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
MidFi, noisy, & not too reliable in my experience - but the guy that I sold it to 20 years ago still uses it; with periodic board contact cleanings it keeps running somehow. I liked the autocorrelator & dynamic expander enough that I picked up a model 1000 which replaced only those functions, but it's been on the shelf now for about 5 years. I should sell it.
Agree with Bob. Basically a vintage boat anchor, that does have some sentimental value to some, and can be sold for a decent buck. Do it while it still works.
Although in my opinion, it can not compete with current low-budget amps, I have heard quite a few and tried to help friends with different problems with this one. Again, the important thing is, if you like it, it does not matter at all what anyone else thinks.
I was a proud owner about 25 years ago. I actually sold a Mac 275 tube amp for it. (I know, I should be horse whipped for that audio stupidity.)I was in love with power at the time.

I remember that period in time very well. Amps were going for power and very low IM and THD distortion values. A Finish engineer by the name of Otela came up with a new measurement about then called Transient IM distortion. This was the first insight into why tube amps actually sounded better than solid state amps, like the PL and Crown DC300.

You could call the Phase Linear 400 one of last of the high TIM beasts. I can remember listening to them. They sounded impressive with all that power but when the music got loud they turned diamand hard.
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

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
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... :- )

No offence intended Sean. If so please accept my apologies. When I was writing my comments I was thinking of the general public. I get a lot of tips from newsgroups and am grateful to all who advice and all who critise.

Incidentally I have a PL 700 series two, NAD 208 and Audionics. I used to have a SUMO but couldn't get a replacement part and have to junk it. All these I would rotate with different speakers and pre-amps and as you said synergy is the way to go.

BTW for others who would like to note I have added a switch to the speakers and switch them on after the amp and off before switching the amps off to avoid the thumps.

Keep the ideas flowing.
For what its worth, JGH once wrote about the PL 400:

"This and the higher-powered P-L 700 have a sound that is characteristically their own: A rather fat, rich quality that one normally associates with good solid-state units of considerably lower power (such as the Citation 12 and the Crown D-60), and the effortless openness that is a sure sign of oodles of reserve power. Both however also have a noticeably fine-grained or 'gray' quality that is substantially less conspicuous in the 400 (which in turn has a shade more of it than the Crown DC-300A). In addition, although it is not easy to overload the 400, it does not respond very gracefully when it is overdriven (usually on heavy, sustained bass passages), and takes a perceptible period of time to recover.

"All in all, we would judge this to be a less successful design than the Dyna Stereo 400 (which sells for $100 more), but would rate it as being the best solid-state amplifier in its price class."

Seems to corroborate Sean's comments, not that we need JGH to corroborate Sean.
James: Thanks for posting that. Where in the world did you ever find that ? Do you still have the original magazine or was it on the net somewhere ?

I guess if you take things in perspective, J. Gordon Holt made some of the same comments that i did i.e. the Phase amps had a grainy haze, the power supply was soft and that the bass lacked sustain and definition. Other than that, it appears that he thought pretty highly of the Phase amps in their day. Obviously, his comments might be somewhat different if he were to look back upon those amps today knowing what he now knows.

The one thing that i have a hard time understanding is that he said that the Dyna 400 was a "more successful" design than the Phase 400, but rated the Phase 400 as being the best in its' price class. Given the difference in price of only $100, was he saying that the Dyna may have sold more ( i.e. "greater success" ) but that the Phase 400 was a better amp ? One cold also take it to mean that the Phase 400 was the best amp for the money, but for another $100, they felt that the Dyna was a step forward ? Without seeing the entire review / commentary, it is hard to tell how to take this comment. Sean
Sean: The quote was taken from the original hard copy magazine The Stereophile, Winter (4), 1973/74, pages 9 and 10. The quote represents the entire review, except for the title, power rating, price, and manufacturer's address. The price was $499. The Dyna 400, which was reviewed on page 11, had a price of $449 in kit form and $599 ready-built. Back then, $100 made for a different price class for JGH -- Whew! I hardly remember it myself. I was looking through my back issues because something I read on Audiogon about Wilson speakers reminded me about the Fulton J Modulars, which are also reviewed in this issue. I stumbled across the PL 400 review and remembered seeing this thread a few days ago.
Thanks for the follow-up James. Just goes to show how much things have changes since then, both in audio and the economy. While JGH thought that $100 was enough to separate one item from another in terms of the price category of a component, we wouldn't think twice about dumping $100 for a piece of wire nowadays. Makes me want to second guess a lot of the decisions that i've made if you know what i mean.... Sean
Hey, at the very least my Phase 400 and 700B had a personality. The faceplates and design aesthetics were typical of the 1970s wonderful creativity. The sound was not bad if you needed gobs of power. The amps were better than the 4000 Preamp. I still look upon the products of the 70s with fondness. The stuff was interesting and mostly all of it was obtainable. This was a time when you could truly call it a HOBBY. Today, well I dont think so........Frank
Chiming in a decade late but with the internet everything's permanent, right? Around the time the PL came out there was a growing high end consensus that very high power was a good thing. There are technical arguments in favor of this. Carver's amp was the first one to offer that kind of power and did so at a cost that some hobbiest types - as opposed to rich sybarites - could afford. In blindfold listening tests the PL400 scored very high, pitted against some fancy name competition. Given Bob Carver's track record of churning out innovative designs one after another there's at least an outside chance that the guy is a good engineer, and that his amp was as good or better than the competition - in fact there wasn't any before his amp caught on. A lot of the negative stuff I read about Phase Linear and Carver is written by people who seem to be haters or hucksters rather than objective and nuanced thinkers.
Given Bob Carver’s track record of churning out innovative designs one after another there’s at least an outside chance that the guy is a good engineer
I am in the middle of a Phase Linear 400 rebuild and saw this post, decided to chime in. I am a fan of Bob Carver designs myself - from speakers to subs to amp to preamps and processors. My sense from working on and rebuilding Carver equipment is that he is a fantastic designer/engineer (very much alive and still making amps to sell on ebay), who also wanted to make big profits and so would cheap-out on components to reduce manufacturing costs (or maybe the bean counters forced him to use inexpensive parts). This weakened the performance and reliability of many of the products he commercialized, but the upside is that we can buy that old hardware (often not working), spend a few hours replacing parts strategically (the Pacom caps in the Sunfire amps is a great example - and there are so many of them!) and end up with a great sounding resto-mod piece of gear. On the Phase Linear 400: great project amp, sounds fantastic when working (I managed to kill mine while trying to add a speaker protection relay - they are notorious for damaging speakers with DC when they fail... will resuscitate it eventually) and can hold its own against modern budget amps. And yes, the PL400 looks great with blue LEDs illuminating the extra large meters, Macintosh-style.
I had a Phase Linear addiction for years, which was replaced by a McIntosh addiction which was replaced by a Citation addiction which was replaced by Krell addiction etc.

I liked the sound of Phase Linear amps. The 400, 700B and especially the Dual 500.  If you needed clean power they were hard to beat. 

I wonder how how many of these negative mid fi comments would apply if the 400 had a levinson, or McIntosh logo on it?

With regard to the size of the caps used its totally meaningless. The amp had well over 200 watts per channel, and nearly 3db of headroom. It was stable as well. I drove the hell out of mine with no issues at all. 
They were widely used in the professional market as well. I've seen stacks of them in the 70's powering rock concerts.  Many high end recording studios use Phase amps, Crown was also commonly seen in these applications. 

Check  I out the absolute sounds ten best amplifiers of all time. It's on the list for good reason. It deserves to be. 

By the way, my Krell addiction has been replaced by a vintage Sansui addiction. For all those mid fi comments, you're welcome to come over for a listen anytime. 


Correction:  That TAS article was not titled, "ten BEST amplifiers of all time", but rather, 'The Ten Most SIGNIFICANT Amplifiers of All Time'.    Most contributors that included Phase Linear in their list, did so(and said so) based on the fact that they had the highest output power of their time. Carver paved the way for high output/low distortion figure, SS amps, about the same time that low-efficiency speakers(ie: Air Suspension) hit the market.  THAT'S what made them, "significant", to the audio industry.  They were great for our electronics repair and speaker reconing business, in Orlando, FL.  We(in that industry) affectionately referred to the 400 and 700 as, "Flame Linear" amps(for good reason).     They made us a LOT of money!    There are many out there that still like the old SS sound.   As long as YOU'RE enjoying your system, that's all that matters.
Was great 40 yrs ago not so much now.