Phase Linear 400

saw a unit on sale in the used market n spend 2 days reading on it (including discussion in this forum) before deciding to buy it for $350.

reasonable physical condition considering the age, VU meter lamps are weak n need replacement, other than that the sound is clean and free of noise or distortion n plays surprisingly loud with very low volume level. highs are extended and lows are taut.

the magic came through when i played my Vivaldi CDs, the strings were like given new life and timing spot on, its like tis amp was made just for Classical music. a very pleasant surprise. now to find time to bring the amp down to my technician in town to give it a look over to see if there are components need changing n new lamps for the VU meters.

 

My memory is that it was considered a great amp when released, almost revolutionary. Still, I am surprised that it is giving "new life" compared to the CA-400 your profile lists.

Congratulations on a great find!

 

yes for the $$ its a nice amp and i love vintage... there is a Kenwood KA7150 integrated in my son's room. its a refurbished unit i got
fm Ebay Germany... haha... buying Japanese from Europe.... well tats me.... i go where they are regardless of geography.

 

That's almost the same price as when it brand new. Back then they advertised "a dollar a watt".
I really enjoyed it when i had mine, plenty of guts and discipline.

PS: By the way, I think it was a Bob Carver design.

 

wow... tats v interesting... over here vintage gears have some good resale value
e.g. a Thoren TD150 Mk2 with new plinith still sell for about $450

and yes its a Bob Carver design. there was also a Sunfire amp by him as well in the market
but i decided against that becos i was told my technician the Sunfire has lots of proprietory stuff inside
where there are no suitable replacement parts.

 

m into the 2nd day since i got tis amp hooked up and played Celine Dion A Decade of Songs CD
and her voice made my hair stand. then i got into The Best of Vanessa Mae CD n i was like
hey... i m literally hearing "new things" from the CD which my mind sort of skimed over previously.
may be another classic case of the older generation stuff are better design n made.
meanwhile i will keep my ear on the sound.... haha...

 

I owned one back in the 70s. There is a wood case that goes with it. Good luck finding one. It was a reliable amp that produced plenty of power.

 

I love that amp

Pink Floyd used one

Audio pioneer Bill Kelsey incorporated American Phase Linear amps into the bands touring kit in 1971. He collaborated with the bands sound engineer Peter Watts and Dave Martin to modify and improve this powerful amplifier for use with the bands custom-built P.A.system.

 

i spoke with my technician today and he is familiar with this amp and told me to send it to him asap
for him to put in the speaker protection circuit and meanwhile do not hook up with speakers that i treasured
but some spares.... so i put up my Sony SSD 11s that i got for $30 at flea mkt.

 

i have a friend who is an excellent speaker builder, i can get him to do some carpentry for the amp n box it up. but then again, will that affect
the cooling of the amp?

 

Cooling "fins" on this amp are on the back side only ( I think )

 

yes they are and large fins too. i googled on the images of the amp and there
are some with wooden box over and the box seemed to cover the fin area as well.
i m not technical but by logic wouldn't that impedes the proper working of the cooling fins by enclosing them in a box?

 

The original case enclosed the amp except for the back. There were no cut out vents , so to speak. The fins on the back of the unit are for the cooling. I don't remember having any issues with overheating. Getting the speaker protection circuitry installed is a good idea.

 

Yes, these are good sounding powerful SS amps. They have an excellent slew rate. They are very fast and responsive.

A friend of mine has five of them.

Your technician was right about the speaker protection circuit.

One thing these amps don't have are protection circuitry.

I would not put it into any enclosure where heat can build up.

When they pull a lot of current, they are prone to heating up and then bad things can and have happened with them.

If the output circuit fails, then you will have about 70-Volts DC running through your speaker's voice coil, very bad thing.

Without modification, I would not connect these amps to any of my speakers, strictly from a safety point of view.

 

yes i too have some thot about leaving the amp with the cooling fins exposed as it is originally designed. also
i have the amp at the lowest rack, so the only visible portion is the face plate.

about speakers being fried.. i had an experience why the amp fails n both my woofers were burnt. there was no drama
just a pop sound, slight burning smell n then a dreaded silence.

so for the last 1.5 days i have taken some risk hooking up my Dali Ikons to the amp, after talking to my technician,
fron now to the time that i bring the amp to him for the modd, i m using my $30 speakers with the amp.

 

I remember when these were released. It was a big deal to have that much power. Their cost back then was the equivalent of $2,000 today.

 

My very first separate amp along with the Phase Linear 4000 pre amp. Later swapped it for the 700B and boy back then it sounded great. Allison One speakers and a Technics turntable. Back in the day.

 

Fusing speaker line also will protect your valued speakers. DC protect is best solution though.

If you like the sound of your 400 now it can get even better with new PCB's from White Oak audio. Can turn your 400 into a near bullet proof fully complimentary amplifier at around 250 watts ch. I have one running mids in my triamp system now.

 

The original problem was there were very few consumer amps like the Phase Linear 400 and 700 producing that much power. Some stupid owners decided to use these to drive PA speakers to insane levels. The PL amps were never made for that abuse. Thus, the bad rap on these amplifiers when they blew up.

 

And btw, stock units that are healthy sound wonderful. I've heard a number of Bob's amplifiers though none of his tube amps and his original 400/700's are by far my favs.

 

on paper, the PL400 is rated 200W x 2 @ 8 ohms.

have anyone tried using the PL400 with a pair of 4ohm speakers?

 

These amps sound good BUT Phase Linear 700s and 400s need circuit protection work, not just speaker protection work. They should not be used with low ohm speaker loads, the cooling fins should definitely not be covered over, and the amp should not be run when it is hot.

You may want to google "Flame Linear" to understand the issue.

 

k, noted with Thanks on the speaker load.
tmw i will be bringing down the unit to my tehnician to have a look over.
he has serviced this model before n should be in a good position to advise what needs to be done
to ensure the amp runs well n safe.

 

I had the original 700 (not the later 'B' model) and spent a lot of time with the original 400. The latter was the better sounding amp in my estimation. The original 700 was notorious for blowing up and taking out speakers. (I ran it though stacked Advents at the time, which was considered a very good set up). Mine blew up, took the Advent tweeters out and I sent it back to the factory, which fixed it in a jiffy. I changed system approaches at around the same time-- I bought my first pair of Quad electrostats. The very idea of a Phase Linear 700 with the original Quad (aka the '57') was the height of mismatch absurdity.
I sold the 700 to a friend, who bought the Advents as well. When I went over to his place, he had the Advents wired in parallel. Man was it loud! We switched to series wiring, for sonics and amp safety. Meanwhile, I had built myself a little Dyna ST 70 to use with the Quads until I had enough money to buy Audio Research components, which at the time, circa 1973-74, were considered top tier. I stayed with tubes after that, but have heard various huge solid state power amps in many systems over the years. At the time Phase Linear was introduced, there were very few amps with that kind of power. Crown's original DC-300 is the only one I can think of that pre-dates the PL. After PL introduced its amps, a number of companies jumped into the high power arena. The other amp that sounded good back in that era was the Ampzilla.