I've been following this thread for a while now, and
I'd like to put my 2 cents in, to hopefully add some
I think that reticuli could benefit from understanding
that the electrical dimension is only one portion
of the "equation".
The other has to do with the inherent mechanical
resonance of the cart in question.
It seems to me, that its been made clear by now,
that the mech-resonance dimension is hard to know...
Since its difficult if not impossible for most users
and Manufacturers don't usually publish data.
Given that, it has to be fine tuned by ear.
Although... calculating the electrical side of it
can likely "get you in the ballbark", but requires
listening, due to the unpredictable nature of
the combined effect of the mechanical side.
If the electrical change hasn't resulted in a sonic
either go back to the way it was before, or keep
I think it likely that the cap/resistor change would
probably indicate which direction to go in further
This is probably the reason its long been thought
of as "black magic voodoo" rather than the
science of cart loading.
Its also one of the things that sent most of the
world into the arms of digital sources.
Ironic a bit, that here we are, "back to the future"
discussing the finer points of cart loading in
Another thing that I feel deserves mention;
Perhaps most have thought it, but no one has yet
I believe, at least, that the idea of adjusting
cap value around the "default" 47k has evolved
for a practicality oriented reason.
Not the 47k part so much... I've no idea how
that evolved... but the cap adjustment end.
Finding sufficently low capacitance cabling, and
perhaps being unwilling to compromise on what
one might prefer to use, plus adding the fixed/inherent
capacitance of the arm's wiring... you likely
have a fairly high value to start with.
Using a small value cap (usually smaller than
what comes stock in most pre's) provides a simple
At least that covers the great majority of MM carts,
I should think.
When you think of the difficulty of finding good
quality caps in small pf values, and the difficulty/compromise
with cabling that yields the desired
its not surprising that ppl started trying to adjust resistance
as a way forward.
I don't mean to advocate for different cap or cable
types making a big difference/improvement.
That topic is to controversial to get into.
Many feel its important though.
Personally, I haven't A/B'd caps to know for sure,
but I have heard enough of a difference in cables
to convince me.. within reason anyway.
I just sleep better knowing that whatever cap
is of decent construction and other reasonable
ppl have given it the benediction.
I haven't had much luck finding poly caps in values
in the neighborhood of 50pf, for instance.
There seem to be ceramics and silver-micas in
those values available with relative ease...
Cheap pre's I've heard with ceramics didn't sound
very good... though I can't be certain its the cap
type at fault.
More ppl than not say silver micas sound harsh.
My better preamps have only poly film caps
I don't feel good about substituting something
If anyone happens to know a source for poly caps
in 50 pf and close to it, plz let me know.
My current situation, I believe, makes the
example fairly well.
I'm completing a turntable project which will
use an SME series III that I've had for years
but not really used.
I also happen to have an AT-15Sa cart which
should suit it well.
I used the AT for a couple of years in the late 70s,
as a sought upgrade from a Shure V-15 III.
My first 2 carts incidently.
Long story short... I pulled the AT due to fatigue
and bought a Grado.
Bearing in mind that I was in my late teens and
had no patience for messing with loading or soldering,
and was clueless on the subject anyway.
Now, this opportunity having presented itself,
I'm getting a AT20SS stylus for it.
A bit of an upgrade, and the low rez berrilium
cantilever to boot.
I'm most curious to hear it with my current (tube/valve)
and a (hopefully) more evolved ear.
Obviously, I'm most curious about loading it
properly, as opposed to just not bothering as
in the past.
I have a feeling it matters with this cart... perhaps
more than with others.. particularly given
its reputation for tizziness.
My own prior experience confirming that.
I'll also be using a DIY cable I've just made.
At 4ft total length and terminated, it measures
The SME arm = 19pf.
Preamp comes with 150pf soldered in.
If I sub a 50pf cap, then:
50pf + 19pf + 87 = 156pf.
According to the Hagerman calcs...
156pf @ 48.7k-ohms = 21hz peak
Not to bad.
A little but gentle rise at the top.
Far cry from what I'd been listening to yrs ago.
(probably compensat for my 50yr old ears'
HF rolloff anyway)
I also have a pair of favorite interconnects that
I use system-wide that measure 9pf/ft.
Unfortunately, they're very stiff... far to stiff
for this suspended table, but I'm using them
with great success on an unsprung table.
Just to use them as an example, I made the
calculation (and for possible future use).
9pf/ft x 4ft = 36pf.
50pf + 19pf + 36pf = 105pf
105pf @ 59.4k-ohms = 25.5hz peak
Probably better, but what the heck.
9pf/ft is fairly rare though, AFAIK.
Seems to me, that at least in my situation, just
putting a 50pf cap in the preamp is the way to
Barring a future choice of a cart that falls way outside
I can just adjust with resistance to get the electrical
aspect "in the balpark".
Then, listening should yield the "final word".