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Cartridge loading explained

the thin end of the wedge

Postby carlosfm » 08 Aug 2006 01:58

Axon wrote:I've been looking at these issues myself, while looking into building a preamp.

How did you derive the resistance values for the cartridges? For most carts, I was under the impression that resistance wasn't broken out, and you had to derive it from impedance + inductance.


I'll give you an example: the Shure M97 has 1550 Ohms resistance, so it says in the booklet.
If I measure across the terminals of one channel (ex: Left to ground) with a multimeter, I get a very close value to this, ~1570, which are just normal tolerances in the manufacture process.
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Postby bastlnut » 08 Aug 2006 09:52

hallo,

what are you recomending here?
are you just explaining relationships, or are you just sharing your experiences with us?

without all these graphs and explenations, the only method most have is to try different cables or phono stages.
for us theoreticians, it is always nice to read a new study.

regards,
bastlnut
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Postby carlosfm » 08 Aug 2006 10:25

bastlnut wrote:what are you recomending here?
are you just explaining relationships, or are you just sharing your experiences with us?


I'm explaining how to load a cartridge.
These basic electrical parameters determine the ideal loading of a cartridge.
There is no voodoo here.
If the resulting sound is as extended as you can get by the proper loading of the cartridge, it all depends on the quality of the stylus. That's where the limitation resides.
I see lots of false preconceptions around (not here, but everywhere) that MM cartridges are peaky in response in the low treble and then fall off steeply, and don't reach 20Khz.
This is only true if the loading is incorrect. I'm trying to show you all, and I hope that I did succeed in doing that in a clear way, that the loading of MM cartridges is as important as with MCs.
The point is getting a neutral, natural sound out of any cartridge.
Also, I went to all this trouble of reporting this under request of a very nice member of this forum. I like open-minded people that are always ready to understand what's going on.

bastlnut wrote:without all these graphs and explenations, the only method most have is to try different cables or phono stages.
for us theoreticians, it is always nice to read a new study.


It is your loss if you use a cartridge incorrectly.
You may be missing something, whatever cartridge it is and how much does it cost.
Changing cables and phono preamps without first understanding how things work will get you nowhere.
To take the maximum of your system, you must get to work and do some things for yourself. If you expect that you can buy everything ready and done, you are wrong.
What's the point of spending a whole lotta money on a phono stage and then use an incorrect loading for your cartridge?
What's the point if the phono stage doesn't have the loading options that you need? You have to change it yourself, as much as it costs you to remove the four screws on the enclosure.
If you spend some time setting up an arm on a turntable and aligning a cartridge with protractors, you will also find the time to set up the ideal loading on your cartridge. Because it's needed.
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Postby bastlnut » 08 Aug 2006 11:36

hallo,

what you say is true.
i understand it because i work with these paramiters.
there are many who read these forums who are not so technically visiert.
i am posting my questions to make it easier for others to understand.

you are also forgetting that everyone is capable of trying out different cables and phono stages and either returning what doesn't work, or selling it again and trying something else.

to make a cartridge sound as good as possible, one must not be a techie....a mathematical geek.
it is important to understand that there are always ways to change things in the hifi set up so it sounds better.
sometimes it isn't even cartridge loading. whether loading with help of different cables, or resistors/capacitors.
dare i mention that even a cinch plug can make a difference in the sound.
it can be an imbalance somewhere else in the chain.

the graphs are very helpful to visualize what you are saying.
the correction method is just as important, and within everyones means for little or lots of money. it is there choice.

regards,
bastlnut
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Postby carlosfm » 08 Aug 2006 12:03

bastlnut wrote:...to make a cartridge sound as good as possible, one must not be a techie....a mathematical geek.
it is important to understand that there are always ways to change things in the hifi set up so it sounds better.
sometimes it isn't even cartridge loading. whether loading with help of different cables, or resistors/capacitors.
dare i mention that even a cinch plug can make a difference in the sound.
it can be an imbalance somewhere else in the chain.

the graphs are very helpful to visualize what you are saying.
the correction method is just as important, and within everyones means for little or lots of money. it is there choice.

regards,
bastlnut


Hi Bastlenut,

I understand what you are saying.
And I'm not a mathematical geek. :D
The software makes the calcs.
The graphs just help to understand how it works, and what's happening.
Trying to simplify things, I've posted these rules of thumb, some posts ago:

carlosfm wrote:- Inductance is your enemy
- Capacitance should be as low as possible
- If the cartridge sounds very explicit, agressive in the treble, it needs a lower value shunt impedance.
- If the cartridge sounds too smooth and shut in, with lack of high treble, it needs a higher value shunt impedance.

Leave capacitance alone, low, the cabling is enough, and just change the resistors.


I hope this helps someone, even if tuning by ear, to understand what's needed, and what to do.
BTW there's no golden-plated high purity silver cable that is going to help you, if that cable has 1.5 meter length.
That alone gives you much more than 200pF capacitance.
You would get much better results by placing the phono pre near the turntable (I have mine on the next shelve, on my rack), instead of making a weak and sensitive signal to travel a long way.
You can have a longer cable at the output of the phono pre, as that is line level.
Why would you use a 70cm interconnect on your CD player and a 1.5 meter cable on the arm of the turntable? I see things like these and I get scared.
The world is upside down... 8)
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Postby Guest » 08 Aug 2006 13:56

Hi,

just to add my 2 cents worth ..........

Cfm's posting describes what is happening in electrical terms.

There is also the not inconsiderable matter of the tip mass / vinyl resonance.

How the physical response combines with the electrical response
determines the overall frequency response and it is this that matters.

Ortofon used to supply stereo 200pF capacitors that slid between their
cartridges pins because some users did not have enough capacitance.
Around 400pF used to be needed to give an overall flat response.
Too low and lower treble dipped and the top end became peaky.

Pity reviews don't measure cartridges anymore, much better than waffle.

Whilst all Cfm's adjustments are viable, it is also viable to adjust capacitance.

And I completely agree that swapping cables and phono stages in the
blind hope that something will work better (and if it does claiming this
is because it is "better") is the sort of thing a peddling charlatan does.

:)/sreten.
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Postby bauzace50 » 08 Aug 2006 14:20

carlosfilipe,
One important detail I have missed (for too many years!): is the resistance loading in shunt, or parallel?! Please tell.
Thanks for the opportunity.
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Postby bastlnut » 08 Aug 2006 14:21

hallo,

there are benefits using cables to correct electrical loads over resistors or capacitors.
electronics can induce echoing and ringing to the sound, not to mention the vibration and resonance problems of capacitors, especially in the headshell.
electronic currents in circuitry can also do more harm than good in some cases.

so yes, it is not so easy to do what one wants sometimes.

besides, now that many hifi stores have gone out of business, there is no longer anyone to help with these problems.
my customers are very happy to have me help with these problems.

if you are trying to do this on your own, there is no better way to find out what works and what doesn't than just trying things.
anyone will soon get the idea of which cable, arm, rca connector, etc..., changes happenings, and in which direction.
sometimes trying things blind is the only way, for lack of knowing better.
make a mistake once, ok.
make it again, and wo be unto you.

regards,
bastlnut
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Postby carlosfm » 08 Aug 2006 14:25

sreten wrote:Ortofon used to supply stereo 200pF capacitors that slid between their cartridges pins because some users did not have enough capacitance.
Around 400pF used to be needed to give an overall flat response.
Too low and lower treble dipped and the top end became peaky.


In some cases it is viable, or let's say desirable.
But those are the rare cases when the response of the cartridge/stylus combination is not neutral, it has an intrinsic dip in response on the audio band.
Capacitance can be used to compensate that.
Let me give you a cheaper example.
I have an AT110E, which I don't use.
Unfortunately I cant't find any references to the inductance of this cartridge, along with other important parameters.
Resistance is easy to measure, though.
Anyway, listening to it and adjusting the loading by ear, the sound is always smooth, sleep inducing. It has good dynamics, though.
No top end to talk about, and even the midband is recessed.
At 75K input impedance on the pre, the treble gained new life.
But the midband maintained that recessed nature.
I know I could easily compensate for this at a flip of a switch (in my case), bringing in the 100pF cap on my phono pre (for a total of ~200pF capacitance).
That would probably bring a new life to the midband and lower treble, but then the high frequencies would be rolled off sooner.
Truth is, with that cheap stylus there's no miracles, and not much one can do to put it singin' properly.

Btw about that Ortofon, I think it is rare that one would need those 200pF caps. And they also add weight to the cartridge.
Most commercial MM preamps have a 220pF cap (and some even more) inside, across the RCA inputs, as a "standard" value, along with 47K impedance.
It is easy to get to the recommended (by Ortofon) 400pF capacitance, if you count with cable capacitance, specially if it's a 1 meter cable.
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Postby carlosfm » 08 Aug 2006 14:39

bauzace50 wrote:carlosfilipe,
One important detail I have missed (for too many years!): is the resistance loading in shunt, or parallel?! Please tell.
Thanks for the opportunity.
bauzace50


By shunt resistance I mean parallel resistance. It's the same thing.
"Shunt" means it goes from signal to ground (shunts).
What the cartridge "sees" is the resistor across the RCA inputs of the phono preamp, and also the cable + capacitor (if any) across those same RCA inputs.
A cable always has a capacitance, which in practice is another capacitor in parallel with the cartridge.
When you have two caps in parallel, you sum the value of the two and you have the total capacitance.
The value of cable capacitance is not negligible, one can't just ignore it.
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Postby bauzace50 » 08 Aug 2006 14:52

Carlos Filipe,
I got lost with the Resistance (sorry). The Resistance spec. is for Shunt (parallel), or Series? Please reiterate. (I am previously well informed as to the capacitance)Thanks.
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Postby carlosfm » 08 Aug 2006 15:24

bauzace50 wrote:Carlos Filipe,
I got lost with the Resistance (sorry). The Resistance spec. is for Shunt (parallel), or Series? Please reiterate. (I am previously well informed as to the capacitance)Thanks.
bauzace50


The resistance spec is the total resistance of the winding across the coil.
It appears on the outputs of the cartridge as parallel (you measure from one channel's terminal to that same channel ground pin), but in fact it can be considered the series output resistance of the cartridge.

I hope I'm not confusing you more...
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Postby bauzace50 » 08 Aug 2006 18:20

Hello all,
Quite apart from the theme, notice how all Engine participants contribute towards the good of vinyl addicts, with no regard to background motivations (sellers, manufacturers, hobbyists)! Great. Of course, faint colorations cannot be eliminated once in a while...understandable.
Great contributions to the Forum!
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Postby audioorigami » 08 Aug 2006 22:26

hi carlosfm

weldone on your hard work

i like the idea of graph testing a cartridge :D ...esp if you can match a tone arm with the idea of lookin what the whole package contritute to the final graphs ...im sure it could help many (your graphs look great for detectin cart loading probs,...(but without the graphs peeps cant benifit on there own equipment)

please tell us what PC software package you are using and any speacial sound card or extra etc is needed to produce a graph :lol:

best wishes for now
j7
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Postby carlosfm » 09 Aug 2006 00:52

Hi,

The software is an electronics simulation package named B2 Spice Workshop, which can be downloaded for free (the Lite version).
Here:
http://www.beigebag.com/demos.htm#v5

It is not a measurement tool, it's a simulation tool, which helps you predict the results that you will have on the final (electronics) circuit.

If you don't know how to work with a software like this, at least keep in mind what I said in this thread, the basic directions are here, and they can help you taking decisions, even if tuning by ear.
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