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Help? Problem With Holding The Groove On A Hot Pressing

I have had a problem holding the groove on several hot pressings and it always occurs in the same spot. I am not sure if it’s my set up or a mastering error.

I am playing a record with very strong sonics that is in Mint condition and midway through the last track it skips. When I look at the area under a strong glass I can see a very hot bass transient that almost collides with the next groove. This happened again tonight when I was playing a first pressing/orignal release of MJ’s Thiriller. It also happened on a Allman Brothers LP as well as one other.

Is this a mastering error or is my TT and cartridge not up for it? I am using a Technics 1200 with an Ortofon Blue cartridge. I have checked the setup several times with a very accurate gram scale (2.5g) and my Geodisc. Should I try for a different cartridge angle geometry?
128x128voiceofvinyl
mijostyn's avatar
mijostyn
8,512 posts
 
Voiceofvinyl you have a set up problem. Your anti skate would have to be way off to cause that alone. You need to check your arm cartridge resonance frequency. If it is too high when the right bass note comes along enough energy will be created to pop the stylus right out of the groove. There is only one way to correctly set anti skating and to adjust the resonance frequency of your arm cartridge system. You get a HIFI News test record and follow the directions. You want to set a resonance frequency between 8 and 10 Hz both vertically and horizontally if you can. Once you get the hang of this it is easy and you will not believe how much better your table will sound and track. If you run into trouble just message me. Oh, and one of the silliest concepts I have ever heard is running an off set tonearm without anti skating. 
voiceofvinyl's avatar
voiceofvinyl OP
93 posts
 
@ mijostyn.
Thanks. I have a few test and set up records inluding the Hi Fi News Analogue Test lp. I will go through it again and test for wobble and warble.

I am also going to slowly add some anti-skating until I get to the point where I start to miss-track a highly modulated low frequency trace (hot groove). Then I will try Almarg’s approach to obtain a median setting. 

Also....
Does cartridge offset that does not meet ideal have anything to due with miss tracking behavour like I am experiencing? I am trying to figure out if I need a headshell that will allow me to change the offset angle of the cartridge body. I currently cannot change the cartridge offset angle. 

voiceofvinyl's avatar
voiceofvinyl OP
93 posts
 
@ o_holter
Thanks. 98% of the occiasional skips I find are the result of some kind of condition flaw or pressing flaw.

In a few rare cases, such as this one and a few others, there was no condition issue. I had to look at the grooves with a strong loop to see that the cause was a very modulated groove in the last track that ejected my cartridge. 
voiceofvinyl's avatar
voiceofvinyl OP
93 posts
 
Hi again

I ran all the tests using a HI Fi News test record. I was especially interested in the lateral and vertical resonant frequency test. Both number ranges I got put the cartridge in the sweet spot now that I have the anti-skating set just slightly below the tracking force. The vertical and lateral resonance doesn't quite match though. 

My question is; how do you "adjust" the resonant frequency? My current values for vertical are: 15 Hz - 7Hz. My lateral values are 14 Hz - 10 Hz. 

Should I even worry about trying to match the vertical and lateral exactly?

atmasphere's avatar
atmasphere
11,761 posts
 
Is there any plausibility that these hot grooves found later in a side would be a result of the physics of cutting?
None whatsoever. The physics of cutting is that the cutterhead responds exactly the same to bass notes at the beginning of the LP as it does at the end. It is simply moved across the lacquer as the signal is played through the cutterhead. There is no compensation in the electronics for its location on the LP, just the compensation for the cutterhead response (being an electro-mechanical device) and the imposed RIAA curve. 

My question is; how do you "adjust" the resonant frequency? My current values for vertical are: 15 Hz - 7Hz. My lateral values are 14 Hz - 10 Hz.
Should I even worry about trying to match the vertical and lateral exactly?

To the latter- no, as long as its in the window of 7-12Hz. The mechanical resonance is not really adjustable on your arm- the way to affect it is to change the cartridge to one of a different compliance or to use a lighter or heavier headshell.

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