Why moving coil
 

"Trevor Wilson" wrote in
message



**Er, not quite. The FR plots of MC carts, in some cases,
CAN be shown to be superior.

In some cases the FR of MM cartriges are at worst the equal.

No, the true hard parameter in the design of a cartridge is the moving mass,
not the inductance of its pickup coils. Less moving mass for a given amount
of brute force strength, the greater the potential of the design.

Brute force strength is an important parameter of a cartrdige for two main
reasons:

(1) Durabilty.
(2) Ability to tracking the rapid undulations of the LP groove.

The beauty of the MM design is that the moving magnet can be structural as
well as being the primary signal generating element. With modern
high-energy magnetic materials the magnetic generating element can be made
as virtually as small as is desired.

A moving coil cartridge's coils can't be as strong of a structural element.
The coils work best if there is also a moving magnetic core. This adds up to
excess weight. Furthermore it is far more difficult to make small coils of
wire and wire leads to transmit the signal, as opposed to simple small
blocks of solid magnetic material that itself has considerable inherent
strength.

The reason, of course, is
blindingly simple. It's all about inductance. The
inductance of (LOW OUTPUT) MC carts is very low, indeed.

The inductance of a MC cartrridge is irrelevant because it can be made to be
whatever is desired. The cost of reducing it is reduced output, but that is
pretty much a given with MC cartridges.

The inductance of a coil is proportional to the square of the number of
turns. The output voltage of a coil in a varying magnetic field is
proportional to the number of turns. Thus, if a cartridge is allowed to have
a mere 3 dB less output, it has half the inductance.

In fact the inductance of MM cartridges is optimized to provide smooth
response, not minimize inductance. Fools that they are, designers of MM
cartrdiges tend to be most interested in high fidelity.

This enables them to produce a very flat, very wide (up
to around 60kHz) frequency response, with a
correspondingly superior rise time.

All of which are well-known to have zero audible benefits.

The real benefit of
such a system is that LC resonance effects are often well
outside the audible range.

Ignores the fact that the resonance that actually dictates the response of a
cartridge in ways that can't be managed is the resonance between the moving
mass of the cartridge stylus and paraphenalia that is attached to it, and
the compliance of the vinyl.

This means that a low output
MC cart may exhibit a very flat phase response within the
audio band.

Which is again well-known to have zero audible benefits.

This may not be the case with high output MC
carts nor with some MM carts.

For the record: Many, well designed, MM carts do not
exhibit any resonance problems without the audio band.

Thus invalidating Trevor's entire argument.

Why moving coil
 

"Ian Bell" wrote in message
news:4419d747.0@entanet
Serge Auckland wrote:

My question is why Moving Coils should be thought to be
better than moving magnets. I can think of several
reasons why they should be worse, lower compliance and
higher mass, but not why they should be better.
Trackability should be better on a MM, as should record
wear due to lower tracking weights.


I am surprised there has been so little development of
cartridges beyond the two basic magnetic types and good
old ceramic. What about an optical cartridge for example?

They exist. One example is the ELP laser turntable.

Why moving coil
 

"AZ Nomad" wrote in message

On Thu, 16 Mar 2006 21:21:59 +0000, Ian Bell
wrote:


Serge Auckland wrote:

My question is why Moving Coils should be thought to be
better than moving magnets. I can think of several
reasons why they should be worse, lower compliance and
higher mass, but not why they should be better.
Trackability should be better on a MM, as should record
wear due to lower tracking weights.


I am surprised there has been so little development of
cartridges beyond the two basic magnetic types and good
old ceramic. What about an optical cartridge for example?

Are you talking about bouncing a laser off the record
groove? It was a failu it was too expensive and
worked worse than traditional methods as it was best at
reading the crud in the groove instead of just pushing it
aside.

I heard and saw an example of that failure producing music at HE2005 about a
year ago. AFAIK its still on the market. If you have the money - they have
the product!

Why moving coil
 

"Serge Auckland" wrote in
message

Interesting theories. Can you tell me a bit more as to
why a compliance of 10-12cu is sufficient for all
records?

It has to do with the mass of the element that tracks the groove and the
compliance of the vinyl.

Interesting that in vinyl's heyday, some
cartridges were providing 30-40 cu.

Static compliance is really mostly a low frequency effect. Low frequency
tracking isn't much of an issue. Tracking high frequencies is a big issue.

It could be a
marketing exercise rather than having a sound engineering
reason for it, but it would be useful to know why such
high compliances are not necessary.

They were just numbers for the sake of numbers.

Why moving coil
 

"Bill Taylor" wrote


I recently changed my turntable. The only reasonably priced one that I
felt that I could trust was the Technics DJ turntable (basically a
1970s HiFi turntable with a speed control). The supplied arm has
quite a high effective mass and with the Shure V15-V that I had to buy
as well the LF resonance is plainly much to low, this cartridge has a
more reasonable compliance of about 23c.u., but it is still too high.
Forunately the Shure damper more or less controls the resonance.


I ran the same cart on a (presumably) similar deck - the Technics SL1210 Mk
2 - and found that the damping brush had virtually no effect on sound
quality.

Interesting to see that word is slowly spreading on the massy, non-suspended
decks (direct drive in particular) - I've been 'into' them for years now and
have been watching with some amusement as the the 'bouncing brigade' have
slowly woken up to the fact that suspension causes as many problems as it
solves (apparently) and is a bugger to keep maintained.....



There is another advantage of MCs that was certainly true in the 60s
and 70s. It is much easier to create a large magnetic field with a big
static magnet in the body of the cartridge than it is with a small
magnet on the end of the cantilever, so in the days of less effective
magnets it would probably be possible to keep the effective tip mass
lower with MC rather than MM cartridges.


Eliminating the need for a x10 stepup between MC and MM isn't entirely
without its advantages either, especially with valve amplification...

Why moving coil
 

"Arny Krueger" wrote in message
...
"Trevor Wilson" wrote in
message



**Er, not quite. The FR plots of MC carts, in some cases,
CAN be shown to be superior.

In some cases the FR of MM cartriges are at worst the equal.

No, the true hard parameter in the design of a cartridge is the moving
mass, not the inductance of its pickup coils. Less moving mass for a
given amount of brute force strength, the greater the potential of the
design.

Brute force strength is an important parameter of a cartrdige for two main
reasons:

(1) Durabilty.
(2) Ability to tracking the rapid undulations of the LP groove.

The beauty of the MM design is that the moving magnet can be structural as
well as being the primary signal generating element. With modern
high-energy magnetic materials the magnetic generating element can be made
as virtually as small as is desired.

A moving coil cartridge's coils can't be as strong of a structural
element. The coils work best if there is also a moving magnetic core. This
adds up to excess weight. Furthermore it is far more difficult to make
small coils of wire and wire leads to transmit the signal, as opposed to
simple small blocks of solid magnetic material that itself has
considerable inherent strength.

The reason, of course, is
blindingly simple. It's all about inductance. The
inductance of (LOW OUTPUT) MC carts is very low, indeed.

The inductance of a MC cartrridge is irrelevant because it can be made to
be whatever is desired. The cost of reducing it is reduced output, but
that is pretty much a given with MC cartridges.

The inductance of a coil is proportional to the square of the number of
turns. The output voltage of a coil in a varying magnetic field is
proportional to the number of turns. Thus, if a cartridge is allowed to
have a mere 3 dB less output, it has half the inductance.

In fact the inductance of MM cartridges is optimized to provide smooth
response, not minimize inductance. Fools that they are, designers of MM
cartrdiges tend to be most interested in high fidelity.

This enables them to produce a very flat, very wide (up
to around 60kHz) frequency response, with a
correspondingly superior rise time.

All of which are well-known to have zero audible benefits.

The real benefit of
such a system is that LC resonance effects are often well
outside the audible range.

Ignores the fact that the resonance that actually dictates the response of
a cartridge in ways that can't be managed is the resonance between the
moving mass of the cartridge stylus and paraphenalia that is attached to
it, and the compliance of the vinyl.

This means that a low output
MC cart may exhibit a very flat phase response within the
audio band.

Which is again well-known to have zero audible benefits.

This may not be the case with high output MC
carts nor with some MM carts.

For the record: Many, well designed, MM carts do not
exhibit any resonance problems without the audio band.

Thus invalidating Trevor's entire argument.



Interesting, succinct and AFAIAC (from what little I know) right on the
money - quite surprising really, as it comes from Usenet's No1 antivinyl
bigot!! :-)

Why moving coil
 

On Fri, 17 Mar 2006 08:06:08 +0000, Ian Bell wrote:


AZ Nomad wrote:

On Thu, 16 Mar 2006 21:21:59 +0000, Ian Bell

I am surprised there has been so little development of cartridges beyond
the two basic magnetic types and good old ceramic. What about an optical
cartridge for example?

Are you talking about bouncing a laser off the record groove? It was a
failu it was too expensive and worked worse than traditional methods as
it was best at reading the crud in the groove instead of just pushing it
aside.

No I was thinking more of a small low mass pair of mirrors in place of the
MM for example with perhaps fibre optics to carry the data - no hum issues
for a start.

No. You'd just have a 2lb brick with the electronics hanging off your
tonearm. :-)
Sure you could do better with today's microelectronics, but making custom
integrated circuits isn't a cheap endevor and I doubt any cartridge makers
forsee enough profits to cover development costs.

Besides, would a mirror really be lighter than a coil? If you wanted to
improve the noise problem, move the preamp into the turntable. The biggest
noise problem has always been the cables.

Why moving coil
 

"Keith G" wrote in message

"Arny Krueger" wrote in message
...
"Trevor Wilson" wrote
in message



**Er, not quite. The FR plots of MC carts, in some
cases, CAN be shown to be superior.

In some cases the FR of MM cartriges are at worst the
equal. No, the true hard parameter in the design of a cartridge
is the moving mass, not the inductance of its pickup
coils. Less moving mass for a given amount of brute
force strength, the greater the potential of the design.

Brute force strength is an important parameter of a
cartrdige for two main reasons:

(1) Durabilty.
(2) Ability to tracking the rapid undulations of the LP
groove. The beauty of the MM design is that the moving magnet
can be structural as well as being the primary signal
generating element. With modern high-energy magnetic
materials the magnetic generating element can be made as
virtually as small as is desired. A moving coil cartridge's coils can't
be as strong of a
structural element. The coils work best if there is also
a moving magnetic core. This adds up to excess weight. Furthermore it is
far more difficult to make small coils
of wire and wire leads to transmit the signal, as
opposed to simple small blocks of solid magnetic
material that itself has considerable inherent strength.
The reason, of course, is
blindingly simple. It's all about inductance. The
inductance of (LOW OUTPUT) MC carts is very low, indeed.

The inductance of a MC cartrridge is irrelevant because
it can be made to be whatever is desired. The cost of
reducing it is reduced output, but that is pretty much a
given with MC cartridges. The inductance of a coil is proportional to the
square
of the number of turns. The output voltage of a coil in
a varying magnetic field is proportional to the number
of turns. Thus, if a cartridge is allowed to have a mere
3 dB less output, it has half the inductance. In fact the inductance of
MM cartridges is optimized to
provide smooth response, not minimize inductance. Fools
that they are, designers of MM cartrdiges tend to be
most interested in high fidelity.
This enables them to produce a very flat, very wide (up
to around 60kHz) frequency response, with a
correspondingly superior rise time.

All of which are well-known to have zero audible
benefits.
The real benefit of
such a system is that LC resonance effects are often
well outside the audible range.

Ignores the fact that the resonance that actually
dictates the response of a cartridge in ways that can't
be managed is the resonance between the moving mass of
the cartridge stylus and paraphenalia that is attached
to it, and the compliance of the vinyl.
This means that a low output
MC cart may exhibit a very flat phase response within
the audio band.

Which is again well-known to have zero audible benefits.

This may not be the case with high output MC
carts nor with some MM carts.

For the record: Many, well designed, MM carts do not
exhibit any resonance problems without the audio band.

Thus invalidating Trevor's entire argument.

Interesting, succinct and AFAIAC (from what little I
know) right on the money - quite surprising really, as it
comes from Usenet's No1 antivinyl bigot!! :-)

There's a huge difference between being a bigot and being well-informed
about the properties of various media. I simply know vinyl and digital's
strengths and weaknesses and speak accordingly.

In fact I have an average vinyl rig that I use for making digital
transcriptions. So I'm a funny kind of antivinyl bigot - one who has a
vinyl rig of his own and uses it from time to time for a productive purpose.
It's not as good as the vinyl rig I had when I switched to digital, but its
good enough for the purpose.

Why moving coil
 

In article , Keith G
wrote:

"Bill Taylor" wrote


I recently changed my turntable. The only reasonably priced one that I
felt that I could trust was the Technics DJ turntable (basically a
1970s HiFi turntable with a speed control). The supplied arm has
quite a high effective mass and with the Shure V15-V that I had to buy
as well the LF resonance is plainly much to low, this cartridge has a
more reasonable compliance of about 23c.u., but it is still too high.
Forunately the Shure damper more or less controls the resonance.


I ran the same cart on a (presumably) similar deck - the Technics SL1210
Mk 2 - and found that the damping brush had virtually no effect on
sound quality.

That isn't particularly surprising. The main effect in practice would show
up on LPs with pronounced levels or warp or surface ripples. If the discs
are fairly flat, then the damper wouldn't be doing much.

FWIW I use my V15/III with an old technics TT/arm so the arm mass is 'too
high', but in general I don't hear any problems as a result, despite the LF
resonance being lower than nominally ideal.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Why moving coil
 

"AZ Nomad" wrote in message

On Fri, 17 Mar 2006 08:06:08 +0000, Ian Bell
wrote:


AZ Nomad wrote:

On Thu, 16 Mar 2006 21:21:59 +0000, Ian Bell


I am surprised there has been so little development of
cartridges beyond the two basic magnetic types and
good old ceramic. What about an optical cartridge for
example?

Are you talking about bouncing a laser off the record
groove? It was a failu it was too expensive and
worked worse than traditional methods as it was best at
reading the crud in the groove instead of just pushing
it aside.

No I was thinking more of a small low mass pair of
mirrors in place of the MM for example with perhaps
fibre optics to carry the data - no hum issues for a
start.

No. You'd just have a 2lb brick with the electronics
hanging off your tonearm. :-)

Not at all. It's painfully obvious to anybody conversant with modern
technology that such minimal electronics as would be required could be
extremely light.

Sure you could do better with today's microelectronics,
but making custom integrated circuits isn't a cheap
endevor and I doubt any cartridge makers forsee enough
profits to cover development costs.

There are zillions of kinds of optical transducers sitting on shelves all
over the world.

Besides, would a mirror really be lighter than a coil?

See my former comments about solid metalic magnets as opposed to tiny coils
of wire.

If you wanted to improve the noise problem, move the
preamp into the turntable. The biggest noise problem has
always been the cables.

Again, simply not true. The biggest noise problem has been stray field
pickup in magnetic cartridges by the coils. However this problem has been a
solved problem for about 35 years.