Amplifier brand/designer with the most unique and consistent “house sound?”


This concept of “house sound” has been pretty fascinating to absorb and consider.  Who here knows amp brands and their house sounds well enough to comment?
redwoodaudio
ayre

from when since charlie started it, and even now after he is gone... remarkably consistent (and lovely) signature
I gotta hear these dang Ayer amps, huh?
Tim deParavicini, may he rest in peace.
You mean "unique and consistent" coloration ?
Got to be Pass and Jadis.
James Bongiorno for his work with SAE, Dynaco, GAS, Sumo and SST! He designed some of the best SS amps ever: SAE MkIII, Dynaco 400, GAS Ampzilla, Sumo Andromeda and the Nine, SST Ampzilla and the Son! A record spanning four decades! 
Plus he worked on loudspeaker design at Rectilinear in Brooklyn! 
I agree with both Ayre and Pass.  Very consistent sounds, but perhaps for different reasons.

Ayre uses the diamond output stage, Pass deliberately looks for circuits to add euphonic distortion.

After these two, Parasound.
I agree with Ayre. Doesn't Pass have slightly different sound signatures depending on the line? I've read the XA-25 is different from the XA-30.8 which is different from the X150.8 which is different from the X250.8. I found the x150.8 (the only Pass I've herd) to be very enjoyable but not the last word in detail and accuracy.
pass/first watt have more variable sonic signatures across their line than ayre i believe
I would argue that Nelson Pass, especially with his First Watt range might be the most inconsistent. He has become the “Baskin Robbins” of amplifier manufacturers with a variety of flavors, some of which seem to change every month.
Some amp manufacturers have offered factory configurable or even user changeable bridging capabilities, taps, topologies, bias options and feedback controls on specific amplifier models.
How would the house sound of Ayre best be described? 
i recall @erik_squires had a very articulate, apt way of describing the ayre house sound... am sure he will chime in...
If you want honest realism ,and a fantastic value per $$ and great long-standing reputation , over 35 years in business  yet 1/2 the audio community especially the young bloods don’t know of them.
Coda Audio Labs these pioneers designed the classic Threshold Stasis amplifiers back in the 1980s with Nelson Pass, when  Nelson decided to start his own company. Several of Nelson’s design team have been quietly building high end hand built and tested ,and at least 20% less cost  then Pass ,Ayre McIntosh  and at least pas good if not better per dollar spent . Their award winning CSIB integrated amplifier I am waiting on delivery and at $6500 for a true reference integrated ,one of the best kept secrets in all of  Audiophile audio.
McIntosh has quite the house sound. Muddy and grainy or lush and detailed. Depending on how much your drinking. 
"McIntosh has quite the house sound. Muddy and grainy or lush and detailed. Depending on how much you're drinking."

I love it.

Conrad Johnson has literally sounded the same for 40 years. From a PV2AR & MV45A to ET3SE and MF 2550SE, more refined as time goes on, but to my ears still lush and detailed regardless of how much I drink.
Hey @jjss49 

Not sure if I can be as articulate tonight as I have been in the past, but to my earst the Ayre amps seem to darken the room, as if they could suck the noise out of it and leave you with less of your room and more of the music. It's a very distinct feeling.
SONY. Not only amplifiers over decades, but other items, too. Very strange. To me, at least.
Digital Amplifier Company.  Tommy O'Brien's class D's are not an off the shelf module purchased from another company.  He designed the amps himself, and they do everything right.  Airy, soundstage, wide band frequency response.  I have two different versions, the original DAC 4800 upgraded to a Mega version and two STM Cherries.  I also have a DTM on order.  For me, they just present the music better.
Ayre..

Agree totally with Eric Squires.

quoting ERIC

 " Not sure  I can be as articulate tonight as I have been in the past, but to my ears the Ayre amps seem to darken the room, as if they could suck the noise out of it and leave you with less of your room and more of the music. It's a very distinct feeling "

I would say that's true of all their products. I feel the same way about my QX-5 and KX-5. Awesome products and superb friendly service.

Watch some of their you tubes to see what makes them who they are including some with Charley when he was still with us.


Ayre amps seem to darken the room, as if they could suck the noise out of it and leave you with less of your room and more of the music. It’s a very distinct feeling.

to what erik said, i would expand with following points on the ayre ’sound’...

1) the blackness of the background is so distinct... it allows more detail to come through, but without throwing it at you, thus there is a lovely delicacy and finesse to the sound, there is detail and ’hearing into the music’ but without even a trace of harshness or aggressiveness

2) the delicate treble emanating the deep dark background couples with a smooth, dimensional midrange that falls just short of tubey fleshiness but is clean without being lean -- once again there is texture and microdetail but without any forwardness or full-fat feeling from tubes... similar to the better pass amps’ sound in this regard

3) the bass is NOT thundering... it is impactful and tight, but not to the depths of the best krells, d’agostinos, levinsons... but sufficient and in proportion to the upper ranges... no bloat less thunder minimal overhang

as such, i value the ayre sound most in my phono stage (p5xe)... the deep dark background and clean gain with minimal edification and lovely finesse is so key, imho, for first stage phono amplification from which to drive forward from...

others may add to the above as they fit... it is my 2 cents, hope i have captured it fairly accurately
Rob Carver will voice any amp you want. 
 He has made some amazing amplifiers. 
 Have absolute respect for Rob Carver!
if I had the coin, those new silver seven amps at 900W of tube power would be mine.

 And the 350’s in my 2nd system.


Marantz KI signature models.... Sony as mentioned.... And luxman also seem consistent even valve to SS
Another +vote for AYRE. Solid state products with a tube-like Soul.

Happy Listening!
@condosound, @chorus
Never heard Lejonklou or LTA amplifiers?  What is their sound signature?
Pathos Acoustics and Moon by Simaudio.
LTA is very nice gear for sure. 
What are the Pathos and Moon sound signatures?
The concept of a house sound is great,  but the key is to find the gem amp of the brand and all amp makers have them,  that is the key to it all,  finding the one amp that does it all without compromise.
Lejonklou- Absence of background sound. Most detail possible.
+1 on Ayre.  At audio shows, they are the rare solid-state company that always pleases my tube-lovin' ears.
John Curl Parasound gear. Anyone here have a rake on this?

Some one who has designed, built, helped design and build and passed his ideas on for others in the DIY field is Colin Wonfor, maybe best known for the Inca Tech Claymore and SECA amps. He also designed the original Tellurium Q cables, his latest work comes under the name of EWA Designs, but he has built some of the most extraordinary amps ever.
What is house sound?
I mean that a amplifier can be made much more linear and do not deviate as much from a flat line as a speaker does. That has more swing up and down from any kind of line.

I thinking if we want to deviate from a horizontal line with for example more bass and more highs so we get a smiley curve.

If a manufacturer consistent make amplifier that make a in this example a smiley curve.
Is that a definition that that manufacturer has that house sound i guess.

Or is the definition of a house sound something completely different?
The house sound is usually purposely implemented to avoid fatigue or harshness of the overall sound.. They look for a “pleasing” sonic signature for “most”.  Thats how PASS designs their equipment. It is a group effort and they ALL listen to and adjust accordingly.. 
Glad we have choices and various types of designers who give us the flavors we prefer.  I chose the Pass house sound overall mixed with a first watt amp which has its own secret sauce blended sound. the combination works for me. Just right of neutral leaning to warm.. 
also should be dependent on the type of music you mostly listen to.
No right or wrong when it comes to preferences.
OK mikem
If i understand you correctly you are not talking about deviation from the flat line along the frequencies.

When you mentioned PASS so what i think I know is that at least in the first watt case its "sound" is coming from more or less amount of harmonics of different orders depending on amp and amount of feedback.

So some like more 2nd harmonics and says that the amp sounds great, when others will even almost not want to turn it on to listening to the same amp, when it has according to measurements not and them to high distortion (as harmonics are).

So House sound is the amount of distortion/harmonics. Or maybe it can be both deviating from flat line AND have more or less harmonics?
So some like more 2nd harmonics and says that the amp sounds great, when others will even almost not want to turn it on to listening to the same amp, when it has according to measurements not and them to high distortion (as harmonics are).

So House sound is the amount of distortion/harmonics. Or maybe it can be both deviating from flat line AND have more or less harmonics?
The ear treats all forms of distortion as a tonality. The lower orders (2nd, 3rd, 4th) bring richness, bloom, lushness, that sort of thing. The higher orders bring brightness and harshness. The ear is keenly sensitive to the higher orders and really not so much to the lower orders. The ear is more sensitive to higher ordered harmonics than anything else since it uses them to sense sound pressure. For this reason a good amplifier/good system will be low in this and will not sound 'loud' even when it is. The ear is also sensitive to intermodulation distortion; the ear assigns brightness and harshness to IMD.


The 2nd harmonic brings richness, if in sufficient amount to mask the higher ordered harmonics. Amps that express the 2nd as their primary distortion product mathematically have a 'quadratic non-linearity'.

The purest form of this in amplifiers is an SET.


The 3rd harmonic is treated by the ear the same as the 2nd. Amps that express the 3rd as the primary distortion component have a 'cubic non-linearity'. Amps like this tend to have less distortion overall, since as the order of the harmonic is increased, their amplitude falls off at a quicker rate. So you don't need as much 3rd to mask the higher orders, and amps of this type tend to have 10th the amplitude of the primary distortion as opposed to amps with a quadratic non-linearity. So they sound more neutral.

Amps of this type will be fully differential from input to output.


Amps can have both non-linearities if single-ended and push-pull circuits are combined. Algebraic summing occurs, so amps like this tend to also have a prominent 5th harmonic.

Amps with a single-ended input and push-pull output usually fall into this last category, although it is possible to build an amp that has a single-ended input but is fully differential from input to output.

The use of feedback adds complexity to this picture. Traditionally, feedback suppresses distortion but adds some of its own, all of which tend to be higher ordered harmonics (plus some IMD), so it can be quite audible as brightness. If insufficient feedback is used, essentially it will reduce frequency response errors when the amp is driving a speaker since the output impedance will seem lower. But it will also be brighter due to the added distortion. Apparently the ear favors tonality brought on by distortion over actual frequency response. 


If enough feedback is used (over 35-40dB) then the amp can compensate for the distortion caused by the feedback (this also allows it to correct other things, like phase shift). Because this is a bit of a trick, and because solid state amps in particular have needed feedback to operate correctly, we've seen about 60 years worth of harshness and brightness in solid state amps, which is why tubes are still around.

But recently there have been advances in semiconductors and also (more importantly) the will with designers to create **in fact for real actually** neutral amps that have almost no distortion signature (house sound) at all. IOW there are now amps that in fact have enough feedback, something new on the audiophile scene.

In a nutshell, a 'house sound', IOW a distortion signature, should be seen as a bad thing, whether its the ever-loving 2nd harmonic of SETs and many other tube amps, or the brightness and harshness of traditional solid state.


One way to minimize these signatures is to allow the amplifier to drive a load that allows it to make less distortion. In all cases this will be a loudspeaker of higher impedance. This is easily seen in the specs of all amplifiers! The speaker should also be a reasonably good efficiency, so the amp isn't being asked to make full power. SETs are a special case of this; if you want to get the most out of them you need a speaker that will never ask the amp to make more than 20-25% of full power (higher ordered harmonics show up if this rule is broken). Solid state amps don't have the graceful clipping character of tube amps (solid state amps made with Static Induction Transistors being the one exception, but SITs are long out of production) so they should always have more power than would be asked of them as well, but 10% more is often enough.


So IF sound quality is your goal, to get the most out of *any* amplifier a speaker that is higher impedance and higher efficiency should be used. If you really like the 'house sound' anyway, keep in mind its not neutral and by definition less musical, even if the amp has a euphonic character. 


Thanks atmasphere for your explanation!

I am currently playing with a power amp clone of pass ACA 5w+5w (someone measured it to 4.5w before clipping on a oscilloscope)

Why? Of two reasons:
# Amir on Audio Science Review measured the real ACA and it is the WORST measuring amp he probably has measured..
In the same time there is MANY testimonials from owners that loves how it sounds.. 
(This is a power amp that has a lot of 2nd harmonics)
I got fascinated of HOW we can have a amplifier that divides one group that thinking it is do BAD that it is not even worth to power up.. and then there is another group that says it the best thing after sliced bread! 🤔
I got to try it out and listening for my self!😉

# The second reason were i have never tried a class A amplifier and wanted to hear what the fuzz was about..

It would be interesting to compare ACA against a ncore. NC400 that is on the other end of the scale and is one of the best measuring amps.

I guess that NC400 is one of those amplifier without any house sound with almost no distortion at all.


@atmasphere - thank you for such a rich explanation of harmonics, feedback, distortion. In other words, a house sound is a house distortion profile.

That being said, are there other factors aside from harmonic and intermodular distortion that might account for different house sounds? Are there other factors which make different amps sound different, even with negligible distortion of any kind?

For instance, some amps are better with rhythm, tone, attacks, decays, timbre than others. These can be part of the house sound, maybe at expense of other qualities, maybe not. 


I agree with articdeth      Bob Carver.  What a genius and I know that he voiced the Silver 7s 900 on Apogee Scintillas and the 350s were voiced on that ( I have a pair of Crimson, the only color choice they should have IMHO)) and now voiced the 275s on those. Great clean bass and extended highs. I believe but can't prove he voiced his amps based on his ear, not on so-called industry or acoustic specs, etc.  His voicing has changed over the years SS to Tubes and/or power.  If you read his stuff, notice he gives credit and kind words to people other than himself, some living, some dead.  IMO that pushes him over being just "great" to "once in a lifetime".  God bless u Mr. C, the Bobfather.Doc from MI
That being said, are there other factors aside from harmonic and intermodular distortion that might account for different house sounds? Are there other factors which make different amps sound different, even with negligible distortion of any kind?
If the amp is not using enough feedback then bandwidth and related phase shift will also play a role. For example a rolloff at 50KHz can make the amp or preamp sound a bit dark. This is because the phase shift can go down to 1/10th the cutoff frequency. In the same way, a cutoff above 2Hz will affect how the circuit presents bass. If the bass has phase shift it manifests as less impact, up to 10x the cutoff frequency.

This is why wide bandwidth has been such a big deal. But if you have enough feedback, then you don't need so much bandwidth because the circuit can correct phase shift as well as distortion.


What a genius and I know that he voiced the Silver 7s 900 on Apogee Scintillas and the 350s were voiced on that ( I have a pair of Crimson, the only color choice they should have IMHO)) and now voiced the 275s on those. Great clean bass and extended highs. I believe but can't prove he voiced his amps based on his ear, not on so-called industry or acoustic specs, etc.
Its unlikely that the amp was 'voiced'as you describe. As an amp manufacturer I hear about this sort of thing a lot. But 'voicing' really isn't a thing; if you compensate an amp to work a certain way with a certain speaker, you've created a synergy. Another way of putting this is you have one distortion put in place to offset another distortion (and probably one of an entirely different type), which results in compromised performance. So I suspect what is true is that Carver simply used the Apogees to listen to the results of his work. You do the math to design the circuit, but you'd be an idiot if you didn't also put the finished circuit on the bench and see if it needs any tweaking, since the math and the actual parts often aren't the same thing. After it performs well on the bench then you play it and see what you think. But this process isn't voicing because you aren't making changes to make it work on that speaker. You're making changes so that the measurements show you its worth a listen.


Now there is another issue, that of the spec sheet as opposed to what we hear. If you are pragmatic as an engineer, you know that the rules of human hearing are not entirely taken into account on the spec sheets. This is why some amps can measure poorly but seem to sound just fine. Robert Harley commented about this in an article (about amplifier types) for Stereophile a few years back but made the comment (about SETs) that 'no-one knows why' they can sound so good and measure so bad. If you've been reading what I wrote here and in my post above, you can clearly see he only made that statement out of an incorrect assumption that designers didn't know why that can be so. Its certainly possible and advisable if you want to make a listenable amplifier to keep the human hearing rules in mind and design for them rather than spec sheets that ignore how we hear.


(One way spec sheets ignore human hearing is showing a low THD number which looks great on paper. But if that low THD is entirely higher ordered harmonic content the amp is going to sound pretty bad - it will be bright and harsh. If you want the amp to sound right, you have to either keep the higher orders way way down or have enough 2nd and 3rd harmonic to mask their presence. You also **at the same time** must have the same distortion percentage at 100Hz, 1000Hz and 10,000Hz. Many solid state amps have excellent distortion figures at 100Hz, which is why they are usually measured at that frequency. But if you measure at higher frequencies, like 10KHz, you find that the distortion is higher. Amps like this are brighter and harsher on this account, even though they have 'low THD' on paper. This phenomena is caused by insufficient Gain Bandwidth Product to support enough feedback, so as frequency goes up the feedback amount goes down.) 


Now if you're going to say 'that's voicing' when the idea is perhaps to design to keep the higher ordered harmonics inaudible then I'm going to agree, although I simply see it as measuring properly. But that still isn't done for a particular loudspeaker.

Here we go with semantics again.. 
Pass tunes their amp to sound its best based on a group of people listening and adjusting the final sound to their liking. They always seem to measure well and with low distortion according to the reviews. dartzeels lastest amps don’t really measure well either but that doesn’t stop them from being considered amongst if not the best out there.
First watt is a different animal.. minimalistic amps , low power with no feedback, little feedback, added distortions, etc  They aren’t mainstream and need to be properly matched. Sometimes they feel the need to add feedback to get a better sound, Sometimes they don’t use feedback at all. Whichever FW amp you choose, it’s clearly described on how it’s designed and what to expect.. I didn’t choose my amp based on specs or types of supposed distortions.. but what it sounds like in my system..  
I didn’t choose my amp based on specs or types of supposed distortions.. but what it sounds like in my system..  
And there is someone like me that choose the worst measuring amplifier that i could find!

If we say like this: that amplifier in my dedicated 2ch symmetrical and treated room sounds actually great.

But if we for one second imagine that the worst measuring amplifier sounds actually "good".

Then maybe we can start to reflect over how much or little measurements actually says about sound quality?!

OK I will go out on a limb here and post a YouTube video of my system playing a track captured by my crappy phone (maybe some sound quality is preserved somewhere to indicate that a clone of pass ACA with <5w/ch that measure terrible)

"Enjoy":
https://youtu.be/_zHy37X192g
I think this is a very educational discussion.  Well done peoplem
@atmasphere writes 
You also **at the same time** must have the same distortion percentage at 100Hz, 1000Hz and 10,000Hz. Many solid state amps have excellent distortion figures at 100Hz, which is why they are usually measured at that frequency. But if you measure at higher frequencies, like 10KHz, you find that the distortion is higher.
If you get rid of distortion and phase shift across all frequencies, will all amps sound the same?  Should they?  Even with different topologies, parts?  No more house sounds?

What amps have taken this to the mathematical extreme?




If you get rid of distortion and phase shift across all frequencies, will all amps sound the same?  Should they?  Even with different topologies, parts?  No more house sounds?
If their output impedance is also the same then at that point, yes, they will all sound the same assuming their power supplies are up to the task.

I would not characterize doing this as a mathematical extreme. Its simply what you do if you want to get it right.


The key is getting enough feedback and at that point it won't matter if its tube, solid state or class D. This is almost impossible with tubes as there are usually too many frequency poles resulting in a low 'Phase Margin'. If the phase margin of any amp is exceeded when feedback is applied, the amp will go into oscillation. This is one reason why tube amps tend to have less feedback than solid state, the other being that they are also inherently more linear and don't need that much feedback to have acceptable distortion figures.


Designers who have been up to the task of installing enough feedback in traditional solid state designs are rare. But it appears that the Benchmark and the Soulution are two amps where this is exactly what has been done.


In class D this is possible though a different means which is to add so much feedback that the phase margin of the amp is exceeded, causing it to oscillate. The oscillation is then used as the switching frequency. Such amps can employ quite a bit of feedback and the sound of them is really all about how well the power supply is built.