Phono levels and gain

[jnb]

How do I tell how much output I get from my cartridge, I mean if I wanted to put a figure to it. For example, what do I look for if i look at it on a scope?

Another question, what frequency is the gain of a phono preamp taken at because obviously that makes a big difference?

 

[richie00boy]

You should be able to find data for your cartidge from the manufacturer or the web.

Phono stage gain is usually specified at 1kHz as that's the point of flat response.

 

[jnb]

Thanks. Let me see if I understand.

Output is 4mV at 1kHz at 5cm/s.

I want line level, and 2V is 54dB higher than 4mV.

So, I need 54dB of gain at 1kHz which also means 74dB at 20Hz or 34dB at 20kHz?

 

[richie00boy]

Line level would be more commonly around the 800mV mark if you are lucky. CD players output higher than was typical for line level. I believe they are 2V peak not RMS.

Personally I prefer to work in basic muliplication factors rather than dB for this sort of thing as it avoids any conversion errors.

 

[jnb]

OK, so to keep up with my CD player I could drop 3dB from what I said earlier, making it 51dB (gain=354) at 1kHz.

I could guess that my cassette player and tuner are probably within 6dB of that but I don't think that's enough to worry about

 

[kevinkr]

CD line level spec is 2.0Vrms. (2.828Vpk) Old USA standard (or IHF) line level was considered to be 707mVrms. (1Vpk/0dBu)

I have never bothered to match my diy line level components to either specification, I don't normally switch back and forth between sources in normal use, and a lot of my program material has pk levels that vary all over the place forcing me to reset the volume when I change sources anyway.

The key issue is to make sure that you have sufficient gain available overall to allow you to achieve the maximum spls you desire with the program material (and source) you listen to having the lowest average levels.

Of course your opinion and mileage may vary.

 

[jnb]

The key issue is to make sure that you have sufficient gain available overall to allow you to achieve the maximum spls you desire with the program material (and source) you listen to having the lowest average levels.

I can see how this could be a problem if not done right. I think all the above information will help me in doing this and it will also give me a clue where to position my source selector. I don't mind if I'm a little out in the end, I just hope I don't need half a volume control rotation or more to match the sources

 

[hughmon]

Output is 4mV at 1kHz at 5cm/s

The max groove velocity spec for an LP is 30cm/S. At that level the output of your cartridge will be 24mV @ 1KHz. Most phono preamps operate at around 40dB of gain at 1KHz for levels roughly equal to that of CD players. LP mastering can vary quite a bit though, so you may wish to fine tune it a little.

 

[jnb]

Most phono preamps operate at around 40dB of gain at 1KHz

Oh. OK, would you say then that my 4mV/1k/5cms sounds typical enough to be happy with 40dB for CD levels?

 

[hughmon]

It'll be fairly close (withing a few dB), though only you can decide if it's close enough for you. Depends on your LPs too, i.e. if you have a lot that are mastered at an above average or below average level. I usually aim for around 40 or 41 dB myself.