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Accession MM Capacitance/Loading Settings

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Graham Slee View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2023 at 12:00am
Difficult to write about cartridge loading without getting technical, but the MM cartridge has lots of windings of wire which make it very inductive and the letter for inductance is L.

(it's value is roughly 0.5H, or 500 milli-Henries)

The capacitive loading appears in parallel with the input so is in parallel with L.

The letter for capacitance is C.

(and what makes it worse is C is lumped: the arm wiring and cable have a capacitance of approximately 100pF, which adds to whatever the cartridge load capacitance says, so at 100pF it's really 200pF)

And if you were to do the maths of LC, you'd get a peak resonance somewhere in the treble region (say around 16kHz but normalised for the cartridge's constant velocity output is about 11kHz).

And that would sound dreadful, but the letter R comes to the rescue. R is for resistance. The value of 47k damps the LC resonance nicely. The resulting network is called an LCR, and for some reason it's also called a "tank circuit."

(by the way, the cartridge's internal resistance has such a minimal effect it can be forgotten)

So what is the result of all this?

If C is small, the high frequency response has very little in the form of a treble peak - often less than 1dB - and the high frequency losses occur at higher frequencies (say 20kHz).

If C is (comparatively) large there will be a larger treble peak - often 2 to 3 dB - and the high frequency losses will occur at a lower frequency (say 16kHz).

Young ears might immediately detect a difference in sound quality switching between settings provided the music has plenty of percussive sizzle content.

Older ears will not be able to detect much immediate difference, but might be able to judge between two settings after many weeks of listening to the subtleties of well loved albums.

The amplifier however, might perform better one way or the other depending on how it behaves with high frequency content.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ctalcroft Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2023 at 12:18am
Well, thank you, but that tells me what? 

I was wondering whether changing the switch positions on the back of the Accession MM might have a positive effect on the LVB, which, as I say, seems to suppress the lower end of the frequency spectrum relative to the 2M Black. While I like the greater apparent higher-end clarity of the LVB, it seems to come at the expense of the low end. I'm 63 but have fairly good hearing compared with a lot of men my age, but I doubt I can hear beyond about 12kHz. Thanks
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2023 at 4:17am
Sorry if my explanation caused any frustration.

There is a high/low balance which is difficult for any designer to get right, and is due to a lot more things than Mr Marketing Man and Mr High and Mighty Reviewer would comprehend if they lived ten lifetimes.

Unfortunately they offer Alice In Wonderland explanations to get you hooked, and they never say how things work - but at least I am trying to help you!

I quote myself: "The amplifier however, might perform better one way or the other depending on how it behaves with high frequency content."

The Ortofon blurb, and I would have expected better from Leif, says it's a bright cartridge.

"The use of an extremely stiff and lightweight Boron cantilever adds remarkable transparency, speed and responsiveness."

I am trying to point out the known variables that are known to a real designer.

However, as the internet is stuffed full of garbage about everything from what makes a cartridge sound "good" to what makes an amplifier sound "good", with swooning about toroidal transformers in between, then I have a hard job being heard.

So if I come across as being too technical as in "Well, thank you, but that tells me what?" then I'll be a man about it and apologise, where the rest of them don't give a **** about you!

Listen, if the highs are screaming at you, they're also "screaming" inside the circuitry that amplifies the screaming.

If the balance is toward the highs, then your own ears, your speakers, your room acoustics, and the energy usage within amplification circuitry, is going to be toward those highs, which masks the lows.

And the cartridge loading isn't going to do a thing to correct it, because the cartridge is doing something unnaturally mechanical.

Now, if you want me to go into the workings I can go deep - far deeper than any designer alive these days.

But I'm trying not to, because to some, it sounds like I'm trying to be superior. Which I can assure you I am not. How being humble to try and explain how things work can be taken the wrong way, I am completely confused.

And as for Leif's explanation videos, all I can say is he's gifted (at talking to camera, period).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote patientot Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2023 at 2:03pm
No easy answers here.

It would be great if cartridge companies had FR plots (using a CBS or JVC test LP) of their cartridges at different common load settings along with advice on how to precisely load the cartridge to get the best response. Unfortunately, few if any cartridge manufacturers do that. They leave people on their own to experiment, with or without rudimentary measuring tools.

Looking over the spec sheet for the 2M Black LVB, Ortofon recommends 150-300pf loading capacitance. From what I can tell, that is the same loading spec as the regular 2M Black.

We need to consider the cabling that goes from the back of the turntable to the input of the Accession so it is very important to have that number, IME. Unfortunately cable manufacturers don't always specify that. If that number is not at hand, I would contact the manufacturer of said cable. If they do not provide a capacitance spec, I would simply choose another cable where such spec is provided.

One thing to note: some "fancy" tonearm or phono cables have very high capacitance, because the thought is the end user will be using a LOMC cartridge. These cartridges have very low inductance and are not affected by capacitance loading nearly as much as typical MM or MI cartridges. Not the type of cable you want to use with a cartridge like this one.

The main differences between the regular 2M Black and the LVB are that the LVB has a boron cantilever and a slightly different rubber suspension. Either, or both of those things could alter the sound you get vs. the regular 2M Black you are used to. Any changes also come with tradeoffs - no free lunch on any of this stuff.

Once you get the cartridge loaded right, if you don't like the sound, it may just be this cartridge isn't for you. On the other hand, our ears also need time to adjust to new equipment.


SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mikeh Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2023 at 5:51pm
To my understanding, little as it might be, capacitance matching only impact the high frequency response of a cartridge set up.  The aim usually being to tame peaks which some cartridges exhibit.  There is no damage done by changing your Accession setting just to see if you can hear the difference.  To my hearing the difference is not dramatic.
So I would be surprised if the capacitance settings help with your bass response issue.  Maybe it would be worth reassessing the set up to make sure all the basics are right, alignment, tracking force, height, azimuth, screws tight etc.  If the sound is still not right then maybe there is a compatibility issue with the arm, is the compliance significantly  different between the cartridges?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ctalcroft Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2023 at 6:01pm
Thanks everyone for your thoughts. I think the consensus is that fooling with the switches on the back of the Accession is unlikely to significantly alter the way I perceive the bass. Given how hard it is to access the back of any of my equipment, I'll happily pass. (I wish product designers would put switches like this on the front of the box, hidden by a discrete door so that you could get to them). I'm pretty confident the set-up is good as it was done professionally only about a week ago. Nothing looks off.

I think it's just that the LBV presents improvements at the high end (I LIKE what it does in the higher frequencies) but muddies the low end in a way that is not especially attractive to me. I think I'll just stick with the 2M Black. When I change back to the Black, it will be interesting to see if I still like the way it sounds after listening to the LVB for a few days. 

Anyway, thanks again to all. These conversations are always interesting even if a large portion of them goes way over my head. 
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Post Options Post Options   Thanks (2) Thanks(2)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2023 at 12:05am
While I was in business I was unable to mention that Ortofon, Grado, Shure and Sennheiser all bought our products and only Sennheiser UK gave us a tiny bit of recognition, and only until they bought another amp manufacturing company (oh, and I had to bargain with Grado to get them to display our amps that were driving their headphones at one exhibition). So I guess there was some synergy between their transducers and our electronics, not that anybody knew. 
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