Like most of the Carver designs from more than a few years ago, they were high on power / bells & whistles and low on quality control and sonic performance.
The amps were phenomenal power-houses in their day with an overall quite low "dollar per watt" ratio. That alone is what Phase Linear became famous for i.e. "high power, low dollar". In terms of comparing Phase Linear to a company that is currently in business, the first name that comes to my mind is Adcom. Adcom does make some decent stuff, but some of the designs are quite compromised in my opinion. Then again, for the money spent, you can do a lot worse. Such was the case with old Phase products also.
Having said that, these old amps do present a "tinkerer" with a solid platform to build upon. Much of the "hardness" or "brittle" treble response that was so common to early high power SS designs is due to output devices that were not gain matched, lots of negative feedback ( how else do you think they got low THD figures back then ??? ), poorly designed protection circuitry, junk wiring and connectors, etc...
On top of the "shrill" sounding treble, the bottom end was quite soggy and lacked both impact and sustain. This was due to using a decent sized power transformer with way too little filter capacitance and a power cord that couldn't feed enough current to power a flashlight. If i remember correctly, the Phase 400 used two 4700 uF caps in the power supply, which is less than what many "mid-fi" preamps use nowadays. Obviously, that would appear to be an easy thing to fix by adding bigger / more filter caps, but the amp simply does not have the room for it internally. As such, one is either stuck with using a couple slightly larger caps in place of the OEM pieces or going to an outboard capacitor bank, which is not that effective in my opinion.
By addressing all of these problems, one can end up with a high powered amp that sounds nothing like the original product what so ever. Then again, with that much work into the unit, it really would be a different amp and would not resemble the original product what so ever. See, the law of returns still applies : )
Other than that, Phase amps are a source of high power for pennies on the dollar. I would never call one of these amps musical or accurate though. In stock form, they are simply a big beast meant for flogging speakers and assaulting ears with high spl's and little concern for pleasant sonics.
The Phase 4000 preamps were just as Bob Bundus stated i.e. noisy and prone to trouble. One could achieve a much better signal to noise ratio by simply running the -20 dB padded attenuator switch all the time. If you didn't do this and tried to take advantage of the higher gain of the preamp, the end result was a drastically increased noise floor and harder sounding treble. Most of this was the result of how the circuit was designed, which was not very good. I chalk most of this up to the lack of experience that Bob Carver had at the time, as this was his first "big" venture into designing low level circuitry. As Bob Bundus mentioned though, this unit did have some "convenient features" ( dynamic range expansion aka "Peak Unlimiting", vinyl surface noise reduction aka "Auto-Correlation", etc..) which did address problems that were more prevalent during that era.
The Phase 4000 preamp and some of Mr Carver's later inventions, such as the amazingly small 200 wpc "Carver Cube", the very impressive yet unrealistic soundstaging of "Sonic Holography" and being able to mimic the transfer function of a tube amp with SS devices earned him the nick-name from his opponents of "Side-Show Bob". By this, they were saying that Carver was more interested in gimmicks and bells and whistles than he was in top notch sonics i.e. Carver products were relegated to being part of the "freak show" due to their out of the ordinary features and circuitry but could never hold up to the scrutiny of the "spotlight" in terms of "high end" sonics.
Carver's response to his critics came about when he designed and released the Lightstar products. These products, which still made use of some out of the ordinary designs ( even if a chameleon changes colours, it is still a chameleon ), had far superior sonics to anything that Bob Carver had ever designed or marketed prior to that point in time. These products were of limited production quantity though, as Mr Carver struggled for control of the corporation that was named after him. Some of those designs along with newer ideas were carried over into his latest products i.e. the Sunfire Corporation.
Some users of both product lines that i know find the Sunfire products to be slightly "warmer and smoother" ( Bob was trying to emulate tube euphonics with these designs ) than the Lightstar's more "accurate" or "neutral" sound. As to which one you would prefer ( if any ), is a matter of personal taste and system synergy. Sean
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PS... Hope you didn't mind this trip down memory lane and / or refresher course for "newbies" : )
