Douk Audio P6 Mini Tube Preamplifier (Review)

Audio projects have a long tradition at Elektor. Over the past half-century, many audio enthusiasts have built phono-, preamplifiers, or power amplifiers based on Elektor designs. This time, however, it’s not about a DIY project but a ready-made product that caught our attention and is sure to interest Elektor audiophiles: the Douk Audio P6 Mini stereo preamplifier with tubes and Bluetooth—all at a very affordable price.

Additionally, it offers the opportunity for experimentation, as you can replace the tubes or output op-amps with different types.
 

Douk Audio, a Chinese Audio Manufacturer

We have reviewed a lot of Chinese measuring equipment such as multimeters and oscilloscopes. In recent years, however, many Chinese manufacturers have also focused on catering to audio enthusiasts, often delivering good results at highly competitive prices. The Douk Audio P6 Mini, which I am reviewing here, is made by Douk Audio, a company founded in 2014 that specializes exclusively in audio equipment. Currently, they offer more than 80 audio-related products.

The prices of Douk Audio (and other audio-focused Chinese manufacturers) are astonishingly low compared to Western manufacturers, raising the question of whether you're actually getting a quality product for the price. To find out, I tested the P6 Mini.

I chose a preamplifier version (rather than one with a built-in output amplifier) because it can easily integrate into an existing audio setup to add a tube sound without making the rest of your equipment obsolete.

Preamp with Bluetooth

 

The Douk Audio P6 Mini comes packaged in a neat box containing the device, two (also Chinese) 6A2 tubes, a simple 12 V power adapter, and a Bluetooth antenna. The chassis itself measures approximately 10 × 12 × 3 cm and is made entirely of thick anodized aluminum, including the front and back plates.

On the top, there are two openings for the tubes, and behind them is a USB-A port for connecting a memory stick with music. The rear features four gold-plated RCA sockets for stereo inputs and outputs, a power input jack, and a connector for the Bluetooth antenna.

The front side includes a volume control, bass and treble controls, a three-way input selection switch, and three buttons for controlling music playback from a USB stick. The three-way switch allows you to choose between Off, RCA inputs, or USB/Bluetooth. If a USB stick is connected, it takes priority over Bluetooth, which is automatically disabled.

That’s a lot of functionality packed into such a small box!
 

Trying the Douk Audio P6 Mini

After unpacking, inserting the tubes, and connecting the audio and power cables, the P6 Mini is ready to use. Once powered on, the tubes take about 30 seconds to reach their operating temperature, after which the output signal is available at nominal strength.

The controls operate smoothly with tactile clicks, and the switch feels solid and reliable. While the tubes emit an orange glow, it’s not from the tubes themselves, but from orange LEDs mounted beneath their bases. However, the tubes are fully functional. A DC/DC converter inside the unit supplies them with a voltage of just over 100 V.

Measurements

I measured a number of things on the P6 Mini, which I list here:
 

• Input sensitivity for 1 V out: 230 mV
• Max. output voltage: 6.5 V
• Input impedance: approx. 12 kΩ
• Output impedance: < 10 Ω
• Frequency range (−3 dB): 12 Hz…140 kHz
• Harmonic distortion (THD): approx. 0.1% at 1 V out
• Tone control: ±6 dB (treble, at 5 kHz), ±9 dB (bass, at 100 Hz)

The harmonic distortion is primarily influenced by the second and third harmonics, which likely play a significant role in creating the characteristic “tube sound.” The output signal does contain some residual noise in the range of a few hundred kilohertz, originating from the various DC/DC converters in the P6 Mini. However, it is unlikely that this will have any noticeable impact on the performance of the subsequent power amplifier.
 

How Does the Douk Audio P6 Mini Sound?

Of course, I also tested the P6 Mini, both on my stereo system and the speakers next to my PC monitor. In both cases, I found that this preamplifier delivers excellent sound quality that—though it may sound like a cliché—feels slightly warmer, more natural, or softer. Yet, nothing is lost at the top of the spectrum. The P6 Mini produces a respectable sound image, and if you enjoy the characteristic tube sound, this is a splendid and affordable option.

Tweaking the Douk Audio P6 Mini

For those who enjoy experimenting, the P6 Mini offers plenty of possibilities. Douk Audio states that the standard pentode tubes can be swapped for other versions. For example, users have reported good results with the 6J1, 6AK5, 6F32V, and GE5654W.

Additionally, if you're willing to open the case (by loosening the screws on the front and back), you can replace the NE5532 op-amps at the output with pin-compatible alternatives. These are conveniently mounted in IC sockets on the PCB. Some popular replacements include the LM4562, LME49720, and OPA2134. There’s plenty to experiment with.
 

Conclusion

To be honest, I didn’t expect much from the Douk Audio P6 Mini preamplifier, given its price of around 75 euros. However, I was pleasantly surprised. Both its performance and sound quality far exceed what the price would suggest. The hardware is well-designed, everything functions as it should (including the Bluetooth feature), and the overall build quality is excellent.

In this case, you truly get great value for your money. Additionally, the ability to experiment with different tubes and op-amps adds even more appeal. It’s a fantastic choice for anyone looking to add a “tube sound” to their existing audio system.