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Marantz PM 45 MM/MC questions

D

Donal Henry

New Member
Hi all, Newbie but Oldie looking for some thoughts if you’d be so kind … After a 30 year vinyl gap, I recently bought a Pioneer PL 720 in brilliant condition. The spec for the cartridge had MC 3 or 4 all over it so I assumed it was MC as opposed to MM and therefore bought a refurbished Marantz PM45 as a re-intro amp because it can handle either. With the phono switched to MC, the right channel is c15% as loud as the left, so pretty unusable . On MM the balance is pretty equal and overall volume only a touch lower, so listenable ( if that’s a word ! ). Tone and depth seems better on MC but that could be my imagination. I was expecting an MC cartridge to hardly register on an MM amp but that was after some quick pre purchase research…. I may be asking the wrong questions but could there be a channel issue on MC and not on MM ? Could the cartridge actually be MM ? Or an MM/MC switch issue ? Sorry if any of this is nonsense, please feel free to straighten me out !

All the best,

Donal
 
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I’m not a ton of help but it depends on the MC cart. If it’s a high output MC then the MM side will usually work fine. If it’s a low output MC then not so much.
 
What exactly does the cartridge have stamped on it? If it's PC-3MC or PC-4MC, you have a Pioneer stock "high output" moving coil cartridge, which actually uses the MM input. So you got it correct. Keep it in the MM. And yes, it will be a touch lower volume wise than what you're used to because the mV output on such a cart, though "high" for MC, still only about half of what MM puts out.
 
Thanks very much both,

Very helpful and on Boxing Day too !

Think it’s a PC-3MC cart, so do we think that it’s configured for MM amplification despite the MC in it’s name ?

Apologies but my understanding is low and I can’t get my head around the fact that the left channel is lovely and right operates at c15% in MC mode, yet in MM mode both channels are balanced but sound slightly quieter and less resonant.

Could the cart and not the amp account for that channel weakness when MC selected ?

Confused,

Wiltshire !
 
Yes, that cart should be plugged into the MM input. It is moving coil (MC) by design, but is a high-output construction (2.5mV). If it was a true low-output MC cart (around 0.5mV) you would barely hear a thing while plugged into MM input.

I admit I'm a little confused as to how/why you're getting "lovely" sound in one channel when using the MC input. The gain should be too high for that incoming 2.5mV signal. It should sound totally distorted. The MC stage might be faulty, or maybe it's simply reacting strangely to the higher mV input.

Try flipping the turntable's R/L RCA cables at the amp. Then use MC mode. If the "lovely" channel moves to the other speaker, the issue is with the cart/TT. If it remains in the left channel, then the issue is most likely with the MC mode switch.
 
Swapped the turntable to amp L/R RCA cables around and low volume stayed on the same channel so I guess the MC/MM switch is now the main culprit. I’ll have a play and a spray and see if that helps. I was going to return the amp but seeing as the MM mode suits the cart and it only cost £80 I might hang onto it regardless of whether I can get MC to work…

Thanks all,

Donal
 
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