Catridges capacitance loading etc made EZ

This may not e a problem, do the highs sound harsh or exaggerated? The spec may have more to do with CD4 playback where the roll-off would kill the quad signal. If it sounds good it probably is.

 

It is a MMC cart and while it has the performance of MC carts it still uses the MM input of the phono preamp. So treat it as a high end MM cart.

 

Sounds fine to me, but maybe it could sound better. All this pf stuff could be non sense and not really make any audible difference. I don't know enough about it yet to say.

 

Shooting for "suggested" numbers is not going to be an ideal solution. If you are able to measure the response, then you can start changing resistance and capacitance amounts to actually see what they're doing. This combined with your ears is really the only feasible answer. In my system I got my capacitance down as far as I could with very short interconnects, and I still had a 6db peak in my audible band at the recommended load of 47k. I needed a drastic change to 19k to flatten out the peak, and I added a little capacitance to fill out a dip around 10kHz. Now I have flat response up to 17kHz and I'm thrilled with the sound.

 

Agreed that ideally both listening and measuring combined will be much more accurate, but on listening i can get what sounds right in my system, flat? probably not

 

Well my guess is that B&O intended its carts and tables to be used with its electronics and the matching tuner/preamps had the specs in question. I also wonder, if that's B&O's loading recommendation, and given that the B&O carts are made for the B&O tables, if they mean 100 pF loading not including cable capacitance. I'm not really familiar with how the B&O tables are wired, but I suspect that's actually what they're recommending.

It's not all that easy to find a combo of MM phono stage input loading and cable capacitance that totals 100 pF (btw, pF stands for pico Farads, the Farad being the basic unit of measurement of capacitance, which is the ability of a body to store an electrical charge), but it's not impossible. Soundsmith -- which services a lot of B&O carts -- sells a couple of phono pres with 100 pF input capacitance, if that's actually what B&O intends. The Simaudio Moon 110LP which is the company's lowest cost phono stage can be set up for 0 pF or 100 pF loading. Phono stages with the specs you're looking for do exist out there.

 

I have heard this same point made about the AT carts, and suspect you are right.

 

Oh boy. I really think the point here is illustrated - the Op's request for a simplification is at best elusive, and probably impossible IMO. In the article by Werner which STBob linked, Werner concludes " While bringing resistive loading to the set of user-adjustable parameters in the MM cartridge-preamp interface clearly adds a useful degree of freedom to the sound optimisation problem, doing so purely on the basis of the cartridge's electrical specification and attempting to flatten out the electrical frequency response is ill-advised. Both electrical and mechanical aspects must be incorporated, and this means measuring the real thing, or failing that, listening to it." It's not bad advice, IMO.

A few years back I designed a MM phono preamp that doesn't care, works equally well with any cable C, any length, no R loading to worry about, no electrical resonance. Just for my own amusement and to extract myself from this mess, very good it sounds though and I still use it, but only on carts with suitable mechanical performance as per Werner's summary. But that's another whole story. It does show that it could have all been different had the industry sorted it's funky stuff out decades ago IMO !

 

Might be worthwhile to get some in-room measurements as well. There might be a reason an odd loading sounds good. Anyway, I wonder if there might be a market for a very good, highly adjustable MM phono pre. Maybe with zero to 400 pF options and 100k down to 20k resistive loading. I know I might buy one.

 

I'm flummoxed by my cart because the recommended range is so wide. An Ortofon OM-40 is recommended for 200-400... that's a pretty big spread. Why would it be so wide, and what would the difference in sound be on the lower vs. higher end of that spectrum? I've kept things on the "standard" setting (Pro-Ject Tube Box), and thus closer to the lower end, but I *could* load it more, I believe...

 

There are examples of highly adjustable phono pre's out there, and I agree with you, there should be. Unfortunately the ones with many options are typically priced $1k and up. So an affordable design would be fantastic.

As far as room measurements go, that's if you're attempting to tune your speakers or amp. Any cartridge tuning/measurements should be done at the preamp, so before the room even becomes a variable. If your cartridge is neutral, then you start with a better baseline before dealing with any room/speaker adjustments.

The range is possibly so wide because in their tests it's possible that there was little to no affect on the frequency response between 200-400 pF.

 

If you in-room response fall off a cliff after 15 kH, a six db bump at 17 kH might not be less of an issue. That was my thought.

 

You can read that as "season to taste" IMO.

MM carts, by their electrical nature, have (and depend on) a "hump" in their treble response. Imagine its "peak" around 15kHz somewhere (but the rising response can start earlier and there's also a quick drop-off in electrical response above that). Lower capacitance will shift this peak further up in the spectrum (higher than 15kHz in this example) and higher capacitance will do the opposite of course.

 

I don't think obsessing about loading is particularly healthy. If the loading is WAY off, the cartridge will sound bad. If it's close, it will sound pretty much as good as it can, and we can move on and listen to music.

 

Maybe…

 

I think it´s well worth experimenting with different loadings, both C and R. Firstly you will learn about how things work, secondly you might very well find a combination of C and R that will give you a balance that you will prefer, together with your system. These don´t have to be the recommended values. It might take a while to get there, and you must often test back and forth, but it can be rewarding sometimes I think.

 

I am about to order a new Soundsmith smmc1 or smm2. Can't seem to get them on the phone, I emailed but he said to call.

The specs on the mmc2 are: (The capacitance is listed as 100-200 pf) and 400+ pf for a special order.
I wonder if Soundsmith raised the capacitance over the original B&O mmc2s. They were listed as 100pf. And maybe made to be used with a beocenter amp.

I am probably 300pf right now so wondering if the 400+pf version might be better for my 8002 TT. I have no desire to get a beocenter amplifier, I just like the TT.

Also in these specs I don't see the Inductance which that calculator wants. They also have the same cartridges in Wood for quite a bit more. But is a wood mmc3 better than a regular mmc2? Also they have two compliance's listed, a high and a medium, no idea what that is.

Confusing with so many options.

SMMC1 Technical specifications
Stylus Contact Line Nude, 0.100mm SQ
Radius of curvature Optimized Contour Contact Line
Cantilever Ruby
Recommended Tracking force: 10mN / 1.0 gm (high)
13mN / 1.3 gm (medium)
Effective tip mass 0.30 mg
Compliance 28 µm/mN (high)
22 µm/mN (medium)
Frequency response 20-20,000 Hz ± 2.5 dB
Channel Separation
(stereo only) 1000 Hz >28 dB
50-15,000 >20 dB
Channel difference <1.2 dB (Stereo)
<1.0 dB (Mono)
Output voltage >0.6 mV/cm/sec.
5 cm/sec. Lat. RMS >2.12 mV
Cartridge weight 6.8 grams
Load: Resistance >/= 47 kohms
Capacitance: 100 - 200 pF

(400-600 pf available by special order)


This fellow took a soundsmith smmc4 and smmc1 and tweaked them to be flat using resistors. Pretty interesting read.

http://www.tnt-audio.com/sorgenti/soundsmith_e.html

 

Yup, an interesting read alright, thanks for that link

 

From the link it would seem that the inductance is very low. The rise you see in the charts is probably dominated by the mechanical resonance. The electrical resonance seems to be well above 20kHz at 100pf or 500pf.

 

Just a note, my copy of the test record used shows a lift in one channel and not the other. The Cardas record, by comparison, is the same in both channels.

 

Now that is interesting, and perplexing at the same time!

Has one test record had much more use than the other?

I'm a happy little Vegemite ATM as i found someone that measured the miller capacitance of the 6SL7, it was driving me nuts not knowing the total capacitance my cart was seeing!

So the Hagerman calc' with this added info tells me I need to use 41k resistive load.....if I have it right.

 

No, but I would like to know if it is just my copy. When you average the channels, though, it does give deceptive results.

 

Agreed! would be very interesting to hear from someone else with those two, would do my head in not knowing what test LP was telling the truth