it was never going to be able to accurately reproduce everything
in recent years, most stations on digital telly abandoned their high-def channels to allow bandwidth for more (tele-marketing) low res channels :/ 57 of them and nothin on
Thanks guys, but I'm playing a CD with the amp at the moment and it's in phase at the computer, so I think the problem is in the turntable to amp leads.Select to expand quote haircut said:::
apparently with vinyl, a single needle couldn't reproduce stereo out-of-phase signals, and these had to be filtered out prior to pressing the master, so i guess in that way it was never going to be able to accurately reproduce everything
That makes sense, the 2 two channels are on either side of the groove, so the needle has a sideways movement for each channel, as opposed to just a vertical movement for mono. for out of phase signals the needle would have a very strange movement.
I've talked to keen audiophiles who insist vinyl sounds better than CDs, I wonder if that's got something to do with filtering out of phase signals out???????????????
I presume they don't bother doing that with CDs?
So this is embarrassing, problem was at the turntable, must have happened when I updated it, many many years ago, when I was young enough to know better!
I had one side of the pickup connections reversed.
Now music is in phase but some of the clicks are out of phase, which just goes to show that a single needle can do out of phase stereo, but It would probably mangle music a bit.
^ Simple theories are better than complex ones. User error.
I had my headphones out-of-phase for a couple of months before I had enough; "they don't sound as good as they used to". Yeah; it's kinda embarrassing when you've a good setup and you introduce something as awful as that to the sound and you don't even notice. (I still argue out-of-phase on headphones can sound better, but only for a minute or so; affects the soundstage)
As for vinyl; the sound is generated by dragging diamonds across scratches in plastic. [cough cough]
^ How does that even work! And superior to anything that can be done digitally apparently.
An "A" note at 440 hz with the speed of sound 340 m/sec is a 0.77 metre wavelength. So if you're half a wavelength further from one speaker your in phase signals will cancel anyway. Headphones? A bass guitar at 31 hz has a wavelength of 11 metres so you'd have to listen 5.5 metres closer to one speaker to correct for this. I think a pair of ears is pretty good at sorting this acoustic mess out. Which is why you didn't notice in the first place. Don't worry about it.
Select to expand quoteIan K said..
^ How ............superior to anything that can be done digitally apparently.
......
someone's ears said so
and just to change topic slightly
listen to Cat Stephens with some really expensive headphones. mind blown. he was a master at arrangements.
Select to expand quotePoida said..Ian K said..
^ How ............superior to anything that can be done digitally apparently.
......
someone's ears said so
>>>.
It's very interesting, isn't it, what us humans can convince ourselves of. I had this discussion a few months ago with an apparently intelligent man. He was absolutely certain that vinyl is better.
Yep, and I'm a Cat Stevens fan as well.
Select to expand quoteevlPanda said..
>>>>>>>>
As for vinyl; the sound is generated by dragging diamonds across scratches in plastic. [cough cough]
>>>>>>
Love the pics!
My problem now is how to clean the embedded dust etc out of those grooves.
For some reason or another back in the old days I got sucked into using "anti static spray" on my records, can you imagine what that's like 40 years later?
Select to expand quoteIan K said..
^ How does that even work! And superior to anything that can be done digitally apparently.
An "A" note at 440 hz with the speed of sound 340 m/sec is a 0.77 metre wavelength. So if you're half a wavelength further from one speaker your in phase signals will cancel anyway. Headphones? A bass guitar at 31 hz has a wavelength of 11 metres so you'd have to listen 5.5 metres closer to one speaker to correct for this. I think a pair of ears is pretty good at sorting this acoustic mess out. Which is why you didn't notice in the first place. Don't worry about it.
When wiring speakers up, (if you're using uncoded wires), you have to place them face to face about a cm apart, it's only then that out of phase bass notes really cancel out
Well you won't be getting the physical sound waves canceling out, (unless you've got them really loud, and you're getting crashing waves in your head. Although hang on, in phase vibrations are going to be squeezing and stretching your brain, out of phase is just going to move it side to side)
But your head is going to have to work harder to make sense of what's happening with an out of phase signal, I should imagine.
A signal that is reversed in phase from the other signal is quite noticeable on recordings when played on speakers, it will leave a 'hollowness' in the middle.
Even a single speaker or for that mater with both speakers wired incorrectly will result in a lack of lower frequencies.
Reverse phase audio signals at times can actually add to the mix if used correctly and sparingly.
If you want to have a play with your stereo system for some fun connect a single speaker box to the (+ of Left terminal) and the (+ of Right terminal). That speaker then has the 'difference' to create a pseudo surround.
Just thought you might like to see where I spend about 1/3 of my working life.
And for interest in the top picture there is an 'X' on the video monitor..... That is an 'Audio Phase' display meter.
OH Boy you are having fun!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
So here's another puzzle for you.
There's a strange low frequency ripple on the waveform, so I was trying to see where it came from.
the beginning of the wave form is 50hz where the head is shorted out by the raise lower control, the next period is where the head is active but on the way down to the record. then there is the big spike when the needle makes contact.
So the 50hz is in phase, but the next section I make as 13hz is out of phase, and the touch down impact is in phase, once it settles down a bit there's a 10hz in phase ripple before the music starts, which is still accompanied by the 10hz ripple.
I thought the 10hz was a mechanical thing, but it's there before the needle touches anything! Could this be motor induced?
Perhaps I'm wrong about the head being shorted out, perhaps it's o/c because the 50hz virtually disappears once the 13hz starts.
Edit wrong! I just filtered out the 10hz and now I'm just left with the 50hz at the same level before and after the arm lowering starts.
50 hz = mains power
Shield / isolate the pickup arm cabling from the motor, try a bent metal shield from a 'steel' can etc or / and extra shielding around the cables made up from some some video coax cable.... (pull it apart a short length) and put the pickup cable thru it.
Thanks Gizmo, I'll give that a try, the cabling runs through the middle of the arm, that's earthed, there's only a short section of unscreened cable that runs to the cut out switch, I'll see what I can do with that.
But I'm not really that concerned about the mains hum, it's well below most audio levels, it's the 10hz that's getting onto the audio that's puzzling me.
yep, that would work, but where is it coming from????? what does 10hz? It's level is a fair bit more than the mains hum, and that's invasive enough.
Select to expand quotedecrepit said..
yep, that would work, but where is it coming from????? what does 10hz? It's level is a fair bit more than the mains hum, and that's invasive enough.
10Hz ..... bearing rumble
Either in the motor or in the platter. I am assuming it is belt drive and the motor has brass bushings on the drive spindle. These need to be cleaned and re-lubed with a light oil.
The platter will have a shaft with a single ball bearing at the base that needs to be cleaned and re-lubed.
If it is idler wheel drive then the same thing all the bearing / shafts need to be cleaned up. An idler wheel may be hard and brittle.
Chances are that they haven't been done in quite awhile and any lubricant is very kacky.
Select to expand quoteGizmo said..decrepit said..
yep, that would work, but where is it coming from????? what does 10hz? It's level is a fair bit more than the mains hum, and that's invasive enough.
10Hz ..... bearing rumble
Either in the motor or in the platter. I am assuming it is belt drive and the motor has brass bushings on the drive spindle. These need to be cleaned and re-lubed with a light oil.
The platter will have a shaft with a single ball bearing at the base that needs to be cleaned and re-lubed.
If it is idler wheel drive then the same thing all the bearing / shafts need to be cleaned up. An idler wheel may be hard and brittle.
Chances are that they haven't been done in quite awhile and any lubricant is very kacky.
Great answer again Gizmo, and it makes sense for what's happening once the needle hits the record,
EDIT
I may be wrong about the following, something strange is happening, still investigating, get back later.but what's going on when the arm is still on the way down?
There's probably still vibration in the arm, but without the needle making contact with anything, where's the signal coming from?
And of course you're right the turntable hasn't been serviced since I installed it in the 80s and it was 2nd hand then.
I have a feeling it's a belt drive as there's a spare sitting in there.
I know I can't hear as well as I used to, but 10 Hz!
en.wikipedia.org/wiki/Hearing_range
You're down there with the whales!
"Several animal species are able to hear frequencies well beyond the human hearing range. Some dolphins and bats, for example, can hear frequencies up to 100 kHz. Elephants can hear sounds at 14–16 Hz, while some whales can hear subsonic sounds as low as 7 Hz (in water)."
