Walnut F2

Walnut F2 is a versatile device that’s available on Aliexpress for roughly $25-30 USD.

Equipment Used:

Burson V6 Classic
Burson V5i
Burr-Brown OPA2604 (comes stock with F2)
Texas Instruments NE5532

Monolith M570 (planar magnetic driver)
Koss PortaPro (dynamic driver)

Fiio X1 (PCM5142)
Fiio M7(ES9018Q2C)
Zishan Dsds Pro (AK4499)

Disclaimers:

Thanks to Burson Audio for providing V6 op-amp review sample. All other equipment and op-amps used were purchased myself. Opinions are my own, I’m not affiliated with Burson or any other entity.

All equipment has been burned-in for over 100+ with a mix of white noise, pink noise, and sine waves.

Review:

Three use modes are available:

• Can insert SD card and use as screenless DAP. I don’t use this option.

• Can decode digital USB signal and be used as a DAC/amp. DAC chip used is unknown. For Android, there’s no full compatibility with UAPP as the device doesn’t get detected as USB DAC. It does still receive and output sound through UAPP though and sounds pretty good.

• Line-in mode gets the majority of use from me: it accepts a line-level signal from another DAC/DAP and so only F2’s amplification section is utilized.

As mentioned above, I mostly use the device as a portable amp. It allows me to push the limits of my DAPs to get better sound from them. Many DAPs have a well-refined sound yet their power and voltage abilities are frequently not enough to push various head gear to 100% of its capability.

Walnut F2 features both single-ended (3.5mm) and balanced (2.5mm) outputs. This is the first device I’ve tried that features both SE and BAL whereas SE output sounds much better: better vertical and horizontal soundstage extension, tone weight stand out the most. Mids/clarity/detail are roughly the same across both outputs. 95% of listening is done through single-ended output as the result.

With stock OPA2604:

Results are quite impressive from get-go. With stock opamp, sound is strong/raw with a realistic scene and frequency control. Certain sounds bring out harshness and sibilance, while notes on musical instruments, especially with vocals, are not well flushed out leading to average timbre.

With NE5532:

This is a downgrade from stock. Instrument separation in the mids takes a hit, with reduced soundstage size as well. Sibilance and harshness remain, and become more or less obvious depending on specific synergies with the other equipment used in the chain.

With V5i:

This opamp takes F2 to another level. It’s able to control the sound much better, reducing sibilance and harshness. There’s better texture and musically to sound. Notes sound realistic across the board. Vocals are rendered realistically with addictive decay.

With V6 Classic:

This is basically V5i on steroids: same improvements plus holographic soundstage with vocals listed from the rest of sound. Very clean treble extension with no audible shrills. Poor recordings are very listenable. Hires recordings sound like it with proper detail and transparency. Unfortunately, the device’s case cannot be closed due to its sheer size. Battery life takes a significant hit as well.

Conclusion:

With stock OPA2604 inside, this device is a bargain. It’s very listenable and enjoyable in stock form. With either of the Burson opamps, humble Walnut F2 can rival more expensive dedicated portable amps. With V5i inside, it’s on the level with Fiio Mont Blanc with a different sound signature. With V6 Classic, it’s on the level with iFi xCan, with each sounding differently as well.

For pandemic times, having multiple “chill” spots around the home – I don’t mind having open case and short battery life to get the most out of F2 – as a transportable amp using V6 Classic.

Though, V5i is the proper recommendation for Walnut F2. It allows to close the case to properly stack F2 with DAPs. Battery life is almost as good as stock. Sound wise, it offers a lot of what V6 Classic does at a more affordable price level as well.

I am a self appointed audiophile extraordinaire and a self appointed football expert
I bought my Walnut F2 on AliExpress for £23.29.

The supplied charging cable stopped working after 2 charges. That went straight in the bin.

On first use there was a crackling sound audible in-between tracks. This has turned into a humming noise after a few weeks use. This noise may be unique to my unit as another owner on head-fi told me that he does not hear any noise on his F2. The noise doesn’t annoy me as such. I just know that its there. I listen out for it now

The sound from the player is great. The sound is warm with nice bass.

I have tried a few different opamps. OPA2604 is the original. I have tried OPA1612 and NJM5532D. Both seem to have improved the sound. I am enjoying hearing the different sounds that different opamps offer. The opamp can be easily accessed by removing the 4 Allen screws on the top of the device and lifting the top of the unit off. I have replaced all of the Allen bolts with M2 2x8mm bolts with Phillips heads for ease of removal.

The F2 only plays wav or MP3 files. There is no screen.

I love this player for the music quality and the fun factor. I have many different music players but I am finding myself reaching for the F2 every time that I want to listen to music.

Highly recommended.