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Confused about gain: phono + pre, or just phono?

I'm trying to figure out how "low I can go" on my phonostage. I understand that the ideal numbers aren't necessarily "written in stone" in that the cart will still work even if the number isn't exactly hit. I'm looking to try to understand the ideals.

So, when trying to sort out what your phonostage will support, I've seen the formula that takes your cart's output in mV, divides that into 1, takes the log of that, and multiplies it by 20. The result is the targeted minimum that your phonostage should provide. Said another way:

Targeted phono gain (in dB) = 20 * [log * 1/(your cart's output)]

My question: is that resultant just what your phono stage should support, or what your phono+pre supports?

For example, say you have a .25mV cart.

1/.00025 = 4000
Log10 of 4000 = 3.6
20x = 72

So, you need 72dB.

But what if your phono does 60dB and your pre does 12dB? Are you good to go, or do you need 72dB from the phono by itself?
socrates7
hdm
1,062 posts
 
I've had no noise with the DB Systems stage (which is a very inexpensive phono preamp) and the Aqvox but reviews of both have noted that these are extremely "quiet" phono stages. Both are pretty much "CD quiet" both while the music is playing and between tracks. As you point out, it is a matter of the quality of the design.

Of course, it is always a question of YMMV and I think there is a legitimate caveat with respect to pairing tube phono stages and low output cartridges; in general, that can be a combination that leads to a fair bit of noise once you get into and past the high 50's with gain.

I guess I've just been fortunate to own quality phono stages at different price points but, as I said, IME the KAB calculator is just about dead on. Could be I've just been lucky.
dcarol
62 posts
 
The phonostage gain with reference to the cartridge has nothing to do with the following preamplifier.

What your phonostage needs to do is amplify the signal from the cartridge correctly under 'ideal transfer' characteristics which should give you low noise and low hiss as is my and Hdm's case.

Whatever the output level is from your phonostage afterwards is whatever it is. The most important thing here is gain matching the cartridge to phonostage and NOT phonostage to preamplifier.

Most preamplifiers can handle an input signal upto 8V and more if they are 'discrete technology' types. A phonostage without variable gain output would output approx 560mV-660mV with your standard 0.25mV cartridge (depending on cartridge output variances).

I would just set your phonostage for 65dB is you have a 0.25mV cartridge and get on with listening to music.

socrates7 OP
77 posts
 
"I would just set your phonostage for 65dB is you have a 0.25mV cartridge and get on with listening to music."

I would have done just that, but this thread was more "since I don't have one, carts with what parameters should I be looking at".
larryi
4,077 posts
 
From experience, I would say 60 db of gain is adequate for most application for a cartridge rated at .25mV output. I run a .30 mV cartridge into a phonostage with 60 db of gain and there is absolutely no noise issue at all. I do have to crank the linestage fairly wide open (13 db of gain) to feed my Stax headphone amp which apparently has very low gain, but with speakers, gain is not an issue.

With a low output cartridge, whether noise becomes an issue can be dependent on HOW gain is achieved. With solid state, noise is usually not an issue (the one area where solid state is clearly superior). With tubes, getting such high gain using active gainstages can result in high noise level. That is why a lot of people use step up transformers in front of the first active gainstage (transformers do not add noise) in tube phonostages. My tube phonostage has such a step up transformer built into it.
ef227
9 posts
 
Enyone want to enjoy the amazing DL304 the most, should try it with Einstein little big phono ,
although price different doesn't make sense
as a package, it is one of the best combo's you can get around 4000$, dead silence, liquid, smooth and dynamic and highly musical.
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