Tube Preamp Paired with Tube Phono Stage?

05-16-12: Actusreus
... are audiophiles unnecessarily obsessed about resistive loading, and manufacturers simply cater to that obsession? As always, I am sure the answer is more complicated than that.

Hi Marek,

Not necessarily. As Ralph indicated, it can be presumed (or at least suspected) that JC's phono stage design can handle frequency response peaks in the ultrasonic and RF region with relative grace (i.e., with minimal interaction with audible frequencies). But it is probably safe to assume that many other designs will not be able to, which would make the choice of resistive loading more critical in those cases.

And I'm personally not sure if the effect Ralph described is the only means by which differences in resistive loading may affect sonic results when LOMC's are being used. But it is certainly a major one.

It is still unclear to me why, but increasing the volume at a certain gain level will not render the same results as upping the gain at a given volume level. IOW, the sound is much better at a higher gain setting and lower volume, than lower gain and higher volume.

There are a great many variables, many of them unpredictable, that can influence that tradeoff. Some of them are the signal-to-noise characteristics of the phono stage and the preamp; the distortion performance of the two components at various signal levels; side-effects of the preamp's volume control mechanism, that may worsen as the amount of attenuation is increased; ground loop issues that may exist between the two components, whose significance may be lessened if the signal level is greater at the interface between them, etc., etc.

Best regards,
-- Al

Actusreus, how much gain does your preamp have? As Layyi mentioned, his preamp has 13 db of gain, mine has 22 db of gain. Either when combined with a 60db phono stage would be more than enough for most any cartridge I can imagine.
I just sold a phono stage with 66 db of gain while using a cartridge with a 0.24 mV output. Combined with my 22 db of gain from the line preamp, I never turned the volume knob much past 10 o'clock. Together that combo provided 88 db of gain, I'm sure I could have gotten by on 82 db of gain very easily. While doing your KAB number crunching, don't forget to add in your line stage's gain, unless of course your line stage has no gain.

Thank you Al. I've always been interested in the interplay, for lack of a better word, between volume and gain. I understand they are obviously not the same thing, but certainly more gain at a given volume = louder sound. So with variable gain settings gain can also be used as volume control, even though in a more dramatic way.

As a correction to my post regarding resistive loading in the JC-3, it actually has two settings, not one, for MC cartridges: 100 Ohm and 47k Ohm.

Jmcgrogan2,
I'm not sure, but as I mentioned in one of my posts above, my preamp has five gain settings so it certainly does have gain. I might be wrong, but I believe the KAB calculator only considers the gain of the phono stage. It's possible that an assumption is made as to the base line preamp gain. You can read more about this at www.kabusa.com

Btw, for a cart with an output of 0.24 mV, you apparently need 63 dB of gain so it makes sense that you found 66 dB to be more than enough. I just experienced the opposite a few times, so I am always very careful about matching the phono preamp gain with the cartridge output.

The KAB calculator considers preamp gain period. That's phono preamp + preamp gain. So the calculator said I needed 63 db and I had 66 + 22 = 88db of gain. Way more than enough. I probably could have gotten by with a phono stage with a 50-54 db of gain for my 0.24 mV output cartridge. Maybe I could have turned the volume knob up to 1 or 2 o'clock instead of 9 or 10 o'clock.