Cayin RU9 USB DAC Headphone Amplifier with Nutube 6P1

Hero Section

Desktop‑grade emotion and power, now magnetized to your phone

What if your pocket rig could deliver real tube magic, clean studio detail, and the muscle to wake up full‑size headphones? Cayin’s RU9 answers with a hybrid, triple‑timbre USB DAC/amp that fuses the glow of KORG Nutube 6P1 with modern engineering. Swap between classic tube warmth, a cleaner “modern” tube flavor, or a fast, neutral solid‑state voice—then unleash up to 1W balanced in Hyper (DC) mode when your headphones call for more headroom. All this lives in a palm‑size, magnet‑ready chassis that snaps to your phone for a cable‑tidy, go‑anywhere stack.

---

Benefits Section

Why Audiophiles Choose This Product

• • Primary Benefit: Hybrid sound your way
  Two distinct tube tunings plus solid‑state neutrality let you tailor the RU9 to your music, IEMs, or headphones—without swapping gear.

• • Technical Benefit: Proven silicon, serious topology
  Dual AKM AK4493SEQ DACs in dual‑mono feed Cayin’s Gen5 three‑stage amplification (JFET buffer → Nutube 6P1 gain → output buffer) with switchable global feedback in “Modern Tube” mode to lower THD.

• • Practical Benefit: Pocketable, readable, controllable
  A 0.96" color display, tactile volume knob, three gain levels, and PO/LO switching on both 3.5 mm and 4.4 mm keep daily use simple on desk or commute.

• • Compatibility Benefit: Plays with almost everything
  USB‑C (UAC 1.0/2.0), S/PDIF in/out, and Bluetooth 5.1 (LDAC/aptX HD/aptX LL/AAC/SBC) make the RU9 a chameleon—wired or wireless, phone to PC to console.

• • Unique Benefit: Magnetic back, anti‑vibration Nutube
  The magnetized rear and leather case simplify phone stacking, while Cayin’s custom isolation minimizes Nutube microphonics for clean tube tone on the move.

---

Package Contents

What’s Included

• • Main Product: Cayin RU9 Tube/Solid‑state DAC Amplifier (Nutube 6P1; dual AK4493SEQ)
• • Primary Accessory: USB‑C cable (device interconnect)
• • Secondary Items: USB‑A to USB‑C adapter; fitted leather case
  Note: Some regional bundles also include an L‑shaped USB‑C cable and a magnetic ring for non‑MagSafe cases (check retailer).
• • Documentation: User manual/warranty booklet.

---

Technical Specifications

Technical Specifications

Specification	Value	Notes
Product Type	Portable USB DAC & Headphone Amplifier (with BT receiver)	USB‑C data, S/PDIF in/out, Bluetooth 5.1 input.
DAC	Dual AKM AK4493SEQ (dual‑mono)	Low crosstalk; “Velvet Sound” decoding.
Amplification	Gen5 3‑stage hybrid + 3 Timbres (Classic Tube/Modern Tube/Solid‑state)	Modern Tube uses global NFB for lower THD.
Decoding (USB)	Up to 32‑bit/768 kHz PCM, DSD512 (reported by pro reviews); manual lists PCM 44.1–384 kHz, DSD64/128/256	Capability varies by source/firmware; confirm in your setup.
Inputs	USB‑C (UAC 1.0/2.0), Bluetooth 5.1, S/PDIF (coax)	QCC5125 BT with LDAC/aptX HD/aptX LL/AAC/SBC.
Outputs	3.5 mm SE PO/LO; 4.4 mm balanced PO/LO; S/PDIF out	Fixed LO levels selectable; digital out via coax.
Output Power (BAT)	620 mW @ 32 Ω (bal); 310 mW @ 32 Ω (SE)	For portable drive with headroom.
Output Power (DC Hyper)	1000 mW @ 32 Ω (bal); 420 mW @ 32 Ω (SE)	Toggle to DC mode and connect 5 V adapter.
Line‑out Level	2.4 Vrms (bal); 1.2 Vrms (SE)	Fixed LO for external amps.
Volume Control	JRC NJW1195A 4‑channel	Precise, low‑noise attenuation.
Battery	2000 mAh Li‑Po; QC3.0/PD2.0 fast charge (~1.3 h)	Typical 3.1–4.7 h depending on mode/output.
Display	0.96" color TFT	Shows source, rate, mode, gain, output.
Dimensions/Weight	100 × 70 × 15 mm / ~150 g	Pocket‑friendly, magnet‑ready back.

---

Professional Recognition

• • Reviews
  “If you want serious sound, genuine versatility, and real tube character… the Cayin RU9 stands alone.” — ecoustics.
  “Three distinct sound signatures… genuinely different and genuinely useful.” — ecoustics.
  Headfonia highlights the dual AK4493SEQ + Nutube design and 1 W Hyper mode as class‑leading for a dongle form factor.
  Headfonics praises the thoughtful UI (input/output, gain, USB class, DAC filters) and magnetized case for stacking.

• • Heritage
  Cayin is the personal‑audio brand of Zhuhai Spark Electronic Equipment (est. 1993), renowned for tube amplification and modern portable solutions.

• • Innovation
  RU9 brings KORG Nutube 6P1 to a compact DAC/amp “dongle,” pairing tube timbres with solid‑state agility and optional DC Hyper power.

---

Conclusion

The Bottom Line

Cayin RU9 delivers what most portable stacks promise but rarely achieve: real tube expressiveness, reference‑grade silicon, and desktop‑like drive in a pocketable, magnet‑ready form. With three tunings, robust wired/wireless inputs, and Hyper (DC) power on tap, it can be your daily driver, travel rig, and late‑night desk setup in one. Choose it for the sound—keep it for the flexibility.

---