Burl B2 Bomber DAC Review: Holy Sh**, This is Good

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by purr1n, Jul 14, 2020.

  1. Cspirou

    Cspirou They call me Sparky

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    Goddamn, even with an SMPS power supply. Output stage must be class A.
     
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  2. penguins

    penguins Friend, formerly known as fp627

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    Thank you for loaning the DAC out @Clemmaster
    Saved me from having to hunt one down to try myself.

    On a different note I suspect (based only on triangulation) that this would be a pretty good DAC paired with a Phonitor... Enough of both of their strengths without going over the line in any way... hmmm.... ideas.....
     
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  3. purr1n

    purr1n Super Friend

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    The amp I used just so happens to be "Phonitorish" in tonal signature - it's a tube amp, but hardly bloomy. Overall the B2 is only slightly warm, more hidden or internally warm than overtly warm, and close to, but not quite as timbrally dense as the Schiit A2 models. Any neutralish amp would do really. Something super organic like BW2 may not be a good fit. And I don't like cool or antiseptic sounding amps regardless because those never seem to have any slam.

    I still plan on finding one for an SBAF loaner. If anything to complete the cycle of Solaris, Convert-2, and B2 pro DACs.
     
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    Last edited: Jul 15, 2020
  4. purr1n

    purr1n Super Friend

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    Almost forgot, one bit thing I should mention: the output level dial changes the sound, the saturation effect. The DAC could sound warmer with the output level dial turned clockwise.

    Burl B2 Bomber DAC
    THD+N vs Input (dbFS)
    -8dBu output setting or 12dBu max output (GRN/RED)
    -18dBu output setting or 22dBu max output (BLU/ORA)
    upload_2020-7-15_16-46-34.png

    The lower output at the -8db setting results in overall higher THD+N (it's the noise floor) than the -18dBu setting, but the distortion harmonics are overall lower and don't climb up as high. In fact, about -12dbFS to full output, the SINAD of the -8db is higher than that of the hotter -18dbu setting.
     
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    Last edited: Jul 15, 2020
  5. purr1n

    purr1n Super Friend

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    Here, confirming onsite of distortion comes on later at the lower output setting. Note that the distortion patterns are the same.

    Burl B2 Bomber
    -8dBu output setting
    -20dbFS 1kHz
    upload_2020-7-15_16-52-30.png

    Burl B2 Bomber
    -8dBu output setting
    -15dbFS 1kHz
    upload_2020-7-15_16-54-31.png

    Burl B2 Bomber
    -8dBu output setting
    -10dbFS 1kHz
    upload_2020-7-15_16-55-47.png

    Burl B2 Bomber
    -8dBu output setting
    -5dbFS 1kHz
    upload_2020-7-15_16-56-55.png

    Burl B2 Bomber
    -8dBu output setting
    0dbFS 1kHz
    upload_2020-7-15_16-57-44.png
     
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  6. Clemmaster

    Clemmaster Friend

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    Cool, I wasn't imagining things!
     
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  7. purr1n

    purr1n Super Friend

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    I was just going to ask you to confirm. I turned the knob to max output (-18db) and I was like WTF, why is everything sounding so warm. I preferred the lighter touch of -12 or -10db. So there you go @fp627: the tonality is adjustable! FWIW, all my impressions so far were with the -12db output level setting in the middle.
     
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  8. beemerphile

    beemerphile Friend

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    I wonder what the logic was for a half-assed RCA connector instead of a proper 75 ohm BNC for S/PDIF. Hell, there's already three BNC's on the back panel, why not one more?
     
  9. Clemmaster

    Clemmaster Friend

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    I was wondering if it was the DSHA-3F's input transformers reacting to the hotter signal or what.
     
  10. Clemmaster

    Clemmaster Friend

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    Because pros use Dante or AES :p
     
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  11. penguins

    penguins Friend, formerly known as fp627

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    *insert excitement here*

    At first I didn't think this would work with Stellaris which is what I want my 2nd DAC for - what you describe with this B2 somewhat reminds me of Stellaris with EML Mesh 5U4G - very good and similar traits, maybe technically better than my RCA 5U4G, but just not my preference... but with adjustable tone, based on the other stuff described here, it may just work.

    Also too bad the phonitor is barely on the wrong side of "can drive an HE6 properly" to my ears...
     
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    Last edited: Jul 15, 2020
  12. purr1n

    purr1n Super Friend

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    Keep in mind that Donald usually shows off the Stellaris with the Sonic Frontiers and even Dan switched to Yggdrasil GS from XSP for his Starlett.
     
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  13. lehmanhill

    lehmanhill Almost "Made"

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    To help my understanding, please explain the "intentional distortion/tape saturation effect a bit further.

    There seems to be a subjective correlation between the general mild warmth across all the music and this tape saturation effect. But it appears that the tip up in distortion only happens at very loud parts of the music. Do you feel that the warmth across the range is part of a larger tuning result or related to the tip up in distortion at the louder levels?

    What I can imagine is that the tape saturation effect would allow a tuning with great slam at lower than maximum signal levels and the saturation would slightly soften that on the loudest passages which would result in smooth with slam. Or am I off on a side trail here?

    Jac
     
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  14. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Is this necessarily audible? And is this marketed as some sort of tape saturation effect or otherwise?

    Not doubting subjective impressions, but distortion results like that I wouldn't normally correlate so much to one sort of sound characteristic over another.
     
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  15. purr1n

    purr1n Super Friend

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    The distortion at 0dfBS is the zone of "good enough" but not in the zone of "doesn't matter / no correlation / sub-atomic particles." The distortion is on par with EC tube amps running tubes that haven't been run into shit.

    upload_2020-7-16_8-16-0.png

    Well first of all, I didn't think that the Burl was necessarily really all that warm sounding, especially in an overt way at the -10 to -12db output setting. We are talking about a touch of internal warmth like on the Motu Ultralite mk4 units. I did feel the Burl exhibited sort of a vintagey kind of sound that reminded me of tape. And in that respect, we are taking about hitting the yellow or an occasional red on the LEDs at the peaks, not blowing the shit out of the levels where the sound goes goo and softens into melted cheese.

    At the highest setting -18db output setting, the DAC did sound overall warmer, both overt and internal warmth. It could be because the onset of the dose of distortion comes on earlier and at less hot levels.

    It is possible that part of this internal warmth could be an aspect of the saturation effect, whether it be tape or transformers. We are still learning here, trying to correlate measurement behaviors to what we hear. We could be on to something here - probably stuff that the ancients already knew and took for granted.

    Answered above.

    --

    An interesting test may be to use digital attenuation of -20db and sending that data to the B2 Bomber. This way, the levels never get hot enough to hit the range where distortion comes into play with the trade-off being higher noise floor.
     
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    Last edited: Jul 16, 2020
  16. Psalmanazar

    Psalmanazar Most improved member; A+

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    Yes. Most discrete opamps are crap. They run out of open loop gain in the audible band or just have parasitics. They just distort. The ones that don’t distort aren’t very popular but are quiet good. The Burl does not have tape saturation, it’s just tuned op amp distortion but not so well that you don’t have to tune the DAC yourself via input gain. Tape saturation looks different and can be quite nastier.

    Download the demo of Uhe Satin on maximum oversampling to avoid aliasing to see what tape saturation is. Ferric TDS is still out there too and I’m testing a new open source tape sim soon. Most of the big brands (Slate, Waves, Softube) alias hard. They’re super digitally dirty.
     
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  17. purr1n

    purr1n Super Friend

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    Yeah. It's more like tape or transformer behavior when they close to their limits. It's not blowing out the levels past their limits.
     
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  18. Clemmaster

    Clemmaster Friend

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    [​IMG]
     
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  19. purr1n

    purr1n Super Friend

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    No time.
     
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  20. Collusion

    Collusion Friend

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    OK, I've know had my unit for three nights and I'm ready to share some initial impressions and general observations about the B2 bomber DAC.

    As you may already know (from my personal SBAF twitter feed), I bought my unit second hand and it had a pretty distinctive tobacco smell. Probably used in a studio where smoking was allowed. I took the whole thing apart and cleaned what I could with isopropyl alcohol. At the same time I had a change to snap a couple of pictures. Luckily the insides didn't seem to be that heavily affected as the smell has now been all but faded away.

    burl_b2_bomber.jpg

    My unit is an older revision without the Dante networking option and actually also the toslink input is missing. Not a huge loss I guess, either way it would be connected to the Pi2Aes via AES/EBU like it is now. One thing I noticed though is the mainboard revision, which is RevB. Marv had RevE instead. Generally speaking, the PSU seems different and there are some differences on the mainboard too. This prompted me to ask about possible audible differences directly from Burl Audio. They were kind enough to answer just within a couple of hours.

    What is interesting, it actually seems mine and Marv's demo unit have both these older generation discrete op amps. Both read as "Burl Audio OPA RevA PCB-OPA-0001" and visually they booth seem identical (difference being they've applied some epoxy on my unit's components to obfuscate things - Marv's demo unit seems to have some sanded components instead). This of course makes our impressions more comparable. Though no comments from Burl on these other visible differences, which do not seem to limit to Dante and toslink functionalities.

    20200722_202822.jpg

    I did actually mail a couple of dealers and ask for a quote for the new discrete op amps. I am not going to give Burl a monetary blowjob, but if they are reasonably priced, I might just go for it. Let's wait and see.

    20200724_170914.jpg

    Rest of my setup is same as before:

    Pi2Aes -> Burl B2 -> SPL Phonitor 2 -> SPL Performer s800 -> Raal SR1a
    and
    Pi2Aes -> Burl B2 -> SPL Phonitor 2 -> Sennheiser HD600

    My very initial impressions were these (Output level @ -12dB and clock source INT):

    - Wow, headstage is now much bigger than with DM Convert-2
    - Wait, is this thing also... brighter?

    Regulars here know DM Convert-2 has a a wrap-around headstage, where sides are closer than the center. You kinda get used to it over time, but when you hear something that is more "normal" in this regard, you'll notice immediately. And B2 is pretty awesome indeed! You kinda feel more like belonging into the whole show, where as CV2 makes you inspect it from the outside (if this makes any sense).

    At this point I am not sure if the B2 is really bright, or Convert-2 just managed to sound a tad dark in my setup. I've been using the CV2 for a quite long time and I do actually think it's slightly tilted down. Also, my other (speaker) setup has also a kind of dark and restrained sound (partially thanks to Bifrost 2), so maybe I've just gotten accustomed to something different. I did check this with the Sennheisers too and switching back to CV2 confirms this. Too early to say if I end up liking this perceived tonal balance or not, so let's leave it at that this time.

    When put againts CV2, most D/S dacs would probably fail to produce equal let alone better or more natural timbre. B2 is certainly in the ballbark here. I do not detect any glaring nastities anywhere... and even if there's more perceived brightness, it isn't due to graininess or sibilance. There's also a certain amount of warmness or liquidness, which makes the sound quite easygoing in the midrange. Good stuff!

    When it comes to overall resolution, I'd give the B2 an edge. CV2 is known to be slightly veiled concerning (micro)details. This can be heard through the whole frequency spectrum and sometimes even quite easily (Example: Bette Midler - Chapel of Love, Bette and background singers distinguish as more separate sources rather than one). From memory, B2 doesn't quite reach the RME ADI-2 DAC's (AK4493) level in this regard, but there's no hint of the velvet sound... and it's certainly better than CV2. And it manages this without sounding too square for my tastes.

    CV2 renders dynamic swings wonderfully, for example, in Celine Dion - Power of Love. With Raal's the volume differences in Celine's voice get rendered instantaneously, or almost explosively. This is a startling experience and when experienced the first time, will almost certainly induce goose bumps. B2 trades some dynamics to increased resolution and manages to conjure quite a beguiling show all the same.

    Other observations:
    - Bass is different, maybe more midbass than in CV2 and in turn less sub-bass
    - Maybe not so sweet/euphonic sounding as CV2... but not outright analytical either

    Music used during this comparison (in Audition mode, but certainly not limited to these):
    Bette Midler - Experience The Divine - Bette Midler Greatest Hits (FLAC, CD rip)
    Celine Dion - My Love collection (FLAC, CD rip)
    Natalie Merchant - Tigerlily
    Beyoncé - Beyoncé
     
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