Pathe Vertical Playback


Pathe Vertical Playback

…an outside-start vertical-cut US pantograph

Pathes use a large radius stylus, usually bigger than a 2-minute Edison stylus. They came in different sizes but the same recording would be available in say 8, 12 and 14 inch sizes so the size doesn’t have anything to do with playing time. The groove width obviously varied with the size, and also the groove diameter. The larger sizes used a very big tip radius, and unlike Edison’s doorknob styli the playing styli were spherical.

Most people assume that you should use the large radius styli as originally used, but I disagree with this. The main reason is that a large spherical stylus is too blunt to cope with the higher frequencies and introduces tracing distortion. This manifests itself in a loss of top frequencies, in bad cases with comb-and-paper distortion, and may be the cause for the effect you can hear where sibilant sounds are there but they sound somehow artificial, as if they have been dubbed on later. For this reason you need in my opinion a stylus with a smaller ‘front-to-back’ radius, like an elliptical. I have never been able to experiment with a very elliptical stylus but I use (complete heresy) a truncated elliptical intended for normal 78s. The thing is that you are only contacting a small portion of the bottom of the groove, which would be fatal on a lateral-cut, where you need to contact the sides. On a vertical-cut the bottom of the groove is where the modulation is. Granted, the stylus probably skates around the bottom of the shallow groove, but the modulation is the same all over it. You might expect the noise to vary, but all I can say is that it doesn’t happen. True, you get more high-frequency noise, but I believe it’s there because that’s what’s on the record. You don’t get it if you use a large radius stylus, but then you don’t get it if you fill your speakers with viscous oil or fill your ears with plaster of Paris (Legal disclaimer – Don’t try this at home). If the noise is there because the record is noisy, better to use filters and do the job without added distortion, let alone medical or repair bills.

But seriously, in my experience a 78 stylus will play Pathes of all sizes. Because the grooves are shallow like cylinder grooves, there is a tendency for the stylus to skip grooves. I had lots of trouble with this until I started to use a heavier arm. I don’t mean more playing weight but an arm with more mass. You might experiment with putting a weight on the cartridge shell, but you then need to be able to adjust the playing weight to cancel this. This lowers the resonant frequency of the arm mass vs cartridge compliance and seems to be better for Pathes. The cartridge is a Shure M-series (M-44?) which has a stylus with a large amount of movement. It is not very compliant by LP standards. The longer the arm the better as well as tracking errors and consequent sideways thrust is minimised. Some sort of anti-skating compensation is useful to APPLY sideways thrust where necessary. For the case of Pathes there are no rules as to how much anti- skating to use, just what works.

The end result of this arrangement is that the stylus-cartridge compliance has to take the brunt of any warps rather than the arm reacting too fast. I know there are people who will say that a modern cartridge and arm have an arm resonance intended for 33 rpm and that for faster speed you should SHORTEN the arm to increase the resonance. (If the natural frequency of a warp and the arm coincide, you’re likely to get tracking problems). My low-compliance stylus will increase the arm resonance, but the heavy arm will reduce it again. All I can say is that I very seldom get groove skipping on Pathes with it.

Next, you need to cope with the speeds of Pathes. Later Pathes with paper labels and outside starts go at a nominal 80rpm which can often be set on a turntable and in any case may be acceptably close to 78rpm to use this. The engraved ‘label’ Pathes nominally go at 90 to 100 rpm and can go outside this range. For these you really do need an infinitely variable turntable which can do these speeds, and from what I’ve heard if these are available new they are very specialised and expensive.

I use an old Lenco turntable with variable speed from below 16 to well above 78. I have adjusted it to go above 100 at the highest range. This is one of the old idler-wheel driven turntables that someone was criticising in a post recently, and I think it’s true that I should be looking around for a substitute. I don’t find it too bad for many 78s, but with vertical-cut discs rumble is a problem because the rumble from a turntable is likely to be worst in the vertical direction. On Pathes there are bass frequencies that are there in the recording, but you have to filter out simply because the rumble is too much. Maybe a belt drive would improve this.

Another way that might work for variable speed is to use a direct-drive turntable. These were pretty common in later vinyl days, and I have seen one that was adapted to do 78. They have a servo speed control and I got a surplus motor for one of them and found that (in this case at least) it was just a matter of setting the voltage on one pin. The problem is likely to be the low torque they develop at higher speeds, so even if they can go up to the desired speed the servo speed correction may not be adequate or the friction of a heavy worn record might stop it altogether. If you have the electronic knowledge or access to it, it might be worth experimenting.

Lastly, you need to make your cartridge sensitive to vertical modulation and not to lateral. This is the easiest part, as you simply use a stereo cartridge, and before putting the two channels in parallel as for mono (lateral), you reverse the connections on one channel first. In other words, if the four pins in a cartridge are Left, Left Ground, Right and Right Ground, for mono you connect the ground pins together to the ground screen of the cartridge lead and connect the Left and Right together for the ‘live’ inner of the lead. For vertical cut, you would connect Right Ground and Left for the screen side of the lead and Left Groung and Right for the live side. Possible problems are that one of the Ground pins is actually connected to the metal case of the cartridge. In this case you just have to make sure that this ground pin is the one which goes to the ground lead. More difficult is if the cartridge has the two ground pins internally connected. This should not happen, but I once had an old cartridge which only had 3 pins because the ground was common. In this case it would be best to get another cartridge! It’s easy to tell whether you’ve wired it correctly as you just play a normal lateral 78 with a suitable stylus and you should hear just noise with virtually no music signal. If one channel isn’t working, you may hear half-way acceptable results with both verticals and laterals, but will be picking up unneccessary noise as well.

Article courtesy Adrian Hindle-Briscall.

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