They tend to like to blow up....
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Working in Orlando, FL; It seemed like we had one to rebuild
every other week(lots of discos, Naval Base clubs, live music
venues, college students, etc. in that area). Of course,
there were a number of other brand amps in for repair also, as
we did pro and home audio, both. But 700s were what we saw
the most often. We liked them(for the cash flow). The
speaker drivers, that they took out, generated revenue for our
reconing department, as well.
I had the original 700, and it did zap out, sent back to the factory- this was circa 1973 or so, and worked ok after that and sold it to go to tube stuff. My recollection was that the 400 (original version, i don't know about the series II) sounded better than the original 700. I used mine with a Quintessence preamp, remember those?
Man, that was a long time ago!
A lot of these amps were misused/abused. Rock bands, loud dorm room systems using double Large Advents that dipped to well under 4 ohms at certain frequencies etc. They sound good, then and now, and I agree that the original 400 sounded better than the original 700. Today they are upgradable and still working fine. Used the way they were intended these are solid amps and still hold their own.
Bill is right --- abused, very nice sounding, and hold their own. The biggest weakness of these were their poor wiring layout and small power supplies which caused instability at high power outputs which are easily fixed. A modified Phase Linear 400 with reworked power supply, good metal films, caps, and reworked protection circuit sounds outstanding and rivals almost anything made today.
I replaced two bridged MC2100 amps with a PL 400 in around 1973 or 74. The PL sounded better to me, a lot better, but it all depends on what sound you like. The Macs were warmer, had lush sound, but were not as clear on the highs and had less control of the bass. This is subjective of course, but that Phase 400 is still with me, the Macs are long gone and not much missed. Make no mistake, the Mac amps were built like tanks, the Phase was built cheaply, but again, taken care of, it has stood the test of time. I am going to have the PL400 gone over and modernized just because. All this old stuff is fun to have and to mess with. I have owned a lot of amps over the years including other Macs and Marantz, ARC and Adcoms. They are all good, I have never had a bad one.