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dcollins

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Apr 23 13 4:16 PM

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From Paul Gold on reproducer calibration:

When setting up a turntable to check test pressings or deal with vinyl in a professional capacity it's a good idea to check it on a turntable calibrated to a standard reference level.


I've found that many don't know that a disk recording system is calibrated to a standard reference level. Just like open reel tape. The standard reference level for stereo recordings is 7cm/sec lateral. Cm/sec is a measurement of velocity. It's a speed measurement like miles per hour. And just like miles per hour you don't have to go 60 miles to be going 60 miles per hour.


There are calibration test records with tones at 7cm/sec lateral. Lateral essentially means mono. The groove moves from side to side (laterally) with correlated material and vertically with uncorrelated signal.


The only tone you need is 1k Hz. You can check frequency response with other tones but they should not be used to calibrate level.


Calibration is straightforward. Play the record and adjust the level until 7cm/sec equals your standard reference level on your meters (hopefully VU meters). Usually +4dBu.


It's difficult to find phono preamps that interface well in a professional audio system. Most are unbalanced -10dBv.


If you are stuck with a consumer style phono pre then using a -10dBv to +4dBu "bump box" will help. You can hang the meters from the output of the bump box and use it for level calibration.


If you haven't checked out records on a calibrated turntable I highly recommend it. It is very helpful when trouble shooting.

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dcollins

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Apr 24 13 11:01 AM

I know there are several test records available, I think the one I have is Analog Productions, is there a modern one that you recommend for the set-up?


DC

 davecollinsmastering.com


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gold

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Apr 24 13 12:03 PM

I think that is the only currently available test record. Most cutters in the US use the NAB record with the blue cover. I've never met two test records that agreed with each other to better than 0.5dB accuracy. I think all the test records I've run across are close enough for government work. I have a pretty extensive collection of test records with multiple copies of many of them.

Paul Gold Salt Mastering

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waltzingbear

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Apr 24 13 12:16 PM

you mean this one?
http://www.elusivedisc.com/ANALOGUE-PRODUCTIONS-ULTIMATE-ANALOG-TEST-180g-LP/productinfo/APLPTEST/

available from amazon for $54 or here for $40, gotta just love amazon for great marketing.

I'll bet James uses a HiFi News and Record Review one, its from across the pond after all.
http://www.needledoctor.com/Hi-Fi-News-Test-Record?sc=2&category=438

actually would love to hear from someone using it. Familiar with the Ultimate Analogue disc (Analouge Productions), have several unopened CBS STR disc and a slew of old NAB disc from years gone by, But they are not available to anyone off the shelf.

Alan

ps - should take them all and measure the pb level after Paul's comments.

Alan Garren
Waltzing Bear Audio

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gold

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#5 [url]

Apr 24 13 12:35 PM

IIRC the Hi-Fi news record along with most of the CBS records uses 5.5cm/sec lateral as the reference level. I would recommend using 7cm/ sec as the reference level.

You can compare test records in a relative sense but not an absolute sense. The only way to measure signal amplitude on a record is via a microscope or via the light beam method. Period.

Paul Gold Salt Mastering

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waltzingbear

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#6 [url]

Apr 24 13 1:03 PM

Were the 0.5 db comparisons you quoted earlier Pb or physical measurements? I recall that light/optical measurements are the most telling absolute measurements, its been years since I looked at those methodologies, and Adam has my copy of the AES phonograph reprints at the moment.

Being an electromechanical system, phonographs have their own "unique" set of challenges.

Alan

Alan Garren
Waltzing Bear Audio

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gold

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Apr 24 13 1:17 PM

Playback only. Setting up a microscope or light beam system is no small task. The AES has very little useful published information on the subject. All the research was done prior to the AES being formed. The relavent papers were issued by the Acoustical Society of America in the U.S.

Paul Gold Salt Mastering

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Hermetech Mastering

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Posts: 389 Member Since:22/02/2011

#8 [url]

Apr 24 13 1:35 PM

The Radial J33 phono preamp also has balanced outs, but I have not been able to compare it with anything other than mid range hi-fi phono preamps. Not sure how accurate it is/it's RIAA curve is, but it sounds good to me, and is not too expensive.

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dcollins

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Apr 24 13 2:35 PM




Playback only. Setting up a microscope or light beam system is no small task. The AES has very little useful published information on the subject. All the research was done prior to the AES being formed. The relavent papers were issued by the Acoustical Society of America in the U.S.

-gold

Buchmann-Meyer, right?  Do you know any names of the papers? I'm an ASA member and would like to download them if I can.  Maybe even be able to put some of them here, if it's legal.


I had this BBC paper on an improved method to get the amplitude, but I never read it.

http://www.collinsaudio.com/Prosound_Workshop/BBC_%20LP_Light_Pattern.pdf



DC

 davecollinsmastering.com


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viitalahde

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#10 [url]

Apr 24 13 2:44 PM

First, this topic is a great idea.

2nd, for the past two days, before the sleep, I've been going through the Buchmann-Mayer stuff to grasp it. I now understand the basics, but for sure it's difficult to get it how on earth you can make anything measurable out of it. The AES book has good stuff from it, and I admit I got a little droopy eyed after a few paragraphs.

I'll now look at that paper Dave posted, cheers.

Jaakko Viitalähde Virtalähde Mastering [url]www.virtalahde.com[/url] [url]www.facebook.com/VirtalahdeMastering[/url]

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gold

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#11 [url]

Apr 24 13 3:21 PM



The AES book has good stuff from it, and I admit I got a little droopy eyed after a few paragraphs.



-viitalahde



The original Buchmann Meyer paper is short concise and to the point. The AES treatment is not very good once you read the original paper. I've come to realize that the AES Anthology should be subtitled "Weird, Wacky and Esoteric Papers Related to Disk Recording."




I'll get the number of the Buchmann Meyer paper. It's at home.



Paul Gold Salt Mastering

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gold

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#12 [url]

Apr 24 13 8:29 PM


"A New Optical Method of Measurement For Phonograph Recordings" G. Buchmann and E. Meyer
Acoust. Soc. Am. J. 12(2) :303-306 (1940)

I have another paper somewhere that goes into optical errors in light beam measurement. It would take a little while to dig it out but IIRC it was done by Philips. I have some internal Philips documents describing their proprietary optical measurement system.

Paul Gold Salt Mastering

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jamesperrett

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#13 [url]

Apr 25 13 6:41 AM

 
I'll bet James uses a HiFi News and Record Review one, its from across the pond after all.
[url]
actually would love to hear from someone using it. 

-waltzingbear


I have an old test disc from HiFi for Pleasure magazine but I must admit that it is a while since I last used it.

JRP Music Audio restoration and mastering www.jrpmusic.co.uk

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bonati

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#14 [url]

May 15 13 10:24 AM

I have Al Grundy's Buchmann-Meyer light beam kit. Needs a little restoration (just new cabling) but when I get that done Paul and I will have some experimenting to do. All aboard the fun train.

Josh Bonati Brooklyn, NY www.bonatimastering.com

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waltzingbear

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#16 [url]

May 15 13 11:33 AM

all this leads us to this next question. What breakpoint for the UltraHF? The Neumann breakpoint (as of which cutter electronics?) or the original non breakpoint that goes to infinity?

cheers

Alan

Alan Garren
Waltzing Bear Audio

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gold

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#17 [url]

May 15 13 11:36 AM

In the Neumann SAL74 the high frequency roll off is not incorporated into the RIAA circuit. It is just a normal RC pole that is elsewhere.

Paul Gold Salt Mastering

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zmix

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#20 [url]

May 15 13 11:05 PM

Thanks to Chuck Zwicky for bringing this test record to my attention:With frequencies up to 35kHz! [image]

-dcollins

I should note that on the sleeve they recommend that you bypass the RIAA EQ when playing the ultrasonic test bands.

One day soon I'll plug my cartridge directly into a mic pre and record the test LP at some PONO-graphic sample rate to see if there's anybody up there.

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