Phase Linear 700 & 400 series II

There isn’t much not to love about theses amps. Clean accurate linear signal reproduction. Transparent latency output signal. If they do fail they are very easy to repair. We use to joke that it took longer to get off the shelf and take it apart then to get it back working. Usually an output or two a driver and sometimes a pre-driver along with a diode. The units rarely smoked and if they did they still where an easy fix. Biggest repair mistake was substitution of output and driver components then what was original. Can not be mixed up or blow up. Simple series II repair is to stick with Motorola NpN 15024 and PnP 15025 compliments. Use good heat sink compound or good TO-3 wafers. Watch for stressed PCB wires solder joints to the PL-36 driver board. Make those repair by just doing a complete re-solder to all wire connections. Watch for manufacture solder donut holes at capacitors legs. The old wiggle test with a magnified glass worked well. Check for over heated or discolored emitter resistors at on the main heat sink plane. If you have access to a 10 AMP Variac device using an analog meter at the outputs slowly bring up the amp after repairs and watch for excessive fast load draw. The slow power up should be very smooth and minute amp draw on the meter needle. If you have a dummy load rated up to 8Ω @ 400 watts you may bring the amp to the the rated voltage and perform a current sharing test on each bank. Just saying.
They tend to like to blow up....
"Rarely smoked?" The electronic repair industry
nicknamed them, "FLAME LINEARS."
BTW: That was not just a personal opinion: ie: ( (
The Phase Linear 400 may of had some problems but it was one
of the best sounding amps, tube or solid state, in the mid
Ya...they blowed up real good!
I've had 3 of them (PL400's), but no longer do. How many of you have actually owned one that "blew up"?
Never owned one. Had to work on them though.
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.
Why bother with these old relics? There's amps a'plenty that smoke (no pun intended) those bastards.
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.
I doubt it. Hold their own against what? Something like the newer McIntosh stuff? Puh-leeze. :|
I own a mint PL 400 Series 2 that sees active use in one of my three systems. I've done upgrades that include adding DC protection/output relays.
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.
Poor sounding amps! Even for the 70's.

High frequencies that are like long needles into the eardrum.

Cold, lifeless everywhere else.

High power for their day, which was what sold them.
rivals almost anything made today.

Yeah, right. lol. Also, keep in mind that you said modified and reworked, not stock.
Don c55-I can believe that. Also, you had the big McIntosh amps back then which were/are far superior to the Phase Linear, modified or not.
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.
That's fine. But, you're qualifying the PLs as something great, and the reality is, they're just ok, imo. And the McIntosh model I was referring to was the MC2300. Anyway, we agree to disagree. I'm tired of arguing about this, thanks.
The MC2300 was a great amp. I sold them and lusted for one for several years. The best amp of that era IMO.
Cool. I figured that.