SS amp mosfet 'haze' - ever experienced this?

Tried a new amp in my system on the weekend: the well-reviewed Gamut D200 mkIII (partly based on HP's great review), a single-mosfet SS design. At the dealers' place, it sounded great (speakers were Wilson Benesch Discovery, an isobarak, lower-efficiency design). I can't use a tube amp right now (unfortunately!) due to pending child and the system is on a LOT (2-ch/HT mix), so am looking for the most full-bodied SS amp I can find (prefer fully balanced design to match my modded SF Line 3 pre).

Well, to my surprise, the amp did NOT work out as well at my place. My speakers are 97db Coincident Total Victory. Yes, it was full-bodied, but I was definitely aware of this haze, or veiling around each note. I have a friend who designs amplifiers, and he said that this is inherent of mosfet designs. I called Israel (Coincident) and he was not surprised that I only heard this once I got back to my place, due to the high resolution abilities of my speaker vs the speakers at the dealer's. I guess I will be sticking with my Sim Audio W-3, as it is much 'cleaner' on my system (given that I must stay with SS). Too bad, 'cause my Sim W-3 definitely has the edge in clarity, but the Gamut was a touch more full-bodied.

Has anyone else experienced this 'haze' with a mosfet-based design? I admit, those with higher-efficiency speakers like mine (97db/14ohm) probably are NOT using higher-powered mosfet designs anyways, but I would like to know how others feel about mosfet designs and this issue I had.
Mosfets tend to have a sound that are tube-like where as bipolar transisters tend to be punchy and snappy. This has been taken advantage by desingers who want their amp to emulate the sound of tube. So what you experienced is not unique in that regard.
Yes, but in older Mosfet based designs. Not really the case today. Perhaps you are just too used to the clean house sound of Sim.
I have a speaker that is as revealing as the Wilson Benesch, the Apogee Scintilla. With this speaker all upstream component gliches are easily discernable.

I have previously employed the well respected Pass Labs X600 mosfet (Hexfet) amp to run the power hungry Scintillas. The X600 is reported to have a signal/noise level of 151 db. That figure is astounding!

An aquaintance of mine talked me into trying a diminutive ICE powered analog amp, rated at 117 db S/N, on my speakers. I was understandably derisive of it's potential, until I tried it.

The new sound was like a thick quilt had been lifted from my Scintillas. The bass gained in authority and control. The mids are absolutely transparent, and there are highs suddenly audible. It is obvious to me, the haze report around Mosfets is true. The Pass Labs X surely is an advanced ss amp.
The original gamut mosfet amps were reported to be completely transparent. Designers choice in voicing- not the Mosfet that is misty.

Again, old mosfets yes. New mosfets no haze/mist.
Reb, did you read my post? Are the Hexfets Pass Labs currently putting into their amps antiquated?
...the statement that newer Mosfets dont' exhibit this response. The Gamut amp I tested was the LATEST model (D200 mkIII).
Did you miss the part about voicing by choice. D200 MK1 has no "mist" and it uses Mosfets.
That is what I thought. There are hidden gremlins. I thought the Pass amp was the last word in fidelity. People use my older posts against my evangelizing over the H2O. My defense is, you are only aware of what you know.
It would be interesting to hear from someone else who has heard the Gamut D200 MKIII on reasonably high efficiency speakers...
I use gamut d200 mk3 with sonus faber guarniere( 87 db), before I used audio research vt100 mk2, and the gamut is better, after 30 minutes of warming is better in all aspects.
What brands of solid-state power amplifiers and preamplifiers DO NOT use any MOSFETS at all in their signal paths?
Are there any brands that use bi-polars exclusively?
I have been using the GamuT D-100 Mk 3 for over a year and it is absolutely transparent and grainless. I do know this amp takes several hundred hours to fully break-in. Power cords are important. I have used the JPS Labs AC+, subsequently their Kaptovator and now the Aluminata with improved clarity with each step up. I used the Audience Power Chord with less success. I use Chapman Q6 speakers which are about 89 DB efficent. Multiple reviews on the GamuT amps which have never been discribed as hazy.
According to the Stereophile review of the 14B-SST the amp has "bipolar output transistors". You can always e-mail James Tanner @ Bryston who typicallt reponds to all inquiries the same day
Sheffb- you're not hearing the 'haze' I experienced because your speakers are 89 db efficiency- not a bad thing, as I will say the Gamut sounded very good with a set of lower efficiency/power hungry Wilson Benesch Discovery speakers at a local dealer's place...
try it with different speakers. the coicident speaker is not a good match, and the gamut is one of the finer mosfet designs in the marketplace. otherwise you will go through amplifiers like sherman through atlanta.
I have found the GamuT D-200 III to require at least 250 hours of playing time to sound truly open and transparent. It also likes to be turned on and left on. Other folks have mentioned the break in factor and also the role power cords can play with this amp.

I use the 92 dB, 14-Ohm Coincident Super Eclipse III's with the D200. While I think some tube amps are more "audiophile" impressive with midrange transparency and sound staging, the GamuT D-200 III sounds complete and integrated from top to bottom to me. It's the best SS amp I have ever used in my own system: Plinius SA102 MkII, Goldmund M28, BAT VK500, MF kW500, Spectral DM80, 47 Labs Gaincard S, and Sunfire amp.
I always liked Bi-polar designs over mosfet.. Don't know why but they are more organic sounding, mosfets have a more envelope sound to them and sometimes sharp, basically Mosfets were all the rage I remember with big name audio companies in the 90's and I tried a bunch out, it was kinda a trend like the Class D stuff etc.. going on right now, I find the new Digital designs to sound similar to the Mosfet designs to be honest, so its kinda a new twist on that sound, Cars sound best with mosfet in my opinion, at least the bulk of the designs I heard in the 1000.00 to 6000.00 range of amps.

There are a few big designers still using mosfet stuff, but honestly if you look around at the more expensive and discrete hi-end stuff its exclusivley bi-polar I believe.. I could be wrong but anyway thats what I see for the most part. Companies like boulder, gryphon, Mcintosh, Belles, McCormack, Odyssey etc.. that are the most mentioned and respected amps all seem to use bi-polars.
Wow- a response almost a year later on my original thread- thanks Kalan! OK- you might have something with the Super E/Gamut- interesting observation- what preamp; interconnects; and speaker cables though??
Interesting read...missed it first time around.

A mosfet operates more like a valve (tube) so it is no wonder that many have claimed they sound more 'tube like' than bipolar's. And they do- most of the time.

The 'haze' or 'mist' isn't a characteristic of the mosfet; it's a characteristic of the implementation. I think it was Sam Tellig that coined the phrase 'mosfet mist'. This from a guy who raved about the Unison gear that uses tubes and mosfets. Go figure.

By the way, Belles uses mosfets in the 150A Hotrod. John Hillig uses mosfets exclusively; as does Frank Van Alstine. None of these amps sound 'hazey'.

Sutts: Yes, I took a chance on answering a thread that had not had activity for a year. Interesting topic, though. You asked, "...what preamp; interconnects; and speaker cables though??"

Pre-amp = First Sound 4.0/Paramout Plus upgrade
Interconnects from CDP (Ayre CX-7) to pre' and to power amp = Shunyata Altair.
IC's from TT rig (TNT 3.5/SME V/Benz LP) to phono stage (modified Luckaschek PP-1) = Audience Au24.
Speaker wire = Shunyata Andromeda

BTW, the First Sound/GamuT combo is fantastic. I expect a pair of Gamut M200 monos to arrive any day now.
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Hello Guys,
Is there a difference in bass performance between mosfets and bi-polars in your opinion?
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Hello Grant,
I think I've heard that one before, but what I'd value even more is a serious discussion of the bass characteristics of Mosfet devices. In my opinion, they are looser sounding, and lack the power of bi-polar devices. Are there exceptions to my above stated opinions concerning Mosfet devices?
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Hey Grant,
No, I didn't, but did you hear this one, "Who is the best rapper of all time, MOS-FET!" I feel like George Constanza in the episode about the shrimp joke.
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Just LISTEN to Pass X series. That will convince you there is no "looseness" or "lack of power" in power MOSFETs. I'm not trying to push the Pass, I'm just trying to get some rationality in this discussion.

Execution and circuit design. These make the difference. Many designers didn't know how to design a circuit to make these MOSFETs do their best. I like the sound of bipolars as well, if implemented correctly. It's not a matter of which device; it's a matter of design.
I did listen to the Pass X series amps, for a period of years. They were my mainstay in powering my system. My last was the X600. I needed the power to drive my difficult speakers. I was fairly happy with the sound. "What could be better," I asked myself.

Well, there is better, a lot better. Mosfets do draw a haze over the signal. It is a thick fog. That is in comparison with my present monos. They are leagues clearer. My X amps bested the solid states, and tube amps that I owned. There was nothing better to be expected. After all, it' s Pass, isn't it? I knew there were deficiencies, like thick midrange, and soft bass, but hey, They are beautiful amps, aren't they?

The future is here. Not everyone knows it.
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I don't want an amp that colors the signal. I color it to my choosing with a tubed DAC. My amp, and preamp's job is to magnify that DAC's sound, and nothing more.

The question was, do we hear Mosfet haze? My answer is a question, relative to what?

On Bipolar amps. I have preamps that are bipolar, and damn they would make a great amp.
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Yeah, but I get to choose the color of the day. You know that about tubes....
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The question still is, "Has anyone else experienced this 'haze' with a mosfet-based design?"

The answer is.......... drum roll........... Yes!
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Tvad, I thought you used Odyssey mono's? Those are bipolar, what is your impression of those vs. the mosfet or any of these others? Just curious for my own knowledge, thanks.
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I had the advantage of replacing my Supersymmetry monos directly with a "chip" amp, same system. Everything became instantly clearer. I could see much deeper into the recording. Thee bass was much more pronounced and tighter. There was no turning back. My "chip" system has evolved greatly beyond that first baptism.
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That did not make a lick of sense, Tvad. I know you are a fan of Pass amps. Are you saying all the bold difference between my present amps and the X600 are those tiny pass component boards? I think not. The huge difference is due to completely different amplifying designs.

I'm a savant if you are a clairvoyant.
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Gentlemen- I will add one note below- an exciting new finding for me... (by the way, no one is going to convince me about that the Mosfet haze doesn't exist- I know what I heard on my reasonably high-efficiency speakers).

I recently auditioned a remarkably uncoloured, yet also extremely communicative set of SS monoblocks. They are the Audiosector 'Patek' SE (the 6Moons guy raved about them I believe). I believed they would be termed a 'gainclone'. The low parts count and superb contruction stunned me, really superb and obviously meticulous build quality- perhaps this translates to the purity of sound I experienced??

I see big potential here- in fact, I compared them to the other 'new technology kid on the block'- digital switching power supply amps, in this case, a set of Bel Canto Ref 1000 monos. The BC's were interesting- but almost TOO quiet between the notes, as if in a vacuum... I found more 'life' in the Pateks...
I wonder if some of Sutts' "haze" impression of the GamuT D200 could have been mitigated by adjusting the internal dip switches that govern gain (and input sensitivity).

Matching with the pre-amp and speakers contributes a lot to the over all performance of a given amp. Lots of break in, careful cabling choices and gain-matching of the GamuT could make or break the impression, IMHO.

The GamuT could have been adjusted for less gain to mate up with the 97-dB sensitive Coincident Victories. I think the manual advises this with high output sources; so, I would imagine some aspect of the same principle would apply for sensitive speakers.

With the First Sound 4.0-Paramount Plus pre-amp, the Gamut amp happens to sound very clear with no gain attenuation--in other words .77 V input sensitivity or 35 dB of gain. (Speakers are Coincident Super Eclipse III's in this case, 14-Ohm, 92dB.) The Gamut amp needs about 300 hours of run-in time to kick in. The dealer's demo unit may not have had enough time on it and could have had its setting not optimized for Sutts' surrounding gear.
Hazy is how the vast majority of SS amps sound.Compressed too.Efficient speakers just highlight it more.
The one exception seems to be chip amps that can sound amazingly clear and fresh on sensitive speakers.
The Kora Aries MOSFET hybrids will knock your socks off. They have a clarity that is unmatched by any BJT or tube amps I have ever had in my system.