Ed,
What is your favorite model of the 700's (700, 700B, 700ll, 700HF)?
I prefer the PL14A/B or PL20 versions, although I want to try the 700HF version as well.
Nick,
My favorite model remains to be seen as I only had the (3) 700HF's only briefly before I sold and traded them off.
Perhaps I should add a 700HF build to the list.
My neighbor Dean (who was the last factory service manager at Phase Linear's) favorite is an original 700 and he is also a musician. When Bob Carver showed up at my friend (Greg's) house in the mid 1970's he brought along with him a 700 not the newer 700B he had designed. (That's a story for another day.)
The original 700 was the quietest of all the 700's Phase Linear built. Over time the amplifiers got progressively noisier in the area of signal-to-noise ratio. On the other hand with the use of better output transistors (in the late 1970's) they became more reliable. After approximately 1973/4 Phase Linear also used carbon film instead of carbon composition resistors and more reliable electrolytic capacitors on the pc boards.
I know you are already aware of the following (from our previous discussions) but I will post some comments for others to see below....
More than likely, the 700HF had the best specs of any Phase Linear 700 series amplifiers with perhaps the exception of T.H.D. (and DC offset). The 700HF was rated at 350 watts per channel from 20Hz to 100KHz at .25%, I suspect it also had the highest slew rate and lowest phase shift as well since they should correlate to the wider bandwidth. Albeit, it will more than likely oscillate with any newer MJ series output transistors and the use of any slow-down or bypass capacitors would limit its bandwidth. In which case, the 700HF might only be built with the older slower output devices: like the XPL 909 (GM Delco DTS411's) or FPL909's (Fairchild FT411's) The trade-off would be its reliability.
So as I often like to say; everything in life is a compromise, you have to give up one thing to gain another.
I am sorry I wasn't able to directly answer your question but after I complete my builds of 700 series amplifiers and conduct measurements and listening tests using nearly every revision of Phase Linear pc boards as well as White Oak audio rev A, D and E boards, I should have some better ideas as to their performance and may be able to come up with some preferences. Then again my ears aren't as trained as they use to be. Nor do I have the ideal speakers and room environment. (NOTE: I would also like to try any of your pc boards.)
Ed
