Phono Preamp Gain Question

Jmcrogan, I am using the same cartridge as you. And as I stated above, my preamp, a Modwright 36.5, has 12db of gain. The responses above have more or less convinced me to not consider the ARC PH6 or the CJ TEA2SE. I think my focus now will be on the Herron VTPH-2 and the Pass X-15. Both of those should have plenty of gain; in fact I know that Dodgealum used the 36.5/VTPH-2 combo recently with great success.

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.

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.

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.

Tee shot: Your question is difficult as there is no specific answer without taking into all of your components from cartridge to speakers. I have a cartridge that has .28 db of gain. My phono stage high gain is 60 db but that is not nearly enough to drive my Soundlabs to acceptable levels (75-80 db levels). My preamp 15 db, amps 20 db,and speaker 86 db? ). Require the volume to be turned up where the noise level is unacceptable. I lowered the gain on my phono stage and added 14 db with a step up which brings my gain to 68 db. I now have a very quiet background that also requires a lower volume on the control dial. So, I would recommend a phono stage that would allow adjustable gain or purchase a step up transformer and experiment with several different brands.

You have a fairly low output cartridge and your line stage isn't on the higher end of gain options. While there is the variable of amp sensitivity and speaker efficiency, Salectric's speakers being very efficient so he needs less gain, I think with average sensitivity and efficiency even a gain of 60 is low for you. Bear in mind less will work, but noise becomes an issue.

My cartridge is .35, my line stage is 18db and my phono stage is 68db. But, my speakers are only 88db efficient. I may have a little more gain than I need from my phono stage, but I've gotten addicted to a dead silent background. You have a lower output cartridge and 6db less gain from your pre amp. Absent something on the amp/speaker end to reduce your gain needs, you need at least 65db.

I really like my Parasound JC3.

Here is the obligatory comment to a question about a phono preamp :-)

Liberty B2B-1

Good listening

Peter

PS I do make them - Thought I'd change up the post a bit :-)

I agree that a phono gain of 56 to 65 or so should be just fine. My setup is pretty similar to yours in terms of gain. My MCs range from .25 to .35mv and my line stage has 15db gain. My power amps span low to high sensitivity, and my speakers range from 90 to 97db. I find a total phono gain (including MC step up) of mid-50's to mid-60's to be just right.

Good comments by the others. Seconding Sarcher's comment, attempting to define "the lowest gain that a moving coil stage of a phono preamp should have" for a particular cartridge is risky, because different phono stages that provide the same amount of gain can differ widely in how much noise they generate in doing so. Also, comparing signal-to-noise ratio numbers for different phono stages is often an exercise in futility, because S/N specs are not consistently defined in terms of reference levels, and in terms of whether and how they are "weighted".

Also, the sensitivity of your power amplifier (the input voltage that is required to drive it to full power) is a factor to consider. If it has particularly low sensitivity, meaning a high sensitivity number, if the sum of the phono stage and line stage gains are too low you may not be able to drive the amp to full power even with the volume control at max.

My suggestion is simply that after coming up with a preliminary list of candidates, try to determine if others have used each of them successfully with the particular cartridge, or at least with similarly specified cartridges.

Regards,
-- Al

I would say you need at least 60db. 66db would be better. It really depends on how quiet the phono stage is. If it claims to have 70db gain but has a high noise floor then you can't really use that 70db. It is very difficult to get high gain and low noise at the same time. It's even more difficult to have both and good sound as well.

I'm using a 0.28 mV cartridge too, 60 db of gain in the phono stage, 20 db of gain in the line stage is MORE than enough for my system. I wouldn't recommend less than 56 db of gain for you.

Gain is in a way a chain, even from Preamp to Amp is important or how easy your amps can drive your speakers... but generally a Phono Stage with 58-64dB will be right.
Don't be fooled from excessive high Phono gain, most do not sound good at a level of >70dB, good Phonostage Design is a real task, even today.