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Finally, someone who has tested multiple amps at the same time. Great Writr-up. I was really interested in your outcome. I had the The Raven Reflection MK2 amp and loved it. Dave T is an awesome guy with some of the best vintage tubes out there. Enjoy your music and congrats on your final selection.
Just a comment to @gareents. You said: "When I say easily, normal listening levels were at only one quarter
volume on the three tube amps. At half volume, the sound level in the
room became uncomfortable"
Just a technical note -- the position of the volume knob on a preamp or amp tells you next to nothing about how much power the amp is putting out nor now close you are to clipping.
Some amps might only need an input of 1 volt to achieve full power output, while another might need 2 volts or more to achieve the same full output. That then gets combined with the voltage output capabilities of the source component -- many have had the experience of needing to adjust the volume knon when switching from, say, a tuner to a CD player. Those two sources had different output voltages.
The final item in the equation is the linearity -- or lack thereof -- of the potentiometer or resistor network used in the volume control itself. Turning the knob up halfway may deliver half of the potential voltage, or something different. I've heard stories in years past that some manufacturers used potentiometers that allowed 3/4ths of the voltage thru at the halfway setting, thus making the amp appear more powerful than others to the casual user.
Thus, the only way to know for sure how much power you are sending to a speaker to achieve a particular listening volume is to use a meter on the amp's output to see what voltage is being delivered.
Having done this for my own system (which also has 88 dB sensitive speakers), I find it takes about 3 volts to achieve an average listening volume of 85 dB, with peaks running to 5 or 6 volts. That translates to under 2 watts average with peaks of 4 or 5 watts. For me this is as loud as I want or enjoy. However, if you listen louder than that, the power need escalates rapidly since volume has a logarithmic relation to watts.
@noromance - I'm sure tube rolling would affect the PrimaLuna and Octave, but didn't have the necessary supplies to try. Plus, wasn't prepared to go down that particular rabbit hole. Since Raven supplies different NOS tubes and encourages one to try them in different positions (row 1 versus row 2), I did switch the Brimar and Phillips tubes around. Significantly different sound. Brimars in row 1 had stronger bass and mid-range with backup instruments more forward. Too forward for me, I preferred the more vocal/lead instrument forward sound of the Phillips in row 1.
@mlsstl - appreciate and understand your edification. What I was trying to convey (poorly) is that ALL three amps had the exact same one quarter and half volume control to speaker response. Found that interesting.
I am shocked, shocked, etc.