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?
Krell, McIntosh, Levinson...and others.
Daltonlanny- My Sim W-3 uses Bipolars exclusively- 8/channel
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.
Do Bryston amps use all bipolar transistors and no MOSFET's?
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.
Musical Fidelity bi-polars are much clearer than Creek Mosfet.
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.
The Moscode 401HR uses MOSFETS also, and it sounds anything but hazy or misty...
Hello Guys,
Is there a difference in bass performance between mosfets and bi-polars in your opinion?
Is there a difference in bass performance between mosfets and bi-polars in your opinion?
Plelko (Threads | Answers)
Bipolar bass players are generally more creative.
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?

08-21-06: Plelko
Hello Grant,
I think I've heard that one before...
Yikes. Really? Have you heard the one about teflon film capacitors?

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.
Thanks for coming, everyone. Be sure to tip your waitress.
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.
Why does this come down to us or them...or to everyone not knowing the future is here?

Look, if someone wants a clear window to the signal, then from what I've heard in my system chip amps are the way to go. Forget analyzing solid state MOSFET or bi-polar output schemes. You want to hear the clear, naked signal? Get a chip amp.

I am borrowing a solid state integrated amp that is clearer than the amp in my system, which happens to use MOSFETs. I have heard two versions of chip amps, and I agree that they are clearer than my MOSFET amp...and my tube amp. But, I prefer the sound of both my MOSFET and tube amp to the clearer sounding, more detailed integrated amplifier...and to the the equally clear and detailed chip amps. In my opinion, the clearer sounding amps don't sound like music. At the core, isn't this discussion of MOSFETs and bi-polar output really about coloration or lack thereof?

We all have our own ideas of what we believe sounds correct, and the opinions run the gamut from complete uncoloration to excessive manipulation of the signal. I suppose MOSFETS may color the sound somewhat compared to other designs, but in my opinion that's a good thing.

Doesn't this all come down to preference, and isn't there room for different tastes? Or is this thread a journey to a new discovery that has not been visited before? It seems similar to me. Perhaps I'm not seeing the angle.
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.
08-22-06: Muralman1
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.
However you approach it, you're creating a colored sound, correct?

IMO, there's no difference between your approach and one that takes an uncolored signal and colors it with amplification. The result is the same. Colored sound.

You say tomato, I say to-mah-to.

If MOSFETs haze, fog or vaseline the be it. The result on the Moscode 401HR is a sound I like, and that's all that matters.
Yeah, but I get to choose the color of the day. You know that about tubes....
08-22-06: Muralman1
Yeah, but I get to choose the color of the day. You know that about tubes....
There's no difference between our systems there either, as I can roll half a dozen or more tubes in both my preamp and amplifier, and by so doing I can change the sound of the system in a number of ways...from uber clarity and resolution, to warm and fuzzy and less resolving.

I'm not trying to one-up you here at all, but you cannot claim "Yeah, but..." as a benefit or difference between your chosen method and mine. It still comes down to shifting the coloration by changing tubes.

Which seems to highlight the superiority of tubed gear, even if a system utilizes only one tubed component. Eureka!
The question still is, "Has anyone else experienced this 'haze' with a mosfet-based design?"

The answer is.......... drum roll........... Yes!
08-22-06: Muralman1
The question still is, "Has anyone else experienced this 'haze' with a mosfet-based design?"

The answer is.......... drum roll........... Yes!
I cannot presume to be able to narrow the cause of the sound of my Moscode 401HR to its MOSFETs, to it's input or driver tubes, or to the utilization of these parts and the rest of the parts in the overall design of the amp, and I'm dubious of anyone's ability to hear and separate any sonic attribute of MOSFETs from the rest of an amplifier's parts, unless that person is an amplifier designer with years and years of experience.

However, I also will not rule out the possibility that all the hobbyists contributing to this thread who claim to be able to hear the difference between MOSFETs and bi-polar outputs, independent of the amplifier designs in which they are used, are audio savants.
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.

08-22-06: Undertow
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.
I owned Odyssey Monos for a short time. I cannot give you a comparison of the two amps based solely on MOSFET vs. bi-polar for reasons expressed in my posts above.

The Moscode is more to my liking than the Odyssey amps in every regard.
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.

08-22-06: Muralman1
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. I have also mentioned above regarding chip amps versus SS. However, I am doubtful that you can conclusively narrow the cause of the sonic differences between the two amps solely to the presence or absence of MOSFETs, which was my point.

But, perhaps you are an audio savant. If so, I salute you, sir.

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.
Muralman1, I believe we are perhaps stating the same position, but have passed like ships in the night. No pun intended. If you contend that the sonic differences you heard between your two amplifiers are due to circuit design, and not merely the use of MOSFETs, then I'm in absolute agreement.

Am I mistaken in my impression that you were taking a position of being able to discern so-called "MOSFET haze" as evidenced by the differences you heard between your supersymmetry monos (I have no idea what these are, and I assume they use MOSFETs), and your chip amps? Because, my position is that few audiophiles, if any, can conclude that any difference they hear between the sound of SS amps utilizing MOSFETs or bi-polar output, or between SS amps with MOSFETs and chips amps, can be attributed solely to the MOSFETs as opposed to the entire circuit which utilizes the MOSFETs. We apparently agree on this, do we not?

I have never heard a Pass amp, and therefore I am neither a fan nor a detractor of their amps.

Hope I made myself more clear. Sorry for any confusion.
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.