Name: Cayin RU9 | Vacuum Tube Portable DAC and Amp
Brand: Cayin
SKU: CAY-RU9
Price: 499.0 USD
Availability: InStock

Cayin RU9 DAC/amp standing front right 3 quarter angle whitebox

Cayin RU9 DAC/amp standing rear right 3 quarter angle whitebox

Cayin RU9 DAC/amp standing front center whitebox

Cayin RU9 DAC/amp lying rotated left Birdseye view top third closeup

Cayin RU9 DAC/amp lying rotated left whitebox

Cayin RU9 DAC/amp standing on left side closeup of power and menu button whitebox

Cayin RU9 DAC/amp standing on right side closeup of volume buttons whitebox

Cayin RU9 DAC/amp lying face down rotated left in leather case whitebox

Cayin RU9 DAC/amp lying face up rotated left in leather case whitebox

Cayin RU9 DAC and amp lying on top of leather case and smartphone showing magnetic back panel and L-shaped USB cable

$499.00

Cayin Expands Their Legacy of Innovation by Introducing RU9, a Pocket-Sized DAC/Amp Featuring a Korg NuTube 6P1 Vacuum Tube

First portable DAC/Amp to implement a Korg NuTube 6P1 Tube
High-performance dual AK4493SEQ DACs
Three timbre options: Classic, Modern and Solid-State
Magnetic back design allows smartphone attachment
3.5mm SE + 4.4mm Balanced phone and line outputs

Bloom's Take

Cayin’s RU9 isn’t just another DAC dongle, it’s a bold reimagining of what portable audio can be. Marrying the richness of tube sound with the convenience of MagSafe, Cayin provides a compact unit that delivers serious desktop-quality sonics from your pocket. With three selectable sound modes: Classic, Modern, and Solid-State, the RU9 adapts to your mood and gear, offering anything from clinical precision to analog warmth. Its tuning is natural and relaxed, allowing your IEMs to shine without imposing its own character, while still delivering a wide soundstage and refined detail.

Whether you’re pairing it with a $100 IEM or a flagship CIEM, the RU9 scales effortlessly and never feels out of place. Add in thoughtful design touches like dual USB-C ports, physical playback controls, and the sheer novelty of MagSafe mounting, and you’ve got one of the most well-rounded portable audio tools we’ve ever tested. The RU9 isn’t just convenient, it’s a joy to use and a true standout in the portable DAC/Amp space.

Read our full review.

Tube Warmth On-the-Go

The Cayin RU9 is the latest addition to the RU series. It is a compact, portable DAC and amp that brings the classic tube sound to your mobile audio experience. Featuring the Korg NuTube 6P1 vacuum tube, the RU9 offers audiophiles a unique blend of classic and modern sound signatures.

Classic. Modern. Solid-State.

The RU9 offers users three distinct timbre options: Classic, Modern and Solid-State. As the name implies, the Classic tube mode delivers a warm, nostalgic sonic flavor - the classic tube sound.

The Modern tube timbre yields a sweet, clear and delicate modern tube sound signature. It's harmonically cleaner, offering a quieter background while preserving the warmth of tubes.

The Solid-State mode is ideal for listening to music with its original, uncolored character. It delivers neutral tonality, fast transients and highly accurate audio reproduction.

NuTube 6P1 Application

The tube circuit adopts a three-stage amplification architecture, consisting of 6 Toshiba 2SK209 audio-specific junction field effect transistors (JFETs) and a manually tested paired KORG Nature 6P1 dual triode tube. Both the single-ended and balanced ports on the RU9 can output rich tube sound.

Cayin RU9 DAC and amp three stage amplification architecture graphic

Premium Components

With years of experience crafting high-end audio equipment, Cayin has applied their expertise to engineer the RU9 with exceptional components. RU9 is equipped with dual Equipped with dual AK4493SEQ DACs, each operating in mono mode. The Left and right channels are decoded separately for lower crosstalk and better channel separation.

Employing the latest generation XMOS XU316 USB processor, RU9 supports native DSD512 and 32bit/768kHz PCM signals. The processed signal is then amplified by a four-channel balanced headphone amplifier circuit. It uses dual ultra-low noise and ultra-low distortion OPA1662 OPAMPs with four Nexperia audio power tubes.

Cayin RU9 DAC and amp XMOS XU316 USB processor chip closeup graphic

Additional Features

Triple Power Supply Modes
The built-in 2000mAh lithium battery offers up to 4.7 hours of playback on a single charge. The RU9 also supports USB power directly from connected devices (bypassing the battery), as well as an external DC power supply for enhanced output performance. It is fully compatible with QC and PD fast charging standards.

Hyper Mode
A specialized feature designed for headphone usage under DC power supply. It increases static operating current and voltage for enhanced audio performance. Producing a strong output, it reaches 1000mW at 32Ω impedance load.

Versatile Use Scenarios
The RU9 is compatible with smartphones, computers, digital audio players, tablets and gaming consoles. A magnetic rear panel allows seamless attachment to smartphones. RU9 supports UAC1.0 (driverless) and UAC2.0 modes.

Cayin RU9 DAC and amp with laptop, Cayin N6iii dap and smartphone showing versatile use

Vibration Isolation
A custom anti-vibration system was designed for the NuTube vacuum tube. It features silicon housing on a FPC flexible PCB and a pin-supported vertical suspension system to eliminate microphonics.

Thoughtful Details
RU9 features a 0.96" color display with adjustable brightness, knurled volume knob and side-mounted indicator light for charging + sample rate/format display.

Specifications

Material: CNC-machined unibody metal chassis
DAC: (2x) AK4493SEQ
Decoding: PCM up to 768kHz/32bit, DSD512
Bluetooth: v5.1 with LDAC, aptX HD and aptX LL support
Bluetooth Chip: Qualcomm QCC5125
Battery: 2000mAh, polymer lithium-ion
Connectivity: USB-C input
Weight: 5oz
Dimensions: 3.9" x 2.7" x 0.6"

In the Box

Cayin RU9 DAC and amp
Leather case
L-shaped USB cable

Cayin RU9 dac and amp attached to standing iphone leaning on shelf right profile view with plant and iems

Portable, powerful, versatile - two negatives

This is a pretty unique piece of equipment. Between the tubes and hybrid mode, as well as the magnetic features, this little amp/DAC is kind of a category of its own.

As the reviews point out, you do get three different sound signature qualities. A warmer tube sound, a more neutral solid state sound, and a hybrid mix in between. The size of the unit is very portable size wise, and with the magnetic back, this little unit will stick to your phone and not move out of place. It's game changing. I'm using this with a pixel 9 pro, but with a peak design everyday case which adds the magnetic feature.

There is one one negative, and that is the battery life is not very long. 3 to 4 hours maybe. But, there are some really affordable magnetic back batteries on Amazon that have been suggested in some audio file communities. The Lisen Brand 5000 mAh battery on Amazon works seamlessly with this. Yes now your rig is a little thicker, but you have double the battery life. Not always needed though. So that kind of helps that negative not hit so hard.

Fantastic sound, adjustable on three modes, which I change depending on genre sometimes - and they each can make the monarch Mark IV really sing.

The second negative is the Bluetooth antenna is extremely weak. Your phone has to be very close for this to even work. I mean it's good the feature is there but they really should have engineered it better. Using a USBC Bluetooth dongle which gives you other codecs, the reception is slightly better. Enough to walk around with the whole setup. But ultimately it's still not ideal.

Five stars if they give it a little bit more battery life and fix the power of the Bluetooth transmission. But even with these negatives it's still four stars because of what it does overall.

Cayin RU9 is awesome

Very nice sounding dac amp with three modes. Awesome unit! Bloom Audio is a great company to work with.

Excellent Service

Phenomenal service as always from the Bloom team! I did not end up keeping the product but an exchange was done literally the same day.

great sound and super portable. Able to fit in most pockets.

Love to your ears

I will first say it will matter what the Canyin is connected to but the love she gives is amazing! I prefer the classic tube mode. Organic, musical and enriched sounds…yeah babe!! I love the magnetic connection with my phone. Put it in pocket at gym & I go to work. The case is nice. That damn usb wire is excellent. Just some thoughtful engineering. I haven’t listened to it Bluetooth yet! My iems of choice with it Fatfreq Quantum, Punch Audio Martillo and Shanglin ME600 zing!!!! If u need a great not good but great DAC don’t hesitate!!! And it arrived fast and was packed with starburst!!! Thanks Bloom Audio

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Cayin RU9 Vacuum Tube Portable DAC and Amp | Bloom Audio

Cayin RU9 | Vacuum Tube Portable DAC and Amp