How to pick a COMPATIBLE phono cartridge

Robd2, an example of what is likely to be a good scenario would be the combination of a 0.5 mv cartridge with a 60 db phono stage and a 10 db line stage. Those numbers are fairly typical for a system utilizing an LOMC cartridge, and the 60 db phono stage gain can be taken as an indication that the designer intended it for use with such a cartridge. Also, the 70 db total gain that is provided by those components (when the volume control on the line stage is turned all the way up) would boost the 0.5 mv output provided by the cartridge under the standard test conditions (which correspond to a volume that is quite loud but not as loud as the dynamic peaks of some recordings) to about 1.5 volts, which is right in the ballpark of the voltage that is required to drive most power amplifiers to max power.

An example of what is likely to be a bad scenario is the one discussed earlier, involving use of a 0.4 mv cartridge in conjunction with a 52 db phono stage and a 25 db line stage. Even though the total of those gains is more than adequate for use with a 0.4 mv cartridge, the four factors I cited suggest that noise performance is likely to be inadequate.

The reason for my repeated use of the word "likely" is that different phono stages having the same gain can have considerably different levels of internally generated noise. And manufacturer specs on signal-to-noise ratios, when and if provided, should be taken with multiple grains of salt because the input or output signal levels they are based on are often not specified, and the "weighting" they may be based on (such as A-weighting) is also often not specified. If Stereophile has reviewed a particular phono stage, though, John Atkinson’s measurements and his associated commentary about noise performance can often be helpful.

Regards,
-- Al

hdm 1-1-2018
Unless you are running a very unusual system (passive pre-amplfier, flea type amplifiers with extreme hi-efficiency speakers, etc.), I think you will find it [the KAB calculator] will give you a very accurate read on the type of gain optimization you need to do with the cartridge/phono stage interface.

This is a good point, which emphasizes that an online calculator should not be applied blindly.

Specifically, the KAB calculator indicates the gain that would result in the cartridge’s rated output being boosted to 0.325 volts. As indicated in its description that value was chosen based on what is appropriate for driving a CD recorder. However power amplifiers will typically require inputs in the vicinity of 1 to 2 volts to drive them to full power, for single-ended inputs, and twice that for balanced inputs. Which means that the gain of a typical active line stage, perhaps 6 to 15 db or so, will be required to assure that the phono stage gain specified by the calculator will make it possible to drive the power amp to full power.

On the other hand, like most CJ preamps Randy’s 16LS provides unusually high gain (25 db) for a line stage. So if a gain problem were to arise it would most likely be in the other direction, resulting in the volume control having to be used at undesirably low settings. That is very unlikely to occur with a cartridge/phono stage combination, but is certainly a possibility with a CD player or other digital source depending on the gain of the power amp and the sensitivity of the speakers.

Regards,
-- Al

First things first...finding compatible cartridges from which to consider by having the basis to do so. After knowing what works, the fun will begin in seeking out the one that has the sound qualities I’m looking for!

Excellent approach!

As I’ve said in a number of past threads the main usefulness of specs and measurements, IMO, is in **ruling out** from consideration candidates for purchase that would not be optimal (or even suitable) for use with other components in the system. Or in some cases that would not be consistent with listener requirements or preferences, an example being the maximum volume and hence dynamic range capability that can be provided by an amp/speaker combination.

Which thereby reduces the randomness of the selection process, and minimizes the likelihood of expensive mistakes.

Best regards,
-- Al

Tablejockey 1-1-2017
Maybe your local store was just referring to only the phono stage, not considering your line stage gain adding to the equation?

Probably so, but please note no. 4 in my previous response.

Regards,
-- Al
 

I’m doubtful that a 0.4 mv cartridge would be suitable for use with your equipment. While as stated earlier the overall gain provided by the phono stage and the preamp would not in itself be an issue, several things suggest to me that unacceptable hiss and/or hum would be likely to result:

1)The phono stage’s specified hum and noise figure of 88 db below a 10 mv input corresponds to only 60 db below 0.4 mv, which seems marginal at best.

2)The 88 db figure may be based on psychoacoustic "weighting" techniques that are commonly used in deriving such figures, meaning that the unweighted performance may be worse.

3)The 52 db max gain spec of the phono stage is about 8 to 10 db less than the gains of most phono stages that are intended for use with cartridges having rated outputs in the vicinity of 0.4 mv.

4)The relation between cartridge output and phono stage signal-to-noise ratio is what primarily determines the amount of hiss that will be present when playing a record. Adding gain further downstream will not improve that; it will just result in using the volume control at lower settings.

I suspect that the 0.8 mv version of the cartridge would be suitable, but I can’t say that with any certainty. If you already haven’t done so, it would be a good idea to research what cartridges others have reported using with the EF-1.

Good luck. Regards,
-- Al