Liquid Amps


What is the most “liquid” sounding solid state amp and is “liquid” even a thing?
puffbojie
How about the term "surgically romantic" published in TAS (1976) by that doyen of the High End - Harry Pearson! He was reviewing and describing James Bongiorno's Great American Sound Ampzilla! This was THE amp to own! Did it sound "liquid"? NO! It sounded as clear as a just-Windexed pane of glass! IT SOUNDED BEAUTIFUL! And that was James's intention: to produce a SS amp with the smoothness of the best tube amps and better transient response than the SS competition! And the ability to drive ANY speaker with full power! Ampzilla did indeed set the bar really high! 
Bongiorno was criticized by The Audio Critic for producing amps and preamps that made all sources sound too beautiful! So I think that the term "liquid" can apply to these now classic SS products from GAS!
Disclaimer: I presently own a Thoebe preamp, two Sons of Ampzilla and a Grandson! Classics indeed!
What is the most “liquid” sounding solid state amp and is “liquid” even a thing?
It is, and its a description of how the amplifier makes distortion, or more to the point, what distortions it **doesn't** make.
Solid state amps have a long standing reputation for sounding brighter and harsher than the actual music, this despite having typically very low distortion overall.
The problem is that the distortion they *do* have is entirely that of types to which the ear is keenly sensitive, moreso in most cases then excellent test equipment. This is because the distortions in question are higher ordered harmonics (5th and above) which the human ear uses to sense sound pressure. You probably don't have to imagine how important it is to be able to tell how loud a sound is! Amounts of 0.005% are thus audible.

For this reason, and also due to the distribution of harmonic structure in musical instruments (which is not a coincidence), the tiny amount of distortion most solid state amps make is actually really audible, hence your opening question!
Some of this is caused by non-linearities in the solid state devices, and some is caused by the application of loop negative feedback, which is used to suppress the distortion of the former. Its a bit of a carrot on a stick: no matter how much feedback is applied, the actual use of feedback will generate its own higher ordered harmonics.
This fact has been known for at least the last 65 years (for those interested, see the writings of Norman Crowhurst)!
Generally speaking, tube amplifiers don't make as many of the higher ordered harmonics and so sound smoother as a result.
But in the late 1970s, Sony developed a new kind of power transistor called a Static Induction Transistor (SIT), also known as a VFET. This transistor had linearity similar to a triode power tube and even had soft clipping characteristics. Unfortunately, Sony, like they were with so many of their innovations, was very precious about the use of their technology, and the only amps built for quite some time were their own VFET amps, which were not particularly reliable. They went by the wayside.
However Nelson Pass took an interest in the device and even had some made at one point, although the semiconductor house that made the SITs for him later went out of business. Because of the rarity of the devices, Nelson never made a production amplifier with them, but he did make a kit, and by all accounts it is easily the amplifier you are looking for- it has the least 'transistor' artifact of any solid state amp I've heard.
The amps don't make a lot of power (about 20 watts), and the kit is not being offered to the best of my knowledge, but you might be able to find one that didn't get assembled that is for sale. It would not be that hard to find someone to build it.


Here is excerpt from Absolute Sound Paul Seydor review of my amplifier Benchmark AHB2:

Because accuracy allied to absolutely reliable performance is the goal of all the Benchmarks, they are not products that tend to attract cults or other sorts of starry-eyed enthusiasts, wholly lacking any of the quirks, foibles, idiosyncrasies, sonic flavorings, euphonic distortions, and so on that characterize the objects of most audio cults. Professionals buy Benchmark because they know the products work and are reliable and accurate—indeed, reference caliber. Music lovers buy them because they are neutral and accurate and thus reproduce the tonal character of voices and instruments correctly (and also, I presume, because they are reasonably priced, most musicians, like most other people, being typically not wealthy). But audiophiles? Well, the longer I’m in this racket, the less I sometimes think I understand what audiophiles really want except that a lot of dallying about with components, equipment swapping, and coloration matching seems to be what amuses them. I’m not sure I can in good conscience recommend this amplifier to them as I am not sure they are in search of what it offers: a precision instrument designed to perform the precisely defined task of reproducing music and sound accurately, which it does essentially to perfection. But to anyone else, the AHB2 gets as high, enthusiastic, and confident a thumbs up as my arm is capable of reaching.

AHB2 employs different technique of correcting transistor nonlinearities.  Instead of applying negative feedback to the input it utilizes two parallel amplifiers for each channel - one for the signal and another for the error (8 power transistors per channel).  Correction of nonlinearities is done at the output instead of the input.  This technology called AAA (Achromatic Audio Amplifier) was bought by Benchmark from THX (George Lucas).  To me this amp is as smooth/liquid as it gets, with wonderful extension on both ends and serious slam.

Ralph, reducing bandwidth at the input to one that amp had before feedback was applied should prevent TIM, but requires fast and linear transistors that are expensive.  Using more feedback instead is very tempting since even shallow 20dB feedback improves everything tenfold (bandwidth, output impedance, THD, IMD).

I would say from my experience, that the original GAS Son of Ampzilla, Pass labs XA.5 series, and Borgiono’s Spread Spectrum Technologies Son of Ampzilla 2000 power amps, all have that "warm", "liquid" sound that is very "rare" in SS amps.

They sound very "natural" IMO.
I agree the Pass Labs are very smooth and tube like without the disadvantages of tubes. They are fast and very fluid in the midrange.
Jim B...now there's a name from the golden days of audio.  A true pioneer who loved what he did and those of us who sold his inventions:

http://www.tnt-audio.com/intervis/bongiorno_e.html

His products were always VERY INTERESTING and sounded as good as he could make them.

RIP, James.
Valvet may also fit what you are looking for.

Good to see Bongiorno's amps getting coverage here.
What kind of speakers do you have and how efficient?

Dunno what "liquid" means to you (no disrespect to Atmasphere/Ralph) but certainly very smooth and non-fatiguing...so consider a Nelson Pass First Watt design.  I have an F7.  Great tone and depth to the presentation but only 20 wpc into 8 ohms (30 wpc into 4).  Reno HiFi allows an in-home audition.  Demo unit available for $2495.  A very good value, in my O-pinion.

Review here:
http://www.theabsolutesound.com/articles/first-watt-f7-stereo-power-amplifier/?page=2

Reno HiFi listing here:
http://www.renohifi.com/FirstUsed/FirstUsedInStock.htm


In my current set up I am running Dali MS4 speakers with a Modwright KWA 150 SE amp and a pair of REL R 528s.  Does anyone have an opinion on that set up with regards to the topic or any other?
Aw, geez, I thought you meant real liquid amps like the one that submerges all the tubes in liquid. 
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darTZeel amps rank among the more liquid and beautiful sounding amplifiers I've heard, tube or solid state
I always prefered tubes. I then tried a Pass First Watt, F6. I realized solid state can sound just as liquid, 3D, and smooth as a good tube amp.
I am not sure, but I think what drew me to tube amps sound, was not the tubes per se, rather it is that I love the sound of Class A topology, which can be  accomplished in a ss amp, as well as a tube amp.
I have enjoyed every Class A amp I have ever heard, to a much larger degree, than non class a.
Mg16
The new 25WPC Pass amp does interest my otherwise tube-centric self, but not enough to replace my amazing (to me anyway) Dennis Had single ended tube amp. I still find it interesting that many great SS amps claim a "tube like" sound, which simply supports my tube appreciation. Besides, it's a fact that tubes are more fun (a fact I made up, but hey...it at least "seems" factish).
It's all good "Wolf".  Our Post-Modern world embraces the fluidity of facts.  Yippee!🧐
@atmasphere explains well why it's a little tough to find "liquid" SS amps.

However, there are many issues with tubes too.  I have both SS (McCormack, McIntosh, digital amps, and others) and tubes (ARC Reference), so it's not like I'm prejudiced toward one or the other.

While people are offering nice suggestions and commentary, they are jumping the gun.  We must first know what speakers you are using.

Many speakers have a definitive preference toward tubes or SS.  Thus, any recommendation is primitive without knowing what speakers you are using with this amp.  20 SS watts won't cut it on certain speakers...conversely, certain high power or high gain SS or digital amps will have problems sounding "liquid" with certain speakers (i.e. horns). 

It's actually something that can often be measured.  For example, the output impedance of a certain tube amplifier can pull down levels in higher octaves on certain speakers while boosting the lower octaves.  This could be a good thing and certainly make the sound seem more "liquid".

In short, you really have to let us know what speakers you are talking about.  In my systems, modified McCormack amp are the most "liquid" sounding with my particular speakers...even moreso than my ARC reference amps.  However, I wouldn't guarantee it would do the same for every set of speakers.  Some may like the strengths/weaknesses of tubes more than the strengths/weaknesses of SS.  (I've had Spendor speaker in the past that loved tubes far more than SS.)

All this being said...I don't think the BIGGEST problem with systems not sounding "liquid" is the fault of higher order distortion in SS amps.  I don't think Atmasphere made the claim that it's the "biggest" problem either, so we may not even disagree per se.  I just want to point out that IME the biggest problem with systems not sounding "liquid" rests with the speakers and source first...not the amp.

It's really amazing what can be accomplished when you get the right pair of speakers and feed it an impeccable source.  An amps strengths/weaknesses can still be apparent, but it become obvious that it's not the driving force behind problems unless you have a really poor amp (or poor combo with a preamp). 

If you're doing digital, the biggest impact on liquid sound is getting rid of jitter.  Focus on the server/renderer even more than the DAC nowadays.  If you're doing vinyl, you probably already know how big an impact the cartridge and phono preamp can make.  Address those things first before thinking a "liquid" SS amp will solve your problem...it can only do so much.
@labtec  Couldn't agree more about the modified McCormack amps.  I recently had a new driver board, wiring and jacks installed by Steve and Co. The sonic performance far exceeds the price for the upgrade.

Regarding your comments about listening to vinyl, the phono stage makes a tremendous difference.  My 25 year old Aragon 47k was pretty much spent as it introduced a persistent hum that I found objectionable.  After seeing how many really inexpensive phono amps are on the market, I thought I would give a Sutherland KC Vibe a shot.  It is a new design from Ron Sutherland and based on his dedication over the years to phono stages, I thought I would give it a shot.

I gave it a few weeks of persistent use to break in and it just was incapable of opening up and revealing the soundstage that I knew was on my recordings. I would call it's performance in my system, "matter of fact".  The notes were there but no subtlety, no ebb and flow and again a greatly restricted soundscape.

I had a very productive conversation with Josh at MusicDirect.  After discussing my system and what I perceived as the Vibe's shortcomings, he suggested the Luxman E-250.  I then researched Luxman and found few reviews, but what I did learn about the design seemed in concert with my listening preferences.

Upon receiving the Luxman for a trial, I also purchased the Cardas burn-in LP with isolated bands of pink noise to facilitate burn-in of the new gear.  The Luxman is a wonderful sounding piece.  A big ball of sound can be heard around the speakers.  Great tight bass with kick drum slam.  Incredibly clean treble with wonderful detail.  Now, this is a $2300 unit, so it should sound better that the $895 KC Vibe.

Lesson learned.  Don't insert a component into your system that is not up to the quality of the rest of your gear.
Boniojo (sp) is now dead his last gasp ampzilla  had power supply issues if I recalll. Is the Co still around?  Serviceability is always a factor when dropping that kind of change on an amp.

It’s like searching for something you can’t have.  Have you looked up the  meaning of Audiophile?   I’ve come to believe we really are all afflicted.   Easy solution: get  a kt150 driven tube amplifier and enjoy the liquid.
@hifiman5 
Slightly off-topic but wanted to chime in on your observations on the Sutherland KC Vibe. Being such a new product there were precious few reviews, but I too bought a unit based on Ron’s pedigree. 

In my my somewhat modest system, I started off enjoying the sound — beautiful, forgiving and slightly polite. It was only in comparison with other (more expensive) units that the Vibe was revealed to be somewhat closed-in and rounded off, leading to the initial perception of “warmth” and lack of nuance/detail. 

I put this down to synergy and went with another option instead, but am glad to read corroboration of my experience....perhaps it is the nature of the Vibe after all. Guessing it is a conscious choice of the designer to hide flaws of more modest systems, which speaks to your point of system matching. 
All this being said...I don’t think the BIGGEST problem with systems not sounding "liquid" is the fault of higher order distortion in SS amps. I don’t think Atmasphere made the claim that it’s the "biggest" problem either, so we may not even disagree per se. I just want to point out that IME the biggest problem with systems not sounding "liquid" rests with the speakers and source first...not the amp.
If the speaker is more revealing, it will totally play the distortion that makes many solid state amps sound bright and harsh.
This distortion is not a lot as far as test instruments are concerned, but to our ears it is, which is why its so easily heard (and why tubes and tube amps are still around decades on after being declared ’obsolete’; if they were really obsolete they would have ceased production long ago).

The real problem we are dealing with is that the audio industry (like many other industries) does not like to deal with inconvenient truths. In this case it is the fact that our ears, while seemingly inaccurate and insensitive to so may aspects of audio, are more sensitive than the best test equipment when it comes to detecting higher ordered harmonics.
BTW this is extremely easy to prove with very simple test equipment!
Anyway, IMO the industry should put a ’weighting’ (like we do on noise) on harmonic distortion. Less weighting on lower orders, higher weighting on higher orders (particularly the 7th) so when you look at a spec sheet, you can finally tell what the amp will sound like! Right now, the spec sheet has marginal usefulness (unless you keep a bird or hamster) since it really doesn’t tell you how the amp sounds. And ’liquidness’ is all about how the amp sounds.
Some solid state designers get this- notably John Curl and Nelson Pass. Both will freely acknowledge that tubes still rule the roost as far as liquid or smooth sound is concerned. I think Nelson has done more work in this area, and the amp I mentioned is easily the smoothest solid state amp made.
BTW I think the McCormick is a very good amp too, but the little VFET amp Nelson came up with totally smokes it in the smoothness/liquid category, without sacrificing detail in any way. Of course, tubes do that too :)
@stringreen , 
let me add something even more bizarre : we have Von Gaylord's World First Liquid Cooled Triode Amp , how is that for a change!! 

Throughout their history, Von Gaylord (formerly Legend) tube amplifiers have produced some of the best sound I’ve encountered. One could certainly use the word liquid in describing them. Beyond that, I normally dislike the sound of 6550 amplifiers. These amps obviously know how to wring especially good sound out of that tube
atmashere, the SIT amps you mentioned earlier appear to be (still) currently available according to the FIRST WATT site. Not sure where to buy and how much.
Atmasphere's suggestion for weighting the type of distortion is excellent.  What's even more important than the type of distortion is where is the distortion located.  Our ears hardly care or notice distortion in the bass regions relative to others.  Most subs have horrendous distortion and are driven by cheap digital amps.  Thus, it's not only the type of distortion that matters, but where the distortion is present too.   

That's why I stand by my original comment.  The speaker and amp purchase cannot be done in a vacuum.  The speaker and it's crossover will play a large role in how the amp behaves and what sound results.  Without factoring in this connection, any universal suggestions are primitive.

As I mentioned, I own lots of stock amps and they can perform well with the right speaker.  However, one can't say arbitrarily that a small amp (like a 10 watt single ended amp from First Watt) that sounds liquid on certain speakers, small rooms, types of music, and/or volume levels will "smoke" a balanced 150 watt amp customize modded for your particular speakers and using the latest and greatest parts and technology (like a modified McCormack circa 2018).

It's really not even debatable and evidences a bigger problem within the hobby than distortion measurements.  Most people buy equipment (and ask/comment online) in a vacuum.  They totally forget about synergy and that's one reason why you consistently hear crap from so many systems with "high pedigree" gear.  It's also why you see such a cottage industry for things such as Autoformers that legitimately can help in some situations because certain speakers and amps are so poorly matched on their own.

Also, the other reason (which I mentioned previously) is that most people skimp on their source which thus creates garbage that no amp or speaker can fix. 

Plus, very few people own a truly full range high end speaker and listen in a room that optimally reproduces music. 

All these other things I've mentioned will impact a "liquid" sound far more than an arbitrary amp recommendation and is probably the REAL CAUSE for the original poster's requested suggestions in the first place.
What's even more important than the type of distortion is where is the distortion located. Our ears hardly care or notice distortion in the bass regions relative to others. Most subs have horrendous distortion and are driven by cheap digital amps. Thus, it's not only the type of distortion that matters, but where the distortion is present too.  
+1 the problem area is seen in the Fletcher Muson curves; our hearing is tuned to be most sensitive at birdsong frequencies, 3-7KHz, where a lot of harmonics of instruments show up, and thus also harmonics generated by the audio chain.

Essentially, this is why tubes are still around- tube amps generally speaking tend to make less distortion that falls into this region.
My subs are older class A/B RELs, and they don't seem to distort in any way I notice, even though they're driven by a 12WPC single ended tube amp signal...efficient main speakers help as nothing has to work too hard, and everything is clear as a bell and more resolving and seemingly accurate than any SS rig I've owned, and I've owned many...atmasphere "guilted" me in to a tube preamp (Schiit Freya) and although I rarely succumb to such heavy handed pressure from his over the top statement which I think was, "tube preamps pick up more detail" or something..."I like it. It's good" (Robbie Robertson line).