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

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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Nsgarsh,sorry to go off topic,but can you help me?I was running a PS Audio P-500 on front end componentry,with fabulous results(Balanced/Regenerated a/c for cd's,lp's,pre/phono only).Yet,it blew up after three weeks.The second replacement lasted for six days.
I am getting my money back,and want to get something as good,yet I realize that "Balanced/Regenerated" power comes at the price of two units,from companies like Exact Power(who are my first choice).I know Equitech makes great stuff(balanced)but no regeneration.
Truthfully,I don't know whether the fabulous sound was the result of the balanced output,or regenerated,but I'd like to go with a one unit approach.Maybe the new Exact Ultra Pure,which is suppoded to be great,and is balanced,yet NO regeneration.HELP!!!BTW,i,previously,had two Ultimate outlets in service,here,but they were "smoked" by the P-500.I'm not trying a third unit,and have no more confidence in PS stuff.
Sorry,guys,for going off topic,but Neil is a maven at technical stuff,and I am banned from my usual haunts.-)
Thanks!

Shadorne...Your technical snow job is inspiring! How would you like to do marketing for me?

Nsgarch...Not "during manufacture" (pressing of the hot vinyl). It's done by the cutting head. And the fidelity of the pre-echo is quite good if you boost the volume enough, and, most important, chop it fast so as to not toast your speakers when the real music starts.