How does the Phase Linear 400 compare?


I have had one for many years and fire it up regularily and think it sounds very good.What are your thoughts? Rob
rob88
oops the 400 was a power amp - I was thinking of the model 4000 preamp above. Never had a 400 PA but I've seen many of them around back in the day; had some nice big meters didn't they? I have no personal opinion regarding the amp - never did a any critical listening. I did have a Dynaco Stereo 400 amp which I drove with the Phase 4000 pre; the ST400 was an OK thing; maybe just another high TIM monster. I sold it when consumer digital first emerged; it wasn't at all forgiving when trying to cope with that, but looking back that may not have been completely the amp's fault.
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" : )
"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."

I have two PL 400 and they use two 6800uf. I have modified one to use two 20000uf. They both sound terrific.
Its not the smoothing caps alone, its the pre and the correct speakers that make the PL400 a glorius amp.

"That alone is what Phase Linear became famous for i.e. "high power, low dollar".

What a pity, when value is the main criteria of the quality of a product. Maybe if the price was ten times the high power, people might have a different view altogether. And maybe if the name was different too ...
ykingfisher: If you have ever read any of my posts, you would know that i am not one to rave about products based on price or brand name. Personally, i would rather pay the least amount possible and obtain the most performance possible. I am VERY much a "bang for the buck" kind of guy.

After thinking back to my comments about the capacitors used in the Phase 400, it was the Phase 700 that used two 4,700 uF caps. As you can see, this is MUCH too small for an amp of this power rating. Thank you for correcting me.

Having said that, i have owned 11 Carver built / designed products over the years. I have multiple Phase 400's, a Phase 400 Series II and a Phase 300 Series II ( even though there was never an original Phase 300 ). I even went so far as to take two of the original 400's and convert them into one TRUE dual mono design on one large chassis. When doing this many moons ago, i performed quite a few upgrades, modifications, circuit changes. As such, the comments that i made were from experience and intimate first hand knowledge of the products. They were not meant to slam anyone or anything, simply to offer my point of view in the grander scheme of things.

In a direct comparison between an old Carver ( Phase Linear or Carver Corp) product and a newer Carver ( Sunfire or Lightstar ) product, the old amps in stock form sound slow, sluggish and have ill-defined bass. The treble is smeared and sibilant. This gets worse as you drive the amp harder. The midrange lacks any form of liquidity and sounds hard in the upper octaves. There is also a grainy, gritty sound throughout the entire spectrum. As such, Bob Carver has obviously learned a WHOLE LOT over his career.

While i do agree with your comments regarding the preamp and speakers i.e. "system synergy", i would also suggest that you might want to check into other products on the market to see what is out there and if the models that you have are still competitive. It is quite possible that your upgraded / modified Phase 400's will do everything that you want out of them as compared to newer, and probably more expensive gear. Then again, one would never know unless they had done such a comparison. It could be either an eye / ear opening event or a strong confirmation that what you already have is sufficient for what you want out of your music reproduction system. Sean
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It makes a pretty darn good, cheap, sub woofer amp...

It was affectionately known in pro audio circles as the "Flame Linear" since it was prone to frying the outputs and drivers, and more when pushed into clipping in PA applications...

I've owned at least a dozen 400s and a few 700s since they first came out in the 1970s.

They're not hard to keep working once you know what is going on inside. The criticism of the filter caps is 100% valid, and it's easy to see the difference between my own Symphony No.1 amplifier design which uses a mere 500,000 ufd and the PL 400 that uses 2 x 6800!

It's not hard to say that I'd rather have one of them for my system than certain other current amplifier offerings that cost much more... :- )

_-_-