Cartridge capacitance load? I have some questions!

[Kuja]

Hi,

I recently got a Shure V15 VxMR.

You can read about my initial dissapointment with it here:

...and here:

Lots of folks on various forums suggested that the capacitance might be the culprit.

Shure recommends capacitance load of 250pF.

My phono preamp's (Graham Slee, GramAmp 2 SE) capacitance is 150 pF.

My SME 3009 S2/imp is rewired with 40 cm of Van den Hul MCS - 150 M cable.
http://www.vandenhul.com/cable/mcs-150m.htm
capacitance is not stated

Cable from tone arm to preamp is Van den Hul D - 502 HYBRID
http://www.vandenhul.com/cable/d-502-h.htm
capacitance is 75pF per 1 meter. I have 1.2 meters cable lenght, so it should be 90pF

Together with preamp's 150pF it makes it 240pF, leaving a reserve of 10pF for tone arm internal wiring, which is unknown but I guess it is higher than that.

Is going a little bit above 250pF, a huge, make or break difference? Can it be the cause of my problem with the Shure?

I could cut in half my Van den Hul, thus lowering it's capacitance - lot cheaper than losing money on selling my V15

But I wouldn't like to ruin a perfectly good cable, just to discover that nothing had changed...

What would happen if I intentionaly go significantly lower than recommended 250 pF (cutting the Van den Hul to only 30 - 40 cm)?

Would I get some aditional boost in the treble?

Some folks said maybe, but some suggested different:
http://www.audioasylum.com/audio/vinyl/messages/432239.html

What do you think?

Thanks,

Aleksandar

 

[Kuja]

I forgot something.

I'm embarassed to admit, but inside my turntable I tied a simple loose knot on a VdH D-502 cable going from tone arm base to my phono preamp.

I did it to prevent my four year old son from yanking it out and breaking something, since it is directly soldered to the pins on the arm's base.

I didn't hear any difference with my previous Ortofon MC1 turbo, but this might be due to MCs not being so fussy about cable capacitance (so I heard ).

Can this be the source of my problem (I could try utying it, but it's 2:36 AM here and I would wake up everybody by playing some loud music )?

Any thoughts?

 

[rayfutrell]

Look at this thread.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=59375

For the Shure V15V I suggest a maximum total capacity of 120 pF.
This gives a resonant Q of about 0.7.
Regards,
Ray

 

[Kuja]

Look at this thread.
http://www.diyaudio.com/forums/show...&threadid=59375

For the Shure V15V I suggest a maximum total capacity of 120 pF.
This gives a resonant Q of about 0.7.
Regards,
Ray

Ray,

Thanks fr the link!

But, since I'm kind of a newbie (but I'm willing to learn ), I only got a mild brain tumor from reading this thread .
I have no background knowledge in electronics and I'm only begining to grasp the concepts.

Please bear with me - I would really like to know what are the sonic consequences of higher vs. lower capacitance in relation to 250pF that is recommended by Shure?

Does higher capacitance cause rolled off treble, something I'm experiencing right now?
Will much lower capacitance bring the treble back?

I can't go as low as 120pF, since my phono preamp is 150pF.

What do I do?

Make the cable between the arm and the preamp as short as possible and live with the fact that the things are not perfect and that the Q (whatever it is) will never be 0.7 ?

Thanks again,

Aleksandar

 

[rayfutrell]

Aleksandar,
The cut off frequency is determined by the Q and the resonant frequency of the cartridge inductance and total shunt capacitance. The higher the capacity, the higher the Q and the lower the resonant frequency. This can cause the high frequency roll off to start at a lower frequency.

I had the same problem with my V15V. Shure recommended 250 pF terminating capacity so I bought a phono cable with an advertised 250 pF of capacity. The sound was terrible. My preamp had 100 pF capacitors shunting the preamp inputs to ground to prevent RFI as well as an elaborate switch network with lots of shielded wire. I estimated the preamp input capacity at about 200 pF. If you include the tonearm wiring the total capacity was probably about 500 pF. I fixed the problem by buying another preamp with an advertised input capacity of 20 pF and used very short lengths of low capacity phono cable for the connections.

Use as short a length of low capacity phono cable as possible.
Regards,
Ray

 

[Kuja]

Thanks!

 

[dnsey]

Before spending much money and time, try the effect of adding some capacitance.
It's counter-intuitive, but cartridges often behave strangely in this respect!

 

[Kuja]

I tried this:

Since my CyrusIII amp has a phono preamp on its own, I plugged the V15 in.

Cyrus' phono input is rated at 50pF, opposed to Gram Amp's 150pF.

With 100pF shaved off, I expected a huge difference.

Well, nothing spectacular happened. There was some difference, but I guess that it was only due to different preamps.

Real acoustic memory lasts only 15 seconds or so and I was fiddling for too long with the cables, ground lead, etc. to be able to do something approaching A/B comparison. But if some huge positive difference was present, I would notice it for sure !

Hmmm... should I go further, drasticaly shortening the IC, or I should try adding some capacitance instead?

How do I add capacitance?

 

[audiobomber]

Hmmm... should I go further, drasticaly shortening the IC, or I should try adding some capacitance instead?

How do I add capacitance?

You can add capacitance by soldering a small (picofarads) cap across the headshell leads or across the RCA's (+ to -) or into the phono stage. Or change the tonearm lead or phono stage to one with higher capacitance.

You are now very close to the manufacturer's spec. Some people may prefer some other value of capacitance, but how wrong could the Shure spec be? IMHO you're barking up the wrong tree. IOW, I don't think capacitance is your problem. Maybe you just don't like the sound of the V15, not everyone does. The Ortofon Turbo is a pretty lively cartridge. Some would say excessively bright. The Shure is on the other end of things sonically. Adding capacitance will make the sound duller, not more lively.

The most common cause for the symptoms you describe (lack of HF life?) is VTA, but you've already tried that, right? Nevertheless, I recommend you try leveling the cartridge and then move the pivot up *very* slightly up from level. I don't know what else it could be, but I think you're wasting your time with capacitance.

Good luck. Let us know what you come up with.