How does the Phase Linear 400 compare?

jim55379,
I have a Phase Linear 4000 series one preamp (I used to have a 4000 series two as well).  It has the widest soundstage I’ve ever heard. The deepest too.  It also excels in detail and dynamics like no other and is whisper quiet.  But I can’t listen to it for more then a couple of hours.  The midrange seems hard and bitting after a while to me.  Not everyone just me.  It’s pristine, and I can’t seem to part with it, even thought it spends most of its life in its original box.  Years ago, it was my favorite preamp, but my taste have changed.  I enjoy my ancient marantz for preamp duties, that or my Sansui 9090db which seems to do everything just right.

Oh, and I had two Carver M-400’s strapped in mono giving 500wpc into 8 ohms.  They were pretty remarkable, but I never thought they were as smooth as the Phase Linear 400, which I’ve also kept over the years.  It actually works well with my marantz 7c.  

Carver’s tube amps are incredible.  Wouldn’t mind a pair of those, any of them.

The Phase Linear 400 ii was a low transient intermodulation distortion (TIM) amplifier. The old post claiming it was a high TIM amplifier is likely based on opinions that were floated against this amplifier because it was priced far below higher end amplifiers. It blew my McIntosh MC2200 out of the water sonically and I'm a long time McIntosh owner and still am along with Conrad Johnson, Modwright and Sonic Frontiers.

Transient intermodulation distortion is generally caused when the forward path of a feedback loop is too slow to make the feedback circuit track the input signal under true transient music conditions. Poor slew rate and or an open loop transfer function can cause TIM.

The Phase Linear 400 ii was designed well after the discovery of TIM and Carver avoided the problem. A properly biased, in spec Phase Linear 400 ii has a very high dampening factor, wide bandwidth and a fast slew rate. They are sonically very accurate and transparent amplifiers that create a very deep sound stage with lots of low level detail.

Now the negatives. The amplifier was built to sound very good at a price point. It lacked any real DC protection for speakers, if the power supply capacitors failed. It also really needed more heat sink surface area and many an audiophile cranked up the bias to true AB1 and accordingly there were some serious failures of these amps that also took out speaker systems hence the nick name, "Flame Linear".

With good caps, upgraded outputs (say MJ15024s), proper bias setting and a DC protection relay added these are still excellent amplifiers and these improvements are pretty easy and low cost to implement.

i bought a new pl400 back in 1973. cheapest power amp back then with 200 watts per chanell!!! 

What does this amp have in common with the pyramids? Its ancient history.

The famous Flame Linear amplifier was a cheap, dangerous, unreliable amplifier in its day and now it is just old and obsolete but one would probably be safe because if it was going to burn up it would probably have done so already!