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Old 22nd February 2008, 07:27 PM   #1
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Question Vinyl Record Cutting Dynamic Range Compression

Hello !

I hope someone out there can give me some advice.....

I am transferring my old record collection onto cd to save wear on my turntable.

In researching the way music was transferred from tape to vinyl, I have found that a number of things were done:

1) Low bass was cut back in the inner grooves.

2) Treble was also cut back.

3) Compression was used to accomadate the lower dynamic range of the vinyl.

Does anyone know any specifics about the three points mentioned ? Regarding what frequencies, what compression ratios etc.

I purchase a dbx 3bx expander and a dbx 1/3 octave eq. for the transfer and would appreciate any information about how to set them up.

It seems that the dynamics and frequency response are better in the outer grooves and that one set of values for the eq and expander is not correct for the entire side of the disc.

Perhaps there are some retired cutting lathe engineers out there who would care to help !!!!!

Thank you in advance for any help

oldheathkitphi
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Old 22nd February 2008, 08:07 PM   #2
Netlist is offline Netlist  Belgium
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I fail to see why you would use a equalizer and/or expander.
All equalisation is done with the RIAA equalizer in your phono preamp.
Here's some interesting links:
http://en.wikipedia.org/wiki/Gramophone_record
http://en.wikipedia.org/wiki/RIAA_equalization

/Hugo
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Old 22nd February 2008, 08:37 PM   #3
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Thank You Hugo,

I would like to try and recover some of the original dynamic range that was lost when the transfer from the master tape to the vinyl cutting lathe was made. The master tape in general should have had a dynamic range of about 65 db whereas the vinyl at best was about 50 db.

Also Treble and high frequency rolloff and bass compression was used to compensate for the lessening ability of the stylus to track properly in the inner grooves.

I am hoping as I transfer a record to cd to adjust the expander and equalizer to compensate for this, but I need to know a few
specifics about how much expansion to use and what frequencies
to raise.

Thank you very much for responding.

oldheathkitphil
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Old 22nd February 2008, 10:16 PM   #4
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Hi oldheathkitphil,

I wonder if you gain something by that. Compression is also done by the sound engineer as an “artistic” tool as part of the complete sound balance. Also some processing is done to keep phase difference between left and right within limited margins (otherwise the needle will jump out of the groove)..

Since you have no knowledge about what and how much processing is done it is almost impossible to reverse process it. To only thing you can do is to fiddle around experimentally to suit your taste.

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Old 23rd February 2008, 08:51 AM   #5
Netlist is offline Netlist  Belgium
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Quote:
Originally posted by oldheathkitphil
I would like to try and recover some of the original dynamic range that was lost when the transfer from the master tape to the vinyl cutting lathe was made.
You try to recreate something that is lost. Unless you can get your hands on the master tapes you will not succeed. Real good equipment will get the most out of the grooves.
There is no such thing as a difference in equalization between the inner and outer grooves, assuming your record collection is post RIAA standards. Before these standards, almost anything was possible and I would agree that experimenting with equalization would be necessary.
On modern records, over the entire surface, the bass is cut back and the highs are boosted within a well defined curve. The phono preamp compensates for that in the opposite way.
(RIAA curve – Inverse RIAA curve)
You do have a proper phono preamp I assume?

/Hugo
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Old 23rd February 2008, 09:06 AM   #6
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I suspect any compression done during the cutting process was "on the fly" as the engineer balanced track dynamics with available groove space on the vinyl, and as such will differ from album to album, and from engineer to engineer.
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Old 25th February 2008, 03:32 PM   #7
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Thank you Piotr and Pinkmouse fro responding.

Over the weekend I found a book in the public library entitled
Sound Recording by John Engle 2nd edition. In the chapter discussing vinyl disc cutting, he describes the various forces on the cutting stylus while it cuts a master disc. There is a graph that shows the natural treble rolloff as the cutting head
goes toward the center of the disc. He also states that this rolloff
can not be compensated for as the cutting head for various reasons would not be able work properly, things like overheating th cutting head coils and waveforms being too small to cut due to the diminished circumference as the head tracks inward.

That was the the general information I think I was looking for and is not the same thing as the RIAA characteristic.

Basically it shows that there is rolloff at about 10kz of 5db by the time the pickup stylus has passed the 5 inch from the center radius point and this rolloff continues to about 8 db at the innermost groove distance of about 3 inches.

Can anyone out there verify this.

Basically it is saying that as one transfers a lp to cd one has to slowly increase the treble to compensate for the rolloff which increase as the stylus tracks into the inner groove area.

Also, along with dimished treble response, compression has to increase so that mistracking of the pickup stylus will not happen when the record is played.

That is why I think if i slowly increase the treble with the equaliser
and slowly do some expansion as the pickup travels inward that I should get a better quality transfer.

Can anyone verify ????

Thank you again in advance for any responses

Oldheathkitphil
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Old 26th February 2008, 01:49 PM   #8
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May i offer you, instead of a technical solution, a more philosophical one? It will take the sorrows away, let us all chill quite a bit, and best of all, it includes redwine and women.

So you have vinyl and want to hear them digital? Fine.
Vinyl won't last forever, this is true. And since you can't take'em with you, once you die, you could sell them aswell.

Since i just recently are a converted analogist, saved from the deamons of the digital domain, i may sound a little enthusiastic here .

Records and Redwine and Women share a common denominator : Saving them up for future times is a bad, bad thing.

It gives me headaches imagening myself sitting infront of a very fine cabernet/women - determined to preserve it/her for futuretimes.
I can instantly comeup with a few dozen people, declaring me a blasphemist
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Old 26th February 2008, 02:13 PM   #9
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The cutting head theory is something I was not aware of. Unfortunately I can't find anything from Mr. Engle on the net.
It has never occured to me that treble was weaker towards the inner grooves and 5 to 8 dB is quite a lot so I'm interested to learn more about the subject.

/Hugo
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Old 26th February 2008, 03:02 PM   #10
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The relationship between seconds of music per meter of groove changes dramatically from the outer tracks to the inner tracks, like a 3:1 ratio. Vinyl should have been made with "constant lenght speed" rather than "constant angular speed", like CDs and DVDs, that spin slower for the outer tracks and faster for the inner ones due to the constant data density. I suppose they just didn't had the technology for dynamic speed change at the time.

I have very little experience with vinyl, but the facts suggest that a substantially reduced sound quality has to be expected in the inner tracks. This is comparable to recording a tape 3 times slower than the rated speed: You pack more data in less length at the expense of a lower trebble cut-off.

In any case, you should rather get good "verbatim" 96/24 wave files from the vinyls first, and then do the processing by trial and error in the digital doman. For example you can compare (by FFT or by ear) the beginning and the end of the tracks and try to match them. There are tools for noise reduction too...

BTW: It's a big shame that, now that we have plenty of digital storage media featuring huge amounts of bit-exact data forever, we are doing the worst ever mastering jobs just to make it loud on boom boxes.
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