Jon S
Super Member
Anyone heard of the new FiiO Warmer R2R Tube Buffer DAC? It just got released for USD$349. Looks impressive for the price. It has a 46 watt linear power supply with a toroidal transformer and weighs a serious 6 lbs. The drawbacks are that the VU display LEDs cannot be disabled and that the unit runs pretty hot because of the four JJ E88CC tubes installed. The JJs retail for $100/quad and from what I understand swapping in the Gold Lion E88CCs makes a difference in the sound, making the center more up front while the JJs are more recessed. Also noteworthy is that the reviewer states that the wide soundstage and layered stereo image makes discerning exact positions of sounds, as well as providing a more immersive experience.
Pricing from China's AliExpress is crazy. They are asking anywhere from $500-700 for a unit. I ordered a unit from APOS direct for $349 but unfortunately they are backordered and I don't expect the unit to arrive until February 2026.
From Darko's site:
First: the R2R DAC circuit. Unlike the delta-sigma chips found in most modern DACs, which rapidly switch between voltage levels to approximate the analogue waveform, R2R (resistor-to-resistor) DACs use precision resistor ladders to convert digital bits to analogue voltages directly.
FiiO’s proprietary implementation, the same ladder (I think) found in its K13 R2R, employs 192 thin-film resistors (48 per channel) with 0.1% tolerance. The Warmer R2R defaults to NOS (non-oversampling) mode for a purist approach, but a toggle switch on the back panel engages OS (oversampling) mode, upsampling all incoming digital signals to 384kHz before decoding.
Connectivity on the Warmer R2R covers the essentials: USB-C (supporting up to 32-bit/384kHz PCM and DSD256), TOSLINK and coaxial inputs, with both single-ended RCA and balanced XLR outputs that can (apparently) be run simultaneously.
Running on a ±28V supply, these tubes inject what FiiO calls “sweet, organic tube flavour” into the signal path. However, these tubes work in tandem with op-amps that handle the heavy lifting of current delivery and impedance matching. The tubes are there only to impart their harmonic signature. It’s a hybrid approach that maintains the tubes’ character without the typical tube amplifier limitations of high output impedance or limited drive capability.
Feeding the Warmer R2R’s circuitry is a 46W ‘low-noise’ toroidal transformer — some might call this ‘proper old-school’ linear power.
James Chung, FiiO’s CEO, has taken a leaf out of Jason Stoddard’s book to share the story behind the Warmer R2R DAC on Head-Fi. It’s a tale of nostalgia, supply chain difficulties and why portable tube gear isn’t happening for FiiO anytime soon. And we’re re-telling Chung’s story here (with FiiO’s explicit permission) because of the sky-high interest in the Warmer R2R’s news announcement.
Two years ago, Chung started collecting vintage equipment. That nostalgia kick sparked FiiO’s entire retro series: the CP13 portable cassette player, the TT13 turntable and the DM13 portable CD player. He admits these are “true sunset products with zero big commercial upside” where sourcing parts is “a nightmare.” But here’s the thing: this retro series has apparently revealed a community of fans that spans generations. Audiophile catnip isn’t just for old timers.
Chung says he is looking beyond the specs and the measurements. “Sure, these technologies are outdated on paper, but they have this irreplaceable charm,” he notes. Cassettes, vinyl and tubes might lag behind digital gear on measured performance, but “that unique flavour? Digital can never fully replicate it.” His philosophy is simple: “The real world is still analogue at its core.”
With transistors and integrated circuits dominating for decades, tubes have become relics. Power-hungry, bulky and hot-running, they’ve been relegated to the tiniest of audiophile niches. The way the Chinese company’s main man tells it, most tube amplifier makers today survive on new ‘old stock’. FiiO needed an ongoing supply of tubes, and in bulk.
But Chinese tube manufacturers apparently wouldn’t play ball. “Some wouldn’t even meet with us, others had limited models and capacity — or [their] pricing just didn’t work,” Chung recalls. The solution came from Slovakia: JJ Electronic, one of the last manufacturers still producing the E88CC tubes at volume.
For a company used to sourcing everything domestically in China, importing tubes meant navigating customs and international logistics for the first time. “The first time is always the toughest,” Chung admits.
Portable tube products typically use thumb-sized tubes like the JAN6418 or the KORG NuTube. They’re tiny, low-power and battery-friendly. But Chung is somewhat blunt about their limitations: “The ‘valve vibe’ feels watered down, not as rich or soulful.” Then there’s the microphonics: the unwanted noise generated by vibrations. “With FiiO’s sky-high standards for reliability and user experience, we’re not there yet.”
Desktop tubes like the JJ E88CC are, according to Chung, different beasts entirely. “They look like honest-to-goodness lightbulbs,” he says, comparing them to their miniature cousins. The size difference, according to the FiiO CEO, translates directly to sound quality.
Tube power amplifiers need higher voltages, which means pricier tubes. Those pricier tubes demand beefier power supplies plus “massive chokes to tame noise.” Quality tube amplifiers also require output transformers that are “expensive, finicky to wind and full of secrets.” Different wire gauges, materials and winding techniques can make or break the sound.
This explains why many modern “tube” amplifiers are hybrids: tubes for voltage amplification up front, transistors for the heavy lifting. “A total cost saver,” Chung notes.
The Warmer R2R reportedly sidesteps these complications: by using tubes only in the buffer stage, FiiO keeps the price accessible whilst delivering a tube’s flavour. As a DAC, it also plays nicely with existing setups: active loudspeakers and headphone amplifiers, plus passive loudspeakers driven by integrateds. Chung calls it “a world of flexible listening scenarios.”
FiiO’s approach is seemingly clear: “We always start from the user’s perspective, prioritising quality, reliable supply and stable pricing.” This isn’t high-end boutique hardware where only a handful of units are manufactured each year. The Chinese manufacturer’s high-volume, low-margin model means unstable component sourcing would be catastrophic to its bottom line. The exception? Massive stockpiles, like the 100,000 Japanese surplus displays used in the original X1 DAP.
The Warmer R2R represents something personal for Chung. After three decades in the audio business, he’s finally brought tubes to FiiO’s lineup. Not because they measure better or because they cost less, but because he reckons some listening experiences can’t be quantified by an Audio Precision analyser. And also because Chung is confident that there is sufficient consumer demand ‘out there’ for tubes in an R2R DAC. The huge number of clicks from Google News to this site yesterday confirms that confidence. I didn’t call it the holy trinity of audiophile catnip for nothing.
Pricing from China's AliExpress is crazy. They are asking anywhere from $500-700 for a unit. I ordered a unit from APOS direct for $349 but unfortunately they are backordered and I don't expect the unit to arrive until February 2026.
From Darko's site:
R2R ladder
First: the R2R DAC circuit. Unlike the delta-sigma chips found in most modern DACs, which rapidly switch between voltage levels to approximate the analogue waveform, R2R (resistor-to-resistor) DACs use precision resistor ladders to convert digital bits to analogue voltages directly.
FiiO’s proprietary implementation, the same ladder (I think) found in its K13 R2R, employs 192 thin-film resistors (48 per channel) with 0.1% tolerance. The Warmer R2R defaults to NOS (non-oversampling) mode for a purist approach, but a toggle switch on the back panel engages OS (oversampling) mode, upsampling all incoming digital signals to 384kHz before decoding.
Connectivity on the Warmer R2R covers the essentials: USB-C (supporting up to 32-bit/384kHz PCM and DSD256), TOSLINK and coaxial inputs, with both single-ended RCA and balanced XLR outputs that can (apparently) be run simultaneously.
Tube buffer
Second: those four JJ Electronics E88CC tubes from Slovakia aren’t amplifying anything. They’re acting as a buffer stage, adding harmonic richness without gain. A tube buffer like this colours the sound with even-order harmonics — the pleasant kind that adds body to, say, a piano’s sound.Running on a ±28V supply, these tubes inject what FiiO calls “sweet, organic tube flavour” into the signal path. However, these tubes work in tandem with op-amps that handle the heavy lifting of current delivery and impedance matching. The tubes are there only to impart their harmonic signature. It’s a hybrid approach that maintains the tubes’ character without the typical tube amplifier limitations of high output impedance or limited drive capability.
Feeding the Warmer R2R’s circuitry is a 46W ‘low-noise’ toroidal transformer — some might call this ‘proper old-school’ linear power.
VU meters
Third: the backlit twin mechanical VU meters. Digital meters might be more accurate, but they’re also synthetic. Mechanical meters move with the music’s dynamics in real-time, their needles excited by electromagnetic force (and not software).James Chung, FiiO’s CEO, has taken a leaf out of Jason Stoddard’s book to share the story behind the Warmer R2R DAC on Head-Fi. It’s a tale of nostalgia, supply chain difficulties and why portable tube gear isn’t happening for FiiO anytime soon. And we’re re-telling Chung’s story here (with FiiO’s explicit permission) because of the sky-high interest in the Warmer R2R’s news announcement.
The nostalgia factor
“I’m a ’70s kid who’s basically semi-retired now,” Chung explains. Whilst his contemporaries are golfing or scaling mountains, the FiiO boss spends his downtime “tinkering with HiFi gear.” The way the Chinese company’s main man tells it, he’s been at this for thirty years, having skipped careers in rockets and aeroplanes because of his audio obsession. “Little did I know it’d turn into a lifelong career.”Two years ago, Chung started collecting vintage equipment. That nostalgia kick sparked FiiO’s entire retro series: the CP13 portable cassette player, the TT13 turntable and the DM13 portable CD player. He admits these are “true sunset products with zero big commercial upside” where sourcing parts is “a nightmare.” But here’s the thing: this retro series has apparently revealed a community of fans that spans generations. Audiophile catnip isn’t just for old timers.
Chung says he is looking beyond the specs and the measurements. “Sure, these technologies are outdated on paper, but they have this irreplaceable charm,” he notes. Cassettes, vinyl and tubes might lag behind digital gear on measured performance, but “that unique flavour? Digital can never fully replicate it.” His philosophy is simple: “The real world is still analogue at its core.”
Sourcing tubes
Finding tubes for the Warmer R2R reportedly proved harder than expected. Chung recalls his first proper tube experience: “It was pure magic, like something straight out of heaven that you rarely get to experience on earth.” That memory reportedly drove a 30-year dream, but making it a reality for FiiO meant confronting modern supply chain realities.With transistors and integrated circuits dominating for decades, tubes have become relics. Power-hungry, bulky and hot-running, they’ve been relegated to the tiniest of audiophile niches. The way the Chinese company’s main man tells it, most tube amplifier makers today survive on new ‘old stock’. FiiO needed an ongoing supply of tubes, and in bulk.
But Chinese tube manufacturers apparently wouldn’t play ball. “Some wouldn’t even meet with us, others had limited models and capacity — or [their] pricing just didn’t work,” Chung recalls. The solution came from Slovakia: JJ Electronic, one of the last manufacturers still producing the E88CC tubes at volume.
For a company used to sourcing everything domestically in China, importing tubes meant navigating customs and international logistics for the first time. “The first time is always the toughest,” Chung admits.
Why not portable?
Chung addresses the elephant in the room: why not portable tube gear? The answer involves physics — and FiiO’s standards.Portable tube products typically use thumb-sized tubes like the JAN6418 or the KORG NuTube. They’re tiny, low-power and battery-friendly. But Chung is somewhat blunt about their limitations: “The ‘valve vibe’ feels watered down, not as rich or soulful.” Then there’s the microphonics: the unwanted noise generated by vibrations. “With FiiO’s sky-high standards for reliability and user experience, we’re not there yet.”
Desktop tubes like the JJ E88CC are, according to Chung, different beasts entirely. “They look like honest-to-goodness lightbulbs,” he says, comparing them to their miniature cousins. The size difference, according to the FiiO CEO, translates directly to sound quality.
Why start with a DAC?
Why start with a DAC rather than a full-blown tube power amplifier? Chung breaks down the brutal economics.Tube power amplifiers need higher voltages, which means pricier tubes. Those pricier tubes demand beefier power supplies plus “massive chokes to tame noise.” Quality tube amplifiers also require output transformers that are “expensive, finicky to wind and full of secrets.” Different wire gauges, materials and winding techniques can make or break the sound.
This explains why many modern “tube” amplifiers are hybrids: tubes for voltage amplification up front, transistors for the heavy lifting. “A total cost saver,” Chung notes.
The Warmer R2R reportedly sidesteps these complications: by using tubes only in the buffer stage, FiiO keeps the price accessible whilst delivering a tube’s flavour. As a DAC, it also plays nicely with existing setups: active loudspeakers and headphone amplifiers, plus passive loudspeakers driven by integrateds. Chung calls it “a world of flexible listening scenarios.”
The bigger picture
However, the Warmer R2R is apparently a long way from being FiiO’s tube endgame. “You can expect more FiiO products featuring authentic vacuum tubes to hit the market soon, with even more variety,” Chung promises.FiiO’s approach is seemingly clear: “We always start from the user’s perspective, prioritising quality, reliable supply and stable pricing.” This isn’t high-end boutique hardware where only a handful of units are manufactured each year. The Chinese manufacturer’s high-volume, low-margin model means unstable component sourcing would be catastrophic to its bottom line. The exception? Massive stockpiles, like the 100,000 Japanese surplus displays used in the original X1 DAP.
The Warmer R2R represents something personal for Chung. After three decades in the audio business, he’s finally brought tubes to FiiO’s lineup. Not because they measure better or because they cost less, but because he reckons some listening experiences can’t be quantified by an Audio Precision analyser. And also because Chung is confident that there is sufficient consumer demand ‘out there’ for tubes in an R2R DAC. The huge number of clicks from Google News to this site yesterday confirms that confidence. I didn’t call it the holy trinity of audiophile catnip for nothing.
see below