What loading capacitance and impedance do to the sound?

the thin end of the wedge
vanakaru
senior member
senior member
Posts: 554
Joined: 24 Mar 2015 09:05

What loading capacitance and impedance do to the sound?

Post by vanakaru » 03 Oct 2019 09:15

Often I read that changing these params affect how the cartridge sounds. Also some carts have recommendation for cap loading. Usually the impedance is 47K and capacitance 100, but I have heard recommendation to rise it for some carts.
I have Phono pre with possibility to tweak these things. What to expect to hear if I go higher/lower. Or there is no general characteristic for any cart used(MM carts for now)?
As for example what happens if I use Shure M75 and go from 47K to 59K and 0pF to 400pF(my cable is about 100)?

wojtekf
member
member
Poland
Posts: 81
Joined: 19 Oct 2018 10:02

Re: What loading capacitance and impedance do to the sound?

Post by wojtekf » 03 Oct 2019 10:25

http://www.hagtech.com/loading.html
Mandatory reading :)

You have to know the inductance of your cartridge (seems to be 720mH for Shure M75) to calculate the resonant frequency.

dagfinn
member
member
Norway
Posts: 213
Joined: 09 Jun 2019 00:29

Re: What loading capacitance and impedance do to the sound?

Post by dagfinn » 03 Oct 2019 11:11

wojtekf wrote:
03 Oct 2019 10:25
http://www.hagtech.com/loading.html
Mandatory reading :)

You have to know the inductance of your cartridge (seems to be 720mH for Shure M75) to calculate the resonant frequency.
Very useful reading, thank you!

billshurv
long player
long player
Posts: 2452
Joined: 16 Oct 2014 15:38

Re: What loading capacitance and impedance do to the sound?

Post by billshurv » 03 Oct 2019 12:14

The Hagtech article is a good start, but there are two issues. The first is that the generator is a lot more complex than a simple inductor with resistor in series, and manufacturer figures are often not that accurate. It needs some collaboration to come up with a 'better way'.

wojtekf
member
member
Poland
Posts: 81
Joined: 19 Oct 2018 10:02

Re: What loading capacitance and impedance do to the sound?

Post by wojtekf » 03 Oct 2019 12:43

And the article states it in the very first paragraph:
Obviously, real-life conditions are far more complex

billshurv
long player
long player
Posts: 2452
Joined: 16 Oct 2014 15:38

Re: What loading capacitance and impedance do to the sound?

Post by billshurv » 03 Oct 2019 13:06

yes quite a bit more. Much still to be explored.
Attachments
AT150MLX-model.jpg
(33.7 KiB) Downloaded 213 times

vanakaru
senior member
senior member
Posts: 554
Joined: 24 Mar 2015 09:05

Re: What loading capacitance and impedance do to the sound?

Post by vanakaru » 03 Oct 2019 15:46

So why I need to take resonance frequency into account? Seems like I am pretty stupid with these things. If I get RF calculated 13.5k what does it mean?

billshurv
long player
long player
Posts: 2452
Joined: 16 Oct 2014 15:38

Re: What loading capacitance and impedance do to the sound?

Post by billshurv » 03 Oct 2019 16:05

as a number it means nothing. You have to see the effect on the frequency response. as per the graph at the top of their page.

tep392
member
member
United States of America
Posts: 205
Joined: 19 Jun 2018 14:57

Re: What loading capacitance and impedance do to the sound?

Post by tep392 » 03 Oct 2019 17:42

Start with the cartridge manufacturers recommendation and tweak to your taste from there. Carts with high inductance will be more sensitive to excessive capacitance pushing the resonant peak into the audible range. If your are going to go thru the calculations, be sure to include the capacitance of the tonearm wire, audio cables and pre-amp. But ultimately it comes down to how does it sound to you.

As an example, I had a noticable peak followed by a large dropoff around 20khz when I used a cheap generic audio cable with my ADC QLM36mkIII cartridge. The receiver I was using at the time had fairly high input capacitance of 220pf. My total capacitance was about 600pf with tonearm wire and cheap audio cable. In listening test, this made the music sound bright because the peak was in the 11khz range. Switching to low capacitance cable flattened the frequency response considerably.

In the end, it's a matter of personal preference. Play around with the setting and decide what you like best.

dagfinn
member
member
Norway
Posts: 213
Joined: 09 Jun 2019 00:29

Re: What loading capacitance and impedance do to the sound?

Post by dagfinn » 03 Oct 2019 21:41

billshurv wrote:
03 Oct 2019 13:06
yes quite a bit more. Much still to be explored.
After reading the Cartridge Loading page, - along with the plots you sent I start to see the issue. It makes me more curious about all the combinations of induction and impedance used in AT VM series, and how it affects sound. The AT2x and TK9 becomes very special as well. Load Resistor Tuning sounds like an interesting idea...?

billshurv
long player
long player
Posts: 2452
Joined: 16 Oct 2014 15:38

Re: What loading capacitance and impedance do to the sound?

Post by billshurv » 03 Oct 2019 22:03

I personally think that there are two areas to explore to get the very best out of a lot of MMs. One is that 47k is rarely the best resistive loading. Sometimes higher, sometimes lower. The second is that some cartridges need a much lower capacitance to work their best. So low that you really need to put the phono stage close to, or in the turntable.

BUT: this is still work in progress and so a lot to be done to actually prove this conjecture. And even if it proves to be right there are not that many maniacs willing to build custom phono stages just to test this :).

vanakaru
senior member
senior member
Posts: 554
Joined: 24 Mar 2015 09:05

Re: What loading capacitance and impedance do to the sound?

Post by vanakaru » 04 Oct 2019 07:30

My question was triggered by surprising experience with an old soviet era phono stage I fixed up finally.
I have been happy with my somewhat modded regular phono derived from Chinese A310. I have compared it with various external and integrated phono stages and I am pretty sure it sounds great.
Now this Latvian thing made in 1980 sounds surprisingly lush and fun with Shure M75 I have on right now. Maybe it is due to different RIAA correction or because it has 59K loading resistors. Or the IC K548UN1 is that sweet.
So I started to wonder as long my regular pre has 5 settings to choose from for cap and res what I should expect to hear if I move either direction - increase or lower given values.

dagfinn
member
member
Norway
Posts: 213
Joined: 09 Jun 2019 00:29

Re: What loading capacitance and impedance do to the sound?

Post by dagfinn » 04 Oct 2019 08:51

I'm no expert, but simply put: more pF on phono stage means more treble. My Audio-Technica I load minimal 47pF (recommended 100-200), while my Ortofon VMS needs 200-300pF extra to sound right. Ortofon recommends 400pF per channel. Try the different settings and listen!

billshurv
long player
long player
Posts: 2452
Joined: 16 Oct 2014 15:38

Re: What loading capacitance and impedance do to the sound?

Post by billshurv » 04 Oct 2019 11:24

To a point. Go too high and you get a big peak at 10kHz then rolls off like a stone. Purely personally I like to get things as flat as possible and adjust treble with a simple shelving filter. But that's just me :)

dagfinn
member
member
Norway
Posts: 213
Joined: 09 Jun 2019 00:29

Re: What loading capacitance and impedance do to the sound?

Post by dagfinn » 04 Oct 2019 11:58

Yes, it can go very wrong as well. I wonder what the FR of VMS looks like without 300pf? I have no treble regulator, (unless I go digital), so getting it as right as possible at basic level is important.

Post Reply