max cooper wrote:Humphrey Bear wrote:,
simmo wrote:With a release my band are putting out, I was hoping to squeeze something in the region of 25 minutes on one side? Too long? Not a chance in hell? Answers muchly appreciated!
Not a good idea; too long. Once you go above 20 minutes, the cutting level will be compromised. It is technically possible to squeeze 25 minutes of music on one side with a loud level but then you will end up with massive amounts of inner groove distortion during the last 5 to 10 minutes of the side
Actually, it's not just inner groove distortion. It increases throughout the entire playback of the record.
Here's the deal.
With a properly aligned cartridge, the tracking error is zero at the beginning and zero at the end of the side. The tracking error is 1 at a point halfway between the beginning and the end. Mentioning this because it's commonly thought that "inner groove distortion" is caused by tracking error.
The cutting head is driven by an amplifier. Say you're making a record of a 60 Hz sinewave. As the lathe moves slower at the center that 60 Hz sinewave will cause the head to cut ever smaller waves in the groove.
The 60 Hz sinewave moves the cutter up and down 60 times a second, but with the tangential velocity reduced that sinewave is represented by a smaller undulation in the material.
And since that undulation will be smaller relative to the diameter of the playback stylus tip, we're talking about a decrease in resolving power of the stylus towards the center.
Which sounds like distortion.
Just thought it might be interesting.
