Break in period

Shadorne -- that mustn't be what I'm referring to. I distinctly remember them comparing distortion figures (3%) I think between two ATC models at specific spl levels...Oh well.

the higher output impedance of a tube (with ouput transformer) coupled with a typical bumpy speaker load. This results in a different frequency response/presentation from a tube/speaker combo versus an SS/Speaker combo

Normally, yes. But one thing that is important in a spkr -- and one thing we do NOT know -- is the strength of each driver's magnet. A very "strong" driver (e.g. a Lowther, etc) paired with a SS will be overdamped and sound like Donald Duck unless tamed (i.e. at xover level). A hi output impedance paired to a very strong (i.e. electrically damped) driver may provide the optimum marriage...

Gregm,

IMHO, although high damping factors is a "pushed" feature of SS amps....I think it is really over rated.

Frankly the driver Qes and Qms coupled with the box design almost entirely dominates driver response...above a damping factor of about 5 a higher damping factor really makes almost negligable difference to the driver response, as the voice coil and magnet size dominate the driver electrical damping. (A good speaker design should be as close to critically damped as can be achieved given a host of other compromises)

I suspect most differences heard with low damping factors are more related to frequency presentation, as a high output imepdance device acts as a filter when coupled with a variable load (speaker)....

After retubing of the PH5 with 4 matched 6922EH (purchased directly from ARC) the magic of the PH5 sound is still there, but i had to turn up the volume several clicks on my ARC-LS26 to obtain gain comparable to the old tubes--matched with the VS55 -- i have now about 35 hours -- is that normal ? VASILI

I truly believe if and when "break in occurs" is basically you can kinda tell by the system just being more efficient and less congested sounding, whether turning up the volume or not.. Its got a looser feel to it, more detailed without feeling like your trying to push it out as hard.. This is my experience, now whether technical measured parameters can be prove on this or not is pretty much a pointless point. I have noted in the past there is a certain fluency that comes with a decent amount of hours on a system after time.. Cable break in is much less realistic, but in electronics a little can occur I feel, and definatley speakers I have heard become more fluent and intergrated with a better bandwith, now I guess if you measure a speaker for 20 - 20 without breaking in its all there, but some frequencys start to become more effortless and increase presence in time…

Why How or whatever reallly makes no difference to me, I mean I just don't get why this is such a Sin in audio to believe that such a thing can occur, No doubt its possible some systems simply sound great and maybe what one would think their best right away and they expect no more, but some can come into their own in time as well… Maybe its just you end up getting use to it, maybe cause all of a sudden your power company is supplying better power, and break in is just simply B.S. I guess some people look at this as an excuse for a not perfect performing out of the box design. So this is the only measurement I can give, if you feel 3 months later your system sounds more effortless and you don't think about it so much as to what you can improve, you have started your "Break in" period. Might happen for some, maybe not for everybody that has the sound they want out of the box already.     

Due to thermal cycling and mechanical flexing, some components may change slightly. I would not lose any sleep over this.