My First Embossing Tests

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grooveguy
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My First Embossing Tests

Post: # 46333Unread post grooveguy
Mon Mar 06, 2017 7:38 pm

With the exception of a Soundscriber dictating maching, which I hotrodded a couple of years ago, I've not had any experience with sound embossing. But even though I have what's for me a lifetime supply of lacquer blanks and microgroove recording styli, I figured that the day may come that I'd regret not experimenting more in the embossing realm.

Some weeks ago, I sent-off for some cheap, generic replacement playback "needles" on eBay. I'd seen that another Troll had disassembled and used these for embossing, so I thought I'd give them a try. I ordered a pack of five for about $12, which included shipping directly from China. The eBay listing is the top image in the photo below.

These are called "diamond" styli, but who knows what (from colored glass to actual diamond) is the tip is, really. The 'jewels' came out with the application of some Jasco Paint and Epoxy Remover, and they turned out to be about 0.016" in diameter.

I got some 1/16" brass rod from a hobby shop, and a #77 (0.018") drill bit. Then I made a little jig that allowed me to cut off a 5/8" length of the brass rod, mill a flat (just like my Capps styli for cutting lacquers), and face the other end at an angle of 15 degrees angling toward the flat. I was then able to drill into the end of the faced-off rod and cement-in the jewel so that it actually sits 15 degrees off vertical with the cutterhead in its usual straight-up position. (Most Trolls who emboss 'lean' their heads, but my Rek-O-Kut won't allow this easily. So the 'lean' is built into the stylus.) The whole stylus and a closeup of the tip are the other two images in this photo:
Photos copy.jpg
So I cut out a couple of 12" Lexan blanks (elesewhere in these postings) and today tried my luck. Before chucking-up the new stylus in my Fairchild (mono) head, I cut a lacquer blank the usual way as a point of reference. It's an old (1950s vintage) blank, with some scrapes and scratches, but this is how the lacquer cut sounds:
Lacquer Cut.mp3
Next I mounted the new stylus and tried embossing in the Lexan without changing either the stylus pressure or the recording level or EQ from the lacquer test cut. I was really surprised that I got grooves with such a light pressure, but they were playable. The first go-round had pretty bad surface noise, so I took the advice given here and put some wax on the blank. The only thing I found around the house was Gel Gloss, and I really don't think it's the right stuff. But the surface noise did go down by about 10dB, and here's the resultant sound embossing. Again, no change in pressure, level or EQ from the lacquer cut, and at approximately the same diameter:
Embossing.mp3
Well, I was pleasantly surprised with the results. The playback level is fairly close to that from the lacquer, the top end sounds about as bright, and only the increase in surface noise (audible at the end on both cuts) is a problem. But I'll try other waxes and fluids and keep going at this. Comments, suggestions and gales of laughter are all welcome. Gosh, this is fun!
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markrob
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Re: My First Embossing Tests

Post: # 46336Unread post markrob
Mon Mar 06, 2017 8:06 pm

Hi,

That sounds really nice! I did a comparison of the two using Har-Bal. My old ears don't hear much difference, but you can see the slight loss at high frequencies of the embossed version (green trace). Still great results.
Emboss vs. Cut Comparison.jpg
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grooveguy
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Re: My First Embossing Tests

Post: # 46337Unread post grooveguy
Mon Mar 06, 2017 8:27 pm

Now, THAT's an interesting study, Mark. I'm assuming that the steps are 10dB per division, as hinted along that axis. Did you normalize levels at all? About a 5dB difference is indicated in the file into, top right. I hear more than a couple of dB difference playing them back 'live.' All this is very encouraging to me, having poo-pooed embossing, based on my dictating machine tests and the Milton Morse article that explains the 'reverse pinch effect' or whatever it was. I think that both the groove depth at a light pressure and the near-identical HF response has to do with using a very tiny embossing tip.

There's more I want to do here, as time permits; I mean, for a first test, it's not nearly as bad as I thought it was going to be, and worth some more effort for sure. I do believe that one advantage of cutting, vs. embossing, is that you get a clean, 'new' groove wall, not an indented one that retains the surface imperfections of the blank material. That is, you cut out the imperfections instead of just pushing them down into your groove. One thing I did notice on this recording, in contrast to my Soundscriber tests: the 'horns' on either side of the groove don't seem to be nearly as big. Again, maybe the small tip radius.

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markrob
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Re: My First Embossing Tests

Post: # 46339Unread post markrob
Mon Mar 06, 2017 8:54 pm

Hi,

I did normalize them to see how close the spectrum was between the two. The graph is 10 db/ major division and I did the analysis using 1/6 octave bands. The tip is of the embossing stylus looks really tiny and I assume that is allowing you to run at very low forces. It also makes the high frequency self erasure much less that a fatter profile.

Mark

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EpicenterBryan
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Re: My First Embossing Tests

Post: # 46350Unread post EpicenterBryan
Tue Mar 07, 2017 12:06 pm

Amazing results!
Man, if that jewel was just a tad shorter that would have been an issue. I guess the tip end of the shank could have been turned down a bit if needed.

Really fun experiment. Thanks for posting!

Bryan

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grooveguy
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Re: My First Embossing Tests

Post: # 46352Unread post grooveguy
Tue Mar 07, 2017 1:27 pm

Thanks for that, Bryan. Among the five jewels I liberated from the Chinese stylus assemblies, there was almost a 2:1 range in length (same amount sticking out of the cantilever for playing, however). The one I used here was the shortest. Drilling into the end of the brass at an angle really requires facing if off to allow a perpendicular approach with the drill. But after the hole's drilled, it might be best to grind the end perpendicular to the axis of the stylus again, up until the grinder just gets to the edge of the hole. You're right, with that bit of the brass hanging down, there's little clearance between it and the record surface.

By the way, my first trials were with aluminum stock, again from the hobby shop. That stuff is useless. The traditional commercial cutting style were usually 'duraluminum,' a harder stuff than what I had; the hobby shop aluminum 'rod' is more like wire, very soft and easily formed into flower holders, etc.

I appreciate Fred's evaluation of the recording, and especially for the accurate level analysis. That 5dB drop in the level of the embossing recording (re: the lacquer cut) must have to do with the Lexan 'springing back' after it's pushed this way and that. I wonder if this can that be compensated by merely raising the recording level, or does Lexan, when heated, exhibit less of this character?

I certainly defer to you guys who have experience in embossing, and have questions relating to heat, wax, angle, etc. I'm sure all will become clear as I get deeper into this groove, if I'm permitted to wax metaphorically.

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