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.
ksaldutti
The old adage of blowing up/flame linear's is a load a hooey.

Take any amp in the day and put it through the abuse the Phase Linear amps went thru, for bands, and they would have been known to fail also.
Mcintosh had the same issues when powering bands.
They all need to be kept cool when powering heavy loads.

Most folks bought used PL amps and whined when they blew up....
DUH!

Anyone that doesn't know the history of an amp cannot bash a brand.
Any used amp with age is not a reliable piece of gear without proceeding with caution...

I've had PL gear since new in 1978.
Never had a problem but, I bought them new.

Just sayin......


The Phase Linear 400 Series 2 amp had many improvements over the series 1. It was much more stable and a low TIM distortion design. It absolutely tested better and sonically blew away my McIntosh MC 2200, throwing a much deeper sound stage with more inner detail. Both bench tested about the same producing about 270 watts per channel. 

It appears many readers don't know the difference between the series one and two amplifier and perhaps don't actually have the test equipment to understand how these amps actually perform with reactive loads. 

"Hand an idiot the keys to a Ferrari and watch what happens."                                                    Based on the plethora of 700/400s requiring repair (way back then): an atypical number of, "idiots" must have owned them.      To the technician: job security.
Funny stuff, the usual bashing.

Hand an idiot the keys to a Ferrari and watch what happens.  Then, the self-ordained keyboard experts will bash Ferrari for being junk.  Says right in the owners manual if the amps are to be used in high power applications to add cooling fans.  Maybe they were right?

From reading though some of the comments, evidently Clair Brothers Audio never got word on what junk the Phase Linear model 700 Series two amps were, or how bad they sounded.  They went ahead and built the largest touring sound and light company in history running them.

Must be some real smart guys with an exceptional business model to have pulled off that feat - maybe just a great accounting department.  :)
also my 400 fried 3 of my speakers with "dc" current. if they were built right with protection, maybe they would'nt be called "flame linears"
i had the 400 and i was reccommened to service it after so many years from the audiogon members. but when it malfunctioned it fried my speakers which is a bad. i guess that's why they are called "flame linears"
The MC2300 was a great amp. I sold them and lusted for one for several years. The best amp of that era IMO.
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.
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.
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.
rivals almost anything made today.

Yeah, right. lol. Also, keep in mind that you said modified and reworked, not stock.
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.
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 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.
I doubt it. Hold their own against what? Something like the newer McIntosh stuff? Puh-leeze. :|
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 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!
Why bother with these old relics? There's amps a'plenty that smoke (no pun intended) those bastards.
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've had 3 of them (PL400's), but no longer do. How many of you have actually owned one that "blew up"?
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
seventies.
BTW: That was not just a personal opinion: ie: (http://forums.stevehoffman.tv/threads/old-phase-linear-equipment.140038/) (http://www.audioheritage.org/vbulletin/showthread.php?25317-Phase-Linear-700)
"Rarely smoked?" The electronic repair industry
nicknamed them, "FLAME LINEARS."