"Serge Auckland" wrote in message
...
Harry Lavo wrote:
Recently there has been some discussion on usenet of the relative
sensitivity to loading of MM and MC cartridges. I learned this from
early issues of the IAR published back in the late '70's early '80s and
have used the knowledge ever since.
The following is a link to audioasylum, to a post that shows the effects
of loading and phase on a late model Shure V15 and an Audio Technica
OC-9. It is very illustrative of the advantages of a properly loaded MC,
and why it is possible to get them to sound (and be) perfectly flat.
Since 1990 my test has been...can I get the cartridge to sound as flat as
a CD of the same material. Once this is achieved, then some other
benefits of cartridges can come to the fore.
Thought many would find this interesting who don't vist Audio Asylum very
much.
http://www.audioasylum.com/audio/vin...es/597184.html
Very interesting, and thanks for the post. However, if I have understood
the graphs correctly, the MC graph shows no effect on frequency response
until well into rf. At af, it would seem that the response is identical
whatever the load.
As it happens, I have now changed my two MM cartridges for low output MCs,
but run them both into 47k inputs perfectly happily. As there is low
coupling between the mechanical and electrical parts of the cartridge, it
seems to me that running into a low impedance, (say 100 ohms or less)
won't make any significant difference to damping the tip/vinyl resonance.
That being so, what other benefit is there from a low impedance? I would
expect the distortion to be lower if the cartridge isn't being asked to
drive any current, although even here I would not expect a noticeable
improvement.
The resistance does affect whether or not the extended frequency response
slopes upward, downward, or remains flat. And the capacitance acts as a
"trim". At least over a broad range of mc's, that's what appeared to be the
case in IAR's work. In my own case, I once owned a Counterpoint SA-2 that
was completely adjustable in loading. I followed the dealer/manufactures
recommended load of 57ohms on my Accuphase AC-2. Believe it or not, a
change to 85ohms in that machine made a fairly substantial difference. With
this loading, the AC-2 in a Syrinx arm on a Linn sounded identical to my
Phillips 880 top-of-the-line CD player....except their was more air behind
and dimensionality in the imaging of individual voices and instruments.
I've also experimented with an adjustable AA Vac-in-the-box, and several mcs
(dynavector, accuphase, alchemist, etc.) and found loading combinations made
a sizeable difference, particularly as you get down to 100 ohms and below.
I still own and use an Accuphase AC-2 (one of several) which was TAS's prize
MC for a year or so early '80's. HP ran it into 47,000 ohms. When I do
that, I can't listen. Sounds thin and "etched" to me. I believe the
ultrasonic peak screws up the transient response, and I seem particularly
sensitive to this aspect of audio reproduction.
With transformers, you have to match the output impedance of the cartridge.
With headamps or phono preamps, the design of the preamp as well as the
loading values seem to come into play...I currently use that same cartridge
through a modified Marcof PPA-2 battery-powered headamp, and it is as flat
as the Counterpoint was at 57 ohms. With most mc's, loading at or below 100
ohms seems to flesh out the midrange and smooth out high-frequency
transients to the point of sounding "natural". But once you get in the
ballpark, some experimentation is in order.