Topping D90 MQA - teardown
This is the MQA version of the D90 reviewed by Amir here: https://www.audiosciencereview.com/...ds/topping-d90-balanced-usb-dac-review.10519/ back in Dec. 2019. As per the above measurements “the D90 is instrument grade digital to analog convert and can be used to test analog audio gear”.
The case is made of aluminum, black anodised, with dedicated grounding points without coating. I can see three grounding points on the back plate, but also couple of more additional grounding points on the bottom too.
Top view of the motherboard.
Bottom view of the motherboard. Notice the copper grounding points and the PVC isolation from backside, to prevent any possible short-circuits.
Rails for the board to fit inside and also for the screws.
Grounding is done through this part of the case too, via the screws from the back and from the bottom as well.
One of the two grounding points from the bottom of the case
Common-mode rejection filter, 120/230V switching board, transformer. Notice the well done wiring job with good isolation around.
I do like to see linear PSU inside such a small DAC case, with the a 120/230V switch on the bottom of the case. The transformer seems beefier then needed, so probably oversized a bit, which is usually a good thing. It is followed by couple of bridge regulators made of 8 x SS34 fast 3 A Schottky diodes. There are three big Nichicon capacitors, 3300uF/25V each, used to lower the AC ripple.
Fast 3A Schottky diodes and big FW Nichicon capacitors.
Two ON-SEMI LM317D2T linear regulators followed by SMD capacitors are lowering AC ripple & noise, then used on both rails of the digital side from the middle of the board. Of course, smaller regulators might be seen on the board, for chips that requires different input voltages.
LM317 linear regulators followed by SMD caps.
TPS7A47 and TPS7A33 are +/–36 V, 1 A, Ultralow-Noise linear voltage regulators and are used, one on each rail, to power the D90 analogue parts and the DAC chip (the right side of the board).
Texas Instruments low noise TPS regulators.
(I needed to use lot of Isopropyl alcohol spray to clean this board's corner, probably due to some resin left over).
Couple of Accusilicon AS318-B Series Professional Audiophile Crystal Oscillators, about 50 USD each. One is 45.1584 MHz and the other one is 49.152 MHz, very low noise both (-100dBc).
Accusilicon clocks.
The DAC used is from AKM, an AK4499EQ 4-channel DAC. The opamps following the DAC chip are four OPA1612 used in I/V conversion and as buffers we can see three LME49720. Just near the XLR & RCA plugs we can spot three muting chips (37190 1941U 16-pin IC) that can be easily activated by remote’s MUTE feature. Four Japanese Nichicon 3300uF/25V capacitors are used to lower the noise in analogue domain from the AKM DAC chip.
The three LME49720 opamps and the 16-pins muting chips (not sure what model are these).
AKM AK4499EQ DAC chip, TI OPA1612 I/V opamps and the big 3.300uF Nichicon caps.
USB downstream traffic is handled by the multicore microcontroller XMOS U11690C20 which is part of the XU216-series vs. the XU208-series on the non-MQA version.
XMOS, ALTERA, ARM and the AK4118 chips.
A “Complex Programmable Logic Device (CPLD)”, ALTERA MAX-II EPM240T100C5N, can be easily seen on the board. This is a programmable device that contains a non-volatile memory inside and is probably used inside D90 to deal with digital processing. Topping advertiser states “clock processing and signal optimisation” and “combines with the accusilicon femtosecond to bring a lower jitter effect”.
AKM AK4118AEQ is a 192kHz 24bit Digital Audio I/F Transceiver used for the S/PDIF output (OPT/COAX/AES). Murata 78601/1JC isolates the S/PDIF input from the board, this a common thing to do when BNC or COAX plugs are installed.
ARM STM32F030 microcontroller from the board features an Arm® Cortex®-M0 core inside that runs at speeds up to 48 MHz. I guess this CPU is the main “core” of D90’s board, taking care of all the commands coming from the computer host or from the external sensors/switches, since pressing the Power ON/OFF, play and decode PCM/DSD/MQA till all the commands available in the LCD menu.
Screen menu has only two rows, but it's clear and visible, with three brightness settings.
This DAC can natively decode PCM32bit / 768 kHz and DSD512 natively via IIS and USB inputs, as well as Bluetooth 5.0 transmission 24bit/96kHz LDAC, AAC, S-BC, APTX, APTX LL, APTX HD via the Qualcomm CSR 8675 chip.
The multitude of In/Out ports. Notice the left & right grounding points and the one from the right side of the AES socket.
Grounding of the case is done when screws are inserted.
D90 has a nice case and a very informative front screen, with enough menu settings. Thesycon ASIO drivers are working perfectly and without any skipping or audio drops. The BT5.0 with LDAC support sounds fine when streaming audio from my phone. The inside wiring and shielding are done with care and responsibility and the soldering is very well done too. Plugs & sockets are of a very good quality and includes both balanced and non-balanced outputs as well as several inputs too, good Nichicon caps can be spotted, so I can not see any flaws.
However, I’d like to have the Bluetooth module completely shut-down, but I guess this is not possible, because it doesn’t seems to have a small SMPS inside to take care of power management. So, unless I want to use the back power switch the BT adapter, and probably other chips from the board, will remain powered ON (very low consumption anyway).
Also, having the power switch on the back, without easier access sometimes, I’d like to see a menu option for the D90 to remain powered-OFF by default instead of existing power-ON, so when I push the power button from back I’d like the D90 to stay OFF until I power it ON from the remote or from the front button.
Remote control is nice, not too small like the one from Apple TV and not too big like TV’s remote. I’m not in love with it’s narrow angle of operation, but I can definitely live with this and if I point the remote straight to the D90 it operates as it should.
Last edited:
