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Putting MM cart through MC phono stage

Once I forgot to switch the phono stage from MC to MM when changing cartridge respectively. At first I was wondering why on earth the volume must be turned only to about 9-10 o'clock whereas before it had to be turned to about 1 or 2 o'clock to get optimum sound. When I realised the mistake I listened it both in MC and MM mode and did not find much difference save for slightly higher hiss level in MM mode when the apm volumu had to be turned high. Anyone has experience with this issue? My guess is that listening a MM cart through MC phono stage might prolong the life of tubes since they are run on lower volume level. Or is this entirely stupid idea?
crockusbird
eldartford
4,262 posts
 
I agree with your last sentence :-)
crockusbird OP
5 posts
 
Thanks guys for reply. But what's the problem - why it is not a good idea?
narrod
1,064 posts
 
Very easy for the high output of a MM cartridge to overload
a MC phono stage in addition to loading and capacitance mismatches.
rgordonpf
82 posts
 
Not all MC phono stages will overload. I have talked to the designers of the Herron and JLTI phono stages. The Herron MC circuit will take 30mv without overloading. The JLTI MC circuit will take even higher voltages without overloading. So overloading is not be a problem with some phono stages.

Most MC phono stages seem to have 47k as one of their default loadings. The inability to adjust capacitance could be a problem, though you could probably solder a capacitor into the circuit without too much problem. Or you could just use a interconnect with high capacitance as your phono cable.

There are lots of solutions to the problem of using a MM cartridge with a MC phono stage. What would really be interesting to know is why Crockusbird's preamp is noisier at 1-2 o'clock than at 9-10 o'clock.
honest1
586 posts
 
Noisier at 1-2 o'clock because everyone logs onto their computers (generating much EMI/RFI on the national power grid) after lunch to see what's new on Audiogon!!!

(Yeah, I know, I know...)
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