Firestone Audio have been making steady strides in desktop audio. To complement this year’s long, hot summer, they pushed out two hot amps: the Rubby power amp and the Libby headphone amplifier. Why they are such big news here at TMA is that both mains-powered amps also feature great USB/Optical/Coax and analogue audio inputs. If you can put two and two together, you’ve probably figured out that this means hi-res audio from the iPad through the Camera Connection Kit (CCK). Recently, I`ve forgone the whole computer thing in favour of just this combination. Still, both amps work great with computers, with external DAC`s, and with other Hifi gear. Nevertheless, TMA will keep the iPad slant in this review, but show just what can be done with these two desktop amps.
Build and Package
It has always been hard to fault Firestone Audio`s build quality. Generally, they package their products in high quality aluminium chassises, that if needs be, can be opened quite easily. Both the Rubby and Libby share the same heritage. Now, I don’t suggest grinding into Firestone`s amps with your favourite screw driver kit; you’ve got a two-year guarantee from Firestone, so if anything goes wrong, take your amp back to the dealer or ship it to them; everything`ll be as right as rain in no time.
And there is no way that either amp will be damaged in shipping as both amps come in rather bullet-proof packaging. They pack everything in hard pressure foam (if you order both at a time) and good ol’ fashioned styrofoam for the rest.
The Rubby comes with a pretty beefy power supply that will adapt from 100-240V and travel easily around the world with you. The Libby, on the other hand, transforms in-body and is available at only one voltage rating at a time. Planning on moving from Sweden to Canada anytime soon? You’ll have to get a new step-down external transformer. Firestone could have powered their unit from an external unit, or include a switching supply inside which would make moving a lot easier. I don`t know if the Libby`s background noise (read on) is a result of the power supply or not.
What they didn’t mistake is front-panel ergonomics. Their accessibility especially with regards to volume pots only seems to get better every iteration. The Rubby and Libby volume pots are as fun to play with as the amps are to listen to! Inputs and frequencies are selected on both amps via the front panel. If you have an iPad and a Camera Connection Kit, you’ll only be concerned about 16-bit USB input, and if you have a DDS i2s machine handy, 24-bit USB input. Bpth amps upconvert the signals, so the actual thumbing-around that you`ll need to do is very light.
Back-panel inputs are well thought-out, especially on the Rubby, which follows a logical switch array from power to analogue input. Both amps can be switched on blindly, but the Rubby’s nubby flip switch, which sticks out from the rear left like a proud nose, requires no reach-around. The Libby headphone amp is switched on a little less comfortably: you have to finger-walk past the IEC power cable to the on switch. It is a small complaint, but one that makes me wonder firstly why the two amps, that look so much alike, couldn’t have shared the same great ergonomics and external power supplies.
The other puzzling thing about Firestone’s amps is one of outputs. The Libby Headphone amp sports a decent analogue output, but the Rubby doesn’t. Typically, the power amp is the staple equipment in a lot of audio setups. Without an analogue or digital output of any sort, it can’t be used with Firestone’s own analogue headphone amplifiers, unless, that is, you bypass the Rubby power amp. This decision is downright naughty if you ask me. Right, the headphone amp, Libby, has an analogue output that connects nicely to the Rubby, but the logic seems backward, unless Firestone intend both amps as 100% stand-alone desktop systems.
Both Libby and Rubby (cute names, eh?) can take in analogue signals from RCA or XLR to power your speakers or headphones of choice. But, their mainstay components are their DAC chips. From coaxial, to optical, to USB, they’ve got their bases covered in both 16 and 24-bit word lengths. Only the Libby headphone amp is class-A biased, meaning that theoretically, it sounds better (and gets hotter). NOTE: USB is only good for 16-bit and up to 48kHz, strange since USB can easily handle 24-bit word lengths up to 96kHz (if you have a Mac).
Each bit and frequency setting is finger-selectable from the front panel, and after a lot of thumbing around, I’ve discovered that no matter the word-length of the original source, music will travel to your speaker of choice without hitch. Kudos for newbie music lovers as audio stuff can get tricky.
Mac users, you can connect USB or optical with no hitches. Windows users, you should be able to get buy with USB, though if you want to head up to 96K 24-bit, you may have to jump through a few hoops. The great thing is that both amps can be connected directly to the iPad via the Camera Connection Kit. Till now, we had to rely on iDevice-only DAC converters that had less value than either the Libby or Rubby. Now, thanks to Apple’s foresight, we’ve got way to connect our favourite music/movie/gaming devices to high end gear. Not to mention, the iPad’s understated grey looks great next to either equally understated Firestone amps.
I can’t stress how cool this is. I’ve used dedicated headphone amps before, and DAC’s, but the latter always get stuck in home systems or fed from computers. Now, plug the white nubby Camera Connection Kit into the end of your iPad, feed a USB cable to it, and you’re off. There is nothing simpler than taking your iPad and its CCK to a mate’s to play high-quality music. Now, the iPad’s USB out isn’t a full-fledged USB, making mains or battery-powered amps necessary. Of course, Rubby and Libby play fine.
Both amps sound purty, too, especially as they are liable to be targeted to desktop users who use headphones or sensitive speakers. Typical Firestone, both are high-resolution devices with good emphasis on all frequencies. That said, Firestone’s Libby and Rubby (yes, they share very similar output tendencies), aim for what I will call gritty sonics.
Both output powerful bass lines, enough to Hulk-smash bass weak headphones. It’s not, however, duffy, smooth bass. Both Rubby and Libby shoulder their way around low notes. They are clean and highly defined with slight bumps in the frequencies with sensitive headphones or speakers. While I carried the Rubby from speaker to speaker at local shops, the Libby got off well with my 64Ω Ultrasone DJ1Pro, but ultimately much better with my excellent 600Ω Beyerdynamic DT880 headphones.
The latter pairing is one of power and control. Even with the 600Ω monster, a turn to about 10:30 on the volume pot was more than enough for most music. 12:00 is right out of the equation with any headphone. Both amps` volume pots accelerate like teenage hormones to dangerous levels at the smallest of turns.
I found this funny and tested it by lowering the output of various sources. The volume pot is well-balanced, showing just slight variance between left and right, but after about 12 o’clock on the volume pot, volume increases slowly and distortion can creep in, though only mildly. Firestone should re-think their design and add a LOT more play in their volume pots. Now, if their amps are aimed at new-to-hifi users, this immediate ‘wow’ factor may impress its clientele who can value volume more than overall usability. But I say: more play in the volume pot would allow for easier left-right tuning, and less chance of accidentally blowing your speakers or headphones.
That is all to say that these amps output a LOT of power. The Rubby is certainly enough to power larger, less sensitive speakers, but I think its best target is the desktop where its boxy, powerful sound will give smaller speakers extra oomph.
I really appreciate Firestone’s emphasis on stereo image. Both amps supply wide separation in channels. The Libby is very much like a more powerful Fubar IV. Both amps brute-force their way around any headphone. At the bottom of the chassis, you can select the best output for your headphones, from 32Ω to 250Ω. Don’t let those numbers fool you though, as there is nothing wrong with hooking up a 600Ω load to the Libby: it’s got the power to blow up the DT880 600Ω.
Where it (and the Fubar IV) somewhat fail is when driving sensitive headphones. They drive them fine and output negligible distortion, but the signal can be hairy. Sensitive headphones from Grado to Ultrasone can reveal background noise. It’s not inordinate; rather, the fine grain dusts everything. Anything over 120Ω reveals nothing but the blackest of black signals. Again, I see this amp used a LOT with 300-600Ω headphones where its power and brute force resolution are often-requested items.
The Rubby, however, has no such problem with noise. It was suggested that the Fubar IV could be upgraded by given a better power supply. Since it was outboard, it was a lot easier to do. The Libby has an on-board power supply which is kind of a bugger. Of course, it could just be a problem with the audio circuit amps such as the Woo Audio 3 and Einar Sound VC01i have better-behaved noise patterns.
So, while I would like to rave about both amps, I find enough to cringe over regardin the Libby. It is a fine amp, but it may need an internal makeover to lessen the noise, and an external makeover to conserve eardrums thanks to an over-active volume pot. Oddly enough, the Rubby power amp has no such issues with background noise and sounds great with sensitive speakers.
Both units hit positive price points: these are powerful amps coupled to excellent DAC’s, combinations that often cost much more. Neither USB input supports more than 44.1 16-bit audio, but their other inputs supply at least 96K and 24-bit word length. The Rubby comes away feeling like a more polished amp, but thanks to the lack of an analogue output, unfinished.
The Libby, as powerful as it is, has some unfortunate design decisions attached to it, namely the too-powerful volume pot and the constant grain that covers almost all sensitive headphones.
Firestone continue to hammer away at great price points. Both the Rubby and Libby perform in general terms above my expectations for their price and feature set, and I feel, are good investments. The Rubby is an impressive piece of for desktop audio and the Libby, more impressive from a feature standpoint, comes away as a less thought-out piece of equipment.
Firestone: add analogue/digital output to the Rubby and you’ll have a power amp/DAC that features in home systems, not just desktop systems. Do that and you’ll have a perfect KISS. The Libby needs an outboard power supply, a rethinking of the volume pot, and less noise in the signal. When you can do that, you’ll see a GRAB or a KISS.