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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?
voiceofvinyl
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
12,171 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.

mijostyn's avatar
mijostyn
8,570 posts
 
They never match perfectly which is OK. I shoot for averages between 10 and 8. You lower the resonance frequency by adding weight to the head shell and raise it by subtracting weight. You can get head shell weights that fit under the cartridge or you can add nuts to the screws etc. Subtracting weight is a bit more difficult. Get out the drill. Warning, if you get down to 3 Hz record warps will send the tone arm skywards! Use the anti skate test track to set the anti skate. If you lift the anti skate weight while playing that track you will notice all the distortion go to one side. If you add too much weight the distortion will go to the other side. You adjust it until the distortion is the same and minimal in both channels.
voiceofvinyl's avatar
voiceofvinyl OP
93 posts
 
Thanks,
If adding or subtracting small amounts of weight to/from the headshell changes the cartridge resonance, why wouldn't adding or subtracting some tracking force accomplish the same? The physics must be different?
atmasphere's avatar
atmasphere
12,171 posts
 
why wouldn't adding or subtracting some tracking force accomplish the same? The physics must be different?
Yes. Triplanar arms are supplied with counterbalanced weights of different sizes. You can use one or multiple weights with different distances from the pivot bearings- and so effect the effective mass and thus change the mechanical resonance. Weights in the headshell are more effective if you need to lower the resonant frequency, going the other way is why Triplanar makes the multiple counterbalance weights. If using a spring loaded arm you can move the counterbalance weight and set the spring differently, but the scale on the arm won't be correct anymore- so you have to use a cartridge tracking weight scale to know if you're at the right tracking pressure.
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