Are you sure? Though I've never even seen a vacuum capacitor in real life, and thus never measured the linearity of one, I could imagine the lack of solid material holding the electrodes apart allowing them to move under the attractive force of their opposite charges at high voltage, causing nonlinearity.
The movement of heavy chunks of copper at 100Mhz will be extremely tiny due to the 1/k/m/((2*pi*f)^2) dependence of displacement with mass and frequency... k is probably in the 10^6 N/m range (100kgf/mm), mass perhaps 0.1kg, f = 10^8.... Even at audio it will be incredibly small as the forces are so very low, perhaps 0.5mN for 100V, assuming 0.1m^2 area and 3mm spacing (300pF), with a compliance of 1/k, that's 0.5nm displacement assuming inertia is insignificant, or less than 1ppm of the plate spacing, and the motion might well be very linear in applied field, not contributing to any distortion anyway, elastic deformation is by definition linear.
Also if you look at the design of these capacitors you'll see just how rigid they are with intermeshing concentric cylinders - most of the plates have equal and opposite electric fields outside and in that balance out. I suppose a vacuum variable capacitor with a loose leadscrew might rattle about a bit though(!)
Also if you look at the design of these capacitors you'll see just how rigid they are with intermeshing concentric cylinders - most of the plates have equal and opposite electric fields outside and in that balance out. I suppose a vacuum variable capacitor with a loose leadscrew might rattle about a bit though(!)
I was able to get a few Hafler pieces, Pro5000 amp, 9505 amp and the 915 preamp, the designer Jim Strickland used a combination of polypropylene and polycarbonate caps.
They were very expensive back in the days, I wonder why he did it that way ?
Why he did not use only one type of film caps. what was the goal ?
Pro5000
9505
They were very expensive back in the days, I wonder why he did it that way ?
Why he did not use only one type of film caps. what was the goal ?
Pro5000
9505
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Hafler was building cost effective designs. Polypropylene where possible, cheaper polyester where it mattered less.
I dont think they were trying to save in costs the pro5000 was $1400 in 1991 and the 9505 was $2200 in the mid 90s
Not during the Rockford fosgate era, the Pro5000 and the 9505 are from that era
in addition polycarbonate was more expensive than polypropylene
in addition polycarbonate was more expensive than polypropylene