Phono Preamp Settings/Question - Help Please

The phono stage has either (appx) 52 or 58dB of gain on the MC setting, the higher number with the +6dB switch engaged. This is based on the spec (p5) of 0.3V out for 0.8mV in. For MM it’s 36/42dB

However this assumes you use the MC inputs and you actually have a Higher output cartridge, the overload limit on the MC input is only 12mV so I’m not sure if you’ll have a headroom problem

Good news is you can also select 47k loading and it seems use the MM capacitance settings while using the MC inputs so at least that’s not a concern

So presumably I would use the MC inputs, even though I have a MM cart, which would provide more gain without any loading issues because I can select 47k? Curious what the overload limit spec means.

Correct, as to whether you will have enough headroom I suspect it will be fine as long as your record diet is not primarily house 12” singles (see here for a discussion of what the 1kHz 5 cm/sec means https://repforums.prosoundweb.com/index.php?topic=26987.0)

i do worry however about high frequencies which per RIAA standard are 20dB up on 1kHz, you’ve only got 10dB of headroom but how many tracks have full scale recordings at 10kHz and up? Let’s suggest you steer clear of test records!

Thanks for your input and the resource!

That’s only half the story. What is the sensitivity, and full output of your amp and the sensitivity of your speakers?

My amp's sensitivity is 2.24v, however its a 500W amp and I've had plenty of success with 2v out from my dac directly driving my amp. I have kef ls50's which I believe are 85db sensitive.

The manual is not so good:

https://www.musicalfidelity.com/uploads/catalogerfiles/mx-vynl/4_MX-VYNL_manual_issue_1.pdf

....but it looks like you can set it for MM with the added 6db switch on and that yields a sensitivity of 2.5 mV for full output, which is 4 volts. If someone reads this differently, please correct me.

I think that, with this setting, your 4mV cartridge will be able to have more than enough gain to output sufficient voltage necessary to drive your amp into clipping without overloading the phono stage and still loading the phono cartridge at 47K, even taking into account the losses of the passive volume control.

Although it is a solid-state phono stage, and so it should not be an issue, the thing that I don’t see is the output impedance, which can be an issue when using passive preamps into solid-state amps with lower input impedances. 

The input impedance of my power amp is 50kohms so I think that should be okay there given a 1:10 ratio even if the spec isn't listed on the musical fidelity. My passive is a TVC so that wont hurt impedance matching either.