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Why is it that?

Posted this on The Asylum as well.

I have a VPI Scout turntable with the JMW9 arm and a ZU DL103 low output moving coil cartridge. My preamp is an Audible Illusions Modulus 3B (their latest and greatest)the tubes which were bought from Audible Illusions are well broken in and the preamp has an excellent phono stage. I use a Denon AU320 SUT between the turntable and the preamp. VPI phono cable is used for the connections from the turntable to the SUT and from the SUT to the turntable.
The cartridge is rated to be used at 40 ohms and my SUT has settings for both 40 and 3 ohms. Besides the significantly lower volume when using the 40 ohm setting, the sound seems a bit more romantic and rich which is good for certain kinds of music. However, when I play my rock from the late 60's up to present, I much prefer the 3 ohm setting as it seems to give me a more lively sound with a little more snap.

What are the differences between the 40 ohms and 3 ohms settings? Is one setting more right or wrong than the other, and why? Eventually, I plan on getting a Bob's Devices SUT, or have the John Curl designed moving coil preamp removed off my Modulus 3A preamp, and put on my Modulus 3B preamp. I am leaning towards the Bobs Devices as it will still allow me to use a moving magnet on the turntable by removing the SUT. Once the mc phono board are installed on the Audible Illusions preamp, you are stuck with using low output moving coils only.

Enlighten me please?
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Showing 3 responses by lewm

lewm
12,429 posts
 
I do it both ways. I have both a full-function preamplifier (Atma-sphere MP1) and an outboard phono stage (revamped Silvaweld SWH550). I use the MP1 for LOMC and the Silvaweld for MM/MI. So I am not as dogmatic as I may have sounded. Nevertheless, given my 'druthers, I'll take the full-function preamplifier. It has to be top-notch in quality, however. I sense the Silvaweld is at a disadvantage, because it requires a cathode-follower output section in order to drive the IC that connects it to the linestage section of the MP1. Plus you've got to more connectors in the signal path. However, there is room on heaven and earth for both approaches.
lewm
12,429 posts
 
Dear Zd,
The debate over "separates" vs full-function preamplifiers is a never-ending one, but suffice to say that there are many advantages to an all in one unit vs separate phono and linestages and vice-versa. But why would you expect "better synergy" and saving money to be advantages associated with separates over an all in one preamplifier? Most assuredly, those would be points in favor of the latter choice. Two more advantages are avoiding purchase and use of a costly, signal degrading interconnect, and the fact that a separate phono stage usually needs a buffer stage to drive said interconnect. The very short internal signal wires used in a full-function preamp to connect its phono section to its linestage can often be implemented in such a way as to avoid a buffer stage.
lewm
12,429 posts
 
What CJ says is spot on, which is why I was wondering at the sonic results. The OP writes that the sound is more "romantic and richer" and moreover that there is an apparent loss of gain, at the 40-ohm setting vs the 3-ohm setting. That does not make sense, if the 40-ohm setting corresponds to an input Z of about 470R or 1000R (seen by the cartridge). That sonic description more fits what I would expect from the 3-ohm setting. Could it be that the Denon SUT is mis-wired such that the 40 setting is actually the 3 setting and vice-versa? ("Romantic", "rich", and apparent reduced cartridge output are associated with using a phono input impedance that is lower than optimal for the cartridge internal impedance. 470R input Z is not going to sound that way with a 33-ohm cartridge internal resistance.)

And FWIW, lots of DL103 users do seem to prefer oddly low phono input Z (breaking the 2X to 6X "rule"), nearly equal to the cartridge internal resistance, for best sound, even though there is some loss of gain associated with such an impedance mismatch.
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