12" 45 RPM records: What's the story?

Onhwy61...I was thinking only in terms of the first groove. But, if I were in the high end audiophile business I might claim to have a secret process to eliminate it throughout the LP, and challenge anyone to prove me wrong :-)

Nsgarch...It's when the master disc is cut, and it is well known that the effect can be minimized or even eliminated by wide groove spacing. In the real world, in order to get acceptable playing time groove spacing is variable as the nature of the program material varies, and the spacing is only wide enough to make the pre-echo "acceptable". With regard to "Dynagroove"...this was a proprietary signal compensation to compensate for vinyl flexure of the groove being played, and had nothing to do with adjacent grooves.

Nsgarch... One more thought. If the pre-echo leads the music by 1.8 seconds (for a 33rpm LP) it isn't print through. (1.33 seconds for a 45 rpm).

Eldartford, I'll say it again: Even if the vinyl did expand/contract/deform slightly in manufacture, it could NOT transfer with ANY degree of accuracy (much less an EXACT copy of) the modulations from one groove to an adjoining groove. Think about it -- it would be physically impossible! Or maybe I don't understand what you mean when you say, "It's when the master disc is cut." What "it" are you referring to?

There is a great explanation of the Dynagroove process at:

http://en.wikipedia.org/wiki/Dynagroove

After reading it, I think maybe I meant Dynaflex (another RCA disaster;--))

Close groove spacing is achieved by a computer driving the lathe which is attached to a "pre-read" head in the master tape playback machine. Not possible in direct-to-disc recording, which is why they customariuloy have less material on them.

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Nsgarch,

First of all, if there was any print through between bands on the master tape, that's easily eliminated when transferring the album to CD, just insert new silences between bands.

Good point I hadn't thought of that...but hang on...if they could do that for a CD then couldn't they do something similar on Vinyl?

Eldartford,

I am with you. Do you need VC capital? How much money do you think there might be in a box between TT and amplifier. A pre-echo could certainly be detected by a simple cross correlation technique. To do this at reasonable cost, all you would need to do is digitize the signal. Then an adaptive filter could be designed to eliminate it. This is done all the time in countless other engineering domains where correlated noise (ghosts, multiples and echos) are removed using adaptive filtering. (Technically this is called a "convolution" filter...and knowing that the echo is 1.8 seconds ahead and behind the main signal would make it fairly easy to detect versus other time correlated information such as a repetitive drum beat...you would simply use a 1.8 second window to cross correlate)

Shad, it's easier (maybe only even possible) to do these manipulations/corrections in the digital domain -- but then there you are...............in the digital domain!!

Which is why, once CD's were available of course, I could never understand the point of buying a "Digitally Mastered" LP?
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