Weird grooves.

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Ben
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Weird grooves.

Post: # 45873Unread post Ben
Mon Jan 30, 2017 4:58 pm

Hello !!

I'm wondering what would be the cause for those wide groove.... I look at my spectrum analyser and I don't see any frequency being too intense... I'm cutting at moderate levels also..
before adjusting the groove distance..I just wanted for someone to refresh my memory on this, is it too much low end, too much volume or too much stereo effect?
Thanks a lot !

Ben
Groove.jpeg
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Greg Reierson
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Re: Weird grooves.

Post: # 45880Unread post Greg Reierson
Tue Jan 31, 2017 9:47 am

Looks like the vertical LF is overwhelming the system and creating very shallow grooves. Could be too much LF stereo content. Could be your depth system needs to be calibrated. Could be both.
Greg Reierson
http://www.RareFormMastering.com
VMS70 :: SAL74B :: SX74

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Ben
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Re: Weird grooves.

Post: # 45885Unread post Ben
Tue Jan 31, 2017 1:07 pm

thanks for your answer,

It's weird because all my low frequency are centered until 200Hz, so you're saying that the groove should look deeper.

At both extremities... it's unmodulated groove, the rest was the begining of a song.... I stopped it when the needle skipped.
That's why there's only a little part modulated.

I'll try to work on the counter weight, I'm around 15-20g with a mid-worn out diamonds

Cheers,

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Greg Reierson
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Re: Weird grooves.

Post: # 45886Unread post Greg Reierson
Tue Jan 31, 2017 1:29 pm

Can you measure the width of the groove in both places? It looks like the groove is almost gone on the upswing. If it's less than 2mil at the narrowest part then you need to tweak your system or the source audio. Run some tests on inverse polarity LF and see what your system can handle. The Neumann calibration tone is 200Hz out of phase at 0VU. What happens when your system sees that?

What system are you cutting on?
Greg Reierson
http://www.RareFormMastering.com
VMS70 :: SAL74B :: SX74

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Ben
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Re: Weird grooves.

Post: # 45887Unread post Ben
Tue Jan 31, 2017 2:32 pm

Thank you so much Greg, really appreciate it !

I will try this test and post the result in this thread, I'm cutting on a Vinyl Recorder with a dynamic head.... I know it's very limited, but until I manage to get a feedback head and feedback amp... I'm gonna try to push the limits to get the most out of it.

So if I understand correctly... I send a 200hz sine wave at 0vu one side polarity flipped in my cutterhead and see what the cut looks like?
And for your first question I don't have a reticule on my microscope... I wouln't know how to measure it.... usually I try to compare with pressed records.
My microscope is x20 and x40.

I will post a pic as soon as I try this tonight!
Thanks for the help
Ben

ps: what exactly you mean by "upswing" ?

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SueDenim
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Re: Weird grooves.

Post: # 45888Unread post SueDenim
Tue Jan 31, 2017 2:34 pm

It might not be related, but I'd also check the dashpot is free to move and replace the oil... just to rule it out of the equation ;)

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Greg Reierson
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Re: Weird grooves.

Post: # 45889Unread post Greg Reierson
Tue Jan 31, 2017 2:37 pm

Upswing - I mean when the stylus is oscillating up and down. That's where the stereo content lives. Too much LF stereo content will cause the stylus to lift up and off the record causing the groove to disappear. Bad! Your groove looks like it's almost there.

Let us know how the narrowest part of the groove compares to other records. I don't know how depth control works that system.
Greg Reierson
http://www.RareFormMastering.com
VMS70 :: SAL74B :: SX74

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Ben
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Re: Weird grooves.

Post: # 45890Unread post Ben
Tue Jan 31, 2017 2:49 pm

Thanks very much to both of you guys :)

Ok perfect I will do that and post my results !! I'm very curious with the 200hz test what it's gonna tell.
The depth of the cut is related to how you adjust the weight of the cutterhead. Souri recommended 15g for new stylus and 20g for old stylus.... So far I've tried to stay in that ballpark. It's not as precise as a Neumann or other machines like that.

So far the dashpost is very smooth but I will change the oil like you mention....we'll see if it help the motion.

Leaving for a Mogwai show tonight :D , tomorrow morning I'll post my results, thanks a lot again... This place is always a life saver!!!
Cheers
Ben

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Ben
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Re: Weird grooves.

Post: # 45911Unread post Ben
Thu Feb 02, 2017 11:29 am

Hello again,

I did the 200hz inverse polarity on one side, but I was not able to do it to 0db, the sound was distorted and I was around -3db. So I prefered to play it safe. I calibrated my 0dbfs on my protools with the 0vu test record Souri gave me.

the first pic is the 200hz inverse polarity at -3, with the same groove distance I had before and the second picture is with a lot more groove distance.... just to be able to see more the groove on the picture.


EDIT: I forgot to mention... I needed to put more weight on the cutterhead around 18g to be able to do it.... otherwise it was distorting way sooner
1.jpeg
2.jpeg
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Greg Reierson
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Re: Weird grooves.

Post: # 45913Unread post Greg Reierson
Thu Feb 02, 2017 2:32 pm

If 18g sounds better then it probably is better but since I have no experience with this system I'll defer to Souri or others who know how to set it up. So many moving targets with vinyl...

The first image still looks too narrow but I don't have a reference. The second image is a little confusing. I see a groove and a land but there is also a bit of a shadow. Probably just the light. If the groove does not get narrower than about 2mil and you don't have groove collisions then you're probably OK. How about the 200Hz in-polarity groove? Is the spacing OK?
Greg Reierson
http://www.RareFormMastering.com
VMS70 :: SAL74B :: SX74

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Ben
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Re: Weird grooves.

Post: # 45914Unread post Ben
Thu Feb 02, 2017 2:52 pm

thanks so much Greg,

Yes you're right the fist image was too narrow and it sounded weird, since I put more weight and put a little bit more distance between the goove....now it's way better! I'm really starting to believe that was the problem, I was trying to pack the grooves too tight to avoid being near the center... especially with the dynamic head.

Actually, when the signal was in phase at 200hz, the spacing was ok because I changed it a little, Instead on relying on the groove distance potientiometer, I measure the voltage right at the motor... so now I can adjust it with way more precision now.... and going back to an earlier job is way more easy.

I really need to buy a reticle for my microscope... otherwise, it's pointless to look in the microscope I cannot even tell what is what. I need to find a place for that.

Thanks again for everything
Ben

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Greg Reierson
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Re: Weird grooves.

Post: # 45915Unread post Greg Reierson
Thu Feb 02, 2017 2:59 pm

Progress!

If you have a good caliper you can "calibrate" your microscope - at lest to a certain degree. It takes some maneuvering but if you set the caliper to exactly 0.002" and position it in exactly the same orientation as the groove then you'll know how wide an unmodulated groove should be. You'll also know how far apart the grooves are. It'll do in a pinch but a reticle on a microscope is really great to have.
Greg Reierson
http://www.RareFormMastering.com
VMS70 :: SAL74B :: SX74

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