I've done a bit of studying on "current-driven" phono since you started this thread, Pani. Do you or does Chakster know what is the input resistance/impedance of the Miyabi cartridge that makes it such a good candidate for current drive? Cartridge output is also a factor. According to one recommended criterion, the Ortofon MC2000 for example is not a great candidate for current drive despite its very low internal resistance of 2 ohms. This is due to its very very low output of .05mV. So, you'd want a cartridge with at least 0.2mV output and less than 10 ohms internal resistance. (There is a minimal recommended ratio between these two parameters, but I cannot recall the value.) These rules can be broken, but the result might not be optimal. The manufacturers like to say that the input resistance of their current drive phono is 0, but that cannot be true, I think, because in that case the signal would go directly to ground, thus "muting" the output. The input resistance must be at least a few ohms above ground. If I am wrong, I am interested to be corrected. Also,from what I can tell, current driven phono stages simply use (typically) a solid state gain device which can thrive with a very low input resistance as the first stage of amplification. The output from that stage is then fed to a conventional RIAA circuit for filtering and further gain if needed. It's not magic. In fact, it's kind of an alternative to using a SUT or a conventional outboard active gain stage in lieu of a SUT, except for that exceeding low input resistance which therefore sees the cartridge as a current producing device.
Cartridge options for current gain phonostages (47 Labs)
Hi,
I have a 47 Labs phonocube which I have not been using because I do not have a "matching" cartridge. It is a current gain phonostage. Its input impedance is 0 ohms and it amplifies current rather than voltage. That basically means a low impedance cartridge is the first thing it needs. I had the ART-9 which is a 12 ohm cartridge and it was not a great pairing with phonocube. I am now in the market for a new cartridge and would like to buy a low impedance high current cartridge. The Transfiguration Proteus is one of them but it is expensive.
Looking for suggestions on other options. Primarily the higher is the voltage/impedance value the better.
Budget is around $2k.
I have a 47 Labs phonocube which I have not been using because I do not have a "matching" cartridge. It is a current gain phonostage. Its input impedance is 0 ohms and it amplifies current rather than voltage. That basically means a low impedance cartridge is the first thing it needs. I had the ART-9 which is a 12 ohm cartridge and it was not a great pairing with phonocube. I am now in the market for a new cartridge and would like to buy a low impedance high current cartridge. The Transfiguration Proteus is one of them but it is expensive.
Looking for suggestions on other options. Primarily the higher is the voltage/impedance value the better.
Budget is around $2k.
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- 18 posts total
"The Miyabi Standard has an output voltage of 0.2mV and an internal impedance of 2.0 ohms, while the Miyabi/47 has 0.3mV output voltage and an internal impedance of 2.0 ohms". Pretty much as nearly all my favorite MC cartridges, they are all low impedance 2-3 Ohm and low output 0.15 - 0.25 (but not extremely low as the Ortofon MC2000 @lewm ). The 47 Labs 4712 Phono cube has been made at the time when Miyabi 47 (designed by Takeda for 47 Labs) was in production and distribution in the USA by Sakura Systems. Anyway, the difference between Pani and me in this thread is that i bought my current drive phono stage especially for my old Miyabi collection. So i don’t care about other cartridges capabilities with Phono Cube or vice versa. But i'm pretty sure that all similar low output and low impedance carts can be used with 47 Labs Phono Cube. |
I know nothing about the Phono Cube, but what Chak says is interesting. In voltage world, 75db gain ought to be more than enough for even the MC2000. I can't imagine what cartridge needs 90db. pcosta, What you say about the 75db vs the 90db versions of the Phono Cube is interesting and surprising to me, because one would think that MC cartridges with higher internal impedances would be those with higher voltage output, because higher impedance is associated with more turns of wire in the coil, which usually means higher output. But since I know nothing about the Phono Cube, I'll take your word for it. |
- 18 posts total