cartridge capacitance matching

[cyto]

I was wondering how closely the recommended capacitance load of the cartridge should match what is really there.

I am using an AT120e/t recommended capacitance load 100-200pf.

My Hagerman Cornet 2 is 40pf, my tonearm and cables add 35pf (measured). So I have a total capacitance of 75pf.

Is this too low? I could add capacitance but really wonder if I need to.

Opinions?

 

[boreas]

Is this based on actual measurements that you've made? Have you accounted for the capacitance of the cables from the TT to the preamp and from the preamp to the amp?

John

 

[cyto]

Have you accounted for the capacitance of the cables from the TT to the preamp and from the preamp to the amp?

John

As I said I measured the capacitance of the tonearm and cable going to the phono stage input and it was 35pf.

If the preamp input is 40pf why would I need capacitance of the output ?

 

[boreas]

As I said I measured the capacitance of the tonearm and cable going to the phono stage input and it was 35pf.

If the preamp input is 40pf why would I need capacitance of the output ?

Actually, you only mentioned a number. You never said that you had made the measurement or where it came from.

I think you need to measure the capacitance of everything in the signal path all the way to the amp.

[EDIT] Actually, I'm probably wrong since the signal leaving the pre is essentially line level.

Also, it strikes me that total capacitance of the turntable plus cables, at 35pF, is exceedingly low. Good quality low capacitance cables are a bit under 20pF/ft. So we're talking about an interconnect length of around 2 ft. max and we still haven't accounted for the tonearm wires.

John

 

[cyto]

This is from my original post:

My Hagerman Cornet 2 is 40pf, my tonearm and cables add 35pf (measured). So I have a total capacitance of 75pf.

I thought the word (measured) next to 35pf would suffice to indicate I measured it, my apologies.

My understanding of cartridge loading is that the tonearm, cables and phonostage input capacitance add to create the total capacitance that one should match to the cartridge.

My cables are Emotive X series at 56pf/M, I am using 1/2 M, so my measurement fits when adding the tonearm. I left the cables connected to the TT when I measured to get a more accurate reading.

I am not concerned that I am adding the capacitance properly (I am pretty sure I am correct on that) but wondering if my total of 75pf is close enough for a cart that wants 100 to 200pf.

 

[gusten]

Does it sound OK in the treble, is it how You like it to be. You´re the one who can tell. You can also do a frequency plot.
gusten

 

[cyto]

Does it sound OK in the treble, is it how You like it to be. You´re the one who can tell. You can also do a frequency plot.
gusten

It sounds good, not too bright and I am using Klipsch Heresy IIs. As with most people here I always wonder, will it sound better if I .....

 

[seminole54]

You are fine, leave it alone.

 

[Phantom]

75pf per channel, total of 150 pf right?

 

[crossram]

Does it sound OK in the treble, is it how You like it to be. You´re the one who can tell. You can also do a frequency plot.
gusten

Exactly.

 

[nailer]

It's been my experience that AT moving magnets are not all that sensitive to the capacitance load they see. In this case let your ears be your guide. It might be fun to add 75pf per channel and hear what happens.

 

[thinker10]

Mostly vintage cartridge needs more capacitance than stock

Stock can be from about 20 to 100 pf internal

Cable from about 90 to 200 pf at 3 to 4 feet long

So about 300 pf worst case

Just about right

50 pf difference is going to be hard to hear


Some vintage cart need an additional 200 to 300 pf


Don't worry to much about it


Or get a Grado ....


I would look an phono overload which I think is quite way to low on on lot of phono preamp for the standard 40 dB gain

 

[skriefal]

thinker, you appear to be forgetting the input capacitance of the phono stage. If you have 100 pF in the tonearm wiring, plus 200 pF in the interconnect, and then another 220 pF (a common number) input capacitance in the phono stage -- that's 520 pF total. Even most vintage cartridges don't recommend a capacitance load that high.

 

[gusten]

It sounds good, not too bright and I am using Klipsch Heresy IIs. As with most people here I always wonder, will it sound better if I .....

I use 100pF total with ATs. If I want to adjust the treble a little I adjust it by changing the resistance load.
My guess is if You add 75pF it might be difficult to hear, but I´m not sure, it could be heard as a very slight increase of the highest treble, maybe.
gusten

 

[oldvinyldude]

It sounds good, not too bright and I am using Klipsch Heresy IIs. As with most people here I always wonder, will it sound better if I .....

As 'good' sound is highly subjective, I would not fret about it. Get some cheaper interconnects which measure higher capaticance, and swap them in/out, and then decide. A ten dollar experiment.

 

[Wirehead]

Actually, don't bother with capacitance at all. Get the lowest possible capacitance so the resonant frequency (your cartridge + cables creates an LC-tank) is out of the audio-range. After that, get the flattest response by changing out the loading resistor. It's a bit fussier though, and involves soldering on most preamps. However it's the best way to do it. Seeing that you clearly know the actual values of your cables etc, that's the cleanest way to do it. You can calculate the ideal load resistor at http://www.hagtech.com/loading.html

 

[cyto]

Actually, don't bother with capacitance at all. Get the lowest possible capacitance so the resonant frequency (your cartridge + cables creates an LC-tank) is out of the audio-range. After that, get the flattest response by changing out the loading resistor. It's a bit fussier though, and involves soldering on most preamps. However it's the best way to do it. Seeing that you clearly know the actual values of your cables etc, that's the cleanest way to do it. You can calculate the ideal load resistor at http://www.hagtech.com/loading.html

Thanks for the link Wirehead, did the calculation and the optimal load resistance came to 80.8k, I may try swapping resistors the next time I have the Cornet 2 apart just to see what happens :scratch2:

 

[Wirehead]

I can highly recommend it, as in my case, it was really helpful. The inductance of my cart is pretty high, so with a non-optimised system, you can hear that resonant frequency (sounded a bit like sibilance, distortion,.. it was at about 13kHz) Getting capacitance down and changing the load resistance (100k here) brought that frequency out of the audio band and presto, what I thought was bad tracking at first, is now completely gone

 

[gusten]

Of course the mechanical resonance is not part of the electrical one, so the actual values needed for a reasonably flat response can differ rather much from the calculated ones. Cannot say I have had any help from these calculations.
One can of course try these calculated values, but mostly IME they don´t fit, as I said, the mechanical response is difficult to predict.
gusten

 

[dlaloum]

To get a flat frequency response, you need to balance the natural resonance of the cantilever (depending on design and materials anywhere from 10kHz to 75kHz - comes up as a bell curve of amplitude boost extending 1 octave either side with a peak of around 6db to 12db depending on the damping in the suspension of the cantilever), with the electrical resonance generated by the combination of inductance, resistance and capacitance.

If you have a really really really good stylus with a super light cantilever (like on the Technics EPC100mk4 as an example) - the resonance out at 75kHz, means that the bell curve finishes at around 35kHz - so you want to keep things as neutral and flat as possible - low inductance, and low capacitance is the way to go.... avoid any resonance, and minimise high frequency drop off.

If on the other hand you have a standard aluminium cantilever, with a resonance somewhere between 10kHz and 16kHz -then you need to carefully balance the parameters to reduce the mechanical resonance while keeping as much of the highs as possible - usual result if you manage to get it flat to 15kHz is a dramatic dropoff after that.

Another thing is that most (almost ALL !) cantilevers have losses in the upper midrange / lower high end (probably caused by flexing of the cantilever - appears as increase in THD) - depending on design this can be balanced out by selecting R/C/Z values that have a slight boost in that zone (electrical resonance!) - followed by a steep drop (to balance out the cantilever mechanical resonance)

If you think this is a tricky balancing act - you are spot on - and well nigh impossible to get right without measurement !

Varying the C or Z will shift the "knee" of the electrical response curve either up or down the frequency spectrum, raising R will make the knee more pronounced and boost the amplitude at that knee frequency by generating a resonance at that point.

Calculators like the hagerman only provide information on the electrical resonance - they don't tell you about the mechanical resonance.

Only way to work out the mechanical resonance is to measure it - preferably with a very low C & Z ( to keep electrical resonance out of the picture - even if in operation you will be running with higher C & Z to balance things out) - that way you keep things electrically "flat" and expose the mechanical behaviour of the cantilever.

Then you calculate what C/Z/R will be required to balance out the measured mechanical resonance - and that will get you on the way to an objectively improved configuration.

Through the 60's, 70's and early 80's the holy grail was flat frequency response.

Around the time CD came out, things went very strange - Ortofon did a series of listening tests with "Golden eared" experts, and concluded that audiophiles preferred a rising top end - all their designs after that had that type of voicing.
Shure on the other hand concluded that audiophiles preferred a drooping top end and released their new series of cartridges (the "x" versions V15VxMR and M97xE) with an accordingly droopy top end.

I think around this same period (and presumably associated to it) was the blooming of the subjectivist school of audiophiles - adjust it till you like it, if you like it then it must be perfect....

To put it really simply - getting flat frequency response from such an imperfect medium as vinyl by using a vibrating needle on a mechanical cantilever attached to a magnetic generator is an incredible feat of advanced engineering.... and very very few setups will every achieve it.

The best setups get close though! and can sound wonderful. They will also sound different with every differing recording played - whereas setups that have frequency anomalies will impose those colourations on every recording - giving them an artificial similarity that they should not have. (but that the listener may enjoy....)

just my 2 or 3c ....

bye for now

David