Phono Preamp Gain Question

The KAB calculator is very helpful in getting a broad handle on the gain necessary to lift a low output cartridge. It can be found here:

http://www.kabusa.com/pregain.htm

Scroll down the page a bit and you will find it.

Just remember that there are at least two different test conditions that are used to determine cart output. ZYX LOMCs are specified at 0.25 or 0.28 but the test conditions make that equivalent to almost 50% higher output when equated to more typical test conditions.

Well the KAB calculator is based on the 5cm/s output (CBS standard). If your cartridge's output was measured on the JVC standard (3.54 cm/s), you will have to multiply your cartridge output by 5/3.54 = 1.41 to translate it to the CBS standard to input into the KAB calculator.

In other words, if your 0.28 is measured at 5cm/s, you can just plug it in, if it was measured at 3.54 cm/s, you will need to plug it in as a .39 mV (0.28 X 1.41).

I don't know how accurate that calculator is though. I have an identical cartridge output as you, 0.28 mV. KAB recommends an 'optimum' gain of 61 db, my phono stage has 60 db of gain, and that is MORE than enough. I never turn the volume knob past 10 o'clock. Granted, maybe you listen louder than I do, but I think KAB's measurements are overall preamp gain, including line stage.

KABs calculator is based on phono preamp gain, it says it right there. Why I said that it helps to get a broad handle on gain is because the gain of the line stage will be unknown. Many modern line stages have very low gain, from unity to 8db. Tube line stages that do not use feedback can easily run to 20db of gain.

Where one sets the volume control has nothing at all to do with the gain of a preamp. I have a cartridge that outputs .3mv at 5cm/sec and a combined gain (transformer and phono stage) of 63db and that is about optimal in my system as far as noise archituecture goes, with 20db gain in my line stage, it's a bit excessive in terms of gain.

To answer the OPs question, however, I would not go below 54db gain in the phono stage, and 60db would be better still.

Marty, since KAB doesn't know what kind of line gain the user will be using, they also must consider a passive line stage, with no gain. That's why I alluded to the fact that the 61 db of 'optimum' gain should be PLENTY, if using an active preamp.

Because I'm running a cart with the same output (0.28 mV) into a phono stage with 60 db of gain and a line stage with 20 db of gain and the gain is way more than I need. It seems like your situation is almost identical to mine, with similar results 80-83 db of total gain is much more than enough.

So the 61 recommended 'optimum' reference seemed pretty high to me using a line stage with an additional 20 db of gain. Though I'm sure it wouldn't be excessive if I were using a passive preamp.