Changing the Yamahe C-2a MC Load Impedance


2008-06-12 8:21 am
Hi all,

i just got a Yamaha C-2a preamplifier, sound is nice but the load impedance of the MC Head amplifier is 50 Ohms, but i need 100 Ohms or more for my Denon Dl-103 Cartridge.

I attached the schematic of the head amp in the C-2a, can anybody help me figuring out how the input load can be raised to 100 Ohm ?

Thanks for your help.


  • YamahaC-2headamp.jpg
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I run a Zu/Denon DL-103 and noted no particular issues with cartridge performance into 50 ohms other than the fact that I lost a couple more dB of output relative to the recommended load impedance.

I'm currently using vintage Partridge 977 SUTs with mine with no loading beyond that imposed by the 47K load at the input of my phono-stage because the theoretically optimum load did not result in any improvement I could hear, and also cost me several db of output. (These transformers are very inexpensive on eBay and quite shockingly good)

Loading does not seem that critical.

WRT C-2A the input resistor is 110 ohms, and if as you state the actual input impedance is 50 ohms this implies that the MC circuitry input Z is only slightly over 100 ohms. I would change that 110 ohm resistor to no more than 220 - 330 ohms.

I owned a Yamaha C-2 myself back in the day and was stunned at how much better my first home-brew tube pre-amplifier sounded than the C-2 which up to that point I had thought was pretty good. Not sure why I am telling you this either - obviously anecdotal but perhaps it will inspire you to build SY's "His Master's Noise" and a suitable line stage for your probably solid state pa.