@almarg Re the Luxman EQ-500, I note that depending on the selection between the two LOMC gain modes it provides it presents the cartridge with a load impedance of either 40 ohms or 2.5 ohms. While the OP’s 0.3 mv cartridge has a recommended load impedance of >100 ohms, and an internal impedance of 32 ohms. Doesn’t seem like a good match in either gain mode.
Hi Al,
I’ve become interested in the Luxman EQ-500 but I’m bedeviled by these load impedance specs and hope you can help me to make sense of them. I imagine 2.5 and 40 ohms refer to the primary impedance (if that's the right term) of the step up transformers, which are the first things seen by the MCs, at least according to the schematic in the manual. But I can’t be certain, and Luxman provides little info on its SUTs.
The question for me is how these numbers translate into actual cartridge use.
Now, the EAR MC-4 also denotes its four step-up options by impedance values (again, making little sense to me; I always think it terms of windings and gain) of 3, 6,12, and 40 ohms. These correspond to ratios of 1:30, 1:24, 1:18, and 1:10, respectively, for EAR.
I’m tempted to conclude that Luxman is denoting similarly with these impedance values. The 2.5 ohm setting would therefore suggest something like 1:32 or so; 40 ohms would imply 1:10. The actual load impedances for the cartridges would then be something like 50 and 470 ohms, respectively, for MC-Low and MC-High. Am I getting warm??
But the gain steps in the Luxman don’t correspond precisely what one would expect from those to those SUT windings. 1:32 would typically add around 30 db of gain--more than the 27db provided by the Luxman MC-Low option. And if the 40 ohm setting translates to 1:10, or 20db of gain, that’s little more than the 19db offered by MC-High. Perhaps some gain is lost because of other aspects of the Luxman circuit?
If all this wild surmise is valid, then the OP’s cartridge with internal impedance of 32 ohms at 0.3 mV, set at the MC-High setting (if it’s a 1:10 SUT) would see 470 ohms as a load, which may well be fine. The gain might be a little low, though, at 59db (default 36 + 4 from gain knob + 19 from the SUT). Seem right?
I am tempted by this phono stage, at least for an audition, but first I’d like to be able to predict how it will work with various cartridges. You’re just the man to ask. Thanks in advance.
Bill
