Cartridge options for current gain phonostages (47 Labs)

I couldn’t think of the name when this thread was more current, but look @ the new Lyra Delos thread as the Delos should be a good match (and on budget).

Also, I've recently seen the 47 labs cartridge heavily discounted, if you wish to spend less.

DeKay

Well, i’m in, hope it’s not too late :)

As the owner of two different Miyabi cartridges (MCA and Standard) i just bought 47 Labs 4712 Phonocube with Humpty.

Pani told me he never tried his ex 47 Labs phono cube with Miyabi cartridge. This is exactly what i’m gonna try!

Fascinated by Nelson Pass current source power amp (First Watt F2J) in my system i am up for "current injection" phono stage with ZERO load impedance finally.

Hope i am not alone ... 

MORE ABOUT PHONOCUBE:

Input impedance 0 ohm
Most of currently available phono equalizers are designed to amplify the voltage that appears at both ends of a resistor when a current generated by the cartridge is carried to the ground through this resistor. Our Phonocube has a unique and original circuitry ( with input impedance of 0 ohm), which enables all of the current generated by the cartridge to flow directly into the amplifying circuit.

Unique equalizing circuit with advantages of both NF and CR types.
Although NF type circuitry is known for its high S/N ratio, a rise in the high frequency is always inevitable. The unique equalizing circuit of Phonocube allows the same level of high S/N ratio while maintaining the smooth and accurate equalizing character of the CR type.

Extreme simplicity --- minimum circuitry
To preserve the freshness of the sound, we reduced the number of parts as much as possible, 25 per channel, and achieved the shortest signal pass length ever (44 m/m).

Rigid and compact chassis construction
The chassis of Phonocube is constructed from two aluminum tubular frames ( 40 x 80 m/m section ) and front and rear panels of 10 m/m thick machined aluminum. Each circuit of left and right channels is encased in a separate chassis to eliminate interference between them and to achieve ideal dual mono structure.

Compatibility:

Most of MC cartridges available in the current market are compatible with the standard version. For those cartridges with an extremely small output level and/or high internal impedance, we have the high-gain version. The standard version has 75dB and the high-gain version has 90dB of gain. Since it is a current amplification device with 0 ohm input impedance, output level is determined by the output amperage of the cartridge (output voltage divided by internal impedance). If you are not sure about which version suites better for your cartridge, please contact SAKURA SYSTEMS.

Features:

• Unique equalizing circuitry that amplifies all the voltage the cartridge generates without loss.
  
• Complete dual mono structure with each channel in a separate chassis.
  
• Rigid and compact aluminum chassis to ensure a quick and smooth release of vibrations.
  
• World's smallest number of parts --------- 25 parts per channel
  
• World's shortest signal pass length -------------- 44 m/m
  
• Powerful voltage regulation with high capacity transformer - 170 VA cut-core transformer +- Individual coils
  
• To be upgraded into complete mono structure by adding another Model 4700.
  

Specifications:

• Input impedance : 0
  
• Output impedance : 47
  
• Gain : 2 types to match the internal impedance of different cartridges
   type A ( standard ) / type B ( high gain )

Waiting for your opinion @chakster 

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.

"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.