Firestone Audio Bobby Balanced Headphone Amplifier Page 2


A Balanced Approach
I spent most of my time evaluating the Firestone Bobby being fed a balanced signal from the matching Tobby DAC, connected via USB to a MacBook Air running Audirvana Plus. I also tried the more expensive Anedio D2 and Resonessence Labs Invicta DACs just for grins. I used a wide variety of headphones and made sure to try balanced mode as well as single ended operation.

Spoiler alert: the Firestone Bobby sounds quite good! The presentation is characterized by a clean, neutral sound, highly capable and with very little color of its own. I started by listening to the usual audiophile cliches—hi-res stuff from Herbie Hancock, Bill Evans Trio, Jazz at the Pawn Shop, that sort of thing. If a system can't make Diana Krall or Norah Jones sound amazing, then you can forget about "regular" music having any chance. The Bobby did not let me down with the typical audiophile fare—Jacintha was suitably sultry, Marta Gomez was playful and expressive, Tom Waits had the proper amount of gravel in his throat. Everything was fairly lifelike and "real" for lack of a better word. This is the kind of stuff playing in most audio showrooms and it's pretty obvious why: it's hard to mess up! Yes, certain gear will take it even higher, but the baseline starts at "pretty damn good" and goes up from there.

But what happens when we play something a little more realistic? I broke out some of the more rare gems in my collection and got to listening. First up was Matumbi with their 1978 reggae gem Seven Seals. This album was strictly vinyl save for a little known Toshiba EMI (now EMI Music Japan) release in 1993. Some of the tracks ended up on a later Best Of release from Front Line Records...not only is it missing some of my favorite songs, but the mastering is mediocre at best. In contrast, the Japan release is one of the best examples of the genre I've ever heard. While Peter Tosh or Bob Marley & The Wailers get fancy hi-res releases, Matumbi is limited to plain old redbook, but it doesn't matter, this album still sounds killer. The Bobby is able to capture the deep pulsating basslines and the intricate rhythm interplay about as well as I've heard this side of a state-of-the-art megabuck amp. I used the Audeze LCD-2 and HiFiMAN HE-500 to test the limits on the low end; the Bobby indeed hits hard and deep, with excellent texture and nuance. I switched to the Sennheiser HD800 to get a feel for how expansive the amp could be. While reggae in general doesn't compete with classical or jazz in terms of spaciousness, the Bobby nevertheless sounded suitably open. It can be a challenge for solid state amps to keep from sounding "boxed in" at times but the Bobby definitely gets it right. Overall a fine showing.

Next I broke out Starchild by East Coast rapper O.C., which is also a somewhat rare album. A single pressing of about 20,000 discs was released in Japan, but the US launch was scrapped due to copyright issues with some of the samples used. You can buy it in MP3 format from Amazon or iTunes but those of us wanting a legal, lossless digital version are out of luck. Used examples of the CD tend to fetch $40 or more, when you can even find one. This type of music doesn't normally lend itself to audiophile listening but what can I say? I like the artist and this is my favorite album of his. Anyway, the Bobby is no miracle worker but it does what it can; in cases like these I mostly look for the chain to do the least amount of damage. The production on this album is actually reasonably well done for the genre but it certainly doesn't need any grit or grain added from the system. A warmer, smoother amp might be more forgiving and I could see how that would be desirable in some cases. But this album doesn't quite reach that level of griminess; it's still worth hearing everything there is to hear. If we switch to something like Aesop Rock's None Shall Pass or any classic Wu Tang Clan album then I'd definitely welcome the more colored sounding option.

Getting off my rare album high horse, I spent some time with one of my favorite releases ever, "O" by Damien Rice. I don't care how many times "Cannonball" gets bastardized by some X-Factor wannabe, the original is still a remarkable song that I never tire of hearing. There's just so much raw emotion in the vocals, and that guitar hook will stick with you for days. The Bobby definitely has that "you are there" thing going on, with no added sibilance or other distractions to take away from the experience. Speaking of experiences, the track "Cold Water", played on a good system, makes the hair on the back of my neck stand up every time, and the Bobby was able to pull it off very well. What starts as a very simple vocal-oriented track with minimalist acoustic backing, builds up to a layered and complex final act with quite a lot going on. The Firestone amp didn't falter here, allowing me to hear deep into the mix and pick out individual parts without obscuring the macro-presentation and collective emotion. I particularly like how the Bobby rendered Rice's raw, honest vocals with striking realism. Pretty impressive stuff.

I got over the weirdness of the labeling, but I can't quite agree with Firestone in their recommended uses. When I try low impedance Grados or Audio Technicas on the jack marked "low" (but measuring high), I just don't care for the results. Sure, they get a bit of extra warmth and can sound "fun", but at the cost of definition in the lower frequencies and clarity through the rest of the spectrum. Granted, some headphones may accidentally end up sounding better this way—the fairly anemic Audio Technica W1000 is one such model—but in most cases it's a bad choice. Switching to the other jack with the 10 Ohm output impedance, I get far better results. Still not quite ideal but at least the damping factor shifts away from negative numbers and brings with it the expected levels of control.

I ended up preferring the lower impedance output almost universally compared to the 200+ Ohm option. At times the higher impedance was fun to experiment with using the 300 Ohm Sennheiser HD800 or 600 Ohm Beyerdynamic T1, but even then it was the minority choice compared to the 10 Ohm option. With those headphones, the higher impedance jack produced a warmer, more relaxed presentation, with boosted bass response and a softer top end. It's an interesting alternative and I'm sure some people would really love this sound—probably the same people who prefer these headphones as mated with OTL tube amps which tend to have similarly high output impedance. So I guess I appreciate the option.

Unfortunately even 10 Ohms is somewhat high for most IEMs, which is a shame as the Bobby has everything else going for it: precise volume tracking, well behaved channel balance, and an extremely black background. There aren't a ton of big, powerful Class A amps out there which also play well with IEMs so it's a shame to see the Bobby miss out based on just one attribute. Not that is sounded universally terrible, some of my custom IEMs were pretty enjoyable but in the end I could hear the reduced damping factor and altered frequency response. I definitely would have preferred a near zero Ohm output.

Planar magnetic headphones don't seem to mind though, and I really dig them on this amp. My Smeggy-built Thunderpants TP1 make a particularly good match, though the LCD-2, HE-400, and HE-500 all sound great as well. I have balanced cables for all but the TP1 and I notice a distinct improvement when run in balanced mode. All three headphones sounded more open and spacious that way, and I also heard a noticeable bump in low end extension. Reduced crosstalk? Better noise rejection? Higher current delivery and voltage swing? Don't know, don't care...the improvement is welcome regardless of cause. Not that planars were the only beneficiaries of balanced operation, the HD800 sounded more open and expansive that way, and a borrowed Sony SA5000—not my favorite headphone—sounded almost bearable compared to single-ended mode where I couldn't stomach it for more than a few minutes. Overall I'd say balanced mode is definitely worth exploring if you can possibly get there with your particular headphones. I'm a big proponent of the recent trend of detachable cables which make it easy to go balanced, but I'd even consider recabling a hard-wired pair if this was to be my main amp. It's that much of an improvement, might as well use the amp to its full potential.

The Competition
Is it a perfect amp? Well, no, of course not. Compared to my Violectric V200 the Bobby comes across as slightly "polite", especially in the deep bass region. And the Icon Audio HP8 mkII presents music on a grander scale, with effortless dynamics and a more enveloping soundstage. My Analog Design Labs Svetlana 2, a single-ended triode amp boasting super permalloy output transformers, is significantly more expressive. And the Auralic Taurus digs deeper into the micro-details and minutiae inherent in better recordings. So no, the Bobby isn't the last word in headphone amp goodness. But those are all more expensive amps, and when taken on its own the Bobby doesn't seem lacking in the least.

A more fair comparison would be the recently reviewed (and recommended!) NuForce HAP-100. The Firestone has an MSRP of $200 more but currently lists on Amazon for the same $600 price as the NuForce. These are two very good examples of what can be done when we move beyond the budget class of $200 and $300 amplifiers. The designers have more room to breath with respect to parts selection and overall quality, and it really shows in both of these amps. I'd say the NuForce is a bit more energetic and exciting, while the Firestone is more straight-ahead neutral. This could be called accurate or boring depending on one's point of view. I prefer the NuForce for making the HD800 come alive, and probably the T1 too, while the Firestone definitely does better with all my planar headphones. The HAP-100 will start clipping gracefully at high volumes due to limited current, but the Bobby never seems to run out of steam, and sounds really good in the process. I'm not sure it would excel with the HiFiMAN HE-6 but everything else should be fair game.

At the MSRP of $799, Firestone's flagship Bobby headphone amplifier fills an interesting spot in the market. While entry level users seek amps in the <$300 range, and experienced HeadFiers move upscale to four-figure territory, the middle ground is somewhat overlooked. I'm happy to see Firestone step in and attempt to fill that gap. For the most part I'd say they succeed. I like almost everything about this amp—it looks, feels, and certainly sounds like it could cost a bit more than it does. And when it comes to user experience, the Bobby is top notch, with its only fault being the overly bright power LED. But it does have a few things to watch out for. Balanced mode is essential to extract full performance, and even then some headphones might come off as a bit "boring"—Bobby being a victim of his own neutrality. Still, that's more of a character choice than a flaw per se, and if Bobby had a lower output impedance it could approach "ideal" as far as this price range allows. As it stands Bobby is still a very intriguing choice that deserves more attention than it gets. Recommended.

Firestone Audio Co., Ltd.
Rm. 2, 19 F., No. 97, Sec. 4
Chongsin Rd., Taipei, 24123
+886 2 29753657

tomasz's picture

Thank you for a comprehensive review. I wonder if you could tell us what kind of transistors are used in this amp.

As a small amendment I would only add that OPA2604 are dual amps not mono. 



John Grandberg's picture

Of course I meant OPA604... just updated. OPA2604 must have been on my mind, because I've seen them in several recent headphone amps I investigated. OPA604 doesn't seem to come up as often.

For transistors, I'll have to find my notes (which I seem to have misplaced for the time being). I recall them being MOSFETs, but don't remember the specifics. It was nothing too exotic though - just the basic tried-and-true variety.  

lithium's picture

Hi John,

This seems interesting though it seems there are too many riders attached. For ideal results you have to go balanced and impedance mismatch is also an issue. however, topnotch performance at 600$ is definitely a plus. 

How does it fare againt the yulong A18? Also in other good news the icon audio amp is now 1000$ in the US( no more dealer markup)

John Grandberg's picture

....but no amp is, especially for a three digit price. Overall I still enjoy the Bobby in single-ended mode, it's just not quite as good that way. But I'd still grab it for an HD650 in a heartbeat, as it makes an excellent combo even single ended - with room to grow later when you throw on a balanced cable. 

The Yulong Sabre A18 is definitely more on the warm side, with significantly more impactful bass (and more bass emphasis too). It's also smoother and more forgiving - Bobby is kind of ruthless. I don't really see them as competitors though, since both are good at what they do best: which happens to be very different from one another. You either like one or the other but I can't see being torn between the two. 

lithium's picture

I think there is really an opportunity in the market around this price for a well designed thoughtful product. Thanks for your thoughts. Something like the damping factor knob on the teac- HA-501 is something really interesting and perhaps others should consider something like that to make an amplifier a better fit with a range of headphones.

John Grandberg's picture

...comes really close to being perfect (on paper of course) but a few small things really annoy me. The damping factor knob is great, but how about some actual numbers to show what the choices are? Low and Med and Hi don't tell me anything. None of the marketing literature mentions it, nor does the manual. The only spec shown is "good for headphones from 16-600 ohms." Well, duh.  If it ranged from less than one up to maybe 300 ohms, with sensible steps in between, that would be ideal.

Also, what's with bragging about the fully balanced design but not providing an actual balanced output jack? Seems like a significant opportunity missed. 

lithium's picture

Hi John, if you go to this page and scroll down to Main features and the tab for selectable damping factor. they have a detailed table with damping factors. The lack of a balanced output is a disappointing, but I guess the designer decided to eliminate crosstalk but keep universal headphone applicability. I know disappointing but teac probably decided to go for the broader market with an $850 headphone amplifier!(totally scratching my head here). 

John Grandberg's picture

I somehow missed that part. So the output impedance knob, which they make such a big deal out of, ranges from about .5 ohms at the lowest setting to 5 ohms at the highest setting? Seems like kind of a small range for a feature like that. While I appreciate what they're trying to accomplish with it, a larger usable range would have more of an impact. 

With the exception of perhaps some multi-driver IEMs, the difference between a sub 1 ohm output and a 5 ohm output is not going to be all that massive. The Firestone Bobby, with a 10 ohm and 227 ohm outputs, at least offers some variation. Ideally I'd like Firestone to use a 1 ohm output and then maybe a 40 ohm output for flavor. 

lithium's picture

I hardly ever find something without qualifiers. But as they say the proof of the pudding is in the eating. I just fronted up for the Light harmonic geek DAC and I hope to have a good product without a massive output impedance

exvsynz's picture

Well, it really becomes an insane value when you consider the fact that both the tobby and the bobby can be purchased for 400 usd apiece here in Taiwan

tomscy2000's picture

I'm not sure whether it's only valid in Taiwan, or foreign customers can opt for this too, but FSA just announced that for about 1500 NT (~$50 USD, probably a bit more for foreign customers), users can upgrade their Bobby to become a 10W/channel speaker amp as well. If so, the Bobby becomes an even greater value. I've been contemplating getting a small speaker system; this might be a good thing to use.