Question How does altering the loading on a cartridge affect the sound, (and more importantly, why)?

[Jules_S]

So I know this question has been covered (sort of) a number of times but I'm hoping bring together all the facts needed into one point of reference. I'd like to cover both the "how" and the "why", in terms that non-electronics people can understand, for all types of cartridge and the principle methods of connection, for the benefit of all our members.

I admit that there's a lot of questions here, and I'd like to avoid endless arguments back and forth so if we can keep responses to-the-point and factual rather than subjective, that would be helpful for anyone trying to get their head around the subject.

Moving Magnet Cartridges

Let's start with MM. As I understand it, for an MM cartridge the "loading" parameter that is important to consider is capacitance, and not impedance. I believe that when calculating the capacitance in the replay system it can be affected not only by any settings that the phono stage has but also by the tonearm cable itself. Of course not all phono stages, especially those built into amps, allow adjustment anyway, but presumably they will have an inherent capacitance as a result of the design.

Questions

1. What exactly is "capacitance"? From my schoolboy science days I recall it's a store of electrical energy (potential?) but I can't get my head around how that can have an effect on the sound
2. Aside from tonearm cable and phono stage, is there anything else in the equipment chain that might have a noticeable effect on capacitance?
3. Is it true that each contributing factor to capacitance is additive, i.e. when calculating the total capacitance in the chain, you just sum up the individual values?
4. Can the environment around the system have any impact on capacitance?
5. What effects can one observe from increasing capacitance, and why does it have the effect that it does? And presumably reducing it has the opposite effect?

Moving Coil Cartridges

For Moving Coil cartridges as far as I understand, it's impedance, not capacitance, that is the parameter that has an influence on the ultimate sound. Impedance may be altered by changing settings on a phono stage (where such settings are present).
An additional consideration I believe, is that using a separate Step-Up Transformer (SUT) into a phono stage's MM input (rather than an MC stage with gain), there is an additional impact on the impedance load "seen" by the cartridge, but how that would affect the way any phono stage settings are made I don't understand.

Questions

1. What is it about an MC's design that means capacitance isn't important but impedance is? Ultimately it's still a combination of magnet and coils of wire wiggling around to generate an electrical signal, just in a different arrangement, so what is it about the circuit that changes the influence of the parameters?
2. When considering impedance in the signal chain should we also take into account the contribution of the arm cable, as we do with capacitance for MM? I've never heard anyone mention it. Or is the amount insignificant (and therefore can be ignored)?
3. The specs for most MC cartridges quote an impedance (internal impedance?) - what exactly does this mean and how do you use this information when calculating what "load" to provide from the (SUT and) phono stage?
4. When using a SUT / MM phono combination I think you have to take the ratio of the transformer (primary windings : secondary windings) into account somehow. I've seen a formula for this somewhere but I can't find the thread again.
5. With a SUT / MM setup I believe it's possible for the impedance to be applied on either the primary or secondary side. What difference would that make, and is one a "better" solution than the other? How does that affect the calculations?
6. When you "load" a cartridge by adding impedance, what is actually happening electrically, and why does that have an impact on the sound?

Moving Iron / Fixed Coil Cartridges

I confess that I don't know a great deal about them other than I believe they are similar in some respects to an MM. Presumably, therefore, the parameters that can impact on the sound are the same, i.e. capacitance, is this correct? And are the effects of the same sort of magnitude, greater, lesser?

 

[Beobloke]

There’s a nice summary here, with graphs that explain what happens when you change R or C - http://www.hagtech.com/loading.html

 

[rabski]

I agree with Adam, though you've swapped capacitance and resistance around (capacitance loading changes the resonant frequency for MM and resistance does so for MC). It's an 'age thing'

With ste-up transformers, the equation refers to the square of the ratio. The effective load 'seen' on the primary widing is the load on the seconday winding divided by the square of the ratio. So if you use a 1:20 transformer glued to a standard 47k ohm input impedance MM phono stage, the cartridge you attach to the primary will get 47000 divided by (20 x 20), thus 117.5 ohms.

 

[rabski]

Oh. Loading on a step-up transformer primary or secondary technically makes no difference. In practice, however, transformers are not perfect devices, as there is capacitance between internal windings among other things. These imperfections can cause 'ringing', where the waveform passing through a transformer is affected (loosely speaking). It is often preferable to load the secondary winding to reduce this. Though it is not always the case, it is the 'guide of thumb' preference.

Also, bear in mind that loading (wherever you stick the load) will reduce the total voltage. A 'heavier' load may well damp resonant peaks better and kill any transformer ringing, but may also reduce the output so much as to make it unusable. Everything in life is a balance.

The only definite way is with a test LP, an oscilliscope, endless time and patience, and a large supply of accurate capacitors and resistors.

The alternative method is to start off with the 'lightest' load and try one or two alternatives by ear. If it sounds 'harsh' or sibilant, try loading more.

 

[Beobloke]

I agree with Adam, though you've swapped capacitance and resistance around (capacitance loading changes the resonant frequency for MM and resistance does so for MC). It's an 'age thing'

You’re being very kind but, the fact is that what I wrote was utter shite. I blame this bloody cold that’s filled my head with concrete!

I have deleted all the crap and just left the link to the website where the chap has actually got it right.

I’m going to make another Lemsip now…

 

[rabski]

If it makes you feel better, I've still got some after effects of the flu vax. I spent (wasted) a couple of hours last night with some paper and valve plate curves, and I realised afterwards that I may as well have done it all upside down, as it's all totally wrong.

 

[John (big)]

I use a one of Len Gregory's Musicmaster prototypes this is a moving iron design built in to a Grado body because it worked, everything else Len came up with progressively over 20 + years, including the Sapphire cantilever with it's tiny piece of iron and fine line stylus together with silver coils.
Moving Iron cartridges have the lowest tip mass compared to any MM, MC cartridge & can be lightening fast , whilst in the case of the Musicmaster displaying deep bass & clean un-emphasised mids & treble it does not have much of the upper shimmer of a MC.
MI'S are unaffected by capacitance though few work best at 47K. I use parallel resistance on my Croft phono stage to make 42K of which Len approved, using less himself. In the USA Grado owners use as little as 8K.
Joe Grado held the patent on MC's but chose to make MI's?

I have recently listened to a lot of cartridges as my Musicmaster will not live for ever & is sadly no longer available. I was favoring the Ortofon 2m black MM having heard a couple for me the top end seems over emphasised though comparing a £1750 MI with a £550 MM is maybe not fair this true also of the LVB250. I am now tempted by a Hana ML at £1100 a friend will put a pair of mu-metal covered SUT that he uses with his ML in to the Croft case.

These are my ramblings other ears younger & possibly older than mine may differ as mine may have too if Mrs JB does not approve of the spend as she is still working..

 

[John (big)]

If it makes you feel better, I've still got some after effects of the flu vax. I spent (wasted) a couple of hours last night with some paper and valve plate curves, and I realised afterwards that I may as well have done it all upside down, as it's all totally wrong.

A couple of weeks ago I had my Covid booster & Flu jab in the same arm the following day. I felt rough ie aches & sniffles for a week.