Embossed polycarbonate records and player compatibility

[pentlandsound]

Since the early spring I've been working on getting the best results out of my home-built lathe, embossing grooves on to discs of polycarbonate, and after a great deal of experiment with embossing weights and stylus angles I'm at last producing records that I'm reasonably happy with sonically. As my embossed polycarbonate records will possibly, in the future, be played on a wide variety of record decks and players, I test them on several playback machines to check trackability - that is, that they will play without the stylus either skating across the grooves or getting stuck and repeating the same section of groove. Up until recently my battery of test equipment consisted of fully manually operated decks, and all my embossed records play fine on all of them.

In May I bought a cheap Crosley-type suitcase player. This has a crude auto-shutoff mechanism, operated by a cam attached to the arm. As the arm nears the end of the record, the cam bears against a leaf spring and gradually moves it out of contact with another, thus breaking an electrical connection and stopping the platter motor. This assumes that the record being played has a deep enough groove to allow the spring effectively to bear against the outer groove wall. With embossed records, the spring is strong enough to dislodge the stylus from the much shallower groove, causing playback to jump back and repeat the same revolution, thus never allowing the motor to stop. Given the reputation that Crosleys and similar players have acquired in recent years, I'm not too worried about this, and have concluded that "It won't play on my Crosley" will not be a valid reason for a return.

However, I still wanted to test using some older, 'vintage' players with auto-change, auto-return or auto-stop, of which there are clearly still a great many in circulation. So I recently got hold of two Garrard entry-level decks in 'not working' condition on eBay, and then totally stripped down, cleaned, lubricated and reassembled them, restoring both to full working order. One is an Autoslim (4 speeds, with full auto-change, circa 1959), and the other is an SP25 Mk.III (3 speeds, fully automatic single play, 1970). I have fitted both players with the Audio Technica AT3600L cart and conical stylus, and both can track conventional pressed records perfectly at 3g of tracking force.

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My embossed records will play on the SP25 as long as tracking force is increased to 3.5g or more, but they will not play at all on the Autoslim - the stylus 'gets stuck' almost immediately. This is, I think, partly because of the arm bearing, which in spite of cleaning and relubricating still exhibits some resistance, but mainly because of the auto-trip slider which is gradually advanced by the arm as the record plays. These sliders are similar in both models, but the Autoslim relies on slippage of metal-on-metal whereas in the later SP25 the slider is thinner and lighter and bears against a Delrin insert to reduce friction.

I'm not suggesting that everyone who buys an embossed polycarbonate lathe-cut will want to play it on a 60 year-old changer, but someone might; and my questions, then, are aimed at Trolls who produce embossed records for sale to the public, either directly (eg. recordings of your own band) or via third parties (ie. recordings of their bands). What is your policy for the usability of the records you produce? Under what circumstances do you allow returns of (perceived) faulty discs? Do you (or your clients) have to include an insert with every disc, to the effect "This record will probably play fine on an X, will possibly play on a Y and almost certainly won't play at all on a Z"?

Thanks!
David

[pentlandsound]

A brief update, to record that I have cured the mistracking issue with the Autoslim. Some of the problem was being caused by the vertical pivot (ie. horizontal arm movement), a part of which I had overlooked during my original cleaning session. The pivot rod is sandwiched between two ball bearings, top and bottom, and both were lubricated with 60 year-old grease that had turned to treacle. This was not a problem when playing professionally cut records, of which the groove was deep enough to carry the stylus and arm and overcome the resistance of the old grease, but it resulted in serious mistracking and 'sticking' on the much shallower embossed groove.

Another thing that I had failed to take into account is that these changers must be placed absolutely level or the trip slider will not work properly. Even a slight tilt in one direction will cause the slider to run away and trip the change cycle prematurely; a tilt the other way means that the slider slips backwards along its travel and biffs the arm out of the groove! Using a spirit-level I repositioned the deck, making sure that it is level both front-to-back and left-to-right, and all my embossed records now play perfectly. Tracking force is set at 4.2 grams, which is absolutely fine for the conical stylus and well within the limits recommended for this cartridge.

So I'm pleased to record 100% success, eventually, with playing embossed records on two fully restored and newly serviced vintage decks. However, in the greater scheme of things, purchasers/recipients of embossed records may be playing them on poorly maintained and miscalibrated systems, which may manage to track manufactured 'cut' records more-or-less fine but struggle to track a shallow embossed groove, leading to possible complaints of faulty discs. I'd just tactfully reiterate and rephrase my earlier query, for embossers who sell to the public: how does your business handle and resolve such complaints?

(For anyone reading this who might be interested, I've posted a somewhat tedious YouTube video of the Autoslim playing one of my embossed records here. https://www.youtube.com/watch?v=0mz3u2WyKR8)

[piaptk]

We test every embossed record we make on a Crosley. Its possible with 35-37g of weight on www.recordlatheparts.com styli. However, you have to keep volume under control… too much lateral modulation (especially in the highs) on the shallower grooves will casuse skating and skips.