I was trying to locate something more than a headphone amp for listening to my CD-Player (old Cambridge Audio DVD89), my laptop via USB for high-res streams and other devices I might connect digitally to the inputs. The Topping DX3 Pro+ has a good number of inputs. The least used for me is the Bluetooth, but it’s a nice convenience when I am not concerned about audio quality. I finally figured out how to get sound from the unit when I make a Bluetooth connection from my stereo receiver which is sending LDAC. The Sony receiver’s Bluetooth TX works with Bluetooth headphones without issue and, while it took a little work, turning AAC and LDAC off from the Sony Bluetooth setting then turning them back on let the connection to the DX3 Pro+ start working. My iPhone, MacBook and Windows laptop can connect to the DX3 Pro+ over Bluetooth without issue. On the other inputs, there is one USB, two digital coax and one digital optical input. I am using the optical with the DVD89 and as expected the Topping displays the standard 16bit/44.1KHz rates when playing a CD. I don’t have any SA-CD’s or DVD-audio disks to test with and wonder what it would display for the rates if I did. I took one of the digital coax inputs and added a convertor to take analog input and convert to digital in case I want to connect and old analog device. The primary input for me so far has been the USB connection. On the MacBook Pro midi settings, I am able to configure the bit depth and sampling rates to the maximum supported by the unit without issue. Those specs are 32bit/768kHz – though I am doubtful my old hears hear much improvement on anything more than the red book CD standard of 16bit/44.1kHz. On the output side of the house, the unit has the front headphone jack and a R/L RCA line out on the rear. My current headphones are some Sennheiser 560s cans and are true to their design claim of being reference tuned for balanced clear sound across the spectrum. Personally, I like a little bass boost and need some high frequency increase from old age hearing loss. While not related directly to the DX3 Pro+, my cheapskate solution was to run the line out through a Behringer EQ which is not really made for headphones. With the 120-Ohm impedance, the Sennheiser headphones I have no issues with the adjusted audio output of boosted lows and highs. I also tried my in-ear 32-Ohm 1More Quad Drivers connected directly to the EQ and got some distortion, but those don’t really need the EQ. So, I use them connected to the front headphone output when I need sound isolation not offered from the open back 560s.
Operation of the unit is fairly straight forward with the remote. The circle control toward the top does two things, up and down = volume, while right and left = input selection. The center button in the circle is related to output. Pressing it will activate output to both the headphone jack and line out, while the two buttons to right and left below the circle are headphone out only (left button below circle) and the other is line out only (right button below circle). The next button down the left side (F/R) is for PCM filters while the adjacent right button (M) is for adjusting the gain (6dB or 19dB). The bottom two buttons are for auto standby (left) and display brightness (right). The two top most buttons are power and mute and labeled appropriately.
My impressions on the sound quality are subjective to my ears so I will limit my comments here. I find the sound processing of the signals fed are accurate and convey what I perceive the original sound engineer wanted before I route the output to the EQ. When listening to Amazon Music on the Macbook connected over USB to the DX3 Pro+, I can click the Ultra-HD logo below the song info when the player is along the bottom of the Amazon Music window and see the DX3 Pro+ signal capabilities seen by the app match what I entered in the midi settings. I also see the bit depth and sampling rate for the Amazon file as well as the bit depth and sampling rate being sent and accepted by the unit. I have found a few 24bit/192kHz songs to play and a quick display of that data is made to the Topping display of you watch closely. I am a fan of Dr. Mark Waldrep and currently reading is book on Music and Audio. So I will end with this: The Topping DX3 Pro+ is the most versatile piece of gear I have and the most expensive item in my simple setup for listening from my easy chair (the DVD89 and Optimus EQ (Radio Shack)were bought used). While I would love to report I can hear drastic differences between the standard CD audio and higher resolution songs, I can only say that I do hear subtle background instruments I think I was missing before and find very little bothersome overloaded frequencies in the mid to lower high range and vocals are crisp given my ears and the Sennheiser 560S cans.
Note: I have also used the same setup with some original late ’70s Koss Pro-4AA headphones which belonged to my dad. These have new cushions and work great. The only difference with the Sennheisers are weight and long term listening. The Koss weigh in at 19 ounces, over half a kilo, and the new cushions are velour which makes them more comfortable. From an EQ standpoint, the EQ curve was very similar to the 560s with more reductions in the mid-range and a slight more boost to the high end for the Pro-4AA, which probably is an accurate reflection of the capability of drivers between 40 year old and present day headphones.
Update 7 Apr 2023: Experienced a HP ERR (Headphone Error) today while listening to some FLAC files over USB and output to my EQ and then Sennheiser HD660s headphones. Ended up killing the power make it go away. Decided to check on a firmware update and found a minor update from 1.23 (https://www.tpdz.net/newsinfo/663552.html) to version 1.25. I have applied the update and listening again over USB and all is good so far. Research said some folks experienced the problem with specific songs. So, I went back to the start of my playlist and listening continues….
Mac Users: I used to think leaving the MIDI Settings Application open after setting the bit and sample rate would result in full volume white noise or something going out to the headphones after about 60 seconds. I am not sure what causes it as I have experienced it without the Mac Midi settings app being open, but something does nasty things to the signal being sent to the DAC when listening over USB when it happens.
Some Other reviews:
https://www.audiosciencereview.com/forum/index.php?threads/topping-dx3-pro-review-dac-headphone-amp.27148/
https://primeaudio.org/topping-dx3-pro-dac-review/
https://www.head-fi.org/showcase/topping-dx3-pro.23320/reviews
https://www.headfonia.com/topping-dx3pro-plus-review/
Specifications from Topping:
| Specifications | |
|---|---|
| Product type | DAC Headphone amplifier Preamplifier |
| Inputs | 1x USB-B 1x Optical Toslink 2x Coaxial Bluetooth 5.0 |
| Outputs | 1x Stereo RCA 1x Jack 3.5mm headphone output |
| Amplification chip | TPA 6120A2 |
| DAC chip | ESS ES9038Q2M |
| Bluetooth chip | QCC5125 |
| Supported sampling rates | USB : PCM up to 32bit 768kHz, Native DSD up to DSD512, DSD DoP up to DSD256 Coaxial / Optical : PCM up to 24bit 192kHz, DSD DoP up to DSD64 |
| Supported Bluetooth codecs | AAC, SBC, aptX, aptX LL, aptX HD, LDAC |
| DAC Measurements (@ USB, 96kHz) | |
|---|---|
| THD+N @ 1kHz, A-Weighting | < 0.00015% |
| THD @ 20Hz-20kHz, 90kBW | < 0.0002% |
| SNR @ 1kHz, A-Weighting | 122dB |
| Dynamic range @ 1kHz, A-Weighting | 122dB |
| Frequency response | 20Hz-20kHz (±0.3dB) 20Hz-40kHz (±0.7dB) |
| Output level | 2.1Vrms @ 0dBFS |
| Noise @ A-Weighting | < 1.8µVrms |
| Crosstalk @ 1kHz | -137dB |
| Channel balance | 0.3dB |
| Output impedance | 20Ω |
| Headphone amplifier measurements | |
|---|---|
| THD+N @ 1kHz, A-Weighting | < 0.00015% @ Output=1500mW, 32Ω < 0.00013% @ Output=160mW, 300Ω |
| THD @ 20Hz-20kHz, 90kBW | < 0.0005% @ Output=1500mW, 32Ω < 0.0005% @ Output=160mW, 300Ω |
| SNR @ Max output level, A-Weighting | 120dB |
| Dynamic range @ 1kHz, A-Weighting | 120dB |
| Frequency response | 20Hz-20kHz (±0.3dB) 20Hz-40kHz (±0.7dB) |
| Output level | 5.5Vpp @ G=L 21.5Vpp @ G=H |
| Noise @ A-Weighting | < 2.1µVrms @ G=L < 7µVrms @ G=H |
| Crosstalk @ 1kHz | -90dB |
| Gain | 6dB (Vrms/FS) @ G=L 19dB (Vrms/FS) @ G=H |
| Output impedance | < 0.1Ω |
| Output power | 2x 1800mW @ 32Ω, THD+N < 0.1% 2x 900mW @ 64Ω, THD+N < 0.1% 2x 250mW @ 300Ω, THD+N < 0.1% |
| Adapter impedance | > 8Ω |
| General | |
|---|---|
| Dimensions | 120 x 165 x 40mm |
| Housing material | Aluminum |
| Color | Black |
| Package | 1x Topping DX3Pro+ 1x Power supply 1x Remote control 1x USB Cable 1x Bluetooth antenna |