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Whilst not running as toasty as the class A Libby, Rubby was quick to demonstrate why she didn't care to. Intermittently and with no apparent cause—sometimes playing fine for a whole day, then only for 10 minutes—she'd elicit clicking distress signals, then retreat into self protection. A very toasty chassis suggested thermal runaway. Though shutting down the amp and rebooting it did not magically reset the chassis temperature, it did initially override the trigger. But the amp clearly wasn't stable.

Experimenting with various placements without success, I suspected a design flaw of insufficient thermal management for TI's digital-direct power-processing chip. Engineering I figured had to revisit the design for improved self cooling.


On appearance, build quality and price meanwhile, Libby and Rubby were clearly competitively positioned to duke it out against the newer upper-crust KingRex equivalents. Those do have the flashier thicker face plates.


Given the likelihood of iPod-type sources on the desk top, the Firestone siblings will raise eyebrows with the A/D conversion of their analog inputs. iPod & Co. already perform their own internal D/A conversion. Except for Wadia's 170i/171i and Onkyo's equivalent docks which extract a digital signal but don't convert it—Peachtree Audio's iDecco and Teac's iPod-direct receivers do apply their own conversion—most iPodders must connect to Libby or Rubby analog. This adds a second round of A-to-D-to-A conversion.


How about Libby as Rubby preamp? The particular featurizations and overlap of the two should see precious few prospective owners actually use them in combination. Libby lacks digital outputs yet Rubby's power chip needs a digital input. Connecting Libby and Rubby in the analog domain as the only practical means involves A/D conversion squared. Meanwhile Rubby duplicates all of Libby's digital inputs. Libby becomes redundant when strapped together. Except that Rubby doesn't do headphones. If you want her for speaker drive but also enjoy headphones, you must add Libby for just that. Clearly the two make a very odd couple if you thought they were meant to play together.



Libby's analog output incidentally isn't variable but fixed. Her volume control only affects the headphones. Those don't mute the RCAs so both outputs are live together. That's sensible for a Libby/Rubby duet where it avoids two volume controls in series while adding one more round of format conversion. On Rubby, a variable output would make for a great subwoofer feed except that she doesn't have one.

In the end, these are two discrete components which, though from the same company, are not really intended to work together. While adding a headphone socket to Rubby would make her 'complete', it'd also negate Libby's need to exist. Firestone was apparently keen on having two distinct models in its catalogue. Fair enough. Those keen on minimal box count like yours truly would still lobby for a single do-it-all box. In this instance, it simply seems too late to press that point.


Wrapping up introductions, Libby's unconventional conversion of the analog input to digital has one suspect that Firestone was more interested in the gimmickry of user-selectable upsampling and word length choices than hifi's mandate of first do no harm.


At the very least their rationale for the conversion sounds peculiar. Inside Libby, how long would a properly engineered analog circuit trace have to be before it began to compromise performance? Most listeners run analog interconnects far longer than Libby is deep.

At this juncture, I alerted Firestone to Rubby's misbehavior and inquired about their respective feature sets. "For Rubby, we already tested your issue and found the problem. We have the solution and will replace your unit with the improved one in a few weeks. Regarding Libby, we define the platform as a pure DAC to work into a preamp or integrated amp. Hence the fixed rather than variable outputs. To play around with the sound and to adjust the sampling frequencies, Libby's analog input must be converted. That was a main criteria based on the demands of our distributors and other ODM/OEM collaborators. We want to reintroduce fun to music listening and offer adjustments beyond just volume control. Lastly, we did investigate the potential of Rubby's power processing chip as also a headphone amp but weren't as impressed with that aspect of its performance so decided on a dedicated headphone amp instead. That became Libby. So you're right, these machines were designed for different listeners and applications and are not meant to be used together."

Rubby actually is what Wadia's far earlier efforts in that sector called a PowerDac. The signal is kept in the digital domain all the way to the loudspeakers. With digital sources outputting a raw digital signal, that's as direct as it gets. Analog signals—natively analog or already converted from digital—require (re)conversion of course. That explains why power dacs haven't caught on en masse yet. Until natively analog sources have died out completely, hardcore audiophiles will resist converting them for power processing. Wadia's newer 151PowerDac mini shows how the concept in the affordable compact sector is starting to make inroads however. That's because with PC sources, the all-digital future is already here.


Firestone's thermal fix for both reissued components was additional heatsinking—Rubby grew one right between the binding posts as shown below—and five or eight perforations per side rail (Libby is rather deeper to have longer rails with more holes).


Here is Libby's new heat sink...


... and the new lateral vents. To do full justice to the digital-direct nature of these boxes with what I consider their natural-born source, I had in the meantime acquired an Onkyo ND-S1 dock to tap the iPod digitally via Apple's authentication chip and outputs it via coax or Toslink and an integral 10ppm clock.

My replacement Libby kept blowing fuses so I reverted to the original one and simply scavenged new side rails just in case.


(Upon arrival, something actually went bump in the second Libby's case. This turned out to be a loosened nut on the toroidal's mounting shaft. The transformer bounced when I shook the enclosure. It was easily tightened with a pair of pliers but a lock nut/washer solution would eliminate this eventuality.)