Help in calculating phono preamp headroom

[thinker10]

Hi,

With a high output cartridge of almost 10mv @ 1 kHz how do I calculate what would be a safe overload point ?

Is 120mv @ 1 kHz enough ?

I am learning this stuff.

I guess a active , passive or hybrid design would change thing somehow.

Would 32dB of gain be ideal for that hot cartridge ?




Thank You

[ashok]

If my memory serves me right , I have seen designs that went up as much as 350mV max before overload . BUT that is the execption . 250mV and less was more common and 120 mV should do pretty well. It all depends on the cartridge trackability and sensitivity.

Do you mean 10mV at 5cm/sec ? That would be generally about twice what we normally see. With a trackability of 45cm/sec , a 120 mV capability seems fine. Note that at HF the signals will be higher due to the equalised signal on the vinyl pressing.
HF is typically boosted up to almost 20db at the upper limit. Music content however has much lower levels of high frequency components and you can get away with a lower margin . You will also see that trackability figures at 10Khz are about 25% lower than at 1Khz.

In your case maximum output would be 120mVx40 = 4.8 volts.
This should be well within the capabiity of most opamps.

[jcx]

Originally posted by ashok
...
In your case maximum output would be 120mVx40 = 4.8 volts.
This should be well within the capabiity of most opamps.

if you have a flat gain of 2 the output would be in danger of clipping - not a candidate for the dual gain stage passive eq topology