"Warm Sounding" Solid State Amplifiers

LSR&D is the company logo comprising the initials of 4 partners headed up by the late Dr. Marshall Leach at Georgia Tech University in the 80's. Bickering and in-fighting led to the company's early demise so few examples exist. Dr. Leach did offer the amp in kit form and there is a substantial following on DIY Audio. Lots of info on the net, re: The Leach Amp/ The Leach Superamp/ LSR&D.

Pontifex,
I'm pretty stupid so I don't understand what you mean by "warmth, sweetness and overall pleasant sound."??
I've tracked this thread over the several days it's been active & I see a lot of chatter & recommendations. it's great to see that so many members want to help but you'll always get a recommendation of a particular amp from a person who has that amp - it's inevitable. The problem is that you don't know this person (despite the fact that he is really trying to help for which I can see you are rightly appreciative) & you don't know his music tastes & you don't have his ears & neither do you have his music listening room. So, there are too many variables for you to blindly accept the recommendation.

It would be great for us to know what you mean by "warmth, sweetness and overall pleasant sound." as it will help all of us provide better direction.

From his vast experience, Ralph @ Atmasphere, as usual, has given you some wise words to reflect on. As Ralph has already pointed out - "warm" & "bright" are 2 different forms of distortion; one preferred & the other not. But make no mistake, they are forms of distortion. I don't think you want to spend money on an amp that distorts - long-term this is the wrong way to go about your goal.
I dont agree fully with Ralph that *all* SS amps are high on distortion - there are many that are not but it is true that these few amps are not cheap. There are some less expensive SS amps that are very linear sounding but, yes, they're few & far between. In terms of linearity, tubes does win more often than not since our human ears prefer even order harmonics over odd order harmonics. So, it's not a totally losing game indulging in SS amps. Of course, my opinion & my experience.

You've already provided a list of your equipment & also your budget. Do let us know what you mean by "warmth, sweetness and overall pleasant sound." as it means different things to different people. Thanks.

04-22-15: Geoffkait
Tubes are less distorted when you listen to them. That's my consensus.

I disagree Geoffkait. Tubes have more pleasing distortion than SS. Both SS & tube s can be made linear.
And a "consensus" is a collective opinion. So, are you saying that 3 of you & yourself & your alter-ego collectively endorse tubes?? ;-) ;-)

bad news: its all distorted.

Starts in the recording process and only gets worse from there.

Its a wonder any of us can enjoy any music at all. Go figure!

Nah, it's all in your head. It sounds the way it's supposed to ;)

I agree with Ralph. I have the Atma-Sphere S-30. There is nothing I have ever heard in solid state that even comes close.

Bombaywalla, yes, I'm saying me, myself and I and my evil twin.

Pontifex, I own the Monitor Audio GX300 Gold speakers and use a Musical Fidelity M6PRX amp. This is a warm and wonderful combo.

A good strategy to deal with distortion is to match your speakers to your amp, room and volume preference. If you get that right, distortion shouldn't be an issue, tube or SS.

Sabai, Do you have to turn it too? That's the one I just missed out on. It went for 1200

Bombaywalla,

You are absolutely correct. Everyone's experience is going to be completely unique for any number of reasons or variables and because of that I always take the council of others with an open minded grain of salt, if you will.

In regards to warmth, sweetness and pleasant sound I am using those terms to describe the qualities of a higher musical experience that incites a stronger emotional connection to the material.

To be more specific, when I think of "warmth" I think of lower midrange frequencies that have extra lushness and bloom. When I think of "sweetness" I think of upper midrange and lower highs that speak with a sort of ring or resonance. If one were to describe it in the form of distortion I suppose that they would say that those frequencies are louder or exaggerated in some form or another. That is my very personal take on how I describe these perceived, abstract qualities of sound that I felt my Bryston equipment was lacking.

To further build on your feedback, I paid a visit today to Canada's exclusive Pass Labs dealership - Toronto Home of Audiophile. Even though I knew Pass Labs gear is a little outside of my budget (for the time being) I wanted to take the opportunity to hear for myself rather than go by the general consensus and rhetoric of others. That way I could at least establish some kind of reference point in my mind as to what I am looking for in terms of the qualities I just spoke of.

During my visit I auditioned the XA60.5 monoblocks (60 w/ch pure Class A) and the X250.5 stereo amp (250 w/ch Class A/B) with a PS Audio CD player, Pass Labs preamp and Gershman Acoustics Grand Avant Garde speakers.

In short, it was immediately obvious that the Pass Labs equipment had many of the desirable qualities that I was looking for. It was very lively and enjoyable. The pure Class A amps were the most musical in terms of "warmth" and "sweetness" but the Class A/B offered a more dynamic presentation and wider sound stage yet still very musical. Since I like to listen to lots of symphonic music and rock and roll it seems that a Class A/B amp might be better suited for my tastes. Also a bit more affordable than pure Class A.

I spoke with the sales rep in terms of my equipment, my budget and what I'm looking for and his reccommendation was a Cambridge Audio 851W. He did not recommend an M series NAD. When I get a chance I would love to audition the 851W but I fear I may have spoiled myself! If that is the case then I might just wait a bit longer and save up for a Class A/B Pass Labs.

Zd542

Synergy of components is critical. And your room is always the biggest component!

Geoff, so it's your twin we've been dealing with? That explains everything. Stick around, you're in for a treat!

Pontifex, FWIW I have the x250.5 and agree with your statements. It is a very balanced amp that does just about everything well.

Csontos,

Please explain.

The KNIFE!

Csontos,
Sabai didn't turn it at all - what he wrote was his opinion based on his listening experience. Maybe he'll update it if he does listening to a wider variety of amps & maybe he won't?? Either case as far as I'm concerned he's OK to voice it here in this forum.

Seems like Zd542 has a very similar opinion as I do.....

Pontiflex,
Thanks for the feedback.
Great that you made the effort to listen to some Pass amps. Yes, they are MOSFET output stage amps (as opposed to bipolar) & I believe that also has something to do with the sonics that you heard given that MOSFETs are a square-law semiconductor device.
See if the dealer will allow you an in-home demo - that would seal the deal for you in terms of confirming whether or not you want to save up for Pass amps going forward.

Hey Bomb, it was rhetorical. He reminded me of the S-30 I missed out on buying recently.

i see! it was actually aimed at you inadvertently.... ;-) LOL!

Old Audio Research SS amps {from 1989 to 1993} are warm sounding. So is GAS and Sumo.

All Pass Labs "Class A" and Ampzilla 2000 power amps are warm sounding IMO.

Bedini BA-801 is the most tube-like solid state amplifier that I have ever heard.

Years ago, I picked up a mint Dyna 120 stereo amp at a garage sale really cheap, like for a couple of bucks. I sent it in to Frank Van Alstine for him to install his circuits. The amp that was returned was a real killer of a solid state amp. I found that if I left it on constantly, it sounded pretty amazing. It was paired with a modified Dyna Pas-3 preamp. I listen to a lot of small jazz groups ... and the bass lines had that warm realism.

Here in Southern California, there used to be a DJ on one of the local FM stations that used to have a "Bedini" night. He'd bring his Bedini 25/25 into the studio, along with his TT and other Bedini gear. That was some of the best FM I've ever heard. Maybe a used Bedini amp would cut it for you ... if you can find one.

I also used a pair of Atmosphere M60's for a couple of years on loan from a friend. Can't say they sounded "warm," but on certain nights when the power coming into the house was clean, like late at night with the lights off, those amps sounded REAL. It was like the entire back wall fell down and the stage went back forever.

On the issue of "warmth" in itself ... When I go to a live concert, I do as Ralph suggests and close my eyes and imagine that I'm listening to my home system. So far, no matter how good my system gets, or how much money I spend on it, I have yet to hear my system, or ANY system for that matter, come close to actual live music.

I've heard really expensive systems costing in excess of 300K, but they still sound like reproduced music compared with live. Oh, they may do a great job, but it still ain't live.

What I hear with live music is sound that is really relaxed. It may get loud, but even when it does, there is no "cringe" factor. I think most audiophiles would be put off with this kind of "relaxation" in their home systems.

For that matter, most of the live music we hear is actually amplified music pumped through the venue's sound system. A lot of those are terrible to boot.

Try sitting down in front of a good unamplified string quartet, or a solo classical guitar, or a front row seat right in front of the string section of a full classical orchestra sometime. Its like a breath of fresh air.

I definitely think great tube gear gets us closer to the ideal of "live" more than SS gear, but even so ... it still isn't live.

Just my two cents ...

Another thumbs up for Bedini amps having a very tube-like sonic signature, but in my case, it is my Bedini 25/25. I have not had the pleasure of hearing a Bedini BA-801.

What I hear with live music is sound that is really relaxed. It may get loud, but even when it does, there is no "cringe" factor. I think most audiophiles would be put off with this kind of "relaxation" in their home systems.

not me anymore!! I've learnt that this is the sound that I want from my system & it will be capable of delivering such a sound when I will find components that will keep the phase distortion down to a minimum. That's the reason I turned to 1st order x-over speakers which, when built correctly, are time-coherent speakers & finding electronics that is as true to the original sound as my budget could afford. Having had such an experience you find me endorsing time-coherent speakers every time I can. I've managed to FINALLY sway a few people on this forum that time-coherent speakers is the way to go after THEY heard time-coherent in THEIR system & agreed with that it was the only way to proceed.
Getting an amplifier that is as uncoloured as possible i.e. within one's budget is the right thing to do because an an accurate system will always be a true system long-term.

Try sitting down in front of a good unamplified string quartet, or a solo classical guitar, or a front row seat right in front of the string section of a full classical orchestra sometime. Its like a breath of fresh air.

AMEN!!
That's because there is no phase distortion from the electronics & esp. the speakers. What you are hearing are the fundamental tones + their harmonics directly from the various instruments with no electronics to muck that up. Such a delivery of sonics is *always* welcome & will *always* sound right not matter what the person's age.

I've owned several Bedinis. 25/25, 150MKII, 250/250, 100/100. They're all good amps, not great amps. The thing that's lacking in them is speed. The fastest one is the smallest one, the 25/25. But still too slow imo. I don't get the hyperbole about it. It's not hard to find an amp capable of driving low impedance. Now having said that, I still have the 100/100 which needs work. It has a sound stage that is holographic.

On the Canuckaudiomart there is a deal on for a Musical Fidelity A308 for $1300 CDN. I've been in contact with the seller but I feel like I'd be making too much of an impulse purchase. The few reviews I've found suggest that it is (as its brand name suggests) quite musical.

Can anyone add to or comment on that? Seems like a decent price but I know it's also an older unit and I don't know what the service is like with MF. I have heard many positive things in general about Musical Fidelity.

Google it and surf the banter about it.

There is NO way anyone here can make a credible recommendation to your post without the following:
(1) Knowing you and your likes/dislikes.
(2) Having intimate knowledge of your system and room.
(3) You should have enough knowledge on your own, by now to have a list of components that you'd be willing to audition before even making a post such as this.
(4) If I were in your position, I would not post here for recommendations. I would rely on my past history of listening/reading/and logic.

I assume that after you've been into this hobby for years...which includes lots of money, lots of time, and a whole lot of lost assets... that you'd be in a position to make this purchase on your own.

If now, you need feedback from people you don't know and will never meet to help you make such a personal decision... well, I don't envy you at all! Good luck!

Pontiflex,
if you like the Pass amps that much, it just might be worth your time to look into getting a Threshold amp. These were essentially Pass amps but marketed & sold by Threshold which was a down-market brand compared to a Pass. My brother used to own a T200 (100W/ch pure class-A amp) & i personally thought that it sounded really very good on all his music.
Another pure class-A amp i've liked is the Plinius SA-250Mk4 & it's smaller cousin the SA-100 Mk2 (I think i.e. re. the Mk number). The Plinius amps has a class-A toggle switch meaning that you can run the amp in pure class-A or toggle the switch & run it in class-AB. The Sa-100 plenty of current delivery capacity to drive most speakers & the SA-240 will drive practically any speaker.
FWIW.

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.

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.

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.

Is that not the whole point of a forum?

Bingo!
.

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.

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.

"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.

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....

^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.

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"!

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.

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.

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:)

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.

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.

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

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.

"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.

^^ 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.

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