LCR phono stages we know about

Thekong, Thanks for mentioning the Thomas Mayer LCR phono stages. I had been meaning to do so as well. He seems to sell an LCR phono in kit form, using Dave Slagle LCR modules (aka "Intactaudio"). Very tempting. As to this shoot-out, it is not very helpful, although it seems the participants were having great fun. For one thing, several different SUTs were used with the Mayer LCR; I think the SUT will a major effect on sonics, if not THE major effect. I am somewhat familiar with the Scott Frankland phono stage mentioned. IMO, it is good but not a contender among today's best options. But you've added Thomas Mayer to our list. I wonder what he charges for that kit version?

But I really do not know how one can avoid having either an R or a C in the series signal path and still get to proper RIAA equalization.

Any tube gain stage has its inherent output impedance which can act as the invisible series resistor R in the EQ. That's been done in some designs by the late Allen Wright and others.

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Hi Lewm,

Yes, the shootout was meant to get a feel on the basic characters of the units rather than serious comparison, which you really can’t do in a short time. If I understand correctly, you can order the complete phono from Thomas Mayer, with the option of supplying him with your own LCR module, or take the one he has. My friend’s unit used the Tango module.

I also agree that the SUT has great effect on the sonic, and it take considerable experimentation to match a cartridge to the SUT / phono. Since most of the other units in the shootout had built-in MC gain, we didn't prepare too many SUTs for the Thomas Mayer, which was unfortunate.

Regarding LCR, both the Thomas Mayer and a DIY SS unit that my friend built have a very polite, refine, relax and musical presentation, which make you just want to enjoy the music. It is in contrast to some of the modern phonos which give you the “in your face” resolution and dynamics. I am not sure whether this is a common character of LCR phonos, and I am very interested to audition the Allnic LCR models.

Hiho, The output impedance of the input voltage amplifier or gain stage has to be accounted for in the design of the RIAA. Therefore, as you may be suggesting, output impedance is a factor in determining the values of the reactive components needed to effect an RIAA equalization. But output impedance per se cannot substitute for Rs and Cs that make up the RIAA. Perhaps I don't get what you wish to say. Suffice to say that if you do anything to alter the output Z of the gain stage, you have then to change the values of Rs and maybe the Cs in the RIAA (or at least the value of the first R). This still does not suggest to me how the Emia RIAA topology is achieved. Maybe Dave Slagle will walk by this thread and stop to enlighten us.

Here's one example from a Wright circuit. As you can see, there's no series resistors, the output impedance is the invisible resistor. The downside of such circuit is that tube aging can affect plate resistance and therefore R's value and RIAA accuracy. Wright's circuit uses a lot of regulations to perhaps make the circuit as stable as possible and not affect EQ accuracy. I believe such circuit might need tweaking the RIAA network when changing tubes. There might be other "tricks" in the circuit that I might have missed.

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