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.
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.