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Now I re-listen all the things the we try to measure. To surmised everything I have to tell that Dima’s way to looks for optimum operation point of the tube (setting balance for voltage vs. current sufficiency) turned out to be very successful as I did not see absolutely no discrepancies between auditable and measurable. As long the tube has the identical and symmetric current and voltage clipping it does sound the best. I have no idea why audio  people create so much “cult” about finding the best operation points for tubes and why any controversy exist – it look so simple and so unambiguous – for one stage of course.

Anyhow, I was not able to listen the Single-stage 6E5P with horns. The tolerable volume level I got driving Vitavox with 0.6-0.7V… VERY far from any dangers regions. So, I took 16R speaker with 90dB sensitivity and drove it with Single-stage 6E5P. First - the 0 bias on the tube – it was absolutely unusable, sorry ml8…

The best sound I got from this tube with ~ 6.5-6.8W dissipated on plate. More power made the  sound more stiff less power made… less power…Now current vs. voltage (with 16R load) keeping the same power. More voltage and less current made Sound “brown”, more compressed and in a way “inverted”.  More current and less voltage made it sound suffocated. In a way deficiently in voltage or current both produced that over- damping effect at upper bass and lower midrange but that over-damping sounded different for voltage and different for current. It is have to explain in words but it is VERY much the same as over-damping of bass when we adjust VTA of cartridge vs. lighting of bass when we change the tracking mass.

Ironically the best subjective sound I got in the best measurable point. I did a few blind tests  with different tubes when I was trying to set subjectively the best sound adjusting bias without looking at miliampermeter of the plate current. In all cases, finding this operations point and then driving the amp into distortions I has the perfect symmetrical pictures of voltage vs. current. It all was at the same current but at different bias settings (from minis 3.1V to minis 3.8V). So, the “magic” number was 175V and 38mA…

Now is the quandary… Do I have to for the Single-stage Milq pre-select the tubes or I need to put bias adjustment in there? Perhaps only for upperbass channel where I “might” be important. Now is the biggest question: now important all of this? All those experiments took place with amp outputting 3V but during it live the Single-stage Milq will do less then 1V. I do not have a full range 109dB system to assess subjectively how will sound. Listening single channels I can say that the deviation form perfect voltage vs. current setting is WAY less (if any) auditable at 0.7V. So, I need to think how important it might be in the real world.

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