Amp power need after switching TT from MM to MI?

[Exophile]

I recently upgraded from a MM TT set-up (Ortofon 2M blue on POS TT) to built-in phono stage of a Rotel RA 1572 integrated amp, to a VPI SuperPrimeScout with Soundsmith Zephyr MIMC* cartridge (0.4 mV) to a Vincent PHO 701 phono stage with 60 db gain for MC setting to aux input of amp (and a Telefunken ribbed plate 12AU7; prefer that a bit over the Brimar CV4003). For speaker listening (B&W CM6s), I now have to turn volume up from level 35 to about 45-50 for same sound level.

- Was the Vincent PHO 701 a bad choice because of too low gain for the cartridge?
- Should I look at a more powerful amp so that I am staying in the lower 30% linear range of the amp with plenty of head room?
- Or am I staying in 30% linear range of amp because of low signal input into the amp, so no concerns re turning the volume knob higher?
- Or should I be concerned about noise floor with higher volume setting on amp? (have not noticed it).
- Or is everything just fine? It's easy go get paranoid with this pass-time ;-)

[Light Dependant Resistor]

I recently upgraded from a MM TT set-up (Ortofon 2M blue on POS TT) to built-in phono stage of a Rotel RA 1572 integrated amp, to a VPI SuperPrimeScout with Soundsmith Zephyr MIMC* cartridge (0.4 mV) to a Vincent PHO 701 phono stage with 60 db gain for MC setting to aux input of amp (and a Telefunken ribbed plate 12AU7; prefer that a bit over the Brimar CV4003). For speaker listening (B&W CM6s), I now have to turn volume up from level 35 to about 45-50 for same sound level.

- Was the Vincent PHO 701 a bad choice because of too low gain for the cartridge?
- Should I look at a more powerful amp so that I am staying in the lower 30% linear range of the amp with plenty of head room?
- Or am I staying in 30% linear range of amp because of low signal input into the amp, so no concerns re turning the volume knob higher?
- Or should I be concerned about noise floor with higher volume setting on amp? (have not noticed it).
- Or is everything just fine? It's easy go get paranoid with this pass-time ;-)

You should check that changing from MM to MC the input impedance setting and fine tune settings are set correctly
see page 28 to 31 of the manual https://www.vincent-tac.de/fileadmin/pdf/BDA/Phono/BDA_PHO-701_DE_EN_FR.pdf

[Macca]

As long as you can still get the volume level you want there's nothing to be concerned about. The position of the volume dial does not equate to how much of the amplifier's power you are using.

If the sound gets a bit hard, harsh or shouty on peaks then you are clipping the amp and you need more power. If not then it's fine.

[Firebottle]

The Ortofon Blue has a specified output of 5.5mV, taking the 'standard' gain of an MM stage as 40dB (x100) = 550mV

The Soundsmith Zephyr output is 0.4mV, so with the Vincent gain of 60dB (x1000) = 400mV

Hence the need to rotate the volume control more. The volume control only adjusts the drive level into the power amplifier, not its output power.
As Martin says there is no concern.

[hifi_dave]

As long as you can still get the volume level you want there's nothing to be concerned about. The position of the volume dial does not equate to how much of the amplifier's power you are using.

If the sound gets a bit hard, harsh or shouty on peaks then you are clipping the amp and you need more power. If not then it's fine.

Exactly so.

We may be used to amplifiers giving full output at 1/4 rotation, so having to turn up an amp with less gain, seems strange but it's perfectly fine if you get the volume you need.

[Exophile]

Thanks everybody. The Vincent is set to MC and the Vincent impedance is set to 1000 Ohm, minimum suggested for the Soundsmith is 500, but I like the sound at 1k Ohm a tad better. There is no volume change with changing the impedance on the Vincent.

Alan: thanks for the calculations, that makes it abundantly clear.