Moving Coil cartridge loading

[Oldpinkman]

Moving coil cartridge loading can affect the sound at least as much, if not more, than with some Moving Magnets, but so often cartridges are plugged into a "standard" input resistance.
Just back from France, settled down to listen to the HiFi, and was nagged by a worry about the cartridge. I bought the cartridge blind from Arizona (Technics EPS 310) and whilst waiting for it to arrive, Arthur dug one out of a drawer whilst we listened to his precious Sony. I asked what he thought of it - hoping for rapture. Typical AK "nice - bit soft"

As ever, if you can decode Arthur-speak, this was maddeningly true :steam:. "Nice" means "perfect in all respects, imaging, dynamics, effortless smoothness, detail, powerful bass - except for..." and "bit soft" means "the treble rolls off a bit"

Sue was amazed by the sound - its the first moving coil she has heard and it is a stonking good one, producing almost disturbing detail - like listening to a completely new recording at times, but I was troubled by "bit soft". The roll-off was nowhere near as bad as the valve headphone amp I have posted about (and will now get back to finishing the mods on) but there was a muted sound to cymbals, and a feeling of slight muffling (really slight) to female vocals. (Actually I was pretty amazed, and this is F5 and Arcam. Just cannot imagine FX3 and Integral when I get my hands on them again)

I sent the cartridge specs to OJ who clearly knows the Pip specs, and am still waiting for the right values. So I stuck 180 ohms in as a guess based on how 100 ohms sounded.

http://i1315.photobucket.com/albums/t582/oldpinkman/DSC_0034_zps3d3f62f3.jpg (http://s1315.photobucket.com/user/oldpinkman/media/DSC_0034_zps3d3f62f3.jpg.html)

Have I mentioned before I am a good guesser? (Lousy solderer - I know. I nearly headed this thread "Govt health warning - danger of bad soldering" but I am accused of being too obscure with my thread titles :()

Anyway - whilst I know we can refine this, (I think the resistance is damn close - but maybe a puff or two of capacitance is needed to smooth off the response) it has proved the point. All the qualities of before, and now with that tttzzzing to cymbals, crispness to snare, and sheen on female vocals. I'd like to put it up head to head with AK's precious Sony now - which clearly needed a 100ohm load and so sounded "not soft" straight out of the box.

When auditioning MC cartridges - remember the load (And remember they are affected by capacitance too - not like MM's, but it affects the frequency response)

Time for some more listening :cool:

[pure sound]

What arm are you using it in? Bear in mind it was intended for the lightweight LT arm on the SL10 and originally a P mount type so tracking fairly light at 1.2g.

I have one and occasionally give it a run out. It is nice & probably is on a par with many mcs costing up to £500 or so which is remarkable given its original application.

[Oldpinkman]

It's tracking at 1.25 in the Funk F5 (effective mass probably about 10gm at 1.25gm tracking force)- but I'm really keen to try it in an FX3 (or whatever number it is by now). Plays effortlessly at that force. No easy solution to the loading issue - gonna have to be a test record and measure the response, and I think I'll wait till I can cook a good steak dinner for OJ and let him do it. I've established the principal that it is sensitive to load and 180 is nearer flat than 100ohm. And I have too much day job back-load to get distracted with setting up test gear I haven't used in 20 years and probably didn't understand properly when I was using it. Anyway I find I just cannot read the colour codes on resistors any more (I struggle to see the bloody resistor) and I take that as a hint to stick to counting beans.

Sounding good for the minute, and much better than some more than £500 MC cartridges I can think of (Koetsu rosewood and friends) and by implication from his shifty manner, better than the "virgin" Dynavector XX-2 Arthur was trying to peddle me, although I haven't heard that personally. Similar qualities to the MM U205 but with more weight, and even more detail. But like I say, in a heath-robinson hotch-potch of a system which in reality knowing the 2 individuals I am dependant on for getting what I want, won't be sorted properly before next year at the earliest.

When I get the time to sort this system properly, for the sake of my own sanity, I have to work out WTF is going on with the hum on the AV system before I do anything else. October. Maybe :)

[Reffc]

The DC resistance for that cart is specified as 30 Ohms (quite high) so rule of thumb for loading would be 10 times this value (ie 300 ohms) as a minimum but that is a rule of thumb. The problem with insufficient loading is that it can allow the cart to draw too much current which can burn out the delicate wiring, hence recommended minimum load requirements are usually stipulated by manufacturers. Whilst going over the recommended loading can't do any harm, depending on the gain cell/SUT being used, it can have a bearing on sound although with some phono gain devices, you could load to 600 Ohms or more with no discernible difference, so there's no real generalisations on how much to apply. Too much is always better than too little though. 100 Ohms seems too little imho and you're findings with 180 are what I'd expect. Worth trying a slightly higher (ie 300 Ohms) loading too.

[Oldpinkman]

Thanks for the comment Paul
I'm still enjoying the speaker cables btw.
I might try another "suck it and see" at 300 ohm, if I can read the bloody stripes on the resistors, and avoid melting the plastic on the headers when I fit them (I'm not safe really), but I am quite interested to "do it proper" if I can persuade the boy Jones to do it for me. This was his comment

"Your idea may or may not be nonsense - it all depends upon the mechanical resonance of the cartridge effective tip mass with the vinyl compliance. This may not be as much of an issue as with a moving magnet cartridge but may still have an influence. Therefore, the only way to correctly adjust the cartridge loading is by playing a test record so that the overall frequency response can be determined. You can try suck-it-and-see, but you have a lot of combinations of resistance and capacitance to work through if you try that."

As I pointed out to him, I have already established by ear that the loading affects the frequency response. Whilst obviously what it sounds like is what matters, it would be interesting to see some pretty graphs too, and see if we can get ruler-flat. One day :)

[Reffc]

Thanks for the comment Paul
I'm still enjoying the speaker cables btw.
I might try another "suck it and see" at 300 ohm, if I can read the bloody stripes on the resistors, and avoid melting the plastic on the headers when I fit them (I'm not safe really), but I am quite interested to "do it proper" if I can persuade the boy Jones to do it for me. This was his comment

"Your idea may or may not be nonsense - it all depends upon the mechanical resonance of the cartridge effective tip mass with the vinyl compliance. This may not be as much of an issue as with a moving magnet cartridge but may still have an influence. Therefore, the only way to correctly adjust the cartridge loading is by playing a test record so that the overall frequency response can be determined. You can try suck-it-and-see, but you have a lot of combinations of resistance and capacitance to work through if you try that."

As I pointed out to him, I have already established by ear that the loading affects the frequency response. Whilst obviously what it sounds like is what matters, it would be interesting to see some pretty graphs too, and see if we can get ruler-flat. One day :)

Glad you're still enjoying the speaker cable Richard :)

Your friend has a point but the resistive loading is not primarily there to damp mechanical resonance of the tip (translated to resonance at the generator); This tends only to be an issue at HF and if it is an issue its usually solved via capacitative loading which provides some electrical damping, not resistive on its own. The specified resistive loading is there to protect the cartridge wiring, not to offer mechanical damping. With some cartridges, you may be able to load to 1KOhm with no real big changes but it is very dependant upon your phono stage design and/or SUT. There is an element of suck it and see because playing a test record without being able to measure the FR wont tell you anything. Use your ears and some well recorded material that you're very familiar with would be my advice. You'll know when its right. It's difficult to add anything (ie make the sound brighter) but you can dull the sound, affect LF response and overall balance. Try playing something with plenty of well defined bass, a good dynamic range, with plenty of discernible detail to test the loading.

I wouldn't lose sleep over it, but you're usually best feeding the DC resistance of your cart (being 30 ohms) into ten times that (300 Ohms) which should also provide adequate protection against over-drawing too much current through the windings. Going 100 ohms higher is unlikely to alter the sound much but there could be a difference depending on the circuit. I wouldn't advise (in your case) dropping it too much lower, and certainly not any lower than you already have it. Hope this helps!