Walnut F1: Power For Days


Today we’re taking a brief look at the Walnut F1, a stupidly powerful budget amplifier that has been more than capable of powering anything I’ve tossed it’s way.

My first Walnut experience was with the V2S (review here), a screenless DAP/AMP. Like the F1, it was powerful as all heck and was able to drive everything plugged into it. It too was inexpensive with a build that was more about being durable and functional than it was about eye candy.

The F1 is pretty much everything that the V2S was, but with the DAC removed, a 2.5mm balanced option installed, a cleaner sound and even more power. Let’s take a closer look.


The Walnut F1 was provided free of charge in exchange for a fair and impartial review. The thoughts within are my own and are not representative of Walnut, Penon Audio or any other entity. There is no financial incentive for writing this.

At the time of writing the F1 could be picked up for 29.90 USD: https://penonaudio.com/Walnut-F1


  • Interface: 2.5mm balanced & 3.5mm output interfaces
  • Output power: 300mW
  • Operational Amplifier Chip: OPA2604
  • Class: A
  • Suitable For: 16 ohm-400 ohm
  • SNR: 90dB
  • Lithium battery capacity: 1500mAh
  • Charging Interface: MICRO USB
  • Power Supply: 24v @ 1A

Packaging and Accessories:

Walnut kept things simple with their packaging shipping the Walnut F1 in a brand-free cardboard box. The F1 is protected inside by some foam and wrapped in a plastic bag to prevent scratches should it rub against some of the other inclusions;

  • a microUSB cable for charging
  • a short auxiliary cable terminated in 90 degree angled 3.5mm plugs
  • two silicone straps

It’s all very basic but everything it well constructed and serves a legitimate purpose.


Like the V2s, the F1 has a simple build with an old school feel to it. The shell is entirely metal with the Walnut logo and some printing on the top stating the model and that you’re holding a “Headset Power Amplifier”.

The front face contains the volume knob, the line in input, power out, and a 2.5mm balanced output. Unlike the V2s, the volume knob on the F1 moved smoothly out of the box. The metal knob itself is also of higher quality with cleanly cut knurling and is held in place by a small hex screw vs. the friction fit on the V2s which will be prone to loosening up over time.

The rear contains the power switch and a microUSB input for charging. There are also small cutouts for the orange charging and blue power LED indicators. For the longest time I thought the charging LED didn’t work so I was thankful Penon noted the 2.5 hour charge time on their site. I was very careful to time the charging time of the F1 to prevent damage to the battery caused by overcharging. After a couple weeks of ownership, I knocked the unit off my desk while it was charging and noticed that the charging LED did in fact work, it just wasn’t lined up with the cutout. The only way to see it was to flip the unit over (right side down) and look at it from a 45 degree angle. I’m assuming this will vary unit to unit.

Overall material quality is quite good, and fit and finish is decent keeping in mind the LED indicator issue. It’s not a huge step up from the V2s, but the changes are significant enough and were made in the right areas to make it feel better all around. Holding the two at the same time, the F1 simply feels more dense and durable.

Battery Performance:

The Walnut F1 is rated at 2.5 hours for charging with a 4 to 5 hour run time. I’m not sure what the standby time is, but it’s significantly longer than the V2s whose battery was more often than not dead when I went to use it after having set it aside for a few days. Not the case with the F1. These might not seem like impressive numbers and in the grand scheme of things they definitely are not. That said, given the demanding headphones and earphones this little device is capable of powering and the low price tag, I’m willing to accept the trade off.

For example, my older Topping NX1 absolutely destroys it in terms of battery life with a rated 100 hours of run time over a similar charge time. This 100 hour figure is one I absolutely believe considering I’ve only charged it a handful of times in the multiple years I’ve owned it. That said, even on high gain it is incapable of adequately powering headphones like the HiFiMan Susvara, and requires a much more notable twist of the dial to get the Havi B3 Pro I going, something the F1 can do with it’s eyes closed while sitting on it’s hands.

What I’m getting at is with the F1 you’re choosing between power or stamina when opting to purchase it. It doesn’t give you both. I found it’s battery life perfectly adequate for day to day use, but can see it being a bit of an issue if you’re planning to use it while travelling where you may not have ready access to a place to charge.

Sound Quality:

The F1 sounds to me a lot like the V2s: kinda bright, somewhat edgy and aggressive, and with a touch of grain to the upper mids and treble. The sound stage is open and airy which really helps out warmer and/or darker earphones and headphones like the Brainwavz M100 and thinksound TS03+mic. The brighter signature also helps to bring out finer details and improves overall clarity. Paired with brighter sounding products the F1 is not ideal as it exacerbates treble and upper mid-range peaks and can easily take an earphone from ‘mostly right’ to ‘way too bright’. Such behaviour was noticed with earphones like the TFZ Exclusive 1 and Kinera H3.

Device Pairing:

I was expecting the pairing of the F1 with Walnut’s own V2s to fail spectacularly given they’re both brighter devices, but they actually work exceptionally well together. The clarity these two bring to the table, along with enough power to move the HiFiMan Susvara, should you be crazy enough to go mobile with such a product, makes them a formidable budget setup. For under 65 USD you have a portable unit that can rival and exceed some desktop setups in terms of driving output.

My preferred pairing was with the Shanling M1 which was ended up being compact enough to pocket, with a neutral and fairly smooth signature that paired well with any earphone or headphone I tried, even overly sensitive ones that I would have expected to pick up lots of background noise.


  • When turning the device on, there is a loud pop. When turning the device off, there is a burst of static which moves from one channel to the other followed by another small pop.
  • If you plug an earphone into the input quickly, there is loud burst of static; push it in slowly to avoid this.
  • At low volumes there is a small channel imbalance; this and the above mentioned quirks only showed themselves after the device was charged for the first time (via my laptop USB)

I really wish none of these quirks were present. They’re all pretty minor in the grand scheme of things and the F1 works fine, they just rub me the wrong way.

Final Thoughts:

If you’re looking for a durable, inexpensive portable amplifier with a fairly clean sound and more than enough power to push hard-to-drive headphones, the Walnut F1 is a great option. If you place greater value on having a variety of features, a slim form factor, excellent battery life, or if your ear devices do not require a powerful source, this might not be the product for you.

Thanks for reading!

– B9Scrambler

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