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Firestone Tobby

  1. project86
    Nice DAC for detail lovers
    Written by project86
    Published May 18, 2013
    Pros - Excellent clarity without being too edgy, expansive soundstage, USB input is top notch
    Cons - Bright LEDs on front panel, no DSD support (for now), doesn't sound as good using SPDIF inputs and RCA outputs

    The DAC market is clearly exploding. Seems like every week or so we hear of a new model being launched. Many of them look quite nice, with good specs and plenty of features. Some of them come from established brands like Benchmark, NuForce, Parasound, and PS Audio. Others come from relatively new, smaller (but growing!) companies like Matrix, Schiit, Yulong, and Resonessence Labs. Lots and lots of good choices can be had these days, and it's a great time to be in the market for new gear.
    These new DACs tend to fall into certain categories. There's a big demand for "budget" gear, with numerous brands vying for your money in the $250-400 range, give or take a few hundred. There's even the little Schiit Modi for $99. On the other end of the spectrum, lots of new high-end models have launched within the past year, from the Auralic Vega to the Metrum Hex to the MSB Analog to Calyx Femto... I could go on and on. These multi-thousand-dollar units tend to be well received (for the most part). My attitude is that they had better be, considering the price. 
    Lately, my favorite market segment is the "mid-priced" range, which I define as being above five or six hundred dollars but below $2,000. In fact I might say $1,500 is a better cutoff point though it's hard to choose a specific number. Either way, I've been very pleased with this category. Performance here comes very close to the true high-end DACs for a fraction of their prices, and features are often very comprehensive in this range. I've recently reviewed the NuForce DAC-100 and the Matrix X-Sabre and really enjoyed both of them. Older models, still very good and worth attention, come from Anedio, Yulong, and Violectric among others. And I've not even scratched the surface of this category - I have yet to hear the Mytek Stereo192 DSD, Teac UD-501, Schiit Gugnir, or any number of other candidates. But here I am bringing up another one.
    The subject of this review is the Firestone Audio Tobby which, at $1100, fits squarely into that "mid-priced" category. You may recall Firestone from their line of compact devices such as the Fubar and Spitfire. In the past they seemed to focus on small headphone amps and DACs, though they did have a few other things such as the Big Joe integrated amp, Mass preamp, Supplier PSU, and Bravo reclocker. All of these little units fit squarely in the budget category, and many of them were well respected around here. Recently Firestone seems to be moving upscale - this Tobby DAC, along with the matching Bobby balanced headphone amp ($799), are a whole different class of equipment. 
    As viewed from the front panel, the Tobby is very obviously a DAC. It's got no headphone jack or volume knob - this is a pure DAC with no added functionality. The unit measures roughly 9 inches wide, 8 inches deep, and 2.5 inches tall, and weighs approximately 5 pounds give or take. Build quality is on the high side and brings to mind the Yulong Audio D100, with the brushed aluminum enclosure in black and a thick silver faceplate. It's not quite as substantial as the solid CNC machined Matrix X-Sabre, but it's definitely on par with others in this price class. 
    The front panel is dominated by small buttons and LED lights. On the right side is a bank of four buttons - Source, Resample, Bit, and Pass. Source obviously toggles from one input to the next. Resample is interesting as it engages the upsampling feature but doesn't require integer multiples like nearly all other DACs do. I'll discuss that more later. Bit engages word length padding to 24-bits. Pass is short for passthrough which is just like it sounds, allowing the signal to pass through at its native rate. The left side of the panel has LED indicators keeping track of what the machine is doing. It's all pretty self explanatory. The left side LEDs help you keep track of which options are being used, in a rather bright fashion. 
    Around back we find a good amount of connectivity: USB, coaxial, Toslink, and AES/EBU inputs all support up to 24-bit/192kHz signals. Outputs come in RCA as well as XLR for balanced operation. There is a standard IEC cable receptacle and the unit is marked for 115V operation though it looks as if that can easily be switched inside the case. 
    But all this explaining is boring for you to read, and frankly, it's not very fun to write either. So let's go on a journey with pictures to examine the rest of the design.
    The enclosure has a nice system using "rails" to connect the top and bottom parts together


    Right side

    Left side

    Venting (it doesn't get hot at all though)

    Input section

    Output section

    I believe voltage is adjustable internally, despite what the label says

    Bottom feet

    Another view of the feet in action, pardon the dust


    Internally there's a decent amount going on here. The USB section uses the XMOS chipset in what appears to be a proprietary implementation - it looks very different from the Stello U3 or Matrix X-Sabre or several other XMOS-based designs I have here. But it does still use the SMSC USB3343 USB transceiver which is called for in the XMOS reference board. SPDIF inputs are handled by the AKM4113 and all inputs pass through an SRC4193 asynchronous sample rate converter. Firestone must have preferred using the AKM digital receiver paired with the stand-alone ASRC chip rather than using the SRC4392 which is a combined ASRC and DIR package.
    AKM DIR and TI sample rate converter

    USB section with the XMOS chip has a discrete 26mHz clock for the transceiver function
    but receives 44.1 and 48kHz clocking via the multiclock generator which I'll discuss shortly

    SMSC USB transceiver is the new USB3343 model 


    Also on board is a TI PLL1707 which uses a 27MHz reference clock and generates up to four independent system clocks as needed by the system. This is fairly different - I've never seen it used before in any of my audio gear. The datasheet indicates a 50ps RMS jitter figure which is slightly lower than that of the AKM DIR (70ps), but nowhere near as low as the better oscillators from Crystek and others. Those tend to be rated in the single digits or fractions of a digit. How does this affect the overall jitter spec of the system? I don't know, as Firestone doesn't release that info. To make matters even more confusing there's also a Xilinx FPGA which is probably used for further jitter reduction among other things. 

    Xilinx FPGA

    PLL1707 clock generator, as you can see it ties in to the FGPA


    The Tobby is a fully balanced, dual-mono design. That means aside from the input stage, it essentially has two of everything: dual PCM1794 DACs, mirrored sets of capacitors, separate stages for I/V conversion and LPF each using a trio of socketed OPA2604 opamps, a relay on each XLR jack, etc. Both channels share a single largish toroidal transformer but have separate regulation stages from there on out. Conversion from balanced to single ended is done at the very last stage, handled by another OPA2604 and a separate relay. 
    View from rear

    View from front

    Can you spot the parallel dual-mono signal path?

    Ring Core brand Toroid

    Again, mirrored for each channel


    PCM1794, the current top of the line Burr Brown DAC (along with sibling PCM1792)

    Output stage with socketed opamps

    Relays on the outputs, single ended conversion in the middle

    One last interesting bit - the power supply has an AC to DC converter which puts out a 5Vdc signal. I'm not quite sure about the implications. Firestone tells me it is used to power the various microcontroller chips on board, and allows for extremely low power consumption in standby mode. I thought it might also be used to power the USB section but Firestone seemed to indicate that was not the case. Yet due to the slight language barrier when it comes to technical discussions, I can't be sure either way. 


    On DSD - I asked Firestone about DSD playback and they advised it was something they are looking in to. I'm not sure if that means this unit could be updated down the line to accept DSD signals, or if they would need to release an updated model. From what I can tell, the Tobby is theoretically capable of handling DSD. All the pieces are in place - the XMOS USB input can definitely handle it, and the PCM1794 DAC chips may or may not be capable as well - the PCM1794 is simply the hardware controlled version of the PCM1792, but the spec sheet doesn't list DSD while the PCM1792 does. Interesting. The real limiting factor could be the ASRC reclocking stage which definitely isn't equipped to handle DSD streams, but it may be possible to configure a true "pass through" for DSD signals. In any case, this is all speculation at the moment. I wouldn't buy the Tobby expecting DSD to come in the near future. But it would be a nice bonus if it did show up.
    This is the equipment I used to evaluate the Firestone Tobby DAC:
    Transports: Cambridge 740C, Auraliti PK90 USB with NuForce LPS-1 linear power supply, Acer Aspire netbook, Audiophilleo AP1 with PurePower 
    Amps: Firestone Bobby, Violectric V200, Auralic Taurus, Icon Audio HP8 MkII, Yulong Sabre A18, Analog Design Labs Svetlana 2, Yulong A100, Stax SRA-12S
    Headphones: Stax SR-007mkII, Sennheiser HD800, HiFiMAN HE-500, beyerdynamic T1, Audeze LCD-2.2, Thunderpants, JH Audio JH13FP, Heir Audio 8.A, Westone ES5, Frogbeats C4, Lear LCM-5, Cosmic Ears BA4
    Power Conditioning: PS Audio P3 Power Plant, Yulong Sabre P18
    Cables: Cabledyne Reference AC cables, Cabledyne Reference Silver XLR and RCA interconnects, Cabledyne Reference Silver SPDIF, Charleston Cable Company Auric USB, Headphone cables from Charleston Cable Company and Toxic Cables
    Speaker Setup: JF Digital HDM-03S music server, NuForce HAP-100 preamp, NuForce STA-100 amp, Sjofn (the clue) monitor speakers on Sanus NF30 Stands, Charleston Cable Company AC cables/interconnects/speaker cables
    I let the Tobby burn in for well over 100 hours prior to doing any serious listening.
    Auralic Taurus

    Lots of Cabledyne Reference cables

    Stax, Thunderpants, HE-400

    T1, LCD-2

    HD800 with Toxic Cables Scorpion balanced cable, Icon Audio HP8

    Firestone Bobby 


    The Tobby immediately stuck me as a neutral yet slightly analytical DAC. And I mean that in the nicest possible way. Clarity was excellent, leading edges were very defined, and the whole presentation seemed nicely detailed and transparent. After months of listening and rigorous A/B comparisons with other high quality DACs, that general description still applies. 
    First off - let's be perfectly clear: this is not a bright DAC. It's not thin either. Sure, compared to some warmer and more lush sounding designs, the Tobby might come off as being a bit light in the deeper bass regions, or as having a detail oriented sound as opposed to a more flowing and breezy presentation. But I wouldn't characterize the Tobby as being objectively bright by itself. It's largely neutral overall with just a slight focus on speed and accuracy. 
    To help clarify, I'll throw out some words that do apply to the Tobby - Airy. Effortless. Fast. Clean. Spacious. Tonally Accurate (OK that's two words, sorry!). Some words that don't apply to the Tobby - Brittle. Shrill. Harsh. Cold. Again, I can't stress enough how this is a mild flavor rather than a huge coloration. Consider it a bit of character in an otherwise neutral DAC. And while this flavor may be the deciding factor for some people choosing (or not choosing) the Tobby over a competing model, it isn't an overwhelming characteristic.
    It's probably best to get into some musical examples and direct comparisons. I really love guitars through this DAC - from John Fahey to Sungha Jung, I'd say the Tobby is perfect for this type of music. The transients are strikingly clear, and it really feels like it couldn't get much better - assuming of course that the rest of the chain is up to the task. When I use my Icon Audio HP8 single ended triode amp and the Sennheiser HD800, it seemingly goes beyond a "clear window" situation and is more like "they are in the same room as me". Pretty nice for an $1100 unit - that's certainly not cheap, but in the grand scheme of things it isn't super expensive either. 
    I also really dig the Tobby with classical music. The soundstage is expansive, the imaging tight and accurate, the micro-details plentiful. It's pretty much everything you could ask for in a DAC at this price. I played a wide variety of music from Aaron Copland to Zoe Keating and everyone in between - Hayden and Shostakovich, Holst and Wagner, it all sounded very immersive. Some potentially bright recordings like the XRCD release of Albaniz: Suite Espanola come across as being just shy of too bright at times. It wouldn't be a stretch to push it over the edge with the wrong amp and/or headphones. But in most cases it stayed well controlled and sounded very convincing.
    Switching to other types of music, I found that I enjoy some rock and metal more than others. The Tobby excels with technical metal and that sort of thing. I'm not a fan of the ultra-specific labels for each sub-genre - sludge metal versus doom metal versus post-thrash groove metal - but I am a fan of metal in general, and the Tobby seems well suited for a good portion of it. Bands with a more technical sound and reasonably high recording quality (think Meshuggah for example) sound excellent with a Tobby-based system. Older Metallica and Slayer and Megadeath sounds great as well. The Tobby gives special insight into details like cymbal decay without over-analyzing, and still maintains a good sense of rhythm and drive. On the other hand, it's ruthless on some recordings. For example, I have a hard time with Mastodon's Leviathan, which is an album I love but find requires a more sympathetic pairing. Also some older metal such as King Diamond is a bit cold sounding and the Tobby certainly doesn't warm it up. That same experience translates to a lot of classic rock as well - it sounds very accurate and clean, but could maybe use a little more drive. Or maybe not, depending on your preferences. 
    Let's talk synergy for a minute. There is some gear that I'd consider bright or harsh (or both), at least under certain conditions. Here's a partial list broken down by category:
    CD Players/DACs: Cambridge 740C, Yulong D100 (original version), Benchmark DAC 1, Antelope Zodiac, Audiolab M-DAC, PS Audio NuWave
    Amps: Gilmore GS-1, Yulong A100, Music Hall ph25.2, NuForce HDP (amp section), Meier Concerto
    Headphones: Sennheiser HD800, AKG K701 and variants, lots of models from beyerdynamic, most Grados, Sony SA-5000, Etymotic ER4S
    While assembling a system, I probably wouldn't want to use more than two components off this list. So for example if I used the Yulong D100 DAC paired with the Gilmore GS-1 - both excellent products on their own - I'd rather round out the system with my LCD-2 or Thunderpants or HE-500 rather than anything off the above headphone list. Or when I play CDs with the Cambridge 740C and listen with the HD800 or T1, I prefer a warmer amp in the chain, be it tube or solid state. Hopefully you get the picture. The Firestone Tobby would fit in to the list above - not as the worst offender mind you, but I still don't love it with the Yulong A100 and the HD800 - there really can be too much of a good thing, and that combo just focuses too much on details rather than musical flow. But when I pair it with my slightly warm Violectric V200, or the Yulong Sabre A18, or the Icon Audio HP8, or the matching Firestone Bobby balanced amp, good things happen. Spoiler alert - the Bobby is a very nice sounding and neutral amp, review coming soon at InnerFidelity. 
    I listened on my speaker setup as outlined above. It's a nice system but my (untreated) room is clearly the biggest limitation. Still, I really liked what the Tobby did for it. Before inserting the Tobby into the chain, I had been using the analog outs of my JF Digitial HDM-03S music server. That device is no slouch - overbuilt power supply, dual Wolfson WM8741 DACs, adjustable digital filters, quality opamps in a well-designed output stage. But using it as a transport to feed the Tobby DAC brought a more lively, focused presentation, with no loss in dynamics. My Sjofn speakers have a really smooth top end but are still very capable of revealing fine details and the Tobby really brought them to life in that area. Midrange seemed to blossom too, and soundstage was equally large but became more precise. And with no real downsides to speak of. 
    In terms of inputs and outputs: based on the design, I was worried the RCA outputs would be very compromised in comparison to the balanced outs. The extra stage for single-ended conversion seems to have been well implemented, so it's not a major downgrade. While I do still find balanced mode brings out the most of this unit, the RCA connection is not far behind. There's a small penalty to be paid in terms of transparency, but the general sound signature doesn't change. I've heard units like this where single-ended mode takes a hit in low frequency extension and thus causes the unit to sound brighter overall. The Tobby would not do well if that were the case - thankfully it isn't. Ultimately I'd say users limited to RCA inputs on their amp should still find Tobby to be a compelling choice. If they later upgrade to a balanced amp, it will just be that much better.
    For inputs, I felt like USB was generally superior to the other options. It didn't seem to care if I used a basic laptop, or my Auraliti PK90 with the high-end SOtM USB card, it always sounded the same to me. This shows the Tobby as being very non-source dependent - at least in terms of USB - which is a good thing for a lot of users. Less jumping through hoops to extract the best sound. I tried my Audiophilleo AP1 with PurePower on the coaxial input and was able to just match native USB performance, but not exceed it. Using a Cambridge 740C as transport netted a slight loss of dynamics and flattened out the soundstage for a less engaging performance. Apparently there's still a bit of source dependence when it comes to non-USB inputs. Toslink and AES/EBU sounded fine but I don't have a lot of devices to try those with so I can't comment further. Bottom line is that most users will connect over USB and Firestone rewards them with the best sound this DAC is capable of. 
    Lastly, we should talk about the resampling options. Most DACs automatically apply their upsampling, bringing the sample rate up to whatever frequency they feel is best in their particular design (it's usually somewhere between 90kHz and 192kHz, though not always). Occasionally we get the option of bypassing that upsampling. Rarer still, but sometimes available, is the option to choose upsampling - a 48kHz signal can stay native or else go to 96kHz or 192kHz. The Tobby goes a step further to become the most "configurable" DAC I've yet experienced. It allows basically any signal to be brought to nearly any sample rate or bit depth. Have a 16-bit/48kHz track and want to use the "traditional" rate of 24-bit/192kHz? You certainly can. But you can also keep it at 16-bit if you want, or use a non-integer sample rate like 88.2kHz. Want to downsample a 96kHz track to 48kHz or even 44.1kHz? No problem. The sonic differences between all of these are surprisingly small. Though my brain was telling me these wacky non-standard upsamples or downsamples should sound bad, my ears had a hard time telling them apart. Apparently the FPGA plus ASRC plus multiclock generator makes this less of an issue than I would have anticipated. Sometimes I thought I had figured out a pattern where certain sample rates sound this way or that way.... but then a counter example would present itself and I'd be back to square one. In the end I mostly used the "typical" options just so I could relax, stop focusing on any possible issues, and enjoy the music. Perhaps more time spent with the Tobby as my only DAC would help me get to the bottom of this phenomenon. 
    Keep in mind that I used the stock OPA2604 opamps for this evaluation. Firestone had the insight to make all seven opamps socketed which means they can be swapped out at your leisure. Due to the balanced design you would always want the left and right side to mirror one another, so at least six of the same opamps should probably be used. That last opamp, used for single ended output, could probably be different without causing any trouble. I very briefly auditioned the Tobby with a few other opamps - the usual suspects like AD797, LM4562, and LME49720, and it did hint at being susceptible to changes in the sound. I thought I heard some things I liked and some other areas that I didn't. But I didn't have time to explore this in depth - even if I had time, I mostly have just a few of each opamp rather than six. This again is one of those areas where a long term owner would be a better judge than even the most thorough reviewer. All I can do is point out how the OPA2604 is generally considered a quality opamp, and leaving the door open to further rolling is a wise move on the part of Firestone. 
    The Firestone Tobby, at $1100, is priced right in the middle of some very strong competition. Let's take a look at a few to see how it compares.
    Yulong Sabre D18 ($699): The D18 is kind of similar to the Tobby in that it has a mild coloration to it. But they go in opposite directions, with the D18 being on the warm and smooth side while Tobby is slightly on the quick and detailed side. I feel like the Tobby extracts more fine detail, while the D18 better captures the flow of the music. Both are quite good and I could happily live with either - the difference comes down to system synergy. With a potentially edgy system, using a neutral or brighter amp with the beyer T1 or an Audio Technica W1000X or Etymotic ER4S, I might prefer the D18 to smooth things over a bit. But if I had an LCD-2 or HE-400 or Heir 8.A, all on the warmer side, I would rather have the Tobby in there digging out the maximum amount of detail. 
    Both of these DACs sound better from the balanced outputs than the RCA outs, but the difference is smaller with the Tobby. Interestingly, both DACs present a similarly large soundstage, despite their differences in character. The Yulong initially seems to have a major price advantage, but that gets reduced to some degree when you factor in a high quality USB to SPDIF solution (D18 has no USB input). Tobby already has USB covered - quite well in fact. Ultimately these are both very nice DACs that reach for very different sound signatures. The one that you like best will be determined by your system and your preferences.
    Matrix X-Sabre ($1100): The X-Sabre is a beast of a DAC. It's got all the playback capabilities you could ever ask for with DSD and DXD support over USB. It's got extreme build quality that frankly puts most competitors to shame. And those cool blue front panel LEDs are so much more well done than the blazing lights on the Tobby. In terms of sound though, the Tobby again offers a fresh perspective that's different enough to be worthwhile. I end up liking the Tobby more when used in my speaker rig, and the X-Sabre more when used with most (but not all) of my headphone gear. 
    The X-Sabre has a beguiling midrange presentation that makes the Tobby seem a little lifeless in comparison. It's one of those A/B things where you don't hear any deficiency until you make the direct comparison. After the comparison, going back to normal listening, the deficiency disappears. Weird. As a counterpunch, the Tobby makes the X-Sabre seem a little slow and veiled in the upper registers, again only during direct comparisons. This is not a problem - and actually sometimes welcome - with lesser recordings, but with "audiophile" quality music it becomes a clear benefit for the Firestone unit. And again, after A/B comparisons, the X-Sabre doesn't sound veiled in the least. Funny how that works. 
    Both units share their USB superiority compared to other inputs. Clearly both companies recognize their core audience and the likelihood that USB will be the primary source for these DACs. While the Tobby sounds best via XLR output, the X-Sabre is equally adept through its RCA outs. So that's something to consider. Ultimately, and I realize this sounds like a cop out: these units will each appeal to a different user... my preferences lean more toward the X-Sabre type signature in general but I recognize that a large contingency of folks exist who would be happier with the Tobby instead. 
    NuForce DAC-100 ($1,095): The DAC-100 is very different animal. While the Tobby, like the X-Sabre, is a pure DAC, the NuForce is a DAC, preamp with remote, and headphone amp all rolled into one compact box. So in terms of functionality it has a big lead. The DAC-100 is limited to single-ended outputs though, which could be a disadvantage for some users. 
    The Tobby and the DAC-100 both have a lively top end that manages to not overdo it. But they go about their presentation in different ways. The Tobby is more elegant, sophisticated, "pretty" sounding for lack of a better word. It's got clean, tight bass that always maintains composure no matter how hard it hits. One gets the sense that Firestone engineers value a clean sound with a sense of restraint, and deliberately made sure their device would never give loose, sloppy bass. The DAC-100 is more muscular, with more drive and gusto. It's got a sense of excitement and dynamics, and it certainly doesn't hold back when it comes to low frequencies. The old school audiophile in me says this difference in bass presentation is predictable by glancing at the power supplies, and simply adding up the capacitance. But I've heard my little Violectric V800 equal or surpass the Audio GD Reference 7 in this area, the latter having a massively overbuild power supply, so I no longer think that approach is always the correct one. Regardless, once again the two units appeal to different users. In cheesy audiophile terms, the Tobby is more "effervescent", the DAC-100 more "bold". They compete well with one another and make it that much hard to choose a clear winner.
    PS Audio NuWave ($999): To my ears, the Tobby is everything the NuWave tries to be, but fails. It's got a similar tonality overall but with less sharpness in the upper mids and highs, more believable top-end extension and air, and far more satisfying low frequency extension. I'm starting to think the NuWave I have on hand might be faulty.... but I've chatted with a few other users who hear it just the way I do. Some people on the forums really enjoy it but to me it seems less a case of sound signature preference and more a case of general capabilities. The Tobby just sounds better, cleaner, more accurate, more focused, without being annoying. If I was Firestone Audio I'd bring a NuWave to every show and meet I attended, and allow people to A/B them directly.
    I could go on and on, but I don't think it's necessary. Hopefully you get the point by now - Firestone clearly had a specific sound in mind for this unit, and I think they've achieved what they set out to do. As a result they end up with a great sounding DAC that has enough broad appeal where most people should like it well enough, but enough of a specific character where some people will really love it. 
    Has Firestone Audio shown themselves worthy of selling gear in the ~$1k price range? Based on my observations of the Tobby DAC and Bobby amp, I'd say yes. Rather enthusiastically at that. The Tobby is well designed, smartly executed, and ultimately sounds great. It doesn't blow away fellow competitors in the price range but neither is it blown away, instead offering a worthwhile counterpoint to some of those smoother, warmer models which give less focus on detail. For me, the Tobby brings back memories of the Benchmark DAC 1 - the good memories, which at the time were always tempered by fatigue. The Tobby manages similar levels of detail but to my ears sounds less grating in the process. 
    This is a truly enjoyable DAC no matter how you slice it. Even in a worst case scenario, using the "inferior" SPDIF inputs and RCA outputs, it still manages to sound pretty good. When paired with the right music and the right equipment though, it approaches reference quality for a fraction of what that normally would cost. I've got an Esoteric D-07x sitting here right next to the Tobby and at $5,000 I'm struggling to find it superior in any category. Obviously it looks quite nice, and has more brand name appeal, but that's about the extent of it. I'd say this reflects somewhat poorly on Esoteric, but  also rather favorably on Firestone Audio. If this type of signature gets you going, the Tobby DAC is absolutely worth a listen.