Acoustic reproducers - needle angle
frenchy
record surface... just wondering what the ill effects would be of
running one at a higher angle? Would having the needle at a more
acute angle (closer to perpendicular to the record) cause more wear to
the record? This is in reference to a patent I saw for tungsten
needles and that the patent recommended that the best results were
when the needle was straight up and down at the record. I want to
know if I can run at an angle closer to this, than the usual, given
I'm using tungsten needles. I want to reduce the incidences of my
tips being bent because it's at such a big slant on the record and the
heavy reproducer (Orthophonic).
Thanks
Richard Knoppow
"frenchy" <mf10...@msn.com> wrote in message
news:52d25293-c3a3-4ed0...@2g2000prl.googlegroups.com...
I think this is important mostly for stereo recordings
where a mis-match in angle can reduce channel seperation. In
lateral recording there is an optimum angle at which even
harmonics are most strongly cancelled. In general this angle
should match the cutter angle. I doubt if any damage can be
done by a mis-match.
There is an extensive literature about disc recording
burried away in the Journal of the Audio Engineering
Society.
Note that some early reproducers have slanting needles
to get some vertical compliance where the pickup itself is
too stiff. Lateral recordings also move the needle
vertically due to pinch effect. If the pickup is too stiff
the record is damaged. The vertical modulation is the even
harmonic content so the pickup must be able to move with it
but not generate output. This is also why stereo pickups
should be connected for mono when playing mono discs.
--
Richard Knoppow
Los Angeles
WB6KBL
dick...@ix.netcom.com
frenchy
> Note that some early reproducers have slanting needles
> to get some vertical compliance where the pickup itself is
> too stiff. Lateral recordings also move the needle
> vertically due to pinch effect. If the pickup is too stiff
> the record is damaged. >>
I hadn't thought of that as being the reason for the slant, makes
sense. I guess I thought it was simply to increase the surface area
of the needle contact and thus reduce wear. I am running with the
slant about halved, so I still have *some* angle when I'm using
tungsten tips so maybe I should be ok. That 90 deg angle idea from
the patent definitely sounds like a bad idea. Plus I'm pretty sure
the tungsten tips themselves will have much greater ability to flex
when pushed upward compared to the tip of a regular steel needle.
(The fact that they can get bent in the first place I think proves
that!) So - I'll try to dial in the maximum angle I can run them
with before I start getting bent tips, and also will monitor record
wear at different angles as best I can. Thanks!
Frenchy
Richard Knoppow
Assuming the tip is hemispherical angling it will not
change the contact area with the groove unless the needle is
bent over so far that the sides of the needle begin to make
contact. The idea is to contact the groove with the smallest
area possible for good scanning of the groove. However, this
also requires a pickup that does not bear too heavily on the
record and has excellent compliance. Obtaining greater
compliance is the reason some of the older styli were kinked
into an L shape. The price for this was often loss of high
frequency response.
I don't know of a web site that illustrates the way
needles fit into record grooves, if anyone else does it
would be a service to post a link to this group. This is
illustrated in some of the older books. I can't give a
citation at the moment.
One problem with conventional phonograph records is
that the cutting stylus is shaped differently from the
playing stylus. the cutter is chisel shaped with a sharp
edge that is the length of the depth of the groove. In
addition, the cutter in all professional disc recorders runs
on an overhead bridge arrangement so it traces a straight
line from edge to center. The usual playback arm is hinged
at one end and traces an arc, so there is an error in the
direction the playback stylus moves compared to the groove.
This results in increased distortion. The common method of
alleviating this (but not curing it) is to off-set the
pickup at an angle. An analysis of the geometry shows that
the offset arm is tangent with the groove at two places,
each about a third from the maximum and minimum cut area of
the record where a straight arm is tangent in only one
place. Plus, by averaging out the error the maximum
deviation from the desired angle is reduced all over. The
exact amount of off-set depends on the length of the arm and
the maximum and minimum radius of the grooves. The
calculations are in, among other places, the famous
_Radiotron Designer's Handbook_ 4th edition. Available from
Pete Millette's site (very large files).
I think there may be some discussion of vertical angle
there also but am not sure.
The amount of distortion in disc recordings, both
harmonic and intermodulation is astonishing, especially when
compared to the amounts of distortion expected in
amplifiers. Much of it comes from the error in playback. I
refer to this as scanning because that is indeed what the
process is. Ideally, the playback stylus should follow the
groove as cut and reproduce the original electric signal
that drove the cutter but the problems of getting it to do
so are considerable. At least in lateral recording one has
some cancellation of even harmonic distortion since the
process is essentially push-pull. In vertical recording
there is no cancellation and none in stereo recording since
the reproducer must respond to both vertical and lateral
components of the groove. BTW, this is the reason for the
45/45 system-- it balances the distortion between the two
channels were the earlier vertical/lateral system
concentrates the even harmonics in whatever channel is
recorded vertically.
A note: one trick that was tried in vertical recording
was to re-record using reversed polarity, i.e., the downward
going modulation was re-recorded going upward. To some
degree this will, at least in principle, cancel some of the
distortion.
Vertical recording had a resurgance in the late 1930s
due to the release of the Western Electric 1-A cutter, the
first one to apply feedback (at least in a commercially
available cutter). This cutter had very good performance
compared to the lateral cutters available at the time and
was adopted for broadcast transcription and motion picture
sound purposes.
Pardon me for wandering but its somewhat connected to
the original subject.
Richard Knoppow
"Richard Knoppow" <dick...@ix.netcom.com> wrote in message
news:oO2dnZVW2YsVeWTX...@earthlink.com...
>
> "frenchy" <mf10...@msn.com> wrote in message
> news:c44d3e8c-7b4b-4695...@d9g2000prh.googlegroups.com...
> On Nov 10, 7:50 am, "Richard Knoppow"
> <dickb...@ix.netcom.com> wrote:
>> Note that some early reproducers have slanting needles
>> to get some vertical compliance where the pickup itself
>> is
>> too stiff. Lateral recordings also move the needle
>> vertically due to pinch effect. If the pickup is too
>> stiff
>> the record is damaged. >>
>
reproducers". I have been writing about electrical
recordings. However, all the geometrical stuff, groove
distortion, scanning, arm off-set, etc., applies equally to
acoustical or electrical records.
George Conklin
What a strange answer!!! Since when were Orthophonic recordings stereo?
Played by steel needles?
I've never heard to a vertical playback with steel needles recommended by
anyone.
Richard Knoppow
"George Conklin" <n...@earthlink.net> wrote in message
news:SYydnbWLD8MocWTX...@earthlink.com...
You didn't read very carefully. I was writing
generally. The needle angle applies to stereo as well as
mono lateral recording and, in fact, also to vertical.
You have not seen steel needles suggested for vertical
because nearly all vertical recording was done for
professional purposes and jewelled needles were mostly used.
I don't think steel needles were mentioned in this thread
anyway. Its about vertical angle in the pickup.
Orthophonic is/was a Victor trade name for its
electrical recording.
--
Richard Knoppow
discs. Of course there are also vertical cylinders. I think
these were all intended to be played with jewelled styli.
--
frenchy
> discs. Of course there are also vertical cylinders. I think
> these were all intended to be played with jewelled styli.
For reference, I'm playing both acoustic and electric recordings via a
Victor Orthophonic soundbox. Also it's a 10-50 machine with the
record changer, hence my choice of tungsten-tipped needles so I can
play lots of records without changing the needle.
That tungsten needle patent stated that a totally perpendicular angle
would give the best sound results because the contact area would be
minimized, so as to pick up the finest groove details. Also stated
that this angle could be a problem, as the needle is more likely to
want to chatter vertically. He even went so far as to say the ideal
would be an elliptical tip, so that the contact area would be even
skinnier lengthwise in the groove... again, to pick up the finest
details. Wonder how he planned on making elliptical tungsten wire!?
Oh well.
George Conklin
Of course. Saphires.
George Conklin
---
Edison developed an ellicpital diamond for playing back his LPs. There were
only 12 of them issued, and I've several.
frenchy
(#2, #4 etc.), and 65 degrees on the Orthophonic. The old Victor
manuals I found on the net say 60 for a #2, 68 for Orthophonic (align
the pin with the top set screw hole.) So I now have mine set up
correctly, I had my Orthos slanted too much.