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

Condition

New

Open Box

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

I love it and was exvited listening to my SJY Horizon Carbon closed! Super clean black background. The Korg tubes sound very good.

Tubey loveliness

Excellent device, a welcome change of pace from my collection of solid state sources. With certain IEMs it can add a magical warmth and fullness to the soundstage that is very different from other warm SS dac amps. it sounds as though the instruments and vocalists expand in size on the stage, though the stage itself doesnt necessarily grow in size. very lifelike and analogue, as they say. my first tube device and just love this thing.

Solid choice

What a great product.
I have accrued a small collection of portable dac amps and this one is my end game. The classic and modern tube options are both great, 70/30 classic/modern usage.
Drives my Hifiman HE1000 unveiled and Prestige LTD with ease. They both sound fantastic with the RU9, especially when I plug it into a power source while I'm listening (still great battery wise, don't get it twisted).
I'm been looking to buy a dedicated desktop dac/amp with tubes. Not going to now, thanks Cayin.
Thanks Bloom Audio as always for your great customer service.

I've been waiting for this!

My home headphone amps consist of a solid state, hybrid, and tube amp. For portables, I'd use a btr5 and up. I've always wanted a portable that could rival my home dac amp setups while powering my favorite full sized headphones like the 600 ohm dt880 and hd600. Cayin Ru9 has made my dreams come true! Out the box, I wasn't wowed so I let it burn in and now I am in disbelief when I'm out on the streets listening to my favorite headphones without compromise! The Ru9 is end game for me at this current time for price, performance, and portability. The 3 P's. I'm hearing details I haven't noticed on the go. I get tube sound, depth in soundstage, mids are satisfying, lows are hitting, and the highs are shimmering and not fatiguing to my ears. Everything I want. Get a battery pack with magsafe and it will stick to the case. Long battery life and hyper mode on the go. No compromise. Turns into a giant brick in your pants and you'll be bricked up just from listening, you best believe it.

A Portable Source That's Better than a Lot of Desktop Gear

This thing is awesome. For years now, I've been on the hunt for a portable source that drives headphones well enough that I can enjoy them as much as more powerful desktop gear.

There have been many candidates (Fiio KA17, Hiby R4, etc.) but none of them have satisfied me.

Until I got the Cayin RU9. While it has its limits (I don't enjoy the Sennheiser HD 800S on it, for example, though that's considered a notoriously amp picky headphone by those who believe strongly in synergy), I have thoroughly enjoyed every other headphone I've used with the RU9 - including planars!

My experience has been that dynamic drivers can often sound pretty okay on portable gear, but I hadn't used a single portable device that I enjoyed something like an Arya Stealth or a Moondrop Para 2 on until the RU9.

The Modern and Classic tube modes are both great (I don't really touch the solid state mode, which sounds fine, but the tube modes are just better). I lean toward the Classic tube mode for more neutral/brighter headphones and older/rougher recordings, and the Modern tube mode for well recorded music on warmer headphones (like the Z1R).

The ability to quickly switch between the modes is awesome.

There are only a couple small downsides I've encountered: the 3.5mm connection is not as good as balanced (not unexpected for a device that's built to be balanced) and I have encountered some noise when using it.

The battery life isn't great, but I love that there's a second USB input so you can hook it up to a battery bank and not worry about that. (HyperMode, which gives you over 1W of power, is also awesome to actually get good performance from harder to drive headphones.)

The Bluetooth functionality is awesome and I've used it frequently when I need to charge my phone. LDAC stability and sound quality is great as long as your phone and the RU9 are close together.

This isn't the kind of device you can carry around the house while your phone is in another room and still get good performance. But if you think of the Bluetooth mode as an alternative to USB-C for when you want more freedom (because you're actively on your phone or need to charge your phone) then it's great, and I sort of suspect it may force the highest quality LDAC offers, which would explain why it works awesome close to the source device and not so awesome when you walk away from it.

Overall, this thing is incredible. $500 seemed like a lot for a "dongle" DAC (technically) but it's totally justified by the performance, and I've probably spent as much time on my couch enjoying music with the RU9 in the last month as I spent in the last year doing so on other devices.

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Cayin RU9 Vacuum Tube Portable DAC and Amp | Bloom Audio

Cayin RU9 | Vacuum Tube Portable DAC and Amp