Portable headphone and earphone amplifier

Walnut F1

Rating:
4/5,
  • (Info gathered from Penon Audio)​

    Description

    • The size of the amp is small, 80 * 50 * 20mm, slightly smaller than a bank card, but the small amp also has great wisdom. The sound of this amp should be said that the rivals himing is enough, in simple terms, the sound is sweet. After adding the amp, you can feel out the sound field is significantly large, the originalequipment of amplifier is OPA2604 of the BB. The characteristics of the sound in general is warm and delicate, strong driving force, with "bile". Low-frequency has quality and quantity. At the same time 2.5mm version with a balanced output, balanced output has been applied to professional recording field, balanced output is characterized by high degree of separation, the drive is about twice the power output.
    • The OP amp is used of OPA2604 of BB, OPA2604 is designed for audio and special OP amp, sound mellow, rounded, neutral warm, bile is very strong, is known as the most electronic tube audio amplifier. And it feels like he upgraded version of 5532, all aspects have greatly improved, good resolution, music taste better, there is bile, the sound is relatively thick and a bit rigid, comprehensive quality is very good, especially for music performance.
    • This amp can be replaced by the op amp. Direct plug design, is now the mainstream design, different op amp to bring a different tone.
    • It almost completely used the machine's power supply circuit, up to 24V (+12 V gnd -12V) of the pressure, easy to control the various types of op amp on the market, launched a loud field with strength. It supports charge, when you are listening music.
    • Power supply part of the selection is 24v 1A power supply, ripple very small (using the commonly used three-terminal regulator 78M12 79M12, no noise at the end under normal circumstances), the filter capacitor is high-quality capacitors of Ina vr series and Nikon gold fw series. It is used of the imported high current full-shielded inductors.
    • It used class A current amplification plus op amp voltage amplification, can be better to release low-medium-high impedance in various types of headphones (16 ohm-400 ohm). Meanwhile due to the high supply voltage, prolonged use of the shell will be a slight sign of heat (not more than 30 degrees).
    • The use of 3.7V high-capacity lithium battery-powered, boost to 24v and maximum current is 1A, battery capacity is 1500mah, life 4 to 5 hours or so. When charging, you can use the common charging cable of Android. Don’t use in charging, and the charging time is about 2 and a half hours. (When charging, the red light is on; when stop charging, green light is on)
    • This is the second amp Walnut launched, the use of high-grade components. Output coupling DC blocking capacitor using Nikon FW capacitors, the strength of the extraordinary is enough to be among the ranks of the world's advanced audio capacitors. Using the OFC oxygen-free copper feet, very low distortion (third harmonic distortion-120dB), very small tangential loss, natural silk fiber media, high-quality sound, play silk soft and natural, enhanced resistance to acoustic oscillation design, increase the low-frequency of thickness sense , reduce the high-pass part of the peak feeling and medium-frequency part of the rough sound quality.
    Specification
    • Interface: 2.5mm balanced & 3.5mm output interfaces
    • Output power:300mW
    • Operational Amplifier Chips Model: OPA2604
    • SNR: 90dB
    • Lithium battery capacity: 1500mAh
    • Charging Interface: Standard MICRO USB.
    Package:
    • Headphone Amplifier
    • Charging Cable
    • AUX Cable
    • 2pcs Silicone straps

Recent Reviews

  1. B9Scrambler
    Walnut F1: Power For Days
    Written by B9Scrambler
    Published Nov 24, 2017
    4.0/5,
    Pros - Tons of pushing power - Durable build - Price - Good sound quality
    Cons - Fit and finish could be better - Popping/noise when turning on/off device and when plugging in earphones - Battery life - Size
    Greetings!

    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, 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.

    Disclaimer:

    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

    Specifications:
    • 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
    DSC01928.JPG DSC01929.JPG DSC01931.JPG
    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.

    Build:

    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.

    DSC01932.JPG DSC01937.JPG DSC01942.JPG
    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.

    Quirks:
    • 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.

    DSC01934.JPG DSC01935.JPG DSC01936.JPG
    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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