Uploaded February 2026 | Updated September 2026, 2 weeks ago
Thanks to FiiO for sending the Warmer R2R for review!
Buy from Apos Audio (affiliate link): https://apos.audio/products/fiio-warmer-desktop-r2r-tube-buffer-and-dac?sca_ref=1448954.julYPU81dF
FiiO Product Page: fiio.com/WARMERR2R
Want to support the channel? Consider becoming a member! Or you can join my Patreon here:
patreon.com/wavetheory1
Or make a 1-time donation through PayPal here:
paypal.com/donate/?hosted_button_id=7N7Z8WRLWQ36E
Test Gear…
All files started as digital and were either lossless or hi-rez FLAC or DSD played locally through Roon. Flac files were also streamed from Qobuz through Roon.
Chain 1…
Sonore ultraRendu streamer (youtu.be/qEOOE9rP6Rs) with AudioQuest Forest USB cable into USB input of Warmer R2R. Then Warmer R2R XLR output into LTA Z10e amp (youtu.be/Bft6HUsYDhE) driving either MartinLogan Motion B10 speakers (youtu.be/D47YKAGN8iw) or HiFiMan Susvara Unveiled headphone (youtu.be/WI1gnx2tD7s).
Chain 2…
Windows 11 PC direct USB into Warmer R2R with and without a JDS Labs Synapse USB isolator (youtu.be/m3stCPEl3Q8).
Chain 3…
FiiO SR11 streamer (youtu.be/YuagbK8p0FA) USB into the Warmer R2R. Then XLR output through a Little Bear XLR MC103 Pro switchbox into a Schiit Jotunheim 3 headphone amp (youtu.be/GhLNMFzcr74), then driving a HiFiMan HE1000 Unveiled headphone (youtu.be/pSXKdoYg0Tc). The Jotunheim 3’s single ended preamp output and the single ended output of the Warmer R2R took turns being connected to a Schiit Asgard X headphone amp (youtu.be/n8H8SN3Rdf4).
Compared & Mentioned Competing DACs…
Black Ice Audio Glass FX: youtu.be/RbAFxkxnWas
FiiO K11 R2R: youtu.be/ZRwGHsOvpsg
FiiO K13 R2R: youtu.be/mq3tmDPuT90
LAiV μDAC: youtu.be/A5sqsO76L8w
Schiit Bifrost 2/64: youtu.be/gydqRIWgbrc
Schiit Mimir: youtu.be/JnT_3HpAHt0
Telefunken Black Diamond 6922 tubes (affiliate link): amzn.to/4qhdJ4y
Timestamps...
00:00 Intro, Pricing, Disclaimer
01:31 Shameless Self Promotion
01:59 About Warmer R2R & Use Timestamps...
09:40 Build, I/O, Ergonomics
11:18 Test Gear in Description!
12:01 Sound: Overall Impressions
20:10 Sound: NOS vs OS
25:35 Which Input Should You Use?
28:48 Sound: Balanced vs Single-Ended Outputs
31:03 Sound: Tube Rolling
34:57 Comparison with K13 R2R
37:11 Comparison with Schiit Mimir
43:55 Comparison with Schiit BiFrost 2/64
45:28 Final Thoughts
Thanks to FiiO for sending the Warmer R2R for review!
Buy from Apos Audio (affiliate link): https://apos.audio/products/fiio-warmer-desktop-r2r-tube-buffer-and-dac?sca_ref=1448954.julYPU81dF
FiiO Product Page: fiio.com/WARMERR2R
Want to support the channel? Consider becoming a member! Or you can join my Patreon here:
patreon.com/wavetheory1
Or make a 1-time donation through PayPal here:
paypal.com/donate/?hosted_button_id=7N7Z8WRLWQ36E
Test Gear…
All files started as digital and were either lossless or hi-rez FLAC or DSD played locally through Roon. Flac files were also streamed from Qobuz through Roon.
Chain 1…
Sonore ultraRendu streamer (youtu.be/qEOOE9rP6Rs) with AudioQuest Forest USB cable into USB input of Warmer R2R. Then Warmer R2R XLR output into LTA Z10e amp (youtu.be/Bft6HUsYDhE) driving either MartinLogan Motion B10 speakers (youtu.be/D47YKAGN8iw) or HiFiMan Susvara Unveiled headphone (youtu.be/WI1gnx2tD7s).
Chain 2…
Windows 11 PC direct USB into Warmer R2R with and without a JDS Labs Synapse USB isolator (youtu.be/m3stCPEl3Q8).
Chain 3…
FiiO SR11 streamer (youtu.be/YuagbK8p0FA) USB into the Warmer R2R. Then XLR output through a Little Bear XLR MC103 Pro switchbox into a Schiit Jotunheim 3 headphone amp (youtu.be/GhLNMFzcr74), then driving a HiFiMan HE1000 Unveiled headphone (youtu.be/pSXKdoYg0Tc). The Jotunheim 3’s single ended preamp output and the single ended output of the Warmer R2R took turns being connected to a Schiit Asgard X headphone amp (youtu.be/n8H8SN3Rdf4).
Compared & Mentioned Competing DACs…
Black Ice Audio Glass FX: youtu.be/RbAFxkxnWas
FiiO K11 R2R: youtu.be/ZRwGHsOvpsg
FiiO K13 R2R: youtu.be/mq3tmDPuT90
LAiV μDAC: youtu.be/A5sqsO76L8w
Schiit Bifrost 2/64: youtu.be/gydqRIWgbrc
Schiit Mimir: youtu.be/JnT_3HpAHt0
Telefunken Black Diamond 6922 tubes (affiliate link): amzn.to/4qhdJ4y
Timestamps...
00:00 Intro, Pricing, Disclaimer
01:31 Shameless Self Promotion
01:59 About Warmer R2R & Use Timestamps...
09:40 Build, I/O, Ergonomics
11:18 Test Gear in Description!
12:01 Sound: Overall Impressions
20:10 Sound: NOS vs OS
25:35 Which Input Should You Use?
28:48 Sound: Balanced vs Single-Ended Outputs
31:03 Sound: Tube Rolling
34:57 Comparison with K13 R2R
37:11 Comparison with Schiit Mimir
43:55 Comparison with Schiit BiFrost 2/64
45:28 Final Thoughts
