Burson Audio - Soloist SL - Headphone Amplifier


Headphoneus Supremus
Pros: Value, sound quality, power, versatility
Cons: Not the end all in terms of power
From my R2R-11 review, "I'll be very honest. One of my favorite sub-hobbies in the grand scheme of head-fi is auditioning and discovering giant-killing gear. To me it's pretty fun putting much less expensive gear up against bigger, fancier kits to see how well the David compares to the Goliath."

I'm quoting the above because the Soloist MkII from Burson is another piece of giant-killing gear. It's a diminutive solid state amplifier that offers the sound quality, build quality, and smart design that in a lot of places, costs much more money!

Instead of the normal breakdown - bass, mids, treble, soundstage, etc - I'm going to go through this review according to the pros and cons list above.

For the MSRP of $499, the MkII version of the Burson Soloist is a no-brainer if you're in the market for a solid state amplifier, especially if your primary headphones employ dynamic drivers. I've owned/auditioned several SS desktop amps from the likes of Schiit, Audio-gd, and Cavalli to name a few, and if you're in the market for something that does just about everything well, but can't drop more than $500, I heartily recommend this guy before anything else.

Sound Quality:
In a word, enjoyable. Compared to the RNHP from Rupert Neve (which ain't no slouch!) the Burson throws a more realistic soundstage, offers more texture on the low end, and contributes a bit more air in the upper regions.The Neve might be said to offer a more studio-quality sound while the Soloist pursues a audiophile-quality. I'm a Grado-head to be sure (let the ice-pick, shrill, science project comments fly!) and my go-to headphone is the original PS1000. While just about every other Grado is served best from an all tube design (MAD Ear, Kenzie, WA6), the PS sounds best out of something valve-less. Enter the Burson. It takes the PS deep, stays true to the Grado midrange, and very cleanly and enjoyably portrays a treble range that is neither abrasive nor shrill.

'Comfortable' power:
Here's what I mean by that: Everything I've thrown at it has been driven very well, and what I mean by that is not necessarily that there are gobs of power on tap (I've learned that gobs of power is not always better if it means I only have 10 degrees of play in the volume knob), but rather the drivers are firmly controlled and clean. No weird soundstage or low bass issue, both of which can be affected by insufficient powering. The most difficult to drive headphone that I've used is my pair of Paradox Slants and on hi-gain, these are plenty loud at 1:00. It bears mentioning also that music comes from a very black background. Better than the Schiit Lyr and RNHP for my Grados for sure. Not sure about IEMs because I don't use mine at my desk!

In addition to the aforementioned driving power, the Soloist offers two RCA inputs as well as a high/low gain button. I'll mention here that I appreciate the straightforward approach in this area. While sometimes things like crossfeed switches, additional gain levels, and other options are nice to play with, I generally like to 'set it and forget it.' The MkII lets me do that!

Not really any that I can think of. I suppose that if you're strickly a planar guy, this might not have quite the power that you might want, but that's really a quibble at this point.

So in conclusion... the MkII version of the already acclaimed Soloist from Burson is a great choice for a desktop SS amplifier for the budget-conscious listener. You could certainly spend a lot more money and do a lot worse in this hobby. I bought it on a whim and it's not going anywhere anytime soon!
The real bang-for-buck is the Magni 3. It destroys the original standard for amp pricing and sets its new one for all to follow.
Magni 3 won't put you in the audience. This one would, with right dac and hps.
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500+ Head-Fier
Pros: transparent refined sound, flexible gain stage lets you use from iems to planars
This is review of mk 2 version of this amp. I bought it from directly from Burson Australia. 
Ordering Experience:
Ordering experience was great from Burson. They had a clearance sale going on at that time where it was listed for $400 which is still going now. Product listing showed mk 1 but they sent me mk 2. Extra points for making me happy. I asked them what was shipping cost and they said shipping was included. I thought maybe they will use some cheap shipping method but nope. It was simply best import experience I ever had. They used fedex and amp reached me in a week total. From Australia to India including customs halt which can normally take a month, thanks to superior service by fedex. My guess is it costs Burson around $100 to ship it but they don't make a big deal out of it in their marketing. Understated and classy. I like that. This makes it close to $300 for amp alone, thats close to ifi ican or schiit asgard. You can now probably understand why I called it best value in headfi right now.
Build and packaging:
Amp is shipped in card bord box with generous foam cutouts to keep amp safe. It includes power cable and rca chords of good enough quality. You can use fancy cables if you like. Power chord is iec type, ones that are used in computers. It has on board power supply and does not use power brick. Build quality is stellar and high quality. Its made out of brushed aluminium thats smooth to touch. Not too big or heavy and you can transport it easily from one room to another or safely in its box if you plan to take it to a meet. It looks great in pictures and in real life its as good as marketing shots we see on burson site. (something I cant say about all products, ahem schiit modi/magni) It comes with 2 inputs on back and 2 gain stages switchable by relays. This makes it feel more upmarket than say dip switches. Burson branding is engraved on front face plate and looks cool. Overall stying of amp is understated and classy. One thing I liked better on mk 1 of this amp is chunky volume knob. On mk 2 they have made it a little small. It works well and rotates smooth though. Allows you to make fine adjustments easily even if you listen to iems. ( something I cannot say about portable amps with hard to rotate volume knobs and aggressive gain stages like my fiio E12.)
Sound Quality:
SQ wise I consider it worthy of using with high end hps like Sennheiser HD700, say in $800-1000 range. Its an upgrade over entry level solid state amps like ifi ican or O2. When using AKG K550 and Sennheiser HD700 on something like ifi ican, I can't justify spending more on HD700. But on burson, HD700 pulls ahead enough so that it becomes a clear upgrade. By upgrade I mean more fleshed out instruments, more meat around bones. Clearly you get closer to live performance. 
On bringing something like Sennheiser HD800 in mix, I feel benefits of using higher end hps diminish slightly. HD800 offer superior resolution but not enough to be a huge upgrade. So if TOTL cans are on your shopping list I suggest you look into its elder sibling Soloist, perhaps. For high end hps (under TOTL hps) this is a perfect match and imo you are not spending disproportionately on your rig either on hps or amps.
Or if you have a set of mid fi cans like AKG k550 or philips fidelio X2 that you love and want an amp that brings out all that hp has to offer, this is a good bet.  
Tonal Balance:
Its transparent as far as I can tell. Presentation is on lighter side. Bass is strong and punchy. Mids are resolved and clear. Highs on hps like HD700/800 are well controlled and not at all harsh. Maybe even brighter cans it will be troublesome but with a well balanced hp like HD 700 (it has some warmth) its a stellar pairing. I also loved it with audeze lcd 3. Excellent drive and bass. Creamy mids and gobs of detail without getting harsh. On ethereal cans like AKG k550 or Beyerdynamic iDX200IE, sound is not harsh but ligher character of hp can make it too crystalline. I prefer to use warmer source when using K550 with it.
Overall its transparent enough to allow full character of hp to come out. HD700 sounds even warmer, AKG K550 sounds crystal clear, Sony XBA A1 sounds warm but still clear. Whatever is tuning on your hp it will come out like that.
Special note on IEM usage: if you thought iems have no soundstage and too in-your-head feel, try listening to them on burson soloist sl. It makes my $100 Sony XBA A1 sing. Being hybrid iems they dont have great soundstage so I thought. On burson it sounds like full sized hps. Sound comes from in front of you even when IEMs are tucked in your ears. This has increased my respect for IEMs and its those tiny amps that are at fault and not IEMs.
Soundstage wise its well layered from front to back. Hps with great soundstage like HD700 will benefit immensely from it. Has more depth than width and pin point front to back layering. Bass has its own layer and brings out multiple bass layers out very well if your hp is capable of it.
Value and conclusion:   
As I have already said, its exceptional value considering its $400 shipped. And shipping method is best I can have as well. Its performs on high level and together with HD700 is hard to put down combo. My no of hours I listen to music increased after I got burson cause its so hard to put down.
Special note:
I am including this note on request of Shetzu as he does'nt writes reviews.
I took it to my friends place Mr Aniel goes by handle Shetzu on headfi who used chord mojo to drive his HD800. He instantly ordered one after hearing it and its price to be used as mojo-burson-HD800 rig. That rig is best I have heard. Very transparent, amazing detail on vocals, completely alive image with great microdynamics and detail. To him biggest difference was soundstage that only proper big desktop amps can offer.
Just acquired a pair of DT-1990 headphones and I want an amplifier for them. Beyerdynamic H20 and the Burson MkII are in my affordability. Any views about which one might be the better buy?


100+ Head-Fier
Pros: Small, Good amount of power, Great build quality, Natural tone
Cons: a bit dull sounding, Can't drive planar dynamic headphones to full potential, Noise floor heard on high gain around 2-3 o'clock
I don't want to ramble too much in this review, but I want to give a slightly counter perspective to the majority of reviews for the soloist sl. I used it with a schiit bifrost uber using the usb input, and with my audeze lcd 2 headphones as well as my denon d5000 headphones.
So the first couple days of use the sound was great, basically sounded just like most of the good reviews it has gotten. If you want to know what that sound is like then just read those other reviews because I want to speak about what happened after a couple days. Starting on the third day of use (and by third day I really do mean like 24+ hours of total use by that point) the sound started to lose a little edge, and little liveliness, a little grip. I gave it a few more days, tried every usb port, tried the optical port, switched headphones, used different songs/media players, but the sound remained consistent. It was subtle at first, but it just felt like your brain was having a hard time trying to latch onto the music, if that makes sense? the edge was gone, it always felt like something was missing in the sound, as if it was blurred over slightly or dulled. The bass was still great, the mids were still great, and the treble was still properly detailed, but as a whole the tone seemed to just dull the edges too much, which made the sound feel much less dynamic than it should, and after a while it just hurt my brain because it was being teased with details that just would not appear. The final straw for me to sell it though was the fact that it just did not provide enough power for the lcd 2 (the late 2013 pre-fazor version). Even on high gain I had to put the volume around 2 o'clock to hear the whole frequency range properly, but it always ended up being too loud after a while, but sounding as if it was too quiet. Like it would be too loud for your ears, but you kept making it louder because it seemed like it was missing aspects of the sound. Like the bass was good, but it obviously felt like it needed more power behind it, and the mids were great, that never seemed wrong, and the treble just sounded dull and lacked some detail. It just felt like if there was a bit more power, then I could keep the volume lower while having the sound be properly filled out. Compared to the soloist sl where it definitely felt like it was struggling to get the lcd 2 sounding right. With my denon's it had the proper amount of power, since they are very sensitive headphones, but that dulled sound made the denons pretty bad in the mids. See the denon d5000 already has a slight v curve frequency response, but the burson just made that v-curve even more v shaped. bass was stronger and tighter, treble was brighter, but the mids were too recessed. The lcd 2 sounded a bit better simply because it has a much more linear frequency response to this slight mid recession doesn't impact them nearly as much, but the dulled sound definitely does. On top of all this, the neutral/natural tone of the soloist sl just makes the dulled sound even worse because now it was lacking solidity and fullness, just brighter and dulled. it's a strange combination, but that's its sound signature no matter what you plug them into, or plug into them. Some people like that sound signature, their ears just enjoy that kind of thing, but for me I just really did not like it at all. I am looking at the violectric amps as my choice instead. Also to give some proper information about the soloist sl out there about its power output, it puts out about 650mW into 50 ohms. The 2 watt rating they advertise so much is only at 16 ohms, even my denons which are at 25 ohms only get close to a watt if using high gain, which is a lot for them, but 650 mW for the lcd 2 is only just barely enough to make them listenable and sound good, but very quickly you will feel like it just isn't enough.
So I will advise to definitely listen to a burson product first before you buy, this is not a company that makes products that you can safely buy blindly and enjoy. On youtube there is a guy whose channel name is headphoneaddictdotcom and he also agrees with me on this burson sound signature annoyance when he used a burson conductor for a few months. He also preferred violectric amps or just something more along those lines of sound signature. I have similar tastes to him, as in we like the audeze house sound, pre-fazors, denon dxxxx line, fuller and thicker sounding amps, neutral dacs, etc. If you feel you have a similar taste preference to this, then you might not enjoy the burson products in general. I just don't see that many negative reviews for their stuff, and thats why I originally bought the sl, and was very disappointed as I mentioned above, and just wanted to make sure people have all sides available to them before buying.
Nice review, sax. I have the orig Soloist, and it's excellent with my LCD2.2 I guess Burson compromised too much when they slimmed to the SL. btw, I never play computer files thru Soloist. Only a damn good source, like a CDP or Brsyton's BDP-1BDA-1 will do -- for me! Cheers.
Did you communicate with Burson about this?  Maybe a defective unit?  Interesting review and it's refreshing to read some criticism.  I agree that the soloist is not nearly enough for many planars, I tried the conductor and liked it a lot but -to my ears- it was just a bit too forward/analytical.  As you know I use the Vio V200 and it's overall better for me but not quite what I'm looking for either.  My F5 is fabulous but that's basically a speaker amp.
I dont think there is anything defective with it at all, it performed exactly the way it was supposed to perform. Unless there is some kind of weird defect that causes minor changes in the sound signature? I highly doubt that though. I just think it was not for my ears/my set up. After looking through some of the older threads/random posts about Burson products I can see theres a minority of people who feel the same way as me in terms of hearing a slightly lifeless and dull sound (subtle but there). It is a minority though, so that's maybe something to take into account. Like off the top of my head one specific mention of this is a headfonia review of the lake people g109 and in it it was compared to similar priced amps, the SL being the main one, and there is a sentence that straight up says the reviewer felt the soloist sl sounded lifeless and dull with the lcd 2 (pretty much a quote). I found that after I made my findings. And theres also just some random posts hidden in a bunch of different threads that elude to a similar outcome, mainly with audeze headphones. I noticed that was the main thing in all the posts. And like I said in the review if you go to youtube and find headphoneaddictdotcom, him and i had a lengthy chat agreeing on these findings and our similar taste preferences. We're just the minority lol.


1000+ Head-Fier
Pros: Bassy, wide and Fun sound. Natural Tone. Performance across a range of headphones. Great volume control
Cons: Slightly hesitant in projecting finer details
Two Smooth Solid State amps – Graham Slee UL Diamond and Burson Soloist SL
I’ve long been a fan of solid state amps, especially those with a small footprint. Both of these are ones with a smoother presentation, or as both manufacturers say in their product blurbs – ‘tube like.’
Both of these have had over 300hrs of burn in (the Slee's probably closer to 3000!) and both have impressed me but for different reasons making for an interesting comparison.
Burson Soloist SL £500
Little brother to the Burson Soloist. Analogue volume control rather than a stepped attenuator and slightly less power.
Graham Slee Ultra Linear Diamond Edition £615
Top of the range model from Graham Slee. This is designed to facilitate highly sensitive headphones more so than others in the Slee lineup.
View attachment
1. Function and Usage
2. Sound comparison. (T1, D7k, Ultrasone Sig Pro....)
3. Listening Setup
1. Function and Usage
1.1 Graham Slee UL Diamond
This thing is small. The footprint is awesome actually which is supported well with the physical build quality. It’s not heavy at all yet stays firmly seated on the desk even when tugged by the T1’s heavy cable.
The volume control is very well done. It’s firm with the right amount of resistance to turning and friction on the dial. To me this is quite important for saving my hearing when the dial turns up by accident, say after I brush against it with my sleeve or something (recollection from using the Fiio E9 – excellent amp SQ wise I still think)
It’s £600 so you expect it to be well made and with good jacks/connectors/dials. I like the lowly lit green LED that’s on when it’s powered. Mind you, on the subject of power you might like the big and weighty PSU especially as it doesn’t require a kettle/figure 8 connection to the amp. Small amp, small unobtrusive simple AC connector (don’t know the size of the tip) but beefy, out of the way, PSU.
Switiching between source is well done here as well. Middle selected denotes off and up/down correspond to source1/2. I’ve had two sources at once connected and notice nothing weird going on, so it works well
All in all a nice looking small component that fits comfortably in a small rig (like mine)
View attachment
1.2 Burson soloist SL
Much more weightier and larger than the Slee, but still not something I’d call big. It can sit next to my computer well enough.
The finish on this doesn’t look/feel as good as the slee - just running my hand over the plating and it’s not smooth. Anyway, it’s designed to be listened to more than it is to be physically stroked, so it’s not a problem.
I like how source switching is done with the press of a button where the LED’s have a lowish glow similar to the slee. The volume dial is very very good. Large with a nice weight, feel and resistance – better than the Slee. Really like this feature especially as it’s not a stepped attenuator which incidentally is what made me choose this over it’s bigger brother. I just can’t stand hearing them clicks through my headphones and as a result avoid all stepped attenuators.
2. Sound
2.1 Signatures
Each amp has it’s own kind of character (the burson more so than the slee), which I feel is demonstrated across headphones used in this test (Primary: Ultrasone sig pro, T1, D7k Secondary: mad dog, Ultrasone DJ, Fostex TH900)
The Slee feels like it’s about control and neutrality. The highs are smooth though very true to life it seems. This amp is very revealing of the source and when used with a warmer source the amp shows it in the bass and high range. Soundstage is on the smaller side, though instrument placement and separation is always excellent. It’s a close and intimate sound that's presented here which always seems to hold itself together well.
The Burson has much more of a sound signature (if I'm allowed to say that!). It’s more prominent and forceful than the slee which remains cool and almost understated in comparison. The main difference is that the burson injects a bit of fun into the sound; larger soundstage, more dynamic bass range, thicker, weightier bass/midrange notes and more smoothed out highs. I guess it makes the ultrasone sig pro’s sound more like the D7k’s than anything.
Compared to say a classic solid state, like the lehman black cube linear, the SL definitely has smoother highs and the same can be said when compared to the slee. It also sounds a fair bit ‘less’ detailed. I would't call this amp under-detailed but in terms of projecting micro details and resolution it can sometimes leave me searching. I’ll find them  when I look, but not otherwise. 
View attachment
2.2 Headphone pairings                                                   
The Slee does well with headphones with a more recessed thicker midrange and ones that benefit from a slightly clearer presentation. Presentation where greater instrument separation is desired. Stuff like the D7k, TH900 and the T1’s do better with this than the burson especially because of their midrange where pushing back their midrange just doesn’t sound pleasant. These headphones have big enough soundstages anyway. In this regard the D7k/TH900 especially fit the bill, though I won’t say this slee is the best amp I've come across for them. The inbuilt one on the Beresford bushmaster and a musical fidelity M1HPAP both sound better as what they do is simply wake up the TH900. It’s better than the burson though which puts it even more to sleep!
The Burson likes headphones that are detailed but in want of a larger soundstage and a more cosier, smoother portrayal. Ultrasone Signature pro’s work really well with these as there’s a significant increase in soundstage warmth, weight and grandure compared to the Slee. The edges are more rounded but this ultrasone responds well to it despite the highs not being tizzy/sharp to begin with. Actually, this amp/headphone match is a downright awesome one. Talk about synergy huh?  
From what I've just said you can extract that the Soloist SL is a warm sounding amp but i'd like to warn against thinking it won’t pair well with warm sounding headphones. Mad dog’s simply sound better from this amp which although may be down to planars pairing better, does prove a point. It just feels like the thick bass is maintained and we benefit from the grander sound across all dimensions. 
p.s. I use the low gain settings by the way – don’t hear a difference between this and higher gain.
2.3 Summary
Slee over the Burson
Intimate and controlled, detailed sound.
More neutral than the Burson.
Shimmer on female vocals shines through unsupressed
When thinner than thicker vocals are preferred
More air around instruments
Slightly more Prat. Faster projection
More upfron, un-recessed midrange,
The bass range is better defined. It never sounds as it if lacks detailed – a highly detailed overall amp.
Burson over the Slee
Larger soundstage height and width
Dynamic and impressive sound
Warmth though not without slight undue accentuations
Warmer projection like in a cosy large scale concert, shining through on OST music.
3. Setup
3.1 Testing equipment
Power: Clearer audio copper line alpha power conditioner
Transport: acer s3 (128gb samsung 840 ssd, 4gb ram, i5, W7, Silenced Fan) & Dell Vostro 1500 (128gb kingston ssd, 4gb ram, core 2 duo, custom XP, usb hub)
USB cables: Belkin, Chord silver plus
DAC's: Arcam r-dac, Musical fidelity vdacII, Beresford Bushmaster TC7530
RCA cables: Chord Chameleon vee3, QED profile, Belkin, Mark Grant g1500hd,
3.2 Conditions
Ambient noise levels: Home listening : <<25db (Absolutely dead quiet. I mean it!). 
Humidity and temperature: maintained 21-23c and 50-60% relative humidity
Volume matching: using test tracks of different noise levels calibrate amplifier volume and perceived loudness with headphones. Conducted at every test.
Listening Volume: Extremely important to note. Some headphones prosper/fail at high/low volumes. I listen at low to low-normal listening levels. 
3.3 Albums
FLAC CD Quality files.
Variety of genres, with a sample being:
Riverside (prog rock), Within temptation (rock), Amethystium (New age), Secret Garden (Celtic), Lisa Gerrard (World), Armik (Spanish acoustic), Ah Ne Ma (Acoustic/world), ATB (chillout/trance), Tycho (Electro), Game (hip hop), MJ (pop), Yo Yo Ma (Classical), Hans Zimmer (OST), Diana Krall (Jazz) and the best out of them all... Ludovico Einaudi (Neo-Classical)
the ulde sounds better than the srgII
not so much better you use the srgII with the PSU1
in fact the price difference is not to much when both come with the extra power supply
i prefer the srgII with the psu1 with the hd650: the cans sound more open
how about pairing GS ULDE with rothos? T50rp for example?
what about Musical Fidelity M1 HPAp vs SL diamond edition with hd 650. thank you


Panda Man
Reviewer at Headphone.Guru
Pros: Power, detailed unit, and neutral
Cons: Size, good build, but durability is a bit off. cost
Burson had great success with their Soloist discrete amplifier. So following this generation's niche. Let's make it smaller! And so here we have the Soloist SL. Which has one less gain, and input option than the Soloist. It is a discrete class amp. No integrated circuits, just good ole FETs and a discrete power supply. I wish to thank Burson for sending the Soloist SL to me for review and for their wonderful aftersales support which was wonderful. 

Build Quality:
The Soloist SL is pretty much a solid chunk of 2mm thick aluminum. Everything is bonded together nicely and it is smooth. The back and front panel don't have any build issues in terms of weird streaks, cracks or what not. The Soloist is very 'echo y' when you tap it with your hand of course. As with anything encased in aluminum near completely. Dropping it is not recommended. The buttons on the front felt solid enough as did most of the parts. The volume knobs feel when turning it is quite smooth without much resistance, but still offering some of that low end 'stopping' so that it won't turn by itself of course. The headphone output jack however on the unit I got for review does have some problems. It moves a bit and does cut out one of the channels sometimes(the fix is to turn your headphone cable a bit or to do a slight wiggle). The case's and boards are of course built to a tolerance of +- such and such mm for the volume knob to stick out so it can't be too tight fitting or else it may not fit and other issues. An internal hexagonal ring to secure the headphone jack would be nice though. This of course may just be an isolated issue as this unit is on tour and has been shipped across the entire country and to different people already.

The SL works quite well. It has two inputs availble so that you can connect two DAC's or any analog inputs into the back and switch between them with the touch of a button. It's very simple to use, no need to read the manual even(though I did). The cables that come with it are quite thick, long and blue. They aren't speaker home theater long, but are long enough for a headphone setup. I keep my units close to the wall and the cable did have some problems as it was too thick, meaning I had to move my entire audio set forward so that the cable could have enough space to be plugged in not be hitting the wall. Some may also not like the rear mounted on and off switch. Back when I owned an Audio-gd, my audio setup made this a problem for me as the entire unit was a cm below my monitor. This caused me to have to stand up and reach around to turn on/off the unit. In my new setup, this is not an issue, but I can see how this can be a major one for some. So keep that in mind. You do need to reach to the back to turn it on and off. Having the switch on the front would have looked too tacky is what I think Burson was thinking, because the fronts of them are very minimalist.

I am by no means an expert on electrical engineering and the stuff they teach in it like the differences between everything. Which is why I was sent this unit. But I do have some basic knowledge on IC's vs Discrete's. Discrete units separate out the units or parts such as resistors, transistors and what not into the entire PCB while the integrated circuit(IC) has many of these on the chip itself. These individual proponents means the company that makes the unit more or less has to design EVERYTHING on the unit, and can't just choose to pop in a chip made by TI or AD. This does allow for more fancy, and better units. But of course with such a huge allowance of personally designing the unit comes the risk. The engineers are making the design wholy themselves and are not using chips that have all the functions on it. This means that they must be VERY accurate in making the PCB and how the circuits interact with each other. One wrong move, and the whole prototype pcb is fried. IC units don't have these issues and are much easier to make good units as they have already tested and built IC's from other companies. Discrete designs have to be tested, engineered, tuned and have those steps repeated countless times. This creates a much higher R and D cost for discrete companies(if they don't want to copy other successful discrete diagrams that is). But when done right, can produce great sound. This is basically what Audio-gd and Burson do. The usage of a discrete power supply in the SL also allows them to engineer a low noise PSU and what not. Well there is the beginners lesson of discrete-ness. If I am incorrect in any part, let me know(with sources) please. I am by no means an expert.

Review backstory:
I do not use many high end parts. I have owned the Audio-gd NFB 12.1 and have been sent review samples of many other units. The whole point of this tour was to give people that don't use $600 amplifiers the chance to do a write up on them and what not. So this will just be my own thoughts and do not reflect an actual professional review where the reviewer would have had a plethora of knowledge and experience with units at this price point.

For this review, I used the AKG Q701 and LCD-3 and Objective 2 Amplifier. The constant DAC was the Cirrus Logic CS4398. 

Sound Quality:
Starting from the lows, I noticed that the Burson had a less noticeable low range as opposed to the O2, the extension was about the same. Whereas the O2's had more preference, the Burson layered it out and smoothed out the whole range more. The mids however were where I found it most interesting. The Burson's mids are like a pyramid where the tip was at the lower vocals and the base of the pyramid was at the upper vocals. What I am saying is that the tenacity, and presence of the vocals were more thinned out at the bottom and mids and had a more upper vocal sparkle. I personally preferred the O2's more thick vocal range as to the Burson Soloists but of course, this differs from person to person. The instruments also were more brighter on the Burson. Which I am relating to be from the upper mid focus on these. The highs are much more smoothed out on the Burson's than the O2's. The O2's were noticeably more choppy (not able to keep the pitch in a sense) when related to the Burson's. They weren't fatiguingly bright or anything which is what I prefer. I would finally say that the Burson's are more transparent than the O2. Transparency as in which makes it sound more 'real', where it sounds like you aren't listening to a unit, but to the music itself. And this would have to go to the Burson's which had a better layering than the O2's. Layering as in the separation of mids from the vocals. 

The Burson Soloist SL is a good transparent amp for those that wish to buy it. The upper mid sparkle is not a favorite of mine, but is to many others so that's really it. It is a smooth and transparent amp that many will like.
I'd say that the Burson Soloist SL with the LCD-3 make a good combo in terms of how well the LCD-3 already layers. But there are better amps for the LCD-3 out there.