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Lear FSM-02 v2 portable headphone amplifier review

Lear FSM-02 v2 amp - front

Manufacturer: Lear
Model: FSM-O2 V2
Price: HKD 2,998 + HKD: 200 for shipping ($412 USD shipped)
Product notes: Available in black or silver.
Type: Portable amp


  • Two independent built-in amplifier circuits: independent output MOSFET CLASS-A and replaceable op amp design.
  • Hardware EQ with three settings: high EQ, low EQ, hardware ByPass (skip EQ)
  • Three gain settings
  • Built-in 3000mAh USB rechargeable lithium battery
  • Supports external power supply from 5V to 18V DC
  • Ultra-low output impedance of ≦ 0.04 Ohm with the ability to drive headphones ranging from 8 Ohm to 600 Ohm

Frequency Response: 4Hz ~ 100 kHz (20Hz ~ 20kHzEQ = Flat +-0.002dB)
≦ 0.001% THD + N 16mW @ 15ohm (OPA2227 L GAIN) Internal Battery
≦ 0.001% THD + N 25mW @ 300ohm (OPA2227 L GAIN) Internal Battery
≦ 0.001% THD + N 14mW @ 600ohm (OPA2227 L GAIN) Internal Battery
S / N ratio: ≧ 100dB A-Weighted
Noise Level: ≦ 100nVrms @ L Gain A-weighted
THD + N Distortion: 0.00001% @ 1kHz @ 1Vrms (L GAIN no Load)
IMD Distortion: 0.0001% CCIF; 0.001% SMPTE 100 @ 1Vrms (Lgain no Load)
Output Impedance: ≦ 0.04 Ohm
Crosstalk: ≧ 90dB (no Load @ 10kHz) ≧ 62dB (@ 15ohm Load @ 10kHz)
Charging time: About 5hrs (DC 5V, 500mA)
Charging: DC5 ~ 5.5V (MAX)
EXT Power: DC9V ~ 18V (MAX)
Dimension: 57mm x 105mm x 24mm

Volume control: Analog knob, stud type (notched steps)
Power connector: USB; 5V-18V external power
Battery life: About 10hrs up @ front output, about 4hours @ Back Class-A output
Works with 4 pin headphone plugs: yes
Channel Imbalance: Yes, slight imbalance at low volumes with very high sensitivity CIEMs. 8/10
Hiss: Only with extremely high sensitivity CIEM that hisses with everything 10/10
Interference: None
Noise when turned on/off: Thump when turning on and off.  Class A circuit has electrical noise for the first minute of operation.

The Lear FSM-02 v2 starts with impressing with specifications and features, which includes two full amp circuits and a hardware EQ.  The amp isn’t the smallest or thinnest, but the flat side and subtle curves help make it easy to use on the go with my iPod, iPhone, or any other device, although it is large for something like a Nano.  It isn’t the most stunning in the looks department, but the brushed aluminum finish is well done.  With plenty of switches, some located in difficult to get to places when the amp is connected, the amp doesn’t look like a work of art.  But, my main criteria for an amp is sound quality, and I would suggest continuing to read…

There are two amp circuit options for the FSM-02 v2: the op amp section which comes with the OPA2227 installed and has a 10 hour batter life, and the class A section with 4 hours of battery life.  I compared the FSM-02 v2 with several amps including the Portaphile 627, Ortofon MHd-Q7, Leckerton UHA-6S MKII (AD8610ARZ op amp), Meyer Audio Stepdance, HeadAmp Pico Slim, Headstage Arrow 4G, ADL Cruise, Just Audio uHA 120, and Sunrise Dolphin.  Many headphones were used in my evaluation, a list that is much to long to list, but includes the Audeze LCD-2, Sennheiser IE800, Spiral Ears 5-way Reference, Custom Art Music One, Dream Earz aud-8X, Fit Ear PS-5, Sennheiser HD600, AKG K550, Etymotic ER4P, and many more.

The op amp section performed quite well with a spacious, detailed, natural, and neutral sound.  Elaborating on the neutral sound, many other amps sounded slightly colored in comparison, such as the Dolphin and Pico Slim due to a bit more emphasis in the treble region, or the Arrow with added warmth.  Note decay is not too smooth and not too analytical, falling between the more analytical UHA-6S and smoother MHd-Q7.  Compared with the Stepdance, which I have found performs great in so many regards, didn’t sound as natural, open, or effortless as the Lear.  Amps often have synergy with select headphones, but the FSM-02 v2 paired well with everything and had less variation than I am used to.  Certain headphones did vary in performance from amp to amp such as the aud-8X, LCD-2, IERM, and to an extent Proguard P2+1.  Technically, the op amp section outperforms all but two of the amps I used for comparison: the Ortofon and Portaphile.

The built in EQ boost either bass or treble to suite different headphones with two three position switches for selection.  The selection is more difficult than it has to be as one switch between the input and volume knob must be either in the “BP” for bit perfect position for no EQ or the upper “EQ ON” position for the EQ to work.  Setting the switch to the middle position results in no sound, and I had trouble changing the switch without disconnecting the source cable.  If the switch is in the “BP” setting, the EQ 3 position switch still affects the sound, as setting “1” or 2” lower the volume.  When the switch is in the “EQ ON” position, the EQ switch must be in either the “1” position for bass boost or the “2” position for treble boost.  If the switch is in the “0” position for no EQ, there is no sound.  Using the EQ in position “1” warmed up the sound quite a bit, adding a richness to the single BA Music One and multi-BA LCM-5 without adding any distortion but the bass became too much with the IE800 and Lime Ears LE3b.  With the switch in the “2” position, some headphones improved while others didn’t.  For example, there wasn’t much of a difference between with the IE800 or Lime Ears LE3, although the LE3b did become clearer.

Normally, an amp review would be complete at this point, but the FSM-02 v2 has another amp circuit to test, the Class A portion.  This circuit is a real winner, adding dynamics and punch along with a more spacious and refined presentation adding to the already high performing, musical sound of the op amp output.  Every headphone I paired with it sounded natural and the overall performance closed in on the Portaphile 627.  While it doesn’t quite reach the same technical performance of the 627, it does have a lower noise floor, smaller size, similar battery life, and lower price.  With realism that is on par, but with a bit smaller and slightly less dynamic presentation, the FSM-02 v2 is quite impressive.  The EQ function works like it does via the op amp circuit, but the bass boost isn’t quite as significant and the clarity boost adds a bit more clarity while retaining a more refined and smoother treble.  For example, both the Lime Ears LE3b and Music One became clearer with the clarity boost on.

Using the medium gain with the LCD-2 and HD600 headphones did not change the sound quality from either amp circuit, but when using the high gain the presentation space became ever so slightly larger.  The amp was loud enough for my listening volume on low gain with all the headphones I tested.  I didn’t try the amp with an external power source, although it can accept up to 18V.  I also didn’t try changing op amps, and Lear is developing new op amp modules.  The power LED is bright when in class A mode, which may annoy some people, although the blue LED when the op amp section is on isn’t nearly as bad.

The Lear FSM-02 v2 is an exceptional amp that offers quite a few options combined with competitive sound from the op amp section and class leading sound from the class A amp section, with performance that approaches that of the Portaphile 627.  Features include a built in EQ with a bass or treble boost, the ability to change op amps, and an input for an external power supply up to 18V.  Not the smallest in size, the curves and flat side help the amp pair well with iPods and phones.  Battery life is OK with the op amp output, registering about 10 hours, but the 4 hour class A battery life is a bit on the short side, although it is simple to just plug the amp in to any USB port for charging.  Overall, the Lear FSM-02 v2 is an exceptional amp and an exceptional value when the features and performance are taken into account.  Highly recommended!


Manufacturer Model Price Form Factor DAC Power Charge Option Interference 4 Pin Compatible
Bit Depth Sample Rate
Lear FSM-02 v2 $412 Portable N/A N/A Battery USB Class A None Yes
Lear FSM-02 v2 $412 Portable N/A N/A Battery USB op amp output None Yes

Quantity Warmth Note Sustainment Smoothness Soundstage
Deep Bass Bass Mid-Bass Midrange Upper Mids Treble Width Depth Imaging
6 5 5 5 5 5 5 5 9 8.5 8.5 9
6 5 5 5 5 5 5 5 7.5 8 7.5 9

Bass Mids Treble Transparency Dynamics Resolution/ Detail Clarity Soundstage Score Total – Quality Hiss Imbalance Size/ Portability High sensitivity Total
Quality Quality Quality
10 10 10 10 10 10 10 8.7 9.7 10.0 8.0 4.0 7.9
9.5 9 9 9.5 9 10 9.5 8.2 9.0 10.0 8.0 4.0 7.8

My additional amp reviews can be found here.  A full chart with all amp ratings in png format can be found here.

Lear FSM-02 v2 User Manual





Having a life-long love of high-quality audio and gadgets, average_joe got back in touch with his audiophile side after a hiatus caused by life. His focus became headphones and related gear as the size and price fit his life better than home audio. He believes the entire audio chain is important, and likes to continue to think past the headphone and on into the head, as he believes understanding the details of how we hear will lead to a better audio experience.


2 Responses

  1. Unfortunately I have not paired the HE-400 with portable amps when I auditioned them, so I can’t provide my thoughts on the comparison of the two amps. I do know the FSM-02 sounds great in class A and is more musical than the AB circuit, but not having the Cayin C5, I can’t provide that comparison in general. Joe

  2. hi average_joe! I’m about to buy a used Lear FSM-02 v2 for about $110, do you think that that’s a good deal?
    Also, do you think that it will pair well with Hifiman HE-400i?

    I’m offered a Cayin C5 as well at about the same price ($85), I heard that that one has a more superior soundstage when paired with he-400i than Lear. What do you think about Cayin C5?

    Thanks a bunch!

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