Burson Conductor 3X

If you scroll to the bottom of this review, you'll see the TL;DR version, but if you'd like to see my take on what may be the most capable and natural-sounding combo desktop unit out there, dig in below!

The Chain:
MacBook Pro > Conductor 3XR > HE6, PS1000, PS2000e, Mayflower v1

Test Songs (all FLAC either 16/44 or 24/28):

"Dad Gone Thing" by Gregory Porter - All Rise
"Strasbourg/St. Denis" by The Roy Hargrove Quintet - Earfood
"Grown Folks" by Snarky Puppy - Culcha Vulcha
"Tom Sawyer" by Rush - Moving Pictures (2011 remaster)
"I Will Sing Jesus" by Highlands Worship - Jesus You Alone
"Jupiter, from The Planets" per Sir Adrian Boult and the LSO

Sound: In a word: natural. Yes, admittedly that word is as overused in head-fi as others like musical, fun, or organic, but in my mind, when I say something sounds natural, it means that there's a reproduction that is true-to life. The value of any headphone (or any other audio gear) to me is directly tied to it's ability to reproduce what I'd hear sitting in the audience or in the studio booth. The C3 just that really really well. Most live rooms I've been in have a thick bass presence, slightly forward vocal/midrange, and as much upper end as it bearable without being fatiguing. That's what Burson has in the C3. (Methinks this is why so many enjoy the sound of vinyl...)

Bass: Clean. Traditionally I've preferred the plumpness that comes with tube amplifiers with my headphones of choice: Grados. I've usually been ok giving up a little definition to gain some impact - call me a slam over details guy. I'll say that with the C3 though, I've found the most pleasant happy medium, and maybe my favorite bass presentation I've heard in a combo unit. Kick drums have just the right blend of punch and texture (Snarky Puppy & Rush tunes), synth lines are thick, and even the timbre of upright bass (check out the Roy Hargrove!) or low brass is just really well done. I feel it and I hear it! Bravo to the Burson team for striking the balance that is so difficult to nail.

Mids: Smooth and oh so-slightly prominent. The mids/vocal range reminds me so much of a well-made tube amplifier (looking at you Kenzie!) Voices sit beautifully in front of the band in the worship track as well as Greg Porter's tune. There's a nice open quality that really comes through in breathy vocals a la Norah Jones that I've only experienced in a few other units like the H2 or the RME. Still though, there's a weight to instruments in this range like guitar, sax, and cello that just sounds, well, right.

Treble: I'm sure you're seeing a theme here, but the upper end is so clean! Grados are finicky and it's easy for them to sound bad if upstream source gear is to bright/hard, OR if it's too rolled off. The C3 dodges both bullets and yields detail, smoothness, and air. Really able to see what the PS2000e and HE6 are capable of in this range, especially in the busier parts of 'Jupiter' and Tom Sawyer. Cymbals and strings alike are shimmery, but never too hard or abrasive. Hats off to the Australians for managing to pull this off!

Soundstage/Imaging/Separation: If not the best I've heard, it's up there!

Aesthetics/Build Quality/Accessories: Excellent, bar none.

Qualms: The only semi-qualm I have has been said before. I don't listen to IEMs at my desk a lot, but the C3 does hiss a bit with sensitive in-ears. If that hiss was completely gone, I don't know what you could fault this unit for!

JD's SS Combo Unit Ranking : Conductor 3XR > RME ADI-2 FS > Hugo 2 > Audio-gd R-28 > Singxer SDA-2c > Conductor SL > Questyle CMA600i > Concero HP > Mojo > Questyle CMA400i > Emotiva DC-1 > Audio-gd R2R-11 > O2/ODAC

Final Thoughts: I certainly am a satisfied customer and wholeheartedly recommend the Burson Conductor 3XR. I feel right in saying that the hype is real! If you're looking for a powerful, capable, aesthetically-pleasing combo unit that does just about everything well, this one gets my highest marks. Thanks for reading!

@raoultrifan wrote a great review on this. I knew a lot about why the burson C3X ref is so good but his review significantly improved my understanding. https://www.head-fi.org/showcase/burson-conductor-3x.24156/reviews

My review is a brain dump and not as well written as Raoultrifan. But I hope it helps. I think with the right headphones Burson puts true high fidelity in the reach of many consumers, plus it is an awesome preamp for a speaker based system. And they are progressively upgrading their whole product range with technology that filters down from their flagship. I'd recommend getting on their mailing list as their pre-release deals are great value.

https://www.bursonaudio.com/products/

I have a conductor 3x reference and have previously upgraded my marantz CD80 with burson low jitter digital clock and opamps plus new caps and a double crown TDA1541A S2. I also have a cambridge audio 640c CD player which is sublimely detailed with digital inputs so it functions as a DAC too. Oh and an astell and kern SP1000M and i used to sell hifi and have heard my share of pretty esoteric systems including the marantz two piece CD12LE Transport/DAC we had on the shop floor which was amazing especially with the marantz PM95 integrated and a AU$10,000 nakamichi 200wpc pre power ive forgotten the model number of. We sold top end Spendor, Dali and Dynaudio too.

The reason i upgraded my CD80 was chasing the CD12 sound. I'm not trying to gloat or name drop here i just want to give some context.

Bursons service is outstanding and their products i have used are exceptional. When i contacted them about buying the conductor they very politely said you have great stuff but we are confident the conductor will match it. They were right. The conductor 3X beat all my gear.

I bought the C3X and LCD3s from them unheard as a package deal on trust based on reviews and the quality and honesty of their communication, and their past service.

I got the conductor 3x in a package pre release deal with audeze lcd3s. It is a match made in heaven and that's coming from an atheist. I only expected to use the conductor as a head amp. But the bursons DAC section beats all my other DACs.

While their marketing may take a dig at other product types, especially things with valves, they don't name anyone. Basically they are positioning their product and in my experience they are right. I don't think they are bashing anyone. And there is so much nonsense in the hifi world, it is full of smoke and mirrors and ridiculous claims.

Plus in my experience their points are fair. I have a musical fidelity nuvista preamp #276 of 500. It uses the legendary scientific/military grade 6CW4 nuvistor metal tubes. The nuvista pre is the most beautiful thing ive owned in form and function. I Never thought I'd let it go. But it's going on ebay. The Burson conductor is a better preamp than the nuvista. That was completely unexpected. It is an interesting story and product a review is here https://hometheaterreview.com/musical-fidelity-nu-vista-preamp-reviewed/

The bluetooth section of the conductor is remarkable. I can stream tidal or ripped FLAC CDs from my phone or A&K DAP and it's practically the same as putting a cd in the player or running usb or SPDIF digital in by cable.

So i think burson seems to be run by a dedicated team of fanatics whose aim is to make the best gear they can and they aren't charging stratospheric prices for it. They seem to be in it for love rather than money. My experience is they make exceptional gear that is ridiculously good value at the price point of each item. Note I haven't demoed their entire range. And I have no connection to the company other than owning some of their products.

I also decided I needed some closed back headphones, as the LCD3s project sound into the room like a pair of bookshelf speakers when you turn them up. So I also got some Audeze LCDxc closed back headphones and they are AU$1000 cheaper than the LCD3s but they are very close in performance, they don't sound $1000 cheaper. And they don't leak sound and they isolate really well in noisy environments. And all the service I have got from Audeze has been outstanding also.

To get a speaker based system that sounds as good as the conductor 3x reference/Audeze LCD3 or LCDxc combo in my estimation you would probably have to spend 10 times the amount.

I have a Rotel RB1080 power amp and a pair of Dali suite 3.5 floorstanding speakers and it is a great system, but the Burson has made it better than it was with the Nuvista. I have a seriously good Hertz/Helix system in my car. But the Burson/Audeze combo is the best listening experience I own.

My modded CD80 is beautiful it has a wonderful timbre, and simple acoustic music, including hi quality vocals like kd Lang, Sarah Vaughan and Marlon Williams sounds so amazingly musical and transparent. The Cambridge 840c on the other hand is incredibly detailed. It has a fully balanced layout, twin Analog Devices AD1955 24 bit DACs, true balanced XLR outs, use of DSP processing to up-convert the signal to 24bit/384kHz. The detail it extracts is amazing and it handles complex layered music so well and has an awesome soundstage. It is a few years old now but the technology is impressive and was regarded as best in class by more than one reviewer. I had been tempted to upgrade it with burson op amps and low jitter clock but never got around to it.

Why do I like the conductor so much as a DAC? Well I love my two CD players and the Burson DAC takes the best of both of them and combines it. The burson is incredibly musical, wonderful timbre and incredibly detailed at the same time and has a sensational soundstage. I'm sure there are better products out there but I'd probably have to spend a hell of a lot more money.

Burson's combining of a top end headamp, DAC and preamp with exceptional Bluetooth is an unbelievably good one-box solution for me, someone who has a speaker based system and wants to listen to headphones too.

Just for the record, it had been about a decade since I had upgraded any of my hifi gear. I was really happy with what I had. But neither the 840C or the Nuvista had a headphone socket, and I was due for some new headphones to upgrade some excellent but aging closed back Yamaha professional series I had. So I splurged on the Burson/Audeze package.

Burson's service is exceptional, they were completely honest when offering advice to me, said I had some exceptional gear and were quietly confident about their products.

I think they are too modest. They are a bunch of fanatics who are in this game for love not money. The gear they make is awesome in quality and value. Oh and I have no connection other than being a customer.

The proof is in the listening, and I've no where near come close to tweaking the C3X, it's still just running on the settings straight out of the box. And the fact that I like it more as a preamp than the MF Nuvista, well that is high praise.

The other thing I like about dealing with them is they say if they don't know the answer to your question. They don't gloat or brag and they are straight up front about what they know and don't. It's a lot like dealing with Audeze. They are awesome too. And the synergy between their products is amazing.

And if you think the new Burson range is ugly, well fair enough. But you don't buy it to look at it

Oh I have a 5m Cardas parsec balanced cable so I can sit anywhere in my living room and listen. It's a lovely cable and despite its length I can still drive the LCD3s to extreme levels. The headamp and headphones are such low distortion you can turn it up and have no idea how loud you are really playing it as one of the cues for perceived loudness is distortion, but the CX3 and LCD3 combo is almost impossible to drive to distortion.

As a side note people say you can't drive LCD3s with portable gear. I have an A&K SP1000M that drives them beautifully. Even my older entry level AK70 does a great job. So I splashed out and got Cardas to make a 1.5m parsec cable terminated with a 4 pole balanced 2.5mm connection and it drives my LCD3s wonderfully. And my LCDxc's as well.

I thought the Audeze stock cables are great but the length and terminations weren't exactly what I needed and Audeze wasn't able to make me what I wanted.

Also if you want some 3 pin XLR cables to hook up your C3X in your stereo system Mogami stage gold or Mogami studio gold microphone cables are awesome and a lot cheaper than buying audiophile cables. And these are the kind of cables used in recording studios and on stages. If it's good enough for stadium rock bands its good enough for me. Professional gear can often be a more cost effective path to great sound quality. There are probably pro brands other than Mogami that are just as good, but I haven't bothered hunting them down and comparing, the mogami are great.

I have found an Australian business that will make solid silver cables with teflon dielectric and top shelf connectors at really reasonable prices so I am going to try silver and see how it compares to the cardas parsec copper cables.

Happy listening
Cheers
Sam

The design and the “Cool case” concept vs. former “The Vault”:

By looking 10 years back in time to Burson Audio’s products (Conductor HA160/D, Conductor V1 / V2 / V2+, Timekeeper, Soloist SL) designed to please customers as Hi-Fi equipment for desk/office use, we do see lot of similitudes in how they look: big, heavy, powerful, imposing, shiny & expensive look, audiophile-like quality at first sight. Couple of years ago Burson Audio introduces smaller and lighter desk/office audio equipment like Play/Playmate/Swing/Fun/Bang, Air addressed to customers willing to install these in their own desktop computers or simply deployed on their desks without occupying much space with similar audio quality like their previous designs.

Now I’m looking to latest Burson’s high-end products, Conductor 3 Ref & 3 X, and I realize that their look is way different than the previous versions of Conductor. We now have a smaller case, a bit shaped, still shiny but shades are now space-gray, like the newer MacBooks.


I do love the newly designed case, but given that I’m also old-fashion and quite reticent to new designs, it took me a while to understand why Burson changed the appearance of the previous corner-shaped polished aluminium enclosures (aka “The Vault”) in their latest high-end models. Given they recently swapped the big power supplies with one or two toroid transformers inside (bulky and heavy, about 1Kg each) with their newly developed MCPS technology, now the max. height of the Conductor could be much lower, because transformers were the tallest component from in there, hence the smaller and lighter case of C3Ref and C3X. Worth mentioning that the former Conductor V2+ has a weight of 7Kg, while C3 barely gets to 5Kg.


Also, to improve heat dissipation inside the case with about 300% over their previous TOTL CV2+, they added wrinkles on both top and bottom parts of C3’s case, in a manner that is more good looking and way more thermally efficient. There are no visible screws and no sharp corners, so Conductor 3 looks pretty much like a uni-body design, making it much more appealing when seen and touched live than seen in the pictures.



The front plate contains a shiny slick rotary knob on the right, the big OLED screen and the 4 switches with explanatory icons on top for choosing inputs/outputs/settings are located in the middle, microphone and headphones output sockets on the left side. The power switch is located on left side as well, Their arrangement is straight forward and needs no explanation.

All the analogue and digital inputs and outputs are located on the backside, same as the power socket and BlueTooth antenna.


A bit about the MCPS power supply:

A very bold and inspiring innovation designed by Burson Audio is their Max Current Power Supply technology: https://www.bursonaudio.com/about-us/max-current-power-supply/. No other manufacturer has this technology yet and Burson has been pioneering this new technology since 2017, when the first version of PLAY appeared on the market (Head-fi thread here: https://www.head-fi.org/threads/new-burson-audio-play-amp-dac-2w-16ohm-op-amp-rollers-dream.860882/). To cite them, “Since the main power has a 50-60 Hz working frequency, [...] this frequency is within human hearing hence extremely noisy. [...] The Burson MCPS increases the working frequency to 170khz. Any noise at this frequency is well above the human hearing threshold of 20khz. The result is a pitch black sound-stage critical for micro-details to shine through”.

Most of audio equipment is injecting mains hum (a frequency of 50-60 Hz), to some extend, depending on the shielding used to the transformer, might be audible, might be not, but in any case this mains hum is measurable with proper gear. Burson’s vision is that removal of the big toroid transformers will completely remove any possible mains hum, while lowering the total weight of the device and also increasing the efficiency of the power supply.

While a regular power supply based on transformers then followed by bridge rectifiers, big capacitors and linear regulators has a power efficiency of about 40%, Burson’s transformer-less MCPS has about double efficiency, hence will consume less energy and be more environment friendly. Of course, the heat dissipation will be lower with MCPS vs. the traditional designs.

The C3X DAC/pre-amp.headamp combo is using en external 150W low-noise power supply (measured ripple & noise of only 0.01%), but internally we can find several Texas Instruments boost-regulators, but also TI and ST linear regulators as well.



The analogue stages from C3X are getting the power from dedicated power regulators, they’re not sharing the same supply with the digital stages. I was able to count no less than 11 big linear regulators (LM317/LM337, LM1085, LM7805), as well as 5 low-noise switching regulators (TPS54560), without including the small ones from around the DAC chips or from the USB transport board (AMS1117 etc.). At the input power jack we can find a P-Channel MOSFET IRF4905S, most likely used as buck-converter.

The 4 dual op-amps (2 in I/V and 2 in LPF) are powered by dedicated linear regulators delivering a low noise and free of ripple +/-15.3V, while the beefy output stage is powered by +/-20V delivered from the low-noise boost-regulators (measured ripple & noise of about 400uV RMS, so a 0.002% of ripple). Each of the 4 amplifier-rails are having several bypass capacitors nearby the output stage transistors, hence the maximum current is instantly delivered into the headphones.


I was able to count around 125 electrolytic ELNA capacitors, although the small SMD ones from the motherboard are probably counting more than that, so quite an astonishing decoupling technique by choosing so many capacitors/inch for decoupling instead of going with big ones. This is definitely decreasing the noise coming from the power supply and provides a very clean output to the XLR/jack plugs.


Details about the Digital and Analogue Parts Inside

The DAC is fully balanced, like the SWING, and is created around two ES9038Q2M chips (http://file2.dzsc.com/product/18/05/25/829029_170233543.pdf), each one having a SNR of 129dB. The I/V and LPF stages are created around the SS V6 Vivid op-amps, well-known for bringing all the micro-detailes from the music into the headphones. However, some C3X versions might have different opamps inside (e.g.: SS V6 Classic or JRC5532D), but this won’t affect the performance of the device, although sound perception might differ a bit in soundstage presentation and details retrieval.




The 44-pin ALTERA EPM3064A chip is a CMOS EEPROM–based programmable logic device (PLD, see https://en.wikipedia.org/wiki/Programmable_logic_device for details) where all the programming software is loaded, so that takes care of how C3X will operate properly.



The headphones amplifier is fully balanced as well, so it actually contains four distinct amplifiers inside, two per each channel (for inverted and non-inverted signal). However, in unbalanced operation (when driving headphones via the 6.3 mm jack) only two of these amplifiers are used. The amplifier itself is created around 40 transistors Toshiba 2SA970/2SC2240 (5 pairs per each amplifier rail) in pre-amplification stage and 8 big transistors Toshiba 2SA1930/2SC5171 working in Class-A in the output buffer (2 per each amplifier rail).

Output stage is created around the powerful Toshiba 2SA1930/2SC5171 complementary bi-polar transistors, two pairs per channel when used in balanced mode and twp pairs per channel when working in unbalanced mode. Each single output transistors can sustain a max. theoretical power of 20 Watts, so driving headphones will be piece a cake for them, including the extreme power-hungry planar headphones Hifiman HE-6 that will be driven by C3X to an of 118dB! All the output transistors are connected to the bottom aluminium base via normal screws, so heat dissipation from the output stage is done on the bottom.

The jack and XLR output plugs are getting audio in parallel, so you can listen to both balanced and unbalanced headphones at the same time, as long as you're comfortable with one volume setting for both. Also, don't forget to pause the playing while plugging/unplugging the unbalanced headphones, due to the fact that every stereo jack plug will create a short-circuit when inserted or ejected! This is not happening on mono jack, nor to XLR plugs.

Headphones are protected by a dedicated relay, so there will be no thump when powering up the device, although Burson recommends not keeping headphones plugged in while powering on the device. A small “thump” might be heard if C3X gets powered ON with headphones connected, but this is normal until the op-amps will get warmed-up. However, if a high level of DC will occur, the protection will kick in fast

C3X has inside one of the most powerful headphones amplifier ever built and, as an all-in-one combo (with DAC, pre-amp and BT streaming), is probably the most powerful in the world at this moment. Some data from my own measurements below:

Power rating measured (W) / Load resistance:
13.5W/ 15 Ohms (14.2V RMS)
13.5W/ 30 Ohms (20.1V RMS)
13.5W/ 50 Ohms (26V RMS)
7.5W/100 Ohms (27V RMS)
2.5W/300 Ohms (27.5V RMS)
1.25W/600 Ohms (27.5V RMS)






The streaming playback is looking very similar with the original USB playback, although we can notice the energy from the trebles starting to fade out gently after getting over 17.5KHz (explained why here)
An uncommon but interesting approach I see in the way the pre-amp volume is done, as there is no analogue potentiometer inside, just the digital rotary knob tied-up to the built-in 32-bit volume from the two ESS DAC chips. So Burson's R&D tied-up the XLR inputs to a 123dB SNR ADC chip: AK5394AVS (https://www.es.co.th/Schemetic/PDF/AK5394A.PDF). The digital signals are getting into the 32-bit volume control from the ES9038 chips, so there will be no bits truncation that will affect the sound and no noise added. This is probably the only pre-amp in the world using this concept to control the volume of the analogue inputs, so quite an achievement.




The BlueTooth audio is done around the "Premium tier" Qualcomm® CSR8675 chip (https://www.qualcomm.com/system/fil...-audio-flash-product-brief_87-ce852-1-b_0.pdf). This chip delivers 24-bit/192KHz audio over Bluetooth and aptX HD as well. Linking my cellphone (iPhone 8 Plus) took about 2 seconds after I initially chose the BT output from the C3X LCD menu.



Headphones DC protection circuitry is done around the C1237HA chip and two relays, one for each output socket (6.3mm jack and the 4-pin XLR).

There's a low-power USB hub controller on the USB module, GL850G connected to onboard dedicated 12 MHz crystal. This has an 8-bit RISC processor inside that quickly responds to USB host requests. This USB hub should minimize PC's USB host ripple and noise and also to power the USB chip via the internal low-noise regulators.

The USB transporter is a XMOS XU-208 chip from the latest generation on the market, xCORE-200: XU208-256-TQ64. This is a 32-bit chip powered by 8 x real-time logical cores running at a frequency of 500 MHz. It gets the clock from the onboard 22 MHz and 24 MHz oscillators.



Microphone mono 3.5 mm jack is connected to the CM6327A A/D converter chip that converts the analogue sound received by the microphone socket into the digital samples. This has a max. of 48KHz Sampling Rate and a dynamic range of 96dB.



Headphones Matching - Sound Quality and Idling Noise:

The internal gain of the C3X is higher than CV2+'s gain: CV2+ with a volume setting of 99% was as loud as C3X with a volume setting of 87%. Due to the higher gain, some slight of hiss-noise may be heard when using very sensitive headphones. However, on the 6.3mm unbalanced jack socket, the background noise on C3X is a bit lower that on the CV2+.

Pairing the C3X with high sensitive headphones might not be a very wise thing to do, especially if speaking about 8-16 Ohms IEMs, due to their very high sensitivity. With my extremely sensitive 130dB/V KZ AS10 IEM's I was able to hear some hiss-noise, although these headphones are designed for portable use anyway.

Now comparing the output levels with Audeze LCD-2F between the two headphones outputs XLR/jack, there would be about the same levels to my ears when using a volume setting of:

• C3X - XLR vol. setting of 25
• C3X - Jack vol. setting of 40

Worth mentioning that volume control is somehow logarithmic in the beginning and at the end, but goes linear between volume settings of 40...80. For example, at lower settings, between 1-40, the volume barely raises, instead at a level of 80 power gets twice as much than at a level of 40 and at 100 there will be twice as much power as at 80 and four times more power than at 40.


Below is a summary of sound impressions after listening to different headphones::

Headphones, Sensitivity, Impression

AKG K701 (balanced & unbalanced), 105 dB/V:
- Rather hard to drive headphones, but the “endless” power of the C3X drove them easily and with great authority. I found a very good pairing with all songs I've tested, a big soundstage, a big sound.

Audeze LCD-2F (balanced & unbalanced), 112.5 dB/V:
- Planar technology, but not so hard to drive. I was able to get lot of details and a huge scene with C3X and LCD-2F, probably due to the Solid-State V6 Vivid op-amps and to the discrete output stage too. I totally love the sound coming out of LCD-2F and I so understand now why Burson recommends pairing their amp with planar headphones; probably this is why they had the C3X + LCD3 promo recently.

Hifiman HE-560 (unbalanced & balanced), 100 dB/V (103 dB/V per Innerfidelity):
- Not easy to drive planars, actually these require quite a good amount of power and current to be driven properly. The beefy output stage of C3X drove these planars with ease and bass was striking fast and powerful, without any signs of congestion. I pushed the volume insanely high for few seconds and the low-end bass become more powerful than ever, almost like a subwoofer pumping into my chest.

Fostex T50RP-mk3 (unbalanced), 103 dB/V:
- Clean sounding, very neutral, great for monitoring for sure. Low-powered amps will never drive well these planar headphones, of course, but not the case of C3X.

Beyerdynamic DT-880 600 Ohms (unbalanced), 96 dB/V:
- Very detailed headphones, a bit on the bright side, so I had them tested with V6 Classic and the sound was very detailed, pleasant without being sibilant in the top end (when using V6 Vivid some slight sibilance appears on top end). Despite that these cans are lacking sub-bass per design, when pushing C3X’s volume higher, I was able to get a pretty nice and fast bass, although not much of the impact per their design. The clarity was definitely top-notch, so probably to many details if paired with V6 Vivid. The amount of power C3X amplifier is extreme, on both XLR or jack headphones outputs. I wasn’t even able to push it to half of its max. power with these high-impedance 600 Ohms headphones, so I don’t think there is a headphone out there that C3X will struggle to drive it, not even Hifiman HE-6.

GRADO SR60i (unbalanced), 115 dB/V:
- Not a SR60 fan myself, due to their brightness and lack of sub-bass, especially when paired with SS V6 Vivid, but swapping opamps from SS V6 Vivid to SS V6 Classic will make them sound more “comfortable” and relaxed to my ears, with o larger scene than regular 5532 op-amps.

AKG K550 (balanced & unbalanced), 117.8 db/V:
- Very sensitive headphones, although I got no background noise when using the 6.3mm jack socket. These are made for portable devices, so with volume at 10 in high-gain my ears were already flooded with music. Soundstage was higher than usual, especially when using the balanced 4-pin XLR output, although between tracks a tiny hiss could be heard due to headphones higher sensitivity.

AudioTechnica ATH-M30X (unbalanced), 115 dB/V:
- I use them for monitoring purposes and I only tested them with C3X to check for background noise, but it simply wasn’t there, despite their rather high 115dB/V sensitivity.

Superlux HD381F (16-Ohms IEM), 121dB/V:
- Extremely sensitive IEMs, with only 1 mW applied the music will get to an SPL of 100 dB, so some hiss noise is to be expected from such a powerful amplifier. However, in Low-Gain I was able to find the correct volume level to get from these IEMs a striking and pleasant bass, although the trebles were nicer and softer with V6 Classic vs. the V6 Vivid (most likely due to the headphones freq. response on the trebles).

KZ ZSX (24 Ohms IEMs) & KZ AS10 (22 Ohms IEMs), about 130dB/V:
- Extremely sensitive IEMs, even in low-gain mode the output power of C3X is rather high, also background noise is present during the tracks. By using iFi EarBuddy the C3X becomes absolutely silent with these IEMs, so totally recommended with such powerful headphone amplifiers. The sound is a bliss, totally unexpected, given that C3X was not designed to drive such sensitive headphones. Bass is striking perfectly into my ears, so that’s a good sign that the overall damping factor is low enough to pair C3X+EarBuddy with 22 Ohms headphones, which is a very good thing.


Beats Solo 2 (unbalanced), 118 dB/V:
- Very sensitive dynamic headphones, also very clear sounding and neutral as well. The bass strikes with lot of force, but not boomy at all and the extra details of the V6 solid-state op-amps, even if the scene of these headphones is not the largest possible. In a quiet bedroom at night I felt a faint hiss noise between tracks, although during the day I couldn’t hear it. However, these headphones are designed for use with portable audio gear only.

Superlux HD-662 EVO, 113 dB/V:
- Cheap and balanced dynamic headphones, although a bit harsh on top with some rock songs. Very easy to drive, with a tiny amount of power applied by C3X, these cans were sounded full of bass and with a good scene. I couldn't hear any hiss-noise coming from C3X with these cans.


The “Lavish Musical Experience” Sound:

C3X excels with power-hungry headphones, especially with orthodynamic ones (aka planars). Its huge amount of power is indeed lavish to the listener and combined with the preferred DAC’s digital filter this combo might be an “end-game” for many customers.

While the unbalanced jack output is a very good pair for most headphones, when going balanced the power increases and also the scene gets wider and sound gets more peaceful and pleasant (some might call it a bit warmer). Bass seems to strike a bit deeper and more powerful when going balanced, at least when using planars, probably due to the way balanced driving works or to the different cables used.

BURSON C3X is a very detailed and revealing DAC/headamp combo and with Audeze LCD-2F connected to XLR balanced-out, while listening to DSD256 (11Mhz) and DSD512 (22MHz) tracks, I could actually hear concert hall’s background noise from the beginning of each track and between the piano notes. C3X will forgive no hiss and no rustle from the tracks and in case you haven't heard before when vocals will inhale/exhale or murmur of their lips, now you will, so prepare for an increased clarity and a boost in details retrieval.


[Later edit] Some of the artists I've listened to test Burson C3X:
Cardi B., Norah Jones, Cheloo, Faydee, Antonia, Adelle, Ed Sheraan, Lil Nas X, Irina Rimes, Zdob si Zdub, Vinka, Minelli, Fly Project, INNA, The Black Eyed Peas, French Montana, Jonas Brothers (I'm only writing here about the Dance music, although there are several others in the Jazz, Blues and Classics areas).

In "Clandestina - Filv" bass was striking like a madness, full of authority and without any trace of distortion. The huge power reserve of the built-in discrete amplifier has definitely something to say here. This song contains a very good low-end to test the amplifier, also the headphones. Worth mentioning that even my 8-Ohms speakers were perfectly driving the low-end of this song (totally not recommended to connect speakers with C3X, so don't do like me!!!). Same impact on the low-end I felt it while listening in songs like Old Town Road (Remix) - Lil Nas X feat. Billy Ray Cyrus, Trop beau - Crisologo, Trika Trika - Faydee, Antonia.

I'm also adding to this review that C3X & C3R are based on a modular design, the motherboard containing more parts on top, like the USB XMOS transport card, the Bluetooth card, the front plate module with the rotary knob and headphones sockets, but also the back plate with the XLR/RCA plugs. This is a good thing, because you never know when an updated card will appear as an upgrade on Burson's shop website, but this is also helpful in case of RMA, due to the fact that shipping abroad 1 Kg is way cheaper than shipping 6-7 Kg.


PROs:

• One of the most powerful headphones amplifiers ever built, on both balanced and unbalanced outputs.
• Able to play all kind of 24 & 32-bit PCM files, but also DSD x64, x128, x256 formats natively via the custom-made Thesycon ASIO driver provided, without any pops when switching between the source formats (tested under Windows, Linux and MacOS with Foobar, jRiver, VOX, VLC, Rythmbox, Clementine players).
• Needs no drivers for Linux, MacOS or Windows 10, also it is recommended to install Burson’s driver under Windows for native DSD and low-latency playback.
• A real "detail retrieving" Class-A audio device, especially when using solid-state V6 op-amps.
• Great soundstage and channel separation, especially when going balanced.
• A complete DAC/headamp/pre-amp/streaming audio solution with a very powerful, flat and neutral sound.
• Trebles and bass extensions are easily reaching the edges of audible octaves, due to the direct-coupled amplifier and headphones (no caps in signal path).
• No opamps in audio signal path when using Burson SS V6 transistorized DIP8 amplifiers, designed especially for audio use.
• Smaller size and weight, lower temperature and lack of transformer hum due to the improved transformer-less MCPS design (low noise switching regulators followed by linear regulators).
• Ability to be positioned vertically while LCD can be also rotated from pressing a frontal switch.
• Several Digital filters to choose from will help in getting the desired output sound (pre/post ringing for impulse response etc.).
• Having two digital gain settings is a plus, because it protects our hearing when using sensitive headphones, although it will not lower the background noise when using very sensitive IEM’s (just use an EarBuddy for these IEMs).

CONs:

• Gain is a bit higher than expected, especially when going balanced, so with very sensitive headphones some background noise might be audible. For headphones having a higher sensitivity (>115 dB/V SPL in single-ended, >100 dB/V SPL in balanced operation; if needed, use https://reference-audio-analyzer.pro/en/dbv-dbmw.php for dB/mW to dB/V conversion) you might want to add an iFi EarBuddy or ieMatch.