"Warm Sounding" Solid State Amplifiers

Audio Refinement electronics. No longer manufacturered, but can be had on the second hand market if you are patient. 

I would have a serious look at channel Island amplifiers, I have there small mono block amps which sadly are no longer available  paired with a good tube pre there amps are amazing.The mid range is incredible and I will not be letting them go.Check them out used or new you will have to spend thousands more to get better sound.No I do not work for them it's all in the ears

A bit of a long overdue update on this discussion. 

I definitely didn't realize the can of worms that I was about to open before I began the discussion but it has been highly enlightening.

Earlier in the thread I accused Bryston amps of sounding too neutral and sterile and I wanted something different. Among the Bryston amps I own and have owned are the 7B ST's, 7B THX's, 7B SST2's, 4B THX and some old 4B pros.

I bought a Threshold T-400 in the summer of 2015. When it first arrived at my door I had to send it out for repairs immediately. The repairs were done by an independent tech and the repairs were seemingly successful. The sound was sweet and smooth but the only thing about it that was "warm" was the unit itself. Because of it's 300 watt idling current the damn thing is like a small furnace. Not very ideal in the summer time and also a drag on the electric bills. Listening sessions would be cut short due to the excessive temperature build up in my 2nd floor listening room.

I finally had enough and I pulled the trigger last week on a Bryston 4B THX. Having previously owned a pair of 7B THX's I was very certain of what I was getting myself into. The day after I had committed myself to the 4B THX my friend Murphy paid me a random visit. He's a lawyer and whenever he shows up, things seem to go sideways. In this case the right channel of my Threshold started to distort significantly. After a quick round of trouble shooting it was obvious that it needed to go back to the shop - Again. And this time, to a different shop.

The Threshold is still in the shop but I will wait to "Pass" my final judgement until it has a clean bill of health from my new tech. The T-400 is a highly esteemed amp with somewhat of a cult status to it. Many describe it as one of Nelson's best sounding amps. I found it to be sweet and smooth but even with silver speaker wire (Audioquest Comet) the midrange seemed a little too laid back and the bass always seemed shy or muted through my Monitor Audio Gold GX 300's. Until I plugged in the 4B THX I wasn't really sure if those issues were because of the speakers or the amp.

The 4B THX brought my system to life again. The bass had the weight, depth and control that you can expect from a Bryston amp. The midrange had a forward sounding presence. The soundstage was big and wide and overall very dynamic. I had to change the speaker wire to my Audioquest CV-8 (all copper) to get the right balance but overall I found the Bryston to offer a more musical experience.

I will be fair and re-audition the Threshold once again after it comes back from the shop but it is very likely that the Bryston will stay in my system!

Before considerations of "warm", what about things you are sensitive to in a negative sense?  SS amps with low measured THD but relatively high levels of odd order harmonics?  Hate them.

Tube amps with sloggy, lazy, rotten tomato being hit by a mallet bass?  Hate them.

Also any amp that has colorations in one band but not another?  Hate them too.

So outside of frightfully expensive tubes - they are out for me (in amps, not pre-amps or DACs).  Retubing amps with any sort of top shelf  tube gets very expensive as well.

So, first wipe that type of thing off of your list (things you don't liek).  Are you keeping your speakers a long time?   Good.  What do others say works well with them - good way to start a listening list.

Warm?  Class A, Class A->AB, fets - I think most of your warm amps that are not tubes will be found to have one or more of these traits.  My amp is a Pass X-150, got the A->AB and the right sort of transistors.  Clean, fast, of one piece from top to bottom, depth, accurate with a bit of sweetness, lots of current, will drive ML's, Maggies, even Duettas.  I found mine, hopefully you'll find yours.

I changed my mind. Earlier I posted that the Bedini BA-801 is the most tube-like amplifier I've ever heard.
Nope, not anymore. My recently acquired Audio Research 100.2 takes the prize. Not even close, the 100.2 exudes warm bass, vivid vocals, and sweet highs. Nothing soggy, bloated or ill-defined, it just has a lot of that tube magic. I'm keeping the Bedini because it's good, real good. But the ARC 100.2 surpasses it in every way. No wonder they're in such demand!

Nice pass class a thirty here...For the life of me I don't know why people do what he did???...anyway's I digress...I find my modwright kwi 200 has nice warmth to it.

I find my modwright kwi 200 has a nice warmth to it....

There is a nice pass class 30 watter here/could take some solvent to try and remove the goo that's around power light.

(The things people do?)

My modwright kwi 200 has some nice warmth to it...

I would say stick to tubes. However, this reminds me of a funny thread once where someone asked tube lovers that if a gun were held to their head and they had to listen to a solid state amp, the overwhelming choice was Naim. My brother has one, and it does sound pretty good. I would give them a try if you just have to have solid state.

I was pleasantly surprised by an Audia Flight FL3 integrated. Held up nicely comparing back to back with modern tube gear at the local store. Can be found heavily discounted on demo at a few stores. Might be worth a listen and a google.

maintenance factor for tubes? what is that? they last for a damn long time.

The journey continues...

I have purchased a Threshold T400 power amp. Like the MF A308 it is a dual mono design but the Threshold is pure Class A, as most of you probably know already.

It will be arriving at my house tomorrow and I am looking forward to comparing it to the A308. The A308 is an excellent, musical sounding piece though it is not "warm" and lush sounding like the Pass Labs amps I auditioned a few weeks ago. Threshold was suggested earlier in this thread and I figured I would sieze the opportunity once I found one at a reasonable price.

Stay tuned for more!

Cary cad 200 tube like warm sounding amplifier.

Glad it worked out well!

Sorry for the wait but I have finally picked up the A308 and the GX 300's.

The A308 integrated is a wonderful amp! In a nutshell, it is more on the neutral side of the spectrum but it is very musical. After a 15 to 20 minute warm up it really comes to life.

Compared to the NAD C355BEE it is much more dynamic and unstrained. The sound doesn't come apart at higher intensities and volumes. The bass is also much tighter and controlled. Very solid build quality. Produces a lot more heat than the NAD.

The preamp section is excellent but I still prefer my Bryston BP25 preamp as I find it to be more dynamic, articulated and a lower noise floor. However, I do find the A308's phono stage to be warmer and more musical than the BP25's phono stage. That makes my turntable very happy! :)

The GX 300's are also fantastic speakers. Compared to the Silver RX6's they have more natural sounding highs, very clear mids and deeper bass extension. Superior sound stage as well. Overall more refined sound. Lot's of finesse! Oh... and did I mention how purdy they are? Terrific craftsmanship that makes for some pleasant eye candy for any hi-fi enthusiast!

The only glaring issue is my room size and speaker placement. For the time being I only have a 10 x 12 bedroom to work with. The GX 200's would probably have been a better option. The speakers are off center and approximately 1 foot from the wall. My equipment is somewhat stacked up in between the speakers, my head is right up against the rear wall and there is a queen sized mattress between me and the speakers.

For a bedroom music system it seriously rocks but for a proper hi-fi setup there is much room for improvement. I'm in the process of negotiating some space in the living room but it is plagued with animals and toddlers.

Thanks to everyone who has been following and contributing to the thread! :)

Quite likely! The seller is a gentleman in Southern Ontario. It's like it was waiting there for me! ;)

That must be the A-308 I noticed on CAM just before you announced you found one? Don't you just love it when a plan comes together!

Yes, that's right. An excellent point. From what I understand they still manufacture their higher models in the UK still. Anyway that's very distant on my "radar" I shouldn't really entertain that notion until I have had a good amount of time to listen to the A308 and the GX300's.

"05-03-15: Pontifex
It will still be yet another week or so but I'm very excited to finally introduce myself to the Musical Fidelity brand. If I enjoy their sound signature I could see myself moving up to the M6 series. I want to simplify my rig a bit more and get a CD player with a good DAC rather than use a separate one. So the M6 CD player is also on my radar."

You need to be careful. The piece you bought was from when MF made they're stuff in the UK. The M6 is some of the newer gear made in Taiwan. It doesn't sound anything like what you just bought. Completely different.

It will still be yet another week or so but I'm very excited to finally introduce myself to the Musical Fidelity brand. If I enjoy their sound signature I could see myself moving up to the M6 series. I want to simplify my rig a bit more and get a CD player with a good DAC rather than use a separate one. So the M6 CD player is also on my radar.

I used to have an A308 integrated. It was an excellent amp. I hope you enjoy it.

Arsh

Pontifex,Hope all goes well and they sound Great together!!! Keep us in the loop.

I just sent a pair of those in mono to Hong Kong. Very happy customer.

There are quite a few "great" sounding SS amps, now, and, as far back as the late 70's!

One of those was the H/K Citation 16. If you found one though, expect to get the filter caps replaced.

AVA 450 Synergy amp sounds like a 120 watt Sylvania 6550 amp if there were such a thing

I have been following and hope the best regarding your purchases.

+1 Csontos

There are quite a few "great" sounding SS amps, now, and, as far back as the late 70's!

Just a quick update for anyone who has been following...

I have secured a deal on a Musical Fidelity A308 integrated amplifier for $1300 CDN. That model dates back to 2003 (I think ?) but it was manufactured in Great Britain before MF moved the bulk of their manufacturing operations to Asia. It is a dual mono design with 150 watts/ch and gets many good reviews and is said to be very "musical". I look forward to picking it up next week!

Also, I have secured a deal on a beautiful pair of Monitor Audio Gold GX300's. I probably should have opted for the GX200's because of their easier room placement but we'll see how it all works out. Very excited! :)

Of course not. As you say, and as I've also stated, specs are an indication of potential. What I meant was that sometimes the specs are not window dressing. Lots of horrible sounding amps have great specs but great sounding amps also always have great specs. But the point I was trying to make clear is that truly great sounding amps that happen to be ss are not as rare as you might think.

^^ :) so you are saying you can tell how an amplifier sounds from its specs? Like many analogies there is a certain point where it falls apart.

I find that if anything, there is an inverse relationship with THD (higher will likely sound better) a positive relationship with IM (lower will sound better) and wider bandwidth is usually good. But even knowing that I still can't predict how it will sound.

Well, my experience has been that sometimes the emperor is a good guy whose clothes have been altered.

^^ The number on the bit of paper is a good example of the Emperor's New Clothes.

We all know this- can you definitively say how an amplifier will sound by looking at it specs? We all know we have to take the amp home and play it to see if it will work in our systems. The paper specs are for marketing- the specs were not designed to have very much to do with how we hear; they have everything to do with selling the amp.

Now if we developed specs based on human hearing/perceptual rules then progress would be made.

"Enter the subjective nature of our hobby. I always knew diminishing thd with decreasing power was the way to go. That's what makes sense. It's a shooting gallery out there right now and the prey is ripe for the picking. However I think I have a handle on what the rules are."

After reading some of your posts, I can't help but think that you're focusing way to much on the rules of audio, and not enough on the music. If you continue going in this direction, you'll just get more and more frustrated. You're never going to have all of your questions answered, so you might as well make the best of it and not worry about a number on a piece of paper.

Yes, It's a well known article. But it doesn't really bring up anything we don't all know already. At least those of us 50+. I get all that. I mean I believe it, I remember the 70's:). So what I think you're saying is, it boils down to the question "how much is too much?" IOW, the devil is in the details. Enter the subjective nature of our hobby. I always knew diminishing thd with decreasing power was the way to go. That's what makes sense. It's a shooting gallery out there right now and the prey is ripe for the picking. However I think I have a handle on what the rules are.

Thank you as well, Blackcloud. That is very helpful information.

Csontos, it does not matter if it is live or reproduced, our ears listen for those harmonics (which are always there) regardless. We can't change that!

Quite simply, the application of physics to design equipment to honor our human hearing/perceptual rules will result in better sounding equipment:

What we *can* is change our approach to how we are going to playback recordings; i.e. design the equipment with intention to simply not make those distortions to which our ears are the most sensitive. These distortions are IM (which might also be termed a special form of 'inharmonic distortion') and the higher orders of harmonic distortion, the 5th and above.

(Our amps (Mk3.2) are full power out to about 300KHz since you asked.)

Those designers like Nelson Pass and Charlie Hanson (Ayre) that have sorted out that feedback can be dispensed with are also demonstrating that such leads to a more musical approach. Norman Crowhurst is required reading for anyone designing audio circuits. About 60 years ago he wrote about how the application of loop negative feedback in an amplifier that does not exhibit higher ordered harmonic distortion (like an SET which might have the 2nd, 3rd and 4th harmonics) might well reduce the lower orders to vanishingly low levels, but in the process higher orders (starting with the 5th harmonic) will be added going clear up to the 81st harmonic! In addition, intermodulations can be introduced at the feedback node in the amplifier.

The result is that the noise floor is fundamentally altered. In an amplifier that has no feedback, the noise floor is hiss, not unlike that of the wind and the sound of water moving. Not by coincidence, our ears are adapted such that they can hear into such a noise floor, some say as much as 20 db but to be safe 10 db for sure; this is the *one* exception to the human ear's masking rule. This allow us to hear detail that exists below the noise floor of the amplifier and if you think about it, essential to our survival.

When loop negative feedback is applied (per Crowhurst) this noise floor is altered and while it might sound the same, the peculiarity is that our ear's making principle is in full force- we cannot penetrate that noise floor, so the detail below that point is lost.

This is why amplifiers that employ loop feedback seem to loose low level detail in which room ambiance and imaging detail in the rear of the soundstage resides. To hear this occur, you must start with a recording that has plenty of depth, then you can audition that difference between the two approaches.

Since the application of loop feedback also adds harmonics, this is why any amplifier using it can sound brighter as well, since our ears sense those added loudness cues.

Nelson Pass has a wonderful article on distortion on his website: https://www.passdiy.com/project/articles/audio-distortion-and-feedback; Nelson is one of the leading designers worldwide.

I currently own the NAD M2 and as much as I really like it, I would never consider it warm, technical would be a better way of describing it. My front end is digital so it meets my needs just fine. If I was using a TT, this is an amp I wouldn't buy.

Many years ago I owned a Bedini 25/25 and that is an amp I regret selling. It was what I considered warm in sound but hot to touch. Class A power meant a lot of heat!

When I was thinking of selling my M2, my thought was to go towards NAIM for that warm sound. In the end I thought there was nothing really wrong with the M2 and it sounds great with my Harbeth 30.1.

My favorite thing about the amp is I don't need a separate DAC. My system looks nice and clean, very minimalist.

Good luck with your search.

Ralph, can you describe live unamplified without reference to amplified? Where does 'warm' come from in reference to unamplified? To me, the 'holy grail' is 0 distortion. With that comes perfect neutrality vis-a-vis, 'live', no? Ime, non detectible IMD/TIM results in the intended goal when the FR is truly flat. I truly believe this is what we're all looking for whether we know it or not. It's the jargon that gets in the way of arriving at a real understanding of what constitutes live sound in an amp.

What are the loudness cues our brains use for natural, unamplified sound, or a tube amp? Without higher order harmonics, what do we use?

When you describe "bright" sounding amps, are you comparing to other amps, ie: tube, fet, etc.? Or are you using live unamplified sound as your reference? More often than not the comparisons I read are tube vs. ss.

I think live as an established reference for both tube and ss reveals the only truly accurate yard stick in ranking the performance of an amp.

Both fall short, some deliberately(usually tubed),some not(usually ss).

What you appear to be making very clear is that distortion is the arbiter in judging neutrality. So other than utility, tubes are not necessarily required to achieve the desired goal. And I don't want to beat you up on this but if I may digress, you did use the term 'warm' in reference to live unamplified sound.

Having said all that, I suppose my next question would be, 'typically, how flat is the FR of one of your amps? I mean if you stretched the tape out to 5 feet.

The most notable difference I've experienced among the amps I've owned and still own, is that character you touched on regarding volume. I have only two amps, both ss, that have that quality of high volume without fatigue. This is mine, and I believe everyone else's natural yardstick to recognizing life-like sound and coincidentally, noticeable distortion.

And this is the crux of the situation as they say. It now becomes quite obvious that for the most part, you by default, are correct in that very few ss amps with that characteristic exist. All those apparently 'warm' ss amps are going to hurt just as much as any other low distortion ss amp when cranked.

However, it didn't take $100,000.00 for me to acquire that quality. But it did take time/research. Interestingly enough, my favorite LSR&D amps are also obsolete. I think it serves to point out that these amps are the late Dr. Marshall Leach's famed LOW TIM design. They can still be had as diy projects. Also, this design has been incorporated into some other brands such as Heathkit(vintage), some Crest(sound reinforcement), HK 990, to name a few. The other is my Boothroyd Stewart Meridian 105 monos. The Brits have a pretty good handle on what we're talking about here imo.

Also, I think the famous Bob Carver Challenge has a place in this discussion. Still not sure if Mr. Carver is in a league by himself. On the one hand ostracized for having the ability to mimic the sound of any amp, ss or tubed without having to copy the circuit, and on the other, celebrated for his sonic achievements. He's clearly shown that neutrality is a matter of circuit design and that the question of tubes or ss does not enter into it.

I still wish I would have scooped that S-30 before it was too late, though:)

Csontos, thank-you for your reasoned reply. I thought you might like to hear a number: 600, as in 600V/uS, the risetime of the output section of our amps. Tubes don't have to be slow nor dull any leading edge transients.

I agree with Mapman- there is something that is neutral, neither bright nor dull. The thing is, when audiophiles talk about bright or dull it is rarely about actual frequency response errors. The brain translates distortion into tonality. This is why single-ended circuits (tube or solid state) tend to sound 'warm'; its not a frequency response error, its the brain translating a 2nd ordered harmonic into tonality.

Our ears use the higher orders, 5th and above, as loudness cues- the brain uses these harmonics to calculate how loud a sound is and does not rely on the fundamental tone for that. As a result, our ears are more sensitive to these harmonics than the best test equipment- we can easily hear these harmonics as distortion where its difficult to measure.

This is why two amps on the bench might have the same bandwidth, but one might be bright (has a trace of higher ordered harmonic distortion) while the other does not. In addition, the ear/brain system while translating higher ordered harmonics into brightness, also translates the same into harshness.

Its my stipulation that it does not matter whether the amp is solid state or tube so long as these harmonics are not added by that amplifier. IMO/IME the best systems have a sense of ease at any volume and there is never the quality of 'loud' no matter how loud its actually playing. This BTW is a property of real music.

Sunn made some guitar amplifiers that were solid state back in the 1970s. Now if anyone here plays guitar and uses an amplifier, they know that most guitar amplifiers are vacuum tube, on account of if you want to overdrive (distort) them, you need tubes to have them still sound like music. But Sunn made solid state amps that at the time and to this day were recognized for having a 'warm' sound to them. When you look at the schematic its obvious why: the preamp section employed FETs in a single-ended topology with zero feedback (the FETs being very linear did not need feedback; the primary distortion product being the 2nd harmonic), and the power amp section was also single-ended until converted to push-pull by a driver transformer. So the power amp was rich in 2nd orders as well.

Now I am of the opinion that the 2nd order that is traditionally associated with tubes does not have to be there. That is why we make our amps fully differential and balanced; even orders are canceled not just in the output section but at every stage inside the amp. So while they sound smooth and are detailed and fast, they don't have the warmth associated with a lot of tube amps. The take-away is that topology plays a bigger role.

The Sunn amplifiers are considered obsolete designs, but if you really want warmth as a sonic attribute finding an amplifier of that type (or building one) might be a consideration.

Thanks again folks. The Threshold amps appear to show up at a lower price points on the used markets. Seems worth while to check out! If I'm lucky I might find a seller in Southern Ontario. There's one for sale in Alberta but freighting heavy and expensive things across Canada is somewhat of a costly hassle.

As for Luxman amps I tend to see a lot of the more vintage models for sale.

Try the Luxman Class A amps. The 550AX and 590AX are awesome sounding, tube like SS amps. Not sure what your music likes are but these may not be good for loud hard rock. The 550 goes for $4,900 US and the 590 jumps to around $9,000.

Not sure where you are located in Canada,but the are many retailers who carry this brand in the "Great White North"!

^Also, though Nelson Pass was still there, the "T" series amp(s) that your brother had, were from the pen of Mikael Bladiliaus, Jaynes and Coburn.

Thanks for the correction Unsound.
I didn't forget Forte when I wrote that post. My time-frame must have started when Pass & Threshold + Forte coexisted for some time & in my mind Pass Labs was the upmarket brand with Threshold & Forte following suit in that order of target market segment....

"The more the information, the more objective the assessment."

Why? Information isn't generic. There's a difference between more info and the right info.

"The key is to research sufficiently long enough/thoroughly to get a take on all aspects/perspectives you relate to."

Unless the research includes listening, its not worth all that much.

Well, I do know everything. And everything is that there is some degree of objectivity in assessing information from varying sources. The more the information, the more objective the assessment. We are after all part of the same gene pool. The key is to research sufficiently long enough/thoroughly to get a take on all aspects/perspectives you relate to. I have never been disappointed with a purchase after having done so. And I've made many.

This forum serves as a brainstorming session. You get different perspectives, but in the final analysis you make your own purchasing decisions. I think it's great when individuals provide constructive feedback as opposed to criticism.

Is that not the whole point of a forum?

Bingo!
.

Slaw,

Can I call you Cole? Anyway, I'm not sure if you've been reading through the rest of this thread but Bombaywalla already left some feedback relatively similar to this and I have addressed it.

I've been at this hobby for the better part of 15 years but perhaps only seriously for the past 5 years or so when my career began to take off. I have more money than some people but by no means am I wealthy. I do agree with you on some points that you make but at the same time I see no reason not to ask others to share their knowledge and experiences over the web to help others make more educated decisions.

Is that not the whole point of a forum? I can guarantee you that they do not exist solely for the purpose of condemning the curiosity and ignorance of perfect strangers to perhaps validate your own. But like you said, I should disregard the feedback of people I have never met. Yourself included.

I would not envy myself if I were to walk into a retailer and have a biased sales person make recommendations to me without having done any homework for myself before hand. I do have a LOT to learn but it would be asinine to suggest that one person knows everything.

Bombaywalla, at the risk of appearing petty; while Forte might have been a "...down-market brand..." to Threshold, Threshold was Nelson Pass's top line brand, competitive with most anything in it's day before he sold the company and some years later started Pass Labs.

I suspect you would like Clayton class A amps.
Another amp you might like, and that fits your budget when purchased used, is the BAT VK-500 that runs in class A/B bias and that uses mosfets in the output stage. I would consider that amp somewhat warm and musical sounding but not in the upper echelon wrt resolution and refinement.