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Low-output MM Cartridge?

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Low-output MM Cartridge?

Postby MikeyB456 » 11 Aug 2017 09:36

Recent playing around with my AT95e has revealed to me the evils of high inductance in MM cartridges. I've found that it definitely improves in top-end refinement as you reduce the capacitance it 'sees' - a direct result of the 400mH inductance it has, I think. But, certainly in my set-up, getting down to the 100pf total capacitance loading that I think would be ideal is impossible.

But it occurs to me that the reason it has this high inductance in the first place is because of the 'need' to generate several mV of output, as is the MM cartridge norm. So I've been pondering why no cartridge manufacturer has produced a low-output MM cartridge. It would have the same sort of loading and amplification requirements as MC cartridges, and would presumably have the same sonic virtues too? There's surely no intrinsic difference between waggling a coil at a magnet or waggling a magnet at a coil?

It would have the advantage of relative load insensitivity, but could also retain the advantage of having a user-removable/replaceable stylus. And it would presumably be easier, and therefore cheaper, to manufacture than MC designs.
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Re: Low-output MM Cartridge?

Postby markcass » 11 Aug 2017 09:53

Hi

Not strictly MM, but Grado do make several low-output models in their upmarket wood-bodied range; their high-output models are not very sensitive to capacitance anyway, I believe. The wood Grados have fixed styli, BTW.

Pickering offered some low-output models towards the top of their range. I'm not sure whether there were Stanton equivalents. They would only be available second-hand now.

HTH

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Re: Low-output MM Cartridge?

Postby DeepEnd » 11 Aug 2017 09:59

There have been lower output MM/MI units but they have the same issues of noise performance that low output MC's do.

There are also lower inductance MM/MI (e.g. Grado units) were the capacitive loading has much less effect that avoid the noise issues from very low outputs. There are also units designed to work into higher capacitance and high output MC's as well. These are all more popular as they work into standard MM stages.

Many of the low inductance bodied cartridges are well regarded (Grace F9 anyone.) and are still sought out second hand as some go back to the era of CD-4 records were extended frequency responses were needed and lower inductances were needed.

PS 400mH is not very high inductance most are nearer 500-550mH. Mine is 550mH but designed to work into 200-400pF
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Re: Low-output MM Cartridge?

Postby MikeyB456 » 11 Aug 2017 10:19

My old Ortofon was similarly designed to work with 400pf plus. But I suspect that these designs are offsetting their electrical and mechanical resonances, which feels like a dubious approach somehow.

Grados are interesting - but I've never heard one I actually liked very much. Each to his own, I guess.

And yes, it's apparently OK to make high o/p MC's, but not vice-versa for some reason!
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Re: Low-output MM Cartridge?

Postby billshurv » 11 Aug 2017 10:40

High inductance is not necessarily the evil. Phono designers who don't actually think about the problem are possibly more evil!
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Re: Low-output MM Cartridge?

Postby Delta667 » 11 Aug 2017 10:44

MikeyB456 wrote:Recent playing around with my AT95e has revealed to me the evils of high inductance in MM cartridges. I've found that it definitely improves in top-end refinement as you reduce the capacitance it 'sees' - a direct result of the 400mH inductance it has, I think. But, certainly in my set-up, getting down to the 100pf total capacitance loading that I think would be ideal is impossible.

But it occurs to me that the reason it has this high inductance in the first place is because of the 'need' to generate several mV of output, as is the MM cartridge norm. So I've been pondering why no cartridge manufacturer has produced a low-output MM cartridge. It would have the same sort of loading and amplification requirements as MC cartridges, and would presumably have the same sonic virtues too? There's surely no intrinsic difference between waggling a coil at a magnet or waggling a magnet at a coil?

It would have the advantage of relative load insensitivity, but could also retain the advantage of having a user-removable/replaceable stylus. And it would presumably be easier, and therefore cheaper, to manufacture than MC designs.

Such thoughts were visited not only by you. But also inquisitive fans of vinyl from the company Technics / Panasonic. In 1979 they made a MM cartridge Technics EPC-100Cmk2 with a resistance of 30 Ohm.
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Re: Low-output MM Cartridge?

Postby DeepEnd » 11 Aug 2017 10:59

Most MM cartridges have to balance mechanical and electrical resonances to work well (you do not have much of an option really as they both exist) and even MC's sometimes need help too (have a look at the loading options on the new Rega Fono MC). The choices made and target specs are all part of the great mystery of cartridge design that we are never given enough detail to fully understand.

Soundsmith in the USA makes a whole range of low output "fixed coil" devices (MI to me and you) but again the additional cost of SUT or external phono stage makes them less popular so low volume hand built and the prices reflect that. I think most low output MI/MM now fall into the higher end products.

There are bodies that have lower impedance around from AT, Stanton/Pickering, Grace, JVC etc. that even factoring in a retip would be more cost effective than a SS unit (yes I have never managed to get a Grado to perform well in my system either there must be a trick I am missing) even though my amp does have a MC stage built in.
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Re: Low-output MM Cartridge?

Postby billshurv » 11 Aug 2017 12:22

There are a group of people looking into these mysteries. There may be a lot of old wives tales abounding :). The good news is that there are ways around most of the problems provided you can wield a soldering iron :). No reason for MM not to be as flat in response as MC.
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Re: Low-output MM Cartridge?

Postby Delta667 » 11 Aug 2017 12:48

billshurv wrote:There are a group of people looking into these mysteries. There may be a lot of old wives tales abounding :). The good news is that there are ways around most of the problems provided you can wield a soldering iron :). No reason for MM not to be as flat in response as MC.

A friend of mine, a music lover from Yoshkar-Ola, Sergei has been engaged in a MM head with a "low exhaust" for several years ))
But he categorically does not want to participate in international forums ((
This is unfortunate, because he could tell us a lot about this topic.
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Re: Low-output MM Cartridge?

Postby billshurv » 11 Aug 2017 12:58

There was good discussion on here about it a few years ago, but a lot of posts were lost. Solutions have appeared at various points since the early 60s and then forgotten again. All we are left with is old womans tales in a lot of cases, which are accepted as truth.

I have the parts in now so will start soldering my version of heresy in a MM preamp over the weekend :). I am sadly not skilled enough to mod the cartridges yet :(
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Re: Low-output MM Cartridge?

Postby MikeyB456 » 11 Aug 2017 13:46

billshurv wrote:I have the parts in now so will start soldering my version of heresy in a MM preamp over the weekend :)


I had a look at trying to remove the input shunt caps in the Project Pre, but decided that attempting surgery on such miniscule surface-mounted components was beyond me. I've settled for directly soldering the arm leads to the board, so cutting out as much intermediate wiring and connections as possible.

Interesting comments from others too. How silly of me to even imagine my thoughts were novel!

Back in the late 70's I worked in a HiFi shop (anyone remember Technosound?). Trying out carts/arms/tts was part of my day-to-day routine. I wish I'd kept the notes I made back then...
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Re: Low-output MM Cartridge?

Postby Delta667 » 11 Aug 2017 14:41

Did you happen to cooperate with the shops in Japan?
Or is this a coincidence with the relatives of Adidas and Abibas? ))
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Re: Low-output MM Cartridge?

Postby MikeyB456 » 11 Aug 2017 14:53

LOL no, no relative of ours.
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Re: Low-output MM Cartridge?

Postby billshurv » 11 Aug 2017 15:08

MikeyB456 wrote:
Interesting comments from others too. How silly of me to even imagine my thoughts were novel!



Nothing is new, but much has been forgotten :). It's sifting the wheat from the chaff that is hard. Like why are MM cartridges generally high compliance? Not as high as in the 70s, but still far higher than 90% of arms would really like it to be.
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Re: Low-output MM Cartridge?

Postby Delta667 » 11 Aug 2017 15:10

MikeyB456 wrote:LOL no, no relative of ours.

In life, different coincidences are called ))
I can say that the quality of this Techno(i)sound is very high. Probably in the 70's nebylo need to fear forgery ))
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