Cartridge loading explained

the thin end of the wedge
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Reticuli
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Re: 440ML and Loading

Post by Reticuli » 21 Mar 2009 02:44

rayr0683 wrote:Hello,
Im using a 440ML right now, that is borrowed from a friend. I have a ZETA Vandenhul Silver Wired Tonearm. My Preamp is an Audio Research SP9....there is 560pf of capacitance at the phono inputs of the SP9, and I do not know the Capacitance of my ZETA Tonearm. I started out leaving the 560pf capacitance as is, and used the 47K Loading from factory on SP9. The 440ML sounded a bit bright, and thin....but very detailed, punchy and tight. So, after everyone telling me to take the 560pf of capacitance out of the SP9, and just use the Capacitance from my ZETA Tonearm, and the 47K resistive loading....so I did this. Now I am thinking that it may have sounded better with the 560pf capacitance in the circuit, along with my ZETA Arm capacitance. I didn't mess with the 47K resistor load, because Audio Research told me that I would not be able to hear a difference between the 47K and 32K Ohm Loads....so I just took their word on that. I think that the 440ML does sound detailed and nice...but im feeling that compared to the Grado Signature TLZ or the AT-OC9 it is outclassed. Unless im doing something wrong. Thanks, Ray
The Hagerman function page says for a 47kohm load you should be trying for 220pF total capacitance. So if you stay at that resistance, apparently you should put 100pF caps in.

If you just remove the 560pF capacitance to extend the high frequencies, Hagerman's page predicts you should raise the resistance above 47kohm, not lower it. So Audio Research was correct in that you would not see an improvement at 32kohms.

That Nagoaka mp-11 would probably like your preamp, assuming you left the preamp with the original specs. Werner's review on TNT proved that it could be made essentially flat out to 15khz, or something. I think one of the paper magazines also concluded the same.

Edit: Hifi World May 2007...400pF caps + cables...sorry.

So your preamp was originally optimized (assuming the treble extension thing isn't dealt with) for very high inductance carts. The 440ML is a mid-inductance MM.

rayr0683
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Loading in MM vs. MC

Post by rayr0683 » 21 Mar 2009 13:16

Hello Neo,
Thanks for the reply. Yes, Id have to agree that on the phone, the guy from AR doesnt sound like the sharpest tool in the shed.....so, I would tend to agree with you. I have a question then.....If lowering the Capacitance is so important especially on MM cartridges.....what about MC Cartridges...lets say like the new AT-OC9ML/II Cartridge.....Would this be sensitive to both Resistive and Capacitive Loading???? Or just Resistive??You know the Default of the SP9...its 560pf Capacitance, and actually 50K ohm resistance across the phono inputs.....I do know that the AT-OC9ML/II is recommended to use 100 Ohms of resistance in parallel with the 50K ohms phono input of the SP9. im not using a Step Up Trans. so, it wouldn't be the 20 Ohms....what about Capacitance? Appreciate your view on the MC, especially the OC9.........Thanks, Ray


Reticuli,
No one is recommending that you adhere to the electrical models. They are useful to get an idea of electrical parameters for a given cartridge output. That's the extent of their usefulness.

Your notion of tuning capacitance to inductance to have a non resonating filter, is wrong. It doesn't work that way.

Thinking that a pot, on the output of a phono stage, will change the load on a cartridge, is also wrong. The resistance must be across the input of the phono stage. It is the load your cartridge sees, not the load going to your line stage or amp.

You said that you read the entire thread - maybe you should try again when you're not so tired. This is the only measured response in the entire thread. Did you miss it?
Werner wrote:Here's the M97xe. Measured, not simulated.

The resistive load was 47k. The wiggle at 10kHz is on the test record.

http://www.tnt-audio.com/gif/shure_m97x ... sponse.gif
What's wrong with this picture? Here's a high inductance cartridge. What do you think happens at 62K?

You are right about one thing. The AT440 is too bright. It's an example of a cartridge that does not conform to the electrical models. Maybe the 440 refers to the inductance. I think it (inductance) is more like 490. Changing the resistance flattens out the response. Using capacitance to tame the high end makes it peaky.

Ray,
Although I no longer have an SP9, I'm sure AR gave you some bad advise. I suggest you replace the 440 when you have the opportunity. It is really too compliant for the Zeta (which I also no longer have). The Zeta was designed for lower compliance MCs. It seems to sound best with highly detailed cartridges. If your budget doesn't allow for a $1000 cart, maybe an OC 9 or one of those 33's from Japan would be a good match. A LOMC should work straight in, if it has a healthy output, and you're not short of gain in the first place.

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SP9 Preamp Load

Post by rayr0683 » 21 Mar 2009 17:45

Hi Neo,
thanks again for the reply. I understand all that your saying. In my vase, to achieve 33K Ohms Loading, going into the SP9, I need to put something like 80K Resistors in Parallel with the 47K Factory Loading, to achieve 33K Ohm. I think so anyway.

As for the driving of low output MC Carts. I was able to sucessfully drive the Signet AT-OC9 which was .4mv output. I agree, I probably cant go much lower than that. I was setting the volume at about 12:00 Position, but had no issues driving it. The SP9 Preamp has 67 DB of Gain in the Phono Section. I dont know if this helps any with recommendations.
Thanks, Ray
Ray,
Capacitance doesn't much matter for LOMCs, although I would recommend lowering that value for use with MMs. Something like 100pf would be good for most MMs, until you get a MC. If you do that, and change the resistors to around 30K, I think you'll be pleased. The 100pf should not be a problem when changing to a MC.

Resistors are sometimes sold in batches of 10. I ordered 33K and matched two at 32.4K. All the resistors (5% tolerance) measured slightly lower than the specified value.

The real issue with going straight into an SP-9 with a LOMC, is gain. Even with a .5 mV output (relatively high for a LOMC), you might not have quite enough gain, and it might sound kind of lifeless and not dynamic. If you must go straight in, you might want to consider a HOMC, or a medium output, like a .1mV. I think these MOMCs were developed with AR preamps in mind. The coils will have fewer windings than a high output and offer better performance. Benz makes some nice medium coils and you should consider it. To tell you the truth, the Benz are probably a better match for your arm, compliance-wise. The Glider and the Ace are highly regarded and (I think) they come in med output.

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Post by Reticuli » 21 Mar 2009 22:08

Reticuli,
Your notion of tuning capacitance to inductance to have a non resonating filter, is wrong. It doesn't work that way.

Thinking that a pot, on the output of a phono stage, will change the load on a cartridge, is also wrong. The resistance must be across the input of the phono stage. It is the load your cartridge sees, not the load going to your line stage or amp.

You said that you read the entire thread - maybe you should try again when you're not so tired. This is the only measured response in the entire thread. Did you miss it?
Wait. How exactly is my "notion" incorrect? If you are stuck at 47kohm, changing capacitance to reduce the electrical resonance peak will decrease compression and that white treble ringing etch so many MM cart & preamp combos have. Do you own any effects filters? I own several, analog and digital versions. That's what they do and that's what we're hearing with capacitance/inductance mismatch. Adjusting input capacitance alone is the traditional method phono preamp stages have used for years. And quoting 4-channel vinyl systems' occasional use of 100kohm is only illustrative of the ability to utilize such systems for another purpose: stereo playback originally spec'ed for 47kohm.

Also, I never said putting a pot on the output stage would change the load of the cartridge. I said REWIRING OR MOVING that pot on the TCC preamps from being a volume control to instead connecting it to the RCA inputs would seem to allow you to adjust the impedance of the phono preamp's inputs. The TCC phono preamps with volume controls would appear to have all the necessary components in clearly laid-out discrete fashion for this minimum-capacitance, adjustable-impedance phono stage that is being explored towards the end of this thread. Now, I might be wrong about the TCC's internal parts being ripe for slight modding and rearrangement, but I never said a volume pot left where it is and unmodified would alter input resistance.

And again, I am open to the idea that this thread is onto something and the potential is thrilling...especially if the TCCs are a cheap, high-function solution. But there's a lot of inconclusiveness, contradictions, and a lack of empirical evidence that most of these case-studies are doing anything more than adjusting extreme high frequency and ultrasonic performance well outside normal adult human hearing. Furthermore, there is little supportive evidence that the bass, midrange, and dynamic linearity of these cartridge/preamp combos is being maintained when deviating from the manufacturer's recommended settings. It's all very exciting, but I think further analysis and caution is required...not to mention figuring out why these different math functions programs are giving such wildly different answers, and why individual implementations are often producing quite opposite results.

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Post by missan » 22 Mar 2009 15:10

Reticuli
I think the reason why these programs, calculating the resistance and capacitance needed, will give You answers that are not applicable,
is really, that they only calculate the electrical parameters. That is not how a cartridge work, it´s just as much mechanical, and that is not, and cannot really be calculated.

To be able to figure out what loading is needed You must use a test record, and monitor the output from the phono amp. Then You can change the components to the right values needed for a flat frequency respons, if that is the goal.
/missan

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Post by fastcat » 22 Mar 2009 21:57

hello to all!

The more that I read this thread, the more I get confused!

Does anyone have any real world recommendations on how
to load a Shure V15 IV (capacitance & resistance)? This cart
is rated at 500 mH and 1380 ohms.

I have complete flexibility to change the preamp input parameters.

Many thanks in advance!

fastcat

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Post by Werner » 23 Mar 2009 09:24

What's wrong with this picture? Here's a high inductance cartridge. What do you think happens at 62K?
This:

http://www.tnt-audio.com/gif/m97_plot_var_250p.gif

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Post by Werner » 23 Mar 2009 10:30

Well, given that you see the plots for 47k and 75k and that only the damping of the treble peak seems to be affected I know you all are capable of doing a bit of mental interpolation, not?

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Post by missan » 23 Mar 2009 12:38

Werner
Is this a digitally recorded output from a phonoamp? Is pink noise used?
/missan

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Post by Werner » 23 Mar 2009 13:29

It is pink noise re-equalised to white for a nominally flat spectrum plot.

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Post by Werner » 24 Mar 2009 08:10

"What about cable inductance? Is it so minimal that it's insignificant?"

Compared to a typical MM's coil inductance? Yes, by several orders of magnitude. Further, atypically-low inductance comes with atypically-high capacitance.

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Post by missan » 24 Mar 2009 12:26

Werner wrote:It is pink noise re-equalised to white for a nominally flat spectrum plot.
Thank You.
Is it reasonable to assume that cantilever resonance frequency is around 12kHz according to Your plots.
/missan

MuZak

Post by MuZak » 25 Mar 2009 06:20

I've been following this thread for a while now, and
I'd like to put my 2 cents in, to hopefully add some
further clarity.

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
to measure..
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
improvement...
either go back to the way it was before, or keep
experimenting.
I think it likely that the cap/resistor change would
probably indicate which direction to go in further
experimentation/fine tuning.

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
2009.
-----------

Another thing that I feel deserves mention;
Perhaps most have thought it, but no one has yet
said it.
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
solution.
At least that covers the great majority of MM carts,
I should think.
Then...
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
numbers....
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
throughout.
I don't feel good about substituting something
"less".

Btw...
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)
equipment,
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
87pf.
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
go.
Barring a future choice of a cart that falls way outside
this range...
I can just adjust with resistance to get the electrical
aspect "in the balpark".

Then, listening should yield the "final word".

Werner
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Post by Werner » 25 Mar 2009 07:28

"If anyone happens to know a source for poly caps
in 50 pf "

Wima FKP2 starts at 33pF.

MuZak

Post by MuZak » 26 Mar 2009 03:33

Werner...
Excellent! Thanks!

Incidently, just before reading your post, I found
a 50pf 5% in polystyrene.
Would that be a good choice sonically?
I'd heard that styrene had fallen out of favor.
<shrug>

------------------------------------

Hey neo..
Thanks for the info and suggestions!!

I believe the differences in the AT15 and AT20
are that the 20s were selected out for having
the closer(est) tolerences between coils of each
batch, but all the SS styli have the "super" diamond
profile, and the 20SS styli have the berrillium
cantilever.
Thats my understanding at least... FWIW.

Interesting about the 47k.
I shall try it as is before doing anything else
as soon as the table is running.
I would do that anyway, since I want to refamiliarize with the AT.

RE: tizzy... though I'm sure I could find a
more accurate term if I thought about it a bit..
I won't since its been since 1979 that I've heard it.

I think the reason I found it so has to do with..
Well has to do with the hearing of an 18yr old vs.
a 50yr old...
But I think it has mainly to do with the built in
capacitance of the preamp (receiver actually)
that I was using back then.
First a receiver then a preamp.
I guess I could find out what values they both
had, but as I recall the receiver had something
like 250pf.

I was also using Discwasher "low capacitance"
cables.
Lol..
That was "hi-end" at the time.... pre Fulton even.
Either pre, or I couldn't afford Fulton.

Anywayz...
Using those values would be the most scientific approach,
but why bother really.
Actually, come to think of it... I still have both
that receiver and pre!
I could just hook 'er up and see... maybe I will one day.
(even still have the same spkrs, tho in need of work)

I'll certainly try as is first, and if need be use the
above discussed method.
I'll be patient with break-in too.

I'm very curious about all this, especially since
I'll now be listening thru tubes rather than the
SS back then.

Thanks again,
Greg

PS: Hmm lets see... what should I spin for the
first go around..
Somthing Else maybe? It seems to have a lot
of HF crispness......

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