Ltitle Hercules (or is this amp for real?)

LITTLE HERCULES Or, Is This Headphone Amp Too Good To Be True? A listening experience.
Rummaging around the net I found this curious device in response to the query “balanced portable headphone amp”. The only website links are eBay who won’t ship to India, and a Chinese site called Yoycart who will. I found a lot of pictures here, but the descriptions are only in Chinese. On the eBay page there is information in a kind of English. There appear to be at least 4 variant models ranging from under $400 to under $180. Went back and forth, eventually biting the bait for the PA3. On the web-page, I see a palm sized headphone amp with an all black body with curved edges and a startling number of sockets, buttons and stuff on the front and back panels. The descriptions are in very Chinese English (fever sound, thrust foot, etc), but the claims they make seem to be quite incredible. Follow the numbering in the attached screen grab.


  1. “Fully balanced amp with 4 groups of amplifier circuit”. Four? Does it mean separate amps for right and left, balanced and single ended, each? That’s extraordinary.
  2. Not a false balanced” pretender, but a genuine fully balanced amp. Can’t help noticing their anxiety to not be dismissed as a flaky product.
  3. High voltage power feed: 13 volts is what they say. They have twin batteries rated at 2800 mA. That’s huge for an amp of this size. They also say “ultra low ripple”. I guess they mean low interference.
  4. Independent power feeds for each channel. You only see that on much more expensive A-list amps and DAPs.
  5. If you follow this link to this eBay page (, you will see something at the top of the description that, I think, suggests a rollable op-amp. That’s really neat.
  6. There is also an indication that the components for each channel have been paired by lab testing.
  7. Item #7 on this web page is captioned as “third gear” (read 3 step) gain adjustment, independent for each channel.
Look carefully at the images on Yoycart. There’s one version that offers a 4.4 balanced out. Seen lots of those? The top end one apparently boasts a dual DACs with a switch to select them on and off. Obvious thing straight off the block, these guys are serious!



  1. Very prompt delivery. Lost large swathe of my skin to Indian customs. Really hurt.
  2. Thick black cardboard box.
  3. Amp wrapped in thin spongy sheet, held inside a space in a firm sponge rectangle.
  4. Two thick silicon bands to lash it on to a DAP.
  5. One power / charging cord with LED. Red when charging or playing on DC power; green when done.
  6. Nice silver coloured 90 degree 3.5 male to male SE interconnect cable. Check out the web page. You get to pick a cable from a list. Yoycart mailed me asking me to choose.
  7. Two tiny extra Hi-Res Audio stickers!!
  8. That’s about it.
  9. Oh, no manual.
It’s called HIFI-AMP-PA3. Not a real name (Not to be confused with the Topping PA3, an inexpensive but great desktop digital amp).

Looking at the front and back panels for the first time there’s a definite wtf reaction. Brought back memories of the time I went into a cockpit as a kid. All those knobs, switches, dials. The amp is about 12 cms long (including the volume knob), 7 cms wide, and 2.5 cms thick. Solid feeling body is dressed in a really nice matte black surface, and has broadly rounded edges. In the hand, it feels secure, heftier than its 270 gms, and nice to hold. The thick silicon beadings at either end not only keep the belly from scraping against the table, they allow air to play underneath. Overall, the dull textured black, the rounded shape and the blood-red bands induce a really good visual effect. Everything on the end-plates has a gold border running around it. Very complimentary to the look.
GETTING INTO IT In the absence of a manual, I had to work off the eBay page ( Actually, it does give you a fair amount of general detail, but no real numbers. The top and bottom are hard to tell. I kept holding it upside down until I got used to using a tiny Hi-res Audio sticker as the indicator for the top. The front fascia sports a dinky little switch to its right. It says “B-4” above and “N-3/4” below. This is an output selector. B-4 is balanced, 4 post connector. The other is “Normal” meaning single ended 3-post, or balanced 4-post connector. Basically, the 3.5mm socket supports both SE and Balanced outs, the 2.5mm out is for balanced only. Use the switch to choose. Come to think of it, haven’t seen too many 3.5mm TRRS plugs or sockets on amps or headphones.

There’s a danger sign next to the selector switch. Doesn’t figure on the web page pics of the amp. I’m not sure what it’s there for. Perhaps warning against selecting the wrong output from the one you’re plugged into. Small green LED next to volume knob lights up when its on. Turns red to indicate critically low charge. All the sockets look solid.

The volume pot has a textured grip and really nice resistive action. Turns firmly and smoothly with no wobble or snags right through its arc. You have to look hard for the marker on the knob. Travels from 7 o’clock to 5 o’clock, min to max. The rear panel is alive with stuff! To its right, there’s a small silver button with B above and N below. It’s the input selector for balanced analog and SE. Holy c##p, a balanced input! I had to use it a few times to figure out which one was which. Out is B, and In is SE (N).

Next to it is something that made me blink. Two really small switches side by side, marked “Left and Right Gain” below, “H, L and M” above. Took me a moment to realise these are three level (High Mid and Low) gain switches, independent for right and left channels. When was the last time anyone saw that? Oddly, the gain settings are not in any order. Low is between high and mid. The switches are tiny and toy like. At the start, as I turned the amp over in my hand, the feel of the switches was like something sharp had worked loose from the panels. It seems impossible that the gain switches would have the necessary travel to move into 3 distinct positions. But work them, and they move firmly and reassuringly, clicking into each position with impressive assurance. More to the left, there are two input sockets to exactly match the output ones; 2.5mm Balanced and 3.5mm SE (N). Next is a DC power socket marked 8.4v. That’s a really odd value! Last, to its extreme left, is another one of those unbelievable dinky switches to power the amp on and off. That’s a total of 5 sockets, 4 switches, 1 button, 1 knob and 1 LED bulb on this amp. No room for fries on the side. LISTENING Burn in: 12 hours. (BTW, it plays while charging). These are the headphones I used:
  • Hifiman HE4XX (SE and Balanced)
  • MJ2 (SE and Balanced)
  • Sennheiser HD6XX (SE and Balanced)
  • Mezze 99 Classic (SE and Balanced)
  • Beyer DT880 (Balanced Mod)
  • Hifiman HE 350 (SE and Balanced)
  • AKG K553 Pro (SE)
  • AKG K7XX (SE)
  • Beyer DT990 (SE)
  • Audio-Technica M50X (SE)
  • Samson 850 (SE)
  • Soundmagic HP150 (SE)
  • V-Moda Crossfade (SE)
  1. Onkyo DP-X1 playing native Onkyo HF hi-res player and Google Play Music, Line-Out into 2.5mm TRRS, Digital Filter set to Sharp.
  2. MacBook Pro playing PureMusic and Amarra, Objective DAC, dual RCA to 3.5mm SE connector.
  3. MacBook Pro playing PureMusic and Amarra, Little Dot DAC1 USB DAC, dual XLR to 2.5mm TRRS male.
FLACs, AIFFs, LAMEs and garden variety mp3s. With input silent and volume turned all the way up on high gain, the noise floor is very quiet. I. BY SIGNAL PATH SE input, SE output General sense of aggressiveness about the sound. Distinctly warm tone, almost tube-like. Harmonic distortion is noticeable but pleasant. Midrange is very strong, with mild contraction of soundstage. The highs are a tad soft. Bass is slightly woolly, not enough to blur upper bass detail. This is not a bass-head‘s amp. By the end of a week treble was crisper and bass was tighter and more focused. With M50X and the AKGs, sound is less warm, the former sounds quite bright, the latter is more true and restrained. The K553 Pro deserves praise for stellar poise and insight. With the PA3 breathing down its neck, it stays clean and even-toned with every genre of music. Samson 850 is a $50 open back. Rates 32 ohms but sounds more sensitive than that. It’s an unsophisticated but very listenable headphone that has found favour with a section of audiophiles. The PA3 drives it to death. On low gain, at about 25% volume, it cries for mercy. So does the M50X. With the V-Moda and the Planars it fills out substantially acquiring richness and width. V-Moda over cooks PA3’s bass making it almost unlistenable. The 4XX and T-XO are driven strongly with good tonal balance. The DT990 as expected is brilliant, clinical and very neutral, throwing up more detail. This perfectly foils the PA3’s slightly warm accent. The MJ2 handles the PA3 with authority, taming the strong midrange to deliver a much more evenly balanced spectrum. The Mezze Classic 99, and HP150 are outstanding with this amp, demonstrating rich rounded tone, elbow room in the stage and good detail. You can hear Glenn Gould humming to himself as he plays Bach. The textured warmth of Eric Dolphy’s bass clarinet sounds absolutely real. In comparison, the FiiO Montblanc and the original edition of E17K are smoother, more sophisticated sounding. But the PA3 is more fun. SE Input, Balanced Output (not sure this is recommended) Soundstage opens up a bit. Midrange, vocals, Gerry Mulligan’s grainy baritone sax, high hats, cymbals, lush string movements of the classical orchestra, all sound good. There’s detail, with shuffling feet and bumps from wooden instruments audible through the live classical music. There is still that sense of the sound somehow being “intense”, probably because the midrange dominates the rest of the spectrum. As I A-B between the amp and the DP-X1, the airy comfort about the latter’s signature makes the feeling stronger. Balanced (Analog) Input, Balanced Output Any self respecting audiophile has scars to show from arguments over balanced and single ended systems. I’m not going to get caught in that nutcracker except to say that from the PA3 the balanced in and out path definitely sounds cleaner and more open than the SE path. Unsurprisingly, it is louder. The sound is more spacious, more resolved and more engaging. I think I can hear more detail. Bass is just a tad tighter, with better definition. Treble is sharper with more bite, improved from the slightly soft highs with SE input and output. Midrange is still a bit overbearing with a convex mirror like prominence. Listening mostly with Hifiman 4XX, HE350, Mezze Classic 99, Beyer DT880, MJ2 and Sennheiser 6XX, there is subtle but noticeable improvement in every genre of music. Every headphone prospers on the PM3’s balanced output, but the CustomCans modded DT880 (80 ohms) benefits the most. Already a great headphone, it becomes magical with the PA3’s energetic drive. The Planars and the HE350 sound clean and articulate. HE6XX makes the amp sing for its supper. The PM3 responds with a wholesome, spacious performance. I bought the MJ2s with both expectations and trepidation. Nearest I’ll never get to a Stax! I like it a lot but I’ve always had this niggling feeling (and I hate saying this) that somehow it is just a few cents short of the dollar. With the PA3, it sounds bigger, more resolved and much more sonorous than I have ever heard it. Against the grain of industrial sentiment, I wouldn’t buy 2000 dollar cables even if I could afford them. But I will submit that a $60 to $150 balanced cable from the many custom services on the net sounds indisputably better than a cheap $8 cable. The PA3 rewards a better cable with rich textured music. FLACs, ALACs and LAMEs and well mastered MP3s all sound good. Maybe, just maybe, higher res files sound a bit more spacious and detailed. A-B compared with the DP-X1 balanced out, the DAP sounds more refined, but this difference is not big enough to stop the PA3 from being very pleasurable in its own way.
II. BY GENRE: Classical: FLAC file of Carlos Kleiber in live concert reveals subtle sounds from the orchestra and from the audience, invoking a spacious ambience. At around 3.20 in Christian Thielmann’s hi-res issue of Eroica, the sledgehammer blows of the orchestra ring out with power and detail. Elsewhere, you can feel the force of the drumstick striking the big kettle drum. Clearly audible too the opening and closing of the clarinet keys on the Mozart concertos. Forqueray‘s solo cello suites are delivered with fulsome timbre and texture, revealing the scrape of the bow on the strings and the lingering flutter of the C string playing a bass note. The many tonalities of different piano key strikes are clearly discernible on Einav Yarden’s Finale Presto from Haydn Sonata 41. Through a fast run across the keyboard, you can hear each note separately. The high notes of a violin sonata are sharp, vibrant and without jaggies. The Sitar is an instrument that easily becomes thin and tinny if recorded or reproduced carelessly. From the PA3, it sounds well toned and resonant. The emphatic twang of a plectrum forcefully struck against a Sarod string (an Indian fret-less guitar, used in Indian Classical music) comes through with real power and resonance. On Narciso Yepes’s solo album playing Spanish classics the guitar has a golden warm tone. I can hear his fingers squeak across the strings as he lays out the music, bringing great realism to the recording. The PA3 is lean and taut with bass and lower midrange on the DT880. Warm, rich and widely staged on the Planars and others. The Hifimans are the warmest and most full bodied. The MJ2 and Mezze 99 are less warm and leaner but with great presence. Leaning the other way from it, the roomy, neutral, and precise DT990 is a good counterfoil for the PA3.
Jazz, Blues:
Gerry Mulligan’s baritone sax comes through with a nice gravelly texture and full bodied honk. Ben Webster has a unique technique of letting air escape from the side of the saxophone mouthpiece to control intensity of a note. His recording of My Romance with Sweets Edison is a milestone. I can practically feel air move with the hissing “phhh...” of escaping breath, and hear an occasional low “aah” at the end of a long note. Edison’s neat finish with the muted cornet is very crisp and frizzy. When La Rosita begins, the sound of fingers hitting the taut bongo skin sound utterly real, and the very different tones of Coleman Hawkins and Ben Webster can be clearly told apart. Keith Jarrett’s piano in the live Köln Concert sounds sonorous and rounded with a great sense of space created by the occasional audience interjection. The Hot Sardines and Reve Boheme recordings come through with good instrument separation and accurate tonality of every instrument. Specially with the former, the sense of a jazz group spread over a small stage is quite real. Even remasters of noisy vintage greats like Billie Holiday sound lifelike and musical. Old blues Masters, often recorded in backwater shacks on ancient tape recorders and still found on scratched up 38 rpm bakelites have been remastered into digital files. PA3’s unselfconscious execution gives life to them. Big Bill Broonzy’s emphatic strumming of the guitar is sharp and nicely resolved. Vocals: Vocals sound bold and upfront. On vocal dominant tracks, they seem a bit too forward, but never unpleasant. Where there are a lot of instruments or an orchestra behind the voice, it seems to recede slightly, making me want the vocals to be pushed towards me a bit. Eartha Kitt’s playful nasal twang is faithfully rendered in My Heart Belongs To Daddy. On a remaster of Nat King Cole’s ballads, the warm and grainy baritone is goose pimple inducing. Mel Torme’s almost butter smooth tenor is difficult to get a hold of, but delivered with good definition. I can hear the squeaky breaks in Adele’s voice right from her throat on Rolling In The Deep. Norah Jones’s husky tones layered over the piano, Amy Winehouse’s unrestrained, utterly sincere vocals, and Gregory Porter’s cultured baritone are presented with clarity and realism. With Indian Classical vocals, the vibrations of maestro Bhimsen Joshi’s lightning race up and down the raga scales, along with the incredible timbre of his voice are utterly lifelike.
Rock, Pop:
Hard rock is a loud and belligerent affair. Everything is up in the air and in your face at the same time. Under these conditions finesse and power may become mutually contradictory things, challenging the mettle of the very best audio systems. The PA3 delivers a remarkably meaty and self assured account of itself. Slightly bright and rough edged with the AKG 7XX and AT M50X. Well mannered and exact with the SE DT990. More alive and rounded with the balanced DT880. Full bodied and punchy with the HP150, the Hifiman and other planars. The V-Moda Crossfade being comparatively bass heavy adds a lot of bloat to the lower end. With some tracks the upper midrange-lower bass becomes oppressive. Standard iTunes download of Sultans Of Swing sounds 3-dimensional with great instrument separation. Sounds like it’s being performed in front of you. On Aerosmith’s “Rag Dolls”, the emphatic heavy percussion intro has great heft and is properly dramatic. The almost screaming vocals are delivered with great energy and realism. Mudcrutch has a lyrical and rhythmic style. On “Trailer”, the harmonica intro has the right nasal timbre. The twangy vocal is handled perfectly, the rhythm guitars and drums are sharp and well defined. The live performance of “Sweet Home Chicago” from The Blues Brothers reproduces the sense of a large auditorium and a wildly responsive audience. Steely Dan’s Cousin Dupree is a really neat mp3 with a rhythmic piano intro and hard knocking percussion. The PA3’s rendition is so punchy and crisp, it gets you nodding and foot tapping right from the start. Resolution is superb. The vocals and lyrical guitar lines of Santana’s “You’ve Got To Change Your Evil Ways” have an easy but full bodied feel about them. I could listen to it several times over without fatigue. The last quarter of “29 Palms” has a fantastic lilting guitar motif that PA3 serves up fluid, but tight. Robert Plant’s slightly breathy lower register and clean higher reaches come through with power and clarity. The iconic pulsating score from Berlin’s Take My Breath Away has everything to challenge an amp. Muscular bass lines, drums, rich background refrain, and crisp vocals. The PA3 does a great job delivering this anthem with power and grace.
Paranormal Activity
With headphones connected to SE out, but selector switch mistakenly set to Balanced out, I heard a short crackling sound as from an electric spark, and the power LED turned red. I switched it off and reset the selector. Apparently no damage, but scary as hell. This should never happen if the circuit paths are truly independent and isolated from each other. This kind of mix up is easy with this amp’s complicated layout. Once, when listening through the iEMatch, I noticed the power indicator was red. I guessed because battery was running low. I turned the volume down and it turned green. If I turned the volume up again it would turn red and back to green if I turned it down. Is it normal for the power indicator be on “live” feedback with the current flow? I’m hoping someone with tech know-how will explain why that happened.
Extras These are some additional observations about the PA3:
  1. 12 hours of burn-in made a difference. At the end of a week from there, it sounded really sweet. That’s a lot of time to get an act together, but it’s worth it.
  2. Takes about 2 minutes of warming up to hit nirvana. Long for a solid state amp.
  3. The three levels of gain work very well. At low gain, 32 ohm headphones become too loud at about 25 - 30% volume level. Planars do so at about 50 - 60%. The 990 and Sennheiser 6XX are comfortably listenable at 60%. With each gain step up, approximately 25 to 30% is added to the loudness. Low and Mid gain setting appear to sound the best. Turning up volume all the way on low gain does not distort. In fact brings out the lurking softer sounds.
  4. Most headphones have a recognisable signature. I’ve played those listed above endlessly on DarkVoice, Little Dot and other tube amps, Cavalli Liquid Carbon, NAD and a range of FiiO amps. My experience with PA3 has been that it magnifies these characteristics enough to make a known headphone sound unfamiliar. Careful pairing is crucial. The DT880, HE4XX and HP150 and Senn 6XX were the least affected.
  5. With western classical music, I can occasionally hear faint blowing or scratching sounds in the background. I’ve noticed them most often with the string section playing broad strokes. I’m not sure what they are, but I have never heard them on the DP-X1.
  6. Battery mileage seems too good to be true. When burning in, from a full charge, the amp was still playing after 8 hours. Website doesn’t give a number. Plan to test its endurance sometime.
  7. The front end of the amp gets really warm after 20 mins of playing, just short of hot. Less so with SE in and out, warmer with Balanced. After an hour of playing it is definitely hot. Will this affect the components, given the compact form? I wish the amp had vents.

I bought this amp with the very lowest level of expectation. The whole over-the-top specs thing seemed surreal. I must admit I couldn’t help sneering at the effrontery of a $180 bulk-offer amp getting so far above itself. Didn’t help that Yoyacart said they only ship the amp, and that they wouldn’t accept returns even if it didn’t work! When I took the amp out of the box and held it in my hand for the first time, I lost some of that sneer. The PA3 is an enigma wrapped in a I can never get this right. This amp is no Chord, yet its apparent sophistication is not a sham. The talents it offers are meaningless to anyone but to an audiophile and would be hard to find on the best kitted amps. In a market where you can buy a little Schiit for $100 how does all the bling on the PA3 measure up? Best intentions aside, can you just throw a collection of high-end features into a tiny box and expect high-end functionality? In this specific instance, nearly so! As it plays, I’m thinking this is a really sweet compelling amp that I could keep listening to without complaining too much. Where has it been all this while? Why would you buy the HI-FI-PA3? I did out of sheer intrigue. You might because it sings with heart, almost demanding to be forgiven its lack of pedigree and upper class refinement. There’s the busy appearance, and the learning curve getting used to the controls, despite which, it is a very effective device. This write-up is not about measurements. It’s about an enthusiast’s day out with a strange and fascinating creature that beckoned from the shadows of the internet. I have been listening to it for about an hour a day for 8 weeks and hugely enjoying it. Part of the joy is the visceral thrill of all these bells and whistles for under $180. The other part is admiration for the sheer balls on these guys! Since the time I plugged a pair of headphones into the PA3, I’ve had a smile plastered on my face and it ain’t going away any time soon.
  1. Solid build, nice finish, hard-to-believe features.
  2. Low noise floor.
  3. Very enjoyable sound, though a bit hard hitting.
  4. Warm signature. Reminiscent of a tube amp.
  5. Op amp may be rollable.
  6. Drives “heavy” headphones with glee.
  7. Independent L and R, 3-level gain control.
  8. Balanced (analog) input.
  9. Balanced out includes 2.5 and 3.5 mm options.
  10. Bulky, but portable.
  11. Great battery.
  12. Unbelievable value for money.
  13. Those darned little switches are the cutest things on any headphone amp.
  1. Long burn-in. Gets sweeter with use.
  2. Very unforgiving to poor quality tracks.
  3. Hard pushing. May seem aggressive to some.
  4. Overwhelms easy to drive phones.
  5. Slightly dominating midrange.
  6. Good cable, good source and clean file needed for balanced option to really shine.
  7. Watch out for a slightly loose fitting 2.5mm sockets.
  8. Gets hot. No vents.
  9. Complicated layout, really needs getting used to.
  10. Is getting the connections mixed-up dangerous?
  11. And, who the hell are these guys? How long will the amp last? What about service?
My Ratings: Build: 4 / 5
Design / Layout: 3 / 5
Features: 4 / 5
Sound: 4 / 5
Battery: 4.5 / 5
Value For Money: 4 / 5

Dec 4, 2018
Stumbled upon this little bad boy because of the exact same reason as you. I was searching for fully balanced portable amps. Which there aren't many of. It boggles me why there isnt any information about this amp on the internet? - As much as it did you, it seems. Did you try taking it apart? I'm familiar with that type of case from my 8x TDA1387 DAC/AMP. Usually if you unscrew the 2 bolts on the backplate, you can slide the font end out by pulling the potentiometer. If you're up for it, I would love some hi-res of the internals of this weird fellow. Either way, thanks for the review!
Sujay Rao
Dec 5, 2018
Done. What’s a suicide between friends? :-D Hold on to your butt.
Oct 28, 2018
I could never grasp all the functions/options there in a decade but it seems an incredible little device. You really should post that review at would blow their Hive Mind!
Sujay Rao
Oct 29, 2018
You’re right. I did. They rejected it !!
Oct 24, 2018
Nice review on this. Have been saving up for it!!!
Sujay Rao
Oct 24, 2018
Great. Check out their websites. eBay doesn’t ship to India but they probably ship to where you are. Check for warranty from the seller. Also. heck Yoycart for the other models.
Oct 23, 2018
A great read, looks very interesting! Good job!
Sujay Rao
Oct 23, 2018
Thanks. Since Massdrop is all about bulk purchase advantage, and this amp (and variants) is being offered at bulk prices, maybe there’s a great deal in it somewhere 😊