Cartridge output matching to phono stage.


Greetings everyone! Here is a question that has been bugging me for some time. How does one know if the phonograph cartridge output, stated in "Mv", is properly matched to the phono stage being utilized, stated in "gain"? Some where a chart should exist allowing people to properly match their desired cartridge selection to their phono stage. Also, why is this so important, and what are the ramafications if you go above or below the gain threshold?
Thanks is advance for the feed back.
Regards,
Lou
lbo

Showing 3 responses by marakanetz

it's a very simple arithmetics.
all you have to do is use the following formula to transfer gain from dB to times:

1. 20Log(times gain) = dB gain

2. times gain = 10^(dB gain/20)

"^" sign in the formula bellow represents power of an argument 10 in our case.

thus if your phonostage has a gain of 60dB than using second formula you should bring 10 to the power of three 10^3 = 1000 times i.e. 60dB = 1000 times.

You should always multiply the gain by your cartridge output and get an output voltage arround 500mV or higher.
A phonostage with 60dB gain can be used with the cartridges as low as 0.5mV on the output or higher. A phonostage with 40dB of gain(100times) can only be used with 5mV or higher etc...

I suggest to pick up phono that have at least 50dB of gain.

Sometimes it's enough(depending on the preamp sencitivity) to have the output of your phonostage 200mV or even bellow but that you will have to check on the preamp specification.
For low gain or zero gain or even passive preamps hold up to 500mV or higher.
You're getting some number approx 10^2*sqrt(10) which gives you approx 300 times and doing wrong nothing. So you're getting an approx output voltage of 240mV. Now you should check specs of your preamp in terms of input sencitivity which has to be bellow 240mV and moderate gain of 10...15dB. Otherwise I would pickup a high output version of the same cartridge for its maximum performance.

Happy Listening,
Mara.
a step-up of 20dB will not be enough for the phono input with input sencitivity of 4.5mV. The preamp section will not be having the specified gain and output parameters if you feed a voltage less than input sencitivity.
A step-up transformer with 30dB of gain will be more appropriate but might be very expencive. The times gain will be approximately 32 which will give you ~7.5mV -- an ideal case.
If you will have 23mV you will less-likely overload since most of the phono section can handle upto 100mV. In this case you will be operating in the low volume positions that mean that preamp section is working in attenuation rather than amplification which is considered to be better. The signal might get compressed but it's usually for high gain stages that DO require to use the low output cartridge but your phono section has no-more probably than 35dB i.e. times ~60