I wanted this. It's close to the ultimate low mass high compliance combination that the late 70s produced. Total effective mass 4.5g. Wonderful pointless madness. It does look nice tho.
Also in my research (although no intention to buy another cart at the moment) I found the technics EPC-205II L. This is a low inductance version made 73-76 and has the somewhat incredulous spec of 40mH and 30R for the coil. So 2L-R works. This could be a candidate for the lowest noise MM front end using a transamp. two tens of a gnatfart improvement is pointless, but fun to find the limit
Also in my research (although no intention to buy another cart at the moment) I found the technics EPC-205II L. This is a low inductance version made 73-76 and has the somewhat incredulous spec of 40mH and 30R for the coil. So 2L-R works. This could be a candidate for the lowest noise MM front end using a transamp. two tens of a gnatfart improvement is pointless, but fun to find the limit
Interesting thread, I have not been able to go through it all. With respect to test records, there is really a need for better ones:
Dropbox - Test records and frequency response measurements.pdf
Dropbox - Test records and frequency response measurements.pdf
We have a thread on test records as well. It's currently in cat herding mode, but we hope to get something eventually
I noticed that... so much to read.
What if R1 is negative.
Looks like I wasn't calculating correctly for my B&O mmc2. Total cartridge mH should be ~400. that means per channel it is 200mH, so in the Aurak calc. for R1 this will be negative as the ohms are 800 per channel, even in LDs more generous 3x equation. Is this correct and how to change Han's final schematic for the TP boards?
Thanks!
Looks like I wasn't calculating correctly for my B&O mmc2. Total cartridge mH should be ~400. that means per channel it is 200mH, so in the Aurak calc. for R1 this will be negative as the ohms are 800 per channel, even in LDs more generous 3x equation. Is this correct and how to change Han's final schematic for the TP boards?
Thanks!
Given the Aurak formula for R1 = 2L -Rc I was making the mistake of taking total cartridge mH and then doubling that, when it should be the per channel mH. So my B&O MMC 2 isn't an ideal cart for any current Aurak schema as drawn. Han's hinted that there was a way to alter the schematic to make it work for carts where R1 is negative. If not that's ok, I have another cart I think will work out great.
I just had a look. You use per channel mH values, so 200 was correct, but I cannot find a figure for the cartridge resistance (or even impedance at 1kHz) published. Without that you are missing one of the only 2 numbers you need. If you have a decent DVM you can measure the DC resistance and then proceed.
Thanks Bill, I have three mmc bodies, 2 mmc5s in non working order and my mmc2 which I will test once my new arm is ready. I am basically building everything in my system. So far I have my TT and phono battery PSU finished, next is one of these phono circuits. I have an amp circuit ready to test along with its SMPS. Probably not the final amp I will settle on, that will be a future build. This is why it takes me so long. :-0
The mmc2 measures ~ 780ohm on both sides, mH ~217 each side. The two mmc5s measure 765 ohm and 815 ohm, each side. mH ~235 each side, 230, 250, respectively. Any consensus on when coils don't match? Anyway looks like one might be good for a basic rebuild. I think my mmc2 might need a new suspension rebuild but I will test it first and decide.
I have a Grace F8 Custom that I can use with the balanced Aurak. Which should work great.
I am also building a Wayne Kirkwood balanced flat phono that should be a good fit for the B&O. Hope to use it and the Grace to do some vinyl rips.
My take is, after reading this long thread and the 'Capacifier' thread, is that I will use no capacitor loading and 100k input ohms for the balanced flat phono with the mmc2. The MMC2 seems ideal for MM/MI with respect to electrical and mechanical properties. Both properties seem to move their problems into the inaudible upper range.
Maybe build a capacifier for the Grace? for this balanced flat phono?
The mmc2 measures ~ 780ohm on both sides, mH ~217 each side. The two mmc5s measure 765 ohm and 815 ohm, each side. mH ~235 each side, 230, 250, respectively. Any consensus on when coils don't match? Anyway looks like one might be good for a basic rebuild. I think my mmc2 might need a new suspension rebuild but I will test it first and decide.
I have a Grace F8 Custom that I can use with the balanced Aurak. Which should work great.
I am also building a Wayne Kirkwood balanced flat phono that should be a good fit for the B&O. Hope to use it and the Grace to do some vinyl rips.
My take is, after reading this long thread and the 'Capacifier' thread, is that I will use no capacitor loading and 100k input ohms for the balanced flat phono with the mmc2. The MMC2 seems ideal for MM/MI with respect to electrical and mechanical properties. Both properties seem to move their problems into the inaudible upper range.
Maybe build a capacifier for the Grace? for this balanced flat phono?
The balance I don't see as a worry (Self on the otherhand does). Reason I am not worried is that in the sort of differences you are talking about it only moves the LF pole a few Hz and that shows up as a few 10ths of a dB below 300Hz deviation. As most rooms are all over the shop by there I don't see it as audible.
Your measurements are a bit higher than factory, which could be your meter or could be an error in the factory spec. But taking 250mH and 780R puts your roll off at 577Hz. That can be fixed with a couple of resistor changes and then you would connect the cartridge in directly with no added series resistance.
Your measurements are a bit higher than factory, which could be your meter or could be an error in the factory spec. But taking 250mH and 780R puts your roll off at 577Hz. That can be fixed with a couple of resistor changes and then you would connect the cartridge in directly with no added series resistance.
Bill,
Thanks, I think that the B&O mmc2, mmc1, mmc6000, might be among those rare cartridges where an Aurak or Capacifier don't get ya much. As long as you keep the loading at 100k ohm and cable capacitance to a minimum. Or am I wrong? I think we get MC performance from some of these cartridges under the above conditions. At an investment that is much less that we can expect from a good/great MC, and with ability to quickly swap different stylus. I think that was also Raul's observance in that long Audiogon MM thread.
It seems the main two selection criteria when selecting an MM are what is its inductance(L), how low per channel? What types of replacement stylus' are available? One where the cantilever is made of Saphire/Ruby, Boron, Beryllium. Having that mechanical resonance moved up/out of the audible audio range is key.
A lot of money can be saved to achieve the same level of phono performance if one has the time and right knowledge.
Thanks, I think that the B&O mmc2, mmc1, mmc6000, might be among those rare cartridges where an Aurak or Capacifier don't get ya much. As long as you keep the loading at 100k ohm and cable capacitance to a minimum. Or am I wrong? I think we get MC performance from some of these cartridges under the above conditions. At an investment that is much less that we can expect from a good/great MC, and with ability to quickly swap different stylus. I think that was also Raul's observance in that long Audiogon MM thread.
It seems the main two selection criteria when selecting an MM are what is its inductance(L), how low per channel? What types of replacement stylus' are available? One where the cantilever is made of Saphire/Ruby, Boron, Beryllium. Having that mechanical resonance moved up/out of the audible audio range is key.
A lot of money can be saved to achieve the same level of phono performance if one has the time and right knowledge.
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I wouldn't say that. You still get removal of the HF resonance and control over the electrical frequency response. There is more that one way to achieve this, but I think the Aurak concept will work with pretty much anything. The only issue is where you have a cartridge that doesn't fit a standard formula as in your case. I don't see that as a problem, although others might.
Hmm, ok, I suppose I could have one Aurak where I could use a switch to give me ideal loading for both carts. The Grace f8-C measures ~ 435mH and 520ohms per channel. So it will work fine with my currently built Aurak pair. I think with a Jico SAS, from Shure v15 III, it will be a great performer. I could build a capacifier for it with two of the B&O carts wired in series. A level one Capacifier seems ok, I'd really like to build a level 2 but have no idea on values.
It's not universal, but a few jumpers and you can adjust for most configs. I did for a moment consider putting relays in to allow me to select different setups but decided that I do all I want with a few settings so I'll go for the jumpers. Now I go out of my way to find odd cartridges so I'm the odd one out.
FWIW If I were building a normal voltage mode MM stage I'd do an electrically cooled one. Hans did some calculations recently and it can work rather well. Basically load down to get the HF pole.
FWIW If I were building a normal voltage mode MM stage I'd do an electrically cooled one. Hans did some calculations recently and it can work rather well. Basically load down to get the HF pole.