Mono Reissues and the Conical Stylus
That is my understanding. I just looked at a 1955 London ffrr (Ted Heath ant the London Palladium) and the groove is a V. The bottom does have a slight radius. A stereo cutting stylus specified by Ortophon has a 3-4µm radius which would explain that but that is still a fraction of the radius of even the smallest conical. dave |
Dave, I'm thinking that your London LP should be a microgroove pressing. I suppose technically you're correct, that the shape of the groove is a V looking shape however that groove opening is wider than the later stereo cut grooves. In fact, the grooves on LP's started out wider and progressively got more narrow over time. When Columbia introduced their microgroove pressings, manufacturers complained about how narrow the grooves were in comparison to the earlier records (i.e. 78's) As Lewm mentioned, the U shape description is just a vernacular term for specifying the difference in dimensions in order to clarify the point being made. Mono cartridge makers will use a nude conical stylus because of those earlier groove dimensions. |
Dave, You wrote, "My take is that if the coils remain oriented at a 45º angle to the
record and then wired in series for mono then it is a stereo cartridge
wired for mono and it doesn't matter if it if done internally or
externally. If however the same parts are used for a mono cartridge and
the coil is oriented so there is only pickup in the lateral plane, then
it is a mono cartridge. In this case there would be only be windings
for pickup in the lateral plane and the windings at 90º to that plane
would not be used / wound." That is also what I and many others have been saying here and elsewhere. What I wondered about is whether from a purist standpoint, does the true mono cartridge offer us a level of performance in the mono mode that cannot be had via the bridged stereo approach? I guess that if you use bridging, then cancellation would be imperfect to the degree that the two channels of the cartridge are not perfectly matched, which probably never happens. |
Goofyfoot, the groove width of the London ffrr is about 2.5 mil which is above the max spec for microgroove. Since the groove is v shaped the width has little to do with whether a conical will properly trace it. the only issue that can arise is a 1 mil conical can disengage from a microgroove but a 0.7mil conical will not run into any more issues with a 3.2mil groove than it will with a 2.2mil microgroove. In fact a 0.7 mil playing records previously played with a 1 mil will often be much quieter since it traces a part of the groove that hasn’t been played. |
Just measured a bit closer and the groove with is closer to 3 mil. I should also clarify that the 2.2 and 3.2 mil numbers I gave are the "average" from the link below and not a hard spec. https://dgmono.com/2018/04/06/deep-groove-mono-and-the-great-groove-width-mystery/ |
