Great two chan amplifier to drive a two way system with a cross over at about 500-800 HZ using a true radial horn.

General surface area of TO-3 output heatsinks may have been insufficiently calculated.

While the Phase Linear 400 was the cleanest sounding amp for the mid to late 70’s and early 80’s, (not to mention the best value, "a dollar per watt" ), it was not without its application problems. The amp was perhaps to early for the 70’s home audiophile smitten with its attractive bronze front, large VU meters, and high power, yet seemingly not durable enough for rock and roll bands and sound companies seeking to replace the expensive but reliable industry standard Crown DC-300 at the time. The Phase Linear was seeking a market that had not yet been defined, and might have been 20 years early. The term “ Flame Linear “ was coined by roadies and musicians when the amps were used in a commercial sound application out of the box, although they were never designed to do so. When used in a commercial application the first 400 amps overheated, went into thermal runaway, and literally burned the driver card up taking everything in its path including your speaker voice coils. Thus the term “Flame Linear” In fairness, this condition may have been aggravated by some well meaning but misinformed roadies over-fusing the B- supply with a 20 amp fuse. “ Not recommended ! By the time the rock and roll bands learned that the amp was not suitable in its present state for commercial use, the amp was so popular a practical alternative had to be reached in lieu of abandoning the amplifier altogether. Phase Linear, was overwhelmed with request for new boards, output transistors, drivers and whatever else was not available from your local electronics house or repair shops. ECG or RCA semiconductor generic replacements were not recommended, nor did they meet the spec. Not being able to purchase complete boards from Phase Linear, presented a repair problem since most sound companies had already been smitten by the amplifier and owned a full rack of amps. In an effort to thwart amplifier damage to the new units a sound company based in Philadelphia was the first to develop a practical solution. To combat the thermal instability when used in these type of applications, some 400’s under went slew rate improvements, two fans were installed on the heat sinks as well as the addition of gain controls. Extra fuse capsules were drilled in the face-plate for in-line speaker protection, and rack handles were added to give the 400 that commercial look. The application and new look proved so successful that it was later adapted by Phase Linear and reflected in their later releases. The Phase was once again in its full glory, unfortunately, all the damage had been done by the unjustified previous bad press, (ie) “Flame Linear” Sadly, the amplifiers popularity faded as quickly as it emerged, yet today is making a comeback among audiophiles longing for a truly great analog sound.

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see above

none,except they dont make em anymore

great amp,big soundstage loads of headroom,carver figured out a way to mess with the circuitry so a solid state amp would sound tubelike.I originally purchased the unit because I allways liked the way they looked,I have a audio research amp that most would say is high end,I find myself using the phase linear more and more,In tech terms I cant explain why it sounds better to me,but it does,the depth,the imageing,the overall impact,clarity.Logic says there is no way a 25 year old amp that was maybe 600.00 new should sound as good if not better than my 2500 dollar audio research.Go figure.

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Smooth clean power, very open and uncolored

a little light on bass response, poor VU meters and lights

I bought this amp used about 30 years ago to power AMT4 speakers. Mated it to a SAE mark IX preamp. The SAE is still with me along with the Phase Linear amp. This amp has seen more duty than most reviewers age! Keeps running strong, sounds great and hasn't burned anything except amps costing twice as much. Currently powering Magnapan 1.5QR's with great results. Plan to incorporate it in future hometheater application. You can certainly due better with newer technology, but for it's time an amazing bargain.

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For those of you who post negative reviews shame on you!!! It is generally impossible to destroy this amplifier whilst you douse it with gasoline. The multitude of fuses protect it!

VU Meters are slow? (But who cares, we know how much power it puts out).

This is a follow-up the review that I posted sometime ago. I have to say that I have fell in love with this amp. I might have a bad at work and my alcohol is simply my phase linear 700 amplifier. I pop in "The Beta Band" into my revox b225 cd player, turn up my parasound halo preamp, a BAM!, my bad day is over. I recently experienced a successful save by the 5 amp fuses on board the Phase. I fried a fuse while listening to Bobby Dillan's "Hurricane." I thought I fried the amp. I was reassured once I checked the fuses. 10+

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Great Home audio, not to be used for noe ever intended in its present stock state for keyboards, PA, guitar, or any commercial applications. Its a directly coupled amp and can be extremely clean sounding in the home.

Blue Flame ! Watch your speakers....even if they are fused in line....Old techgnology they do flame..There's only one tech left from Phase Dean he is really up on these things if you want an amp serviced

The 400 was an inexpensive alternative to the Crown DC-300 back in the late 70's early 80's in the pro-audio and disco sound re-inforcement years. We used to stack JBL's for pro-audio and Bose 800's for disco. I was involved as one of the first tech / engineers to mount rack handles, bring the fuses forward, install gain controls, duct, cool, and port the heat sinks, and finally improve the slew rate, which by the way is deficient to this day. We use to call them Blue Flame ! Use your imagination. A great home amp, never intended for commercial use unless of course you are powering a small vocal stage monitor system.

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Gobbles of head room. Very accurate and fast Aesthetically pleasing

None that I have noticed.

WOW! That is all I have to say. I am 28 years old, have owned 7 amps over the last ten years and the Phase Linear 700 blew my young ears away. My most recent purchase, a vintage Rotel RB-2000 (115w/channel) is now on the auction block! The Phase Linear has an amazing sound stage, very accurate mid section, and endless headroom. This amp is driving my MB Quart SL1200's (4 ohm) with ease. Regarding the previous negative posts pertaining to this amp, I am curious to know what conditions these so called 'audioenthusiasts' were running the 700. I have listened to a plethora of solid state amps including a host of krells, levinsons, and aragons. They do not touch the Phase Linear 700 in any respect. The amp is also very nice to look at. The Phase Linear 700 is a keeper for life.

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Brute force in a beautiful box that can be bought for a song. Clarity, depth and headroom if you aren't trying to drive mud (magnepans, etc)

Needs electrolytic caps replaced every after 20 years. Duh!

I have used two PL 400 amplifiers since new (1970's) without failure of anykind but the VU metering lamps fail and the power supply electrolytic capacitors dry out. I replaced tehm with 50 % larger values (which had no noticeable improvement). I have added level controls on each channel similar to the series II's, clipping measurement and LED indicators to both units (LED that turns on when clipping point (252 wpc or so) is reached as determined by a comparator circuit, DC Voltage sense on the outputs with a fast-switch relay that opens BOTH the AC mains input and the speaker terminals as both teh unit's and speaker in-line fusing is way too slow to help with your Tweets voice coils. Folks, DO NOT disable the unit's protection circuitry if you want any trannie protection for your amp. Also, stop complaining about the VU meters slowness. They are no moving coil meters in the world that will keep even a close pace with dynamic music signals. Meter ballistics being what they are, and they are crappy when compared to digitally driven displays such as LED's, VU meters are for steady state use only if accuracy is required, and that is after both meter's coils are matched and the dropping resistors are matched, as well. Even then what they display will have little bearing on power output as the power developed and sent to the load, your speaker, is a function of the load's impedance, which unfortunately, varies as frequency changes, so all you can get is again, a "close" approximation. Relative indication is all they are ever to be used for if no steady state signal. Buy or build an LED Power Meter if you want real-time power monitoring. With all that said, you can see what I use by looking me (jbler) up on eBay, and clicking on my "About Me" page. While these amps were pushing JBL Olympus (S8R) speakers using the internal JBL passive crossovers, I have never had a moment of less than bliss. Now that I have gone 3-way active (Rane AC23's), the PL400's are driving only the LE15A's 15" woofers in the front Olympus'es and the rear JBL L200 LE15B's, it is sheer wonderment. It is all subjective. I recommend this amp to anyone that wants to treat it well - no fast on and offs, surge protection on AC line, fan cooling on the heat sinks, >4 ohm speakers, 6 ohm and up is best, check and replace the power supply caps every 5 years. Thank you, Mr. Carver.

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Must be robust the way this one has been carted around. Even the origional VU's still work!

Needs a fan if driven hard, thats all.

I have used my 400b Phase Linear for nearly twenty years for mobile DJ work and I am simply amazed it has lasted this long. Right now I need a A93 transistor to get it going again. I have rented and hired and borowed other amps of comparable power over the last few months and found that nothing compares with the sound from the 400b. To be honest I did not realise just how good the 400 is until I tried to replace it. I have had a cooling fan on my 400 all the time because I run it up near the top end most of the time. I know you would not find an amp to do the job I have used mine for. It is in a road case and has probably done thousands of miles travelling to gigs in three states of Australia. I bought the amp second hand from a band in the early eighties, it had been used for PA work. I have heard and read a lot of discussion about the output finals should all be the same brand ... mine has had a mixture of three brands for over 20 years and I have had to replace 2. Nearly half of them are still origional RCA 410's! Mind you I am not telling you to do the same, just sharing my own experience with you ... have just advertised here in Brisbane for a 400b and it looks like I might have found a seller! I still want my old one going so please help me find some A93's.

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reliable, powerfull, good looks

dislikes to be turned on and off in short intervals. no relais stage avoiding a "thumb" when turning current off.

I was really amazed about my Phase Linear 400 Series Two Amp built in 1978. It still has its original set of output transistors (FPL 909) which seem to be more reliable than the XPL by Delco. Only the Caps had to be replaced. They seemed to me to be a little bit to small (5900 uF per Channel), so we changed to 22000 uF per channle which results into a much more powerfull bass reproduction. For me, also my eye is "listening", so these unique red LED peak meters are a great surplus show to the sound, which isgiving me full satisfaction. A good amp anyway, and a pity that this great American manufacturer ist no more active.

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Everything back then.

Lets see, Johnkramer, slam an amp because amps build damn near 35+ years later might be better? Get a clue, no kidding. I bought one new back in the late 70''s and back then you could not touch it for under a $1,000. Don''t waste our time with your useless dribble.

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