Polycarbonate Record Played on Gramophone (video link attached)

[santinin]

Hello fellow Trolls. My name is Nick and I am based in Pittsburgh. I have been a lurker on this forum for quite a long time. I have the utmost respect for the members of this forum and with that in mind I humbly submit to you my latest project. I have long been driven, like many others, to find a way to produce a record playable on a gramophone with a steel needle. This subject has been thoroughly thrashed out and the difficulties well highlighted. While there are others who have successfully completed this task, their methods are proprietary or beyond my means. At this time I am not looking to make this into a business or anything of the sort, but rather I’d like to post this method to you in the hopes that it can be improved upon. This is undoubtedly a one-off method, the troubles of finding a suitable material for a pressing plant to use to stand up to the pressure of a gramophone soundbox is for another day.

To begin, the cutting: my lathe is an RCA MI-12701 that has an MI-4889 head. The amplifier is a lowly 50 watt transistorized amp. I am using speak-o-phone branded steel cutting needles that achieve the proper 78 groove width. The cutting material is Makrolon polycarbonate. I am not using heat. While I understand that this combination of steel and poly carb is a no no, I cannot afford a diamond at this time, nor to my knowledge is there a diamond made that can achieve the proper groove width. This poor combination, as you can imagine, leads to an excess of surface noise. This is one area where I’d like to look to the wisdom of this forum. I am aware of MyShank but they do not produce a 78 diamond, nor would it likely be profitable for them to do so. In addition I would likely destroy a MyShank diamond quickly by trying to achieve the groove width necessary, and on polycarb no less. Is there anyone who produces diamonds in the U.S. that would be able to manufacture a 78 diamond for purchase? Or in the alternative is there any way to reduce the surface noise on polycarb using steel. I have tried heating the disc but it really does not make a difference. Is there a chemical method of softening and hardening polycarb?

Now to playback: I have attached a youtube link to a video of one of the records that I cut below. It is played back on an HMV 101 with a rebuild soundbox using a loud-tone needle. Initially I had the foreseeable problem of too much drag in the groove and the turntable would stop. While 78s of a certain period had minerals and other materials to shape the steel needle to the groove and in addition allow it to glide through the groove, polycarbonate does not. To overcome this issue I first played about half of a normal period 78 to shape the needle. Then (and here’s there wacky part) I placed a few drops of 3 in 1oil on the record I made and more or less evenly rubbed it into the grooves. (Now remember this is for gramophone playback, I would never play this with a modern cartridge.) This allows the needle to glide through the grooves. I also suspect that it may be reducing wear on both the steel needle and the record. The polycarb does indeed eventually wear the steel needle down, however through examining the needle under a microscope, I have determined that I can get about 10 plays on these discs before the needle will wear to the point of damaging the disc.

Now here’s the fun part: Using this method I have not noticed any discernable distortion on the record (outside of what was there to begin with) after nearly 30-40 plays. It seems that polycarb stands up to the steel needle at 150 grams remarkably well. To add to this, I have used mostly loud-tone needles which are noted for their special ability to slowly shred electrically recorded records.

Also, a small note about proper eq: Initially, I used standard RIAA eq in an effort to reduce bass. In earlier experiments I found that less bass meant less drag. While workable, the sound was too thin on playback. Having discovered the oil trick, I turned to the eq curves intended for acoustic gramophone playback. Namely Columbia’s 1925 curve and HMV’s 1925 curve. All of these curves produce a well-rounded sound and the difference between them is only a matter of taste. The curve used in the attached video is HMV.

In re: the video. The tune is Masculine Women and Feminine Men by the Savoy Orpheans (1925). The substance collecting around the needle is 3 in 1 oil. Please excuse the low quality of the iphone mic, the sound of the machine in real life is a bit fuller. For the best impression of what this actually sounds like try to play the video through larger speakers than an ipad or a laptop if possible. The video was made today and is around the 30th – 40th play of the record.

To finish up I’d like to say thank you to whomever made it through all of this. I am only a novice at record cutting. I would thoroughly appreciate any feedback or advice and I am happy to answer any questions.

The video can be found here: https://youtu.be/yONKIgXJq5w

Thanks

[markrob]

Hi,

Sounds great! Nice work. The noise level is not too bad considering. Seems like you have a good handle on the EQ needed.

One possible idea. If you playback an existing 78 acoustic era disk using a modern magnetic pickup wired for lateral response (L+R) using a proper stylus for 78's and capture that with a preamp without any RIAA curve (flat response) you you should be able to feed that captured file directly to the RCA cutterhead with no other EQ, have have a nice transfer. The idea being that you will read the playback disk's velocity response and then feed the captured file into your cutterhead that is also flat vs velocity. In effect, you will make the carbon copy of what is in the grooves of the original. Maybe you will need a bit of EQ to season to taste to deal with your cutterhead response. You could also analyze the spectral response of the captured file and use that to develop a recording EQ curve.

Mark

[soeffingodly]

Very well done!

I tested out my Vinyl Recorder for a customer and cut her The Doors "People Are Strange" on a test record at 78rpm. It played and sounded good on her steel needle Victrola! (Could have used a little bit of EQ work but overall sounded very good)

Great job and thanks for sharing.

[aaron]

You may want to email Myshank, I remember having a conversation with them a while back and it sounded like they actually do produce diamonds for 78 grooves.

[santinin]

Thank you all for the feedback and advice I will defiantly try emailing Myshank. However it is my understanding that you are supposed to use only Myshank blanks with their diamonds. Or am I incorrect? My worry is that their blanks may be too soft to stand up to the weight of the soundbox. Defiantly points of inquiry that I will pursue. When I get the funds I will potentially do a comparison and report the results. Also I did try duplicating an acoustic 78 using Mark's suggestion and it produces a pretty good result. I found that I don't have to drive my head quite as hard to overcome the surface noise, which is a big plus.

Thanks,

Nick