DMM questions

[JJZL]

Dear all

I am writting a short article about DMM and have some question.

I'd love that you could help me.

1- Storage pre and post cutting. It appears blanks chrystallize, and then become useless. It appears that after cutting they have to be passivated to avoid corrossion/rusting. Are they stable after that for log periodos of time (Scientology Church technicians appear to think it is possible to store the cuts for long periodos of time)

2- Manufacture of blanks. Are they manufactured in different ways? Is there a provider as Apollo, Transco or DMC? Is there any blank that avoid storage problems, be it pre or post cutting? Are they made electroplating or melting the copper or in some other way?

3- Cutting angle and electronic correction. As the cutting angle is different than lacquer cutting, how is that corrected for correct reproduction? Would that affect reproduction on a laser player?

4- Bias frequency. Is there a high frequency applied during the cutting process in order to make possible or easier the cutting?

5- Burnishing profile. It appears that lacquer cutting stylueses "polish" the groove after the cut while the same is unnecessary with DMM. Is taht the case? (taken from this docuemnt https://www.railroad-tracks.de/media/pdf/TELDEC_DMM_Technology-EN.pdf )

6- Cutterhead suspension system. It appears to be different for lacquer and DMM cutting. Any details or general idea on the differences? Any schematics of both?

7- Pressing machine differences. Is there something important to change at the press machine in order to operate with lacquer or with DMM?

8- Record profile. It appears that they should have an special lateral profile in order to be able to use the DMM logo. Any ideas on the details of the profile, reasons for it and effects on pressing or reproduction?

Thank you in advance

[ectomorphs]

Hi everyone,
Allow me to tag on to this thread created by JJZL which seemingly never got anywhere - Does anyone have any reliable information about the development and history of DMM? Perhaps there is a Teldec archive somewhere? Or maybe someone from the original development team gave an interview once or is even still around? Given current conversions of lathes from lacquer to DMM as a result of lacquer supply issues, I would like to go back to the beginning and cover the story of DMM in a chapter in a book I'm writing about developments in vinyl record manufacturing since it began declining around 1980. I'm mainly interested in whether the development of DMM was a result of simply trying to improve sound quality for the sake of it; reduce costs through reduced plating; reduce reliance on lacquer masters due to concerns about future supply issues; or an attempt to compete directly with newly emerging digital audio. It may well have been all of the above, but some of these could have been "side effects" or post-hoc rationalizations rather than the initial motivation. I have found several quite useful sources, such as:

https://www.pspatialaudio.com/DMM.htm
https://worldradiohistory.com/.../80s/Recording-1985-10.pdf (p.58-73)
https://en.wikipedia.org/wiki/Direct_metal_mastering [articles cited on the DMM wikipedia page]

But PLEASE let me know if you have any more - or know anyone I may want to contact about this. Of course I'm happy to acknowledge anyone in the book who has helped!

To me personally, I think DMM is a case of an innovation that was largely written off as a failure but which has had a lasting impact, especially for pressing plants across Europe. In other words, innovations concerning technologies in decline may not be as useless as they initially appear...

Best wishes,
Rene

[boogievan]

There's this TELDEC_DMM_Technology-EN.pdf which is worth checking...√

[ectomorphs]

Thanks boogievan!

[selectavision]

Hi Rene,

this ist the basic patent concerning DMM from early 80´s. Sorry, it is in german language. It deals about all the details, esp. the interdependence between hardness of the
copper-blanc and excitation of the supersonic frequency which facilitates the cutting process.

Best redards,
Martin

DMM German Patent 0062336001.pdf

[untitledthe]

https://www.pspatialaudio.com/DMM.htm

That was a very interesting rabithole, 2 hours gone! And printed some stuff too.
Thank you.

[ectomorphs]

Hi Rene,

this ist the basic patent concerning DMM from early 80´s. Sorry, it is in german language. It deals about all the details, esp. the interdependence between hardness of the
copper-blanc and excitation of the supersonic frequency which facilitates the cutting process.

Best redards,
Martin

DMM German Patent 0062336001.pdf

Thank you! German is not a problem! In fact it's my native language.

[selectavision]

Some experts claim that the supersonic excitation is not really necessary, but an unwanted side effect while cutting into metal. They assume that Redlich was smart enough to make this essentially undesirable effect part of the Teldec patent. Others say that it generally doesn't work without supersonic biasing. This is why it is important to adhere to the exact Vickers hardness of the copper blancs. The exact electroplating process and production steps of those blancs remain a secret. So far I could not find any further research results on this topic either. And unfortunately there is no VMS82 within reach to experiment with... .

Best regards,
Martin

[ectomorphs]

Thanks Martin,
I had some interesting conversations about the implementation of DMM with several mastering engineers and how those using it today are not adhering to the original specifications that were required to obtain a formal DMM license. Apparently there have been advances since the original release in respect to the blanks, styli, etc. But there are also lots of rumors floating around, which makes it difficult to substantiate all the details; and with respect to the exact technical details I must confess that I'm in no position at all to make any judgments given my non-existent mechanical and electrical engineering knowledge. But I was able to find the original US patents relating to DMM in case anyone's interested:
https://patents.google.com/patent/US4484320A/en
https://patents.google.com/patent/US4538256A/en?oq=US4538256

-Rene

[selectavision]

I had some interesting conversations about the implementation of DMM with several mastering engineers and how those using it today are not adhering to the original specifications that were required to obtain a formal DMM license.

Hi Rene,
I'm wondering if any of them would be willing to share with us the details of how they do DMM today, especially when it comes to the differences to the original process. But they're probably keeping it secret for good reasons... .

Horst Redlich -one of the four leading engineers behind DMM- passed away in 1995 at the age of 72. I'm wondering if there are any other surviving contemporary witnesses from the Redlich development team who could be interviewed... .

Concerning https://patents.google.com/patent/US4538256A/en?oq=US4538256 :

I wasn´t aware of the different cutting angle and that the method of distortion compensation was updated in 1985 to be used in DMM . That seemed to be a core requirement for DMM to function acceptably. Duane Cooper presented the basic research in this regard in the 1960s and 1970s.

Is this the reason why the playback characteristics of early DMMs before 1985 sometimes left something to be desired?

Martin

[martinstamper]

Perhaps of interest to those in this thread.

[ectomorphs]

What is also interesting (at least for nerds like me) is tracking patents by Horst Redlich over time: https://patents.justia.com/inventor/horst-redlich
It seems like the first patent concerning storing audio information in copper disks was filed in March 1979 (after experiments with storing analog video information in metal). The patent filing notes "The cutting of audio signal recordings into metal surfaces is already well-known in the art, typical techniques being disclosed in German Pat. No. 66,942 and French Pat. No. 76 21636." I'm trying to find those referenced patents but no luck so far...

[ectomorphs]

Found it: "The cutting of grooves into metal was first proposed by J. Rosenthal and S. Frank in their German patent dated 13.November 1891." https://oldthing.de/Original-Patent-Louis-Rosenthal-und-S-Frank-in-Frankfurt-a-M-1891-Phonograph-Grammophon-0044419372

[selectavision]

Well,
if the drawing is to scale, the dimensions of the soundbox are quite impressive and might be in the region of the diameter of the record. They propose a thickness of the diaphragm of 2mm and up. Of course that makes sense in the case of cutting into metal. Is it cutting or embossing?

In the 1920´s to 30´s metal blancs were in use in the amateur field. They used aluminum discs for embossing. The goal was not to scratch into the surface but emboss to achieve a quiet "cut". So different lubricants were in use as well.

To me one question of special interest is why in DMM they did use copper instead of a softer sort of metal? Afaik copper is usually really crappy to machine! The only answer to this might be found in the structural properties of a freshly electroplated copper blanc, which is "amorph" and thereofore can be cut easier. Later the blanc "dries out" due to cristallisation of the copper. In this state it can´t be cut anymore.

Martin

[Dub Bull]

Copper is actually soft compared to many metals. The TelDec .pdf mentions that it's amorphous copper and, therefore, is resistant to the elec-Troll -lytic (; processes which take place during electroforming of the sons. They are cutting 'mothers' directly - which is the main reason for developing DMM... Whereas, when cutting masters in lacquers, one is effectively cutting a grandmother, since it's to be used for growing a 'father', innit?. ...and the silvering process is one of the hardest to (...wait for it...) 'pull off' 0; (ducking)

- Fr. José †

[ectomorphs]

Copper is actually soft compared to many metals. The TelDec .pdf mentions that it's amorphous copper and, therefore, is resistant to the elec-Troll -lytic (; processes which take place during electroforming of the sons. They are cutting 'mothers' directly - which is the main reason for developing DMM... Whereas, when cutting masters in lacquers, one is effectively cutting a grandmother, since it's to be used for growing a 'father', innit?. ...and the silvering process is one of the hardest to (...wait for it...) 'pull off' 0; (ducking)

- Fr. José †

Indeed. And thanks for the puns. The original DMM brochure as shared in this thread notes: "Suitable metals for such recording are Copper and also Cadmium under certain conditions. Cadmium was proposed by Wadsworth in his U.S. patent in 1922. Copper is more suitable, since Cadmium is not sufficiently resistant to the electrolytes used in the ensuing plating process. This is also the reason why videodisks are cut into an electrolytically produced Copper coating applied to a substrate." A nice overview of metal hardness can be found here: https://www.industrialheating.com/articles/94192-infographic-mohs-hardness-scale-of-metals
Copper is only slightly harder than aluminum.

[ectomorphs]

Ok, so this is curious... I've been digging around in patent archives to find the Wadsworth patent that apparently suggests Cadmium is the most suitable material. I finally found it (https://patentimages.storage.googleapis.com/d4/ea/3d/3ed3b78a7e6524/US1421045.pdf) but it makes absolutely no mention of Cadmium and instead refers to Aluminum:
"I have discovered that a substantially permanent record groove may be formed in the highly polished surface of suitable fine grain metal, for example, copper, sheet aluminum, pewter etc., with an ordinary smooth-Surfaced stylus. For best results the surface of the blank is first properly prepared by filling the voids therein as by the application there to of an element of wax-like nature which appears to fill the pores or voids between the molecules of material, and thus converts the polished surface into a suitable record receiving surface. The metals I find best adapted are those which take a smooth and high polish, and which are hard enough so that the stylus, on engaging the tablet, does, not readily pass through the surface pre pared by the polishing process, into unhomogeneous material beneath, and yet which are not so hard as to prevent an ordinary stylus point from readily scratching or indenting the burnished surface. Obviously an alloy which possesses the proper characteristics can be used equally as well as an un alloyed metal. I find furthermore, that aluminum possesses all of the characteristics necessary to make a record by my process, and I prefer to use this metal. As a filler therefor I prefer to use a film of wax such as paraffin, which acts also as a lubricant for the recording stylus. This lubricating feature I consider an important element of my invention, as it tends to facilitate the vibrations of the needle on the hard tablet Surface."
So why do Teldec claim that Wadsworth proposed Cadmium? Weird.

[Dub Bull]

Yeah, there's no mention of 'cadmium' in that patent application. Wondering if 'cadmium' was erroneously attributed to Wadsworth because, despite the Decca connection, the authors were from Schleswig-Holstein, and were, therefore, native speakers of German and, being not from America - the only place where the spelling, 'aluminum', is used - they were used to the international spelling for [Al] - 'aluminium'. Written that way, and spoken, it has the 'ium' at the end, like 'cadmium', innit?

Indeed, like cadmium, aluminium is (_also_) quite unsuitable for use as a mandrel in electroforming (nor to be plated);... Whereas fancy means of plating aluminium onto (other) mandrels is cited. But they are not appropriate for these nickel sulfamate baths we use for making stampers.

https://www.finishing.com/121/17.shtml

Grüß Gott. †

[farmersplow]

An interesting and detailed report on the subject

https://www.gammaelectronics.xyz/audio_04-1987_dmm.html

Thomas

[Dub Bull]

Cool article. Only, shellac was never a mastering material (; Also, I would describe the copper disk as a directly-cut 'mother' which is used to make a 'son'. Same (reduced) number of steps as they cite, but they're not really making a 'father' because that more difficult step is made from a silvered lacquer. DMM cuts on copper-plated disks allow an electoformer to skip over the silvering and delicate separating processes. {Fwiw, lacquer grooves are essentially free of tics and pops, as well. It's the silvering and electroforming and physical separation of the matrix from the lacquer which makes most of the noise in a pressing (or conventionally-developed nickel mother). In the late '80s, there was for a short time a sprayable nickel which allowed for improved quality of traditional galvanoplasty using lacquers.} Also, the stamper is not what is separated from a mother. While a son, it's still oversized (for 12" pressings, it's still 14" at that stage and has no center punch, yet, and, for 12", no pre-formed profile, or 'pocket'...) The article is not very 'tight' in its explanations, but it does get most of the gist. and the pictures are cool. gracias √