DAC Chip: Cirrus Logic CS43198 (Dual)
Decoder: 32-bit/384 kHz, DSD256, SNR: 118dB @ 1kHz, THD+N 0.0004%, Power: 2 Vrms, USB Type-C Male, 3.5mm SE (Microphone: NO), 17mm x 50mm x 10.3mm, 25g, All Metal Chassis, SPC Cable
Listening Equipment: Etymotic ER4SR, Etymotic ER2XR, Shure KSE1500, TIN HiFi P1, Monolith M565C
LISTENING EQUIPMENT USED IMPARTED HUGE INFLUENCE TO THE SOUND IMPRESSIONS & RATING
💚PROS
- Euphonic crisp, rich articulate timbre, hint of warmth, very vibrant
- Pristine Treble textures with breathtaking decays, rich airiness
- Vibrant and engaging dynamics all over, very euphonic
- Reference grade Treble extensions, slightly superior to Cayin N6ii and Topping D10s
- Commanding and wholesome Mid-Bass with realistic decays
- Bass exhibit exemplary textures and extensions, Mids richly defined with depth.
- Succulent guitars and stringed instruments attack, addictive riffs, and tremolos
- Reference grade speed and transients handling
- Balanced, and coherent male/female vocals, realistic imaging
- Flagship grade micro details, exceptionally nuanced, great finesse
- Very realistic Piano, Violin and Cello tones, attack, and decays
- Great sibilance resistance throughout, never fatiguing.
- Exemplary clean background with zero floor noise
- Extremely forgiving on Lo-Fi recordings, shines brightly on excellent Hi-Fi
- Bleeding edge sharpness in imaging and spatial projection, not cramped.
- UPDATE: Drives Tin HiFi P1 Magnetic Planar at 60/100 Volume with ease.
💔CONS
- The construction is the 2nd heaviest of all the dongles, edged shape.
- Single Ended output, possibly limiting its true potential.
- Fidelity and stability untested beyond 250Ω
- A step short of being fully analogue sounding.
- “Normal” headstage and soundstage width and depth
- No hardware volume adjuster
- Will likely not be suitable for warm sounding IEMs/Headphones
- Can induce fatigue for long listening sessions
VERDICT
Astell & Kern PEE51. This thing is phenomenal. This is Astell & Kern being Astell & Kern justifying the reasons why they are pricy. The irony is, PEE51 is their cheapest product to date. The great thing, it is in no way being cheaply built or compromised to produce a small form factor – in fact, A&K pushed it quite a bit to squeeze in as much exquisite contents as possible with specially built tantalum components meant just for PEE51. I believe the long legacy and expertise carried from the days of iRiver of old flow strongly in the veins on A&K. I was a hardcore iRiver user between 2008-2010. iRiver H140 and H130 being my preferred DAPs. PEE51 greatest strength, being able to harness such articulate finesse and technical prowess without being dry or sterile sounding – of being able to retain some semblance of warmth and organic element to the pristine output. It makes my ER4SR sounded like an Electrostatic instead of a BA, simply euphonic. I joke you not, PEE51 outclassed the N6ii and Topping duo in almost every areas. I have no other reason to state otherwise because I personally own all these devices and it would have been consoling to me to say that my $1300 DAP and $400 Laptop rig is superior – but that will not be stating the truth. The truth is, PEE51 trumped them a step or two in the capabilities of presenting contents limited to 44.1/16bit and up to 250Ω as tested. I have no idea how far this would stretch but I believe that the N6ii and Toppings would regain their dignity at the mark of over 250Ω all the way to 600Ω.
⭐⭐⭐⭐½ ($170.00)
Best Pairing: Best synergy with bright IEMs and Headphones.
Back to #donglemadness
Andy.EF AudioVault 
A&K says that it is not compatible with iOS devices (iPhone & iPad). Is that true? I just placed an order for my iPhone…
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Yes.Out of the box it will not work with iOS. If you look at my list. Ovidius B1, Apogee Groove, E1DA 9038SG3 and PEE51 all have issues with iOS. These are very powerful dongles and iOS USB 2.0 simply don’t have enough juice to run them. Only Hidizs S9 Pro and S9 can work with iOS without headaches out of the box. So only 1 of all the 5 stars performers work with iOS. Even L&P W2 have issues with iOS (can be made to work)
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Thanks for your fast reply and your amazing work!
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My pleasure
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So I just receive my A&K PEE51 and wanted to try it with my iPhone 12 pro max using the TC28i converter and it works! But I have to push the sound almost to the max and then the sound is kind of awful. Tried with my DT990 Pro and my DQ6. So it works but this is a no go.
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Thanks for confirming issues with iOS on PEE51. So now it seems that four out of six 5 Stars Dongles don’t work with iOS, hmmmmm
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I tested it on my iPad Pro M1 connected directly to the USB-C port and it works flawlessly with Tidal.
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Hi there.
I have PEE51 connected to ddHifi adapter on iPhone XR and works perfectly. Same on iPad mini.
Looks like different iPhones work differently .
Maybe newer ones are restricting power out to save battery life??
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Also adjust the volume from the phones touch screen.
Touch the battery icon then hold the volume slider icon for a second this brings up a bigger volume icon with more precise adjustments.
Don’t use the hardware buttons on the phone.
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What kind of headphones are you using? As I said it works with iPhone but Volume level is almost at 100% and the sound seems saturated. I tested with DT990 Pro 250 ohms.
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My testing gear all listed here:
https://andyaudiovault.com/equipment-used/
However my DT990 came later and was not tested against PEE51. But I did test it on my Magnetic Planar Monolith M565C
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Sorry Andy, my question was for Glen 😉
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Hi powergeek.
I’m using various iems and headphones.
VE monk plus
Ortofon EQ8
Grado GR10e
Westone um1
Westone W60
Grado HF1,HF2, HF3
Sennheiser HD800s.
No it doesn’t drive the HD800s optimally but I connect another amp to it.
Like I said different iPhone allow different amounts of power too be drawn.
The battery drain on the AK is a lot better than the LP W2.
I have never had any problems using the ddHifi lightning to usbc adapter.
All the best Glen.
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Hi Powegeek.
Another dongle that works perfectly for iPhones is the ddHifi pro mountain.
Using it as I write.
Excellent dongle that uses hardly any power and sounds very good with easy to drive gear.
The volume buttons on the phone don’t have massive jumps in between steps either.
All the best Glen.
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Thanks for all the info. I don’t have the ddhifi pro mountain but I use the Audirect Atom 2 with lightning port. I guess they share the same specs and I am very pleased with it. The form factor is perfect when on the move. I also have the ddhifi TC28i to connect my various dongles. I will give it some more tries with the A&K PEE51.
All the best.
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Hi powergeek
I forgot to say I can also get the AK to work when it’s connected to the Apple digital power adapter. So can play and charge at the same time.
All the best Glen.
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I use a magsafe battery for that purpose 😉
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Thanks so much for the comprehensive review site – it is really fantastic! I’m looking for some advice for a dongle DAC. I currently use Ety ER4XRs with custom molded tips (along with a pair of Sony MDR1-BT cans) for Spotify and Amazon Ultra HD (NOTE: not a Tidal MQA user) out of a Samsung Galaxy S21 Ultra +. I am torn between the Helm Bolt, the THX Onyx and the AK Dual DAC. From your review, it seems like the AK is the best sub-$200 DAC, but I am not certain who it will match up with extended response Ety’s and since I am not using Tidal MQA, am I really going to hear big audio benefits over the cheaper Helm Bolt unit? Any guidance that you can give me in this matter would be greatly appreciated.
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Thanks Brian. If you like EE4XR, it means that you have similar sound preference to mine. Me on the other hand is a hardcore ER4SR and ER2XR user, of which it started with ER4S and ER4P since 2006. Now that you asked, from my personal perspective I do not see Helm BOLT as a suitable partner for ER4XR especially when I have had the chance to sample over 100 other dongles with my ER IEMs. At any price point the VERY best partner for Etymotic ER series are CEntrance DACport HD, Cayin RU6, Ovidius B1, Apogee Groove, Questyle M12 and TempoTec Sonata E44. #donglemadness primary IEM is my ER4SR anyway and how the dongles synergize with that ER IEM heavily influence my overall ranking. A&K PEE51 is a great unit, amazing unit in fact, but I prefer not to use it with ER series as it is one of the most euphonic and vibrant Dongles among #donglemadness contestants – of which the energy you would get from that pairing can induce fatigue for extended listening. But of course if that is exactly what you are looking for, then PEE51 just may fit the bill perfectly, Cheers.
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Thank you so much for the detailed response – it is greatly appreciated! I will evaluate the other units that you mentioned.
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Many thanks for your done, will it sufficiently drive Sennheisr HD 650 150 ohm or Buyerdinamic DT 1990 pro 250 ohm ? Has someone tested ?
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Yes it will. I have DT990 Pro 250 Ohm and PEE51 is among those that has lots of power for demanding partners
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WIll this dongle power he400se?
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Yes it can. But must use HiBy Music Player or UAPP USB Exclusive mode to ensure maximum power (if running from Android)
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