Yamaha C-4 and MC cartridge

[boneius]

Hi,

This is a question for anybody, but @avionic might have particular insight, seeing as he recapped and serviced my C-4. I'm getting an Ania MC on a Rega Planar 6. The recommended load is 100 Ohms. The MC input impedance of the C-4 is 50 Ohms according to the manual. What can I expect in terms of sound? Will it have less gain? Will it be less open? If I won't get the best performance, can the C-4 be modded in such a way to (add a resistor or something - I don't have any real knowledge about any of this stuff) get the load to 100 Ohms? BTW, thanks again @avionic, the C-4 is my favorite piece of equipment by a long stretch.

Jim

 

[cobbears]

Output impedance of the Ania is 10ohms so the 50ohms of the C4 is perfectly usable - may not be ideal but should give you a very good idea of what it is capable.
Not got a circuit diagram of the C4 but replacing a resistor on the PCB to convert the load is certainly possible but may be more work than it is worth.
Just found a circuit diagram of it inc the MC - jeez!needs someone better than me!

 

[boneius]

@cobbears , thanks for you reply.

Just found a circuit diagram of it inc the MC - jeez!needs someone better than me!

That's why I tagged @avionic . He really knows these machines inside and out, literally. I appreciate your feedback, though. Will it just be quieter because it isn't at 100 ohms or will it be less detailed as well?

 

[Blue Shadow]

Yup, gonna need Dave to talk to this one. The Phono 3 input at the top is the MC input and it uses that first pile of transistors. The Phono 1 and 2 inputs enter the amplification below the TP5 by the right vertical line at the top half. That is a lot of goings on in the MC phono section. It is not a step up transformer.

 

[boneius]

That schematic looks scary! I definitely know nothing about electronics, but what I've read about the C-4, however, is that once it gets through the head amp, it goes into the same line as the MM with RIAA eq and the gain stage after that. Now, I just said a lot of things that I don't really understand, but wouldn't the signal coming from the Ania, which works best with 100 ohms, get some kind of boost from the gain stage that boosts the MM signal? Anyway, I'll leave to the expert(s) to sort this out. Thanks for the reply, @Blue Shadow.

 

[avionic]

Looks like R121 and R122 (1KΩ 1/4 watt) provides the input load.

 

[Blue Shadow]

wouldn't the signal coming from the Ania, which works best with 100 ohm

Or so you have been told. It will work just fine with the load supplied by the C4 and if you were to change the loading resistors you might not hear much difference. The lower loading is supposed to give a more dynamic sound according to Van den Hul FAQs.

As to the MC stuff before the MM input, yes that is how almost all LOMCs are handled, using a pre-preamp as in the case of the C-4 or an SUT before going into the MM input. These two provide 10-20dB in general, to boost the signal level to the input level of MM phono inputs. Then this stage does the RIAA eq and boosts the signal to Line Level used in the rest of the preamp.

 

[boneius]

Thanks for the response and the tip about Van den Hul FAQ, @Blue Shadow. There is some interesting reading there. The table comes tomorrow, so I guess I'll know soon enough how it will sound. My guess is that it will be fine!

 

[avionic]

That schematic looks scary!

Not as scary as a Yamaha C-1 schematic.