@kevin gilmore has the circuit diagram posted here. Here's the full pcb board.
First, the digital part
You can see the bluetooth module on the top left.
On the middle right is the MS8422N, which is a chip to do routing, replacing LC89058W on earlier topping devices.
The signal then routes to the XMOS for final digital processing (EQ).
On the middle left is the ES9018 DAC. generating analog audio signal and then sending to the synwit processor below.
The Synwit chip will use onboard 12 bit ADC to convert that back to digital signal, and perform the FFT computation.
The FFT bin amplitude will be displayed on the screen as spectrum.
Right side is the I/V module and on the top is the output buffer for RCA using OPA1612.
The power supply is spread across the entire PCB. but below is the main one.
Here're the step down converters that generate +/-15V from the switching power supply. There're also mosfets/bjts that control the on/off of the power rails on the top.
the lower right is the headphone protection circuit, by detecting the sum of 4 (2 ch x 2 phase) outputs, so if any transistor fries, it should be able to prevent your headphone from being destroyed.
Here you see two I/V boards. Op Amps seem to be OPA1656.
I/V boards are dual sided and the front side can be seen as an improved op amp based on this patent.
once the circuit is simplified to equivalent circuit according to the patent,
what remains is a textbook I/V, identical to op1, r1, r2 and C1 in this article
The back side of the board is just the current source to support the differential pairs on the front side.
Below the I/V boards are the DAC chips and passive output stages.
Topping D50 III has the same board. but DX5 II has twice the I/V.
Each board computes the difference of L+/L-/R+/R- and Ref/2 per DAC.
D50III may omit the Ref/2 or just sum the L/R.
The middle part is particularly interesting. There're multiple transistor pairs. The output of those transistors goes to the I/V board's diff pair input.
So it's the reference voltage for the DAC chip. Based on the transistor counts I am pretty sure it's this patent.
D50 III has the same circuit, by the way. It's safe to assume both devices are designed at the similar time frame (2023).
On the right portion there's +/- 5.8V power rails (half of that shown in the photo), which power the op amps.
In kevin's diagram you can find the transistor pair model.
Finally the tiny PCB here is the HP Amp's input and VAS. BJTs are power source, similar to the I/V. The transistor pairs are the input stage (differential pairs).
The input signal is from the bottom motherboard's resistor group, which has the I/V output and HP amp feedback signal, with gain control / mute switches.
The Op Amp (looks like OPA1612) is the VAS. It finally goes to the heat sink on the right (not in the photo) for output.
The output stage is nothing special but a classic class B amplifier. Thanks to the global feedback and tons of compensation it doesn't show any signs of crossover distortion.
The efficiency of the amplifier is also how Topping can cram so much power inside this small box.
First, the digital part
You can see the bluetooth module on the top left.
On the middle right is the MS8422N, which is a chip to do routing, replacing LC89058W on earlier topping devices.
The signal then routes to the XMOS for final digital processing (EQ).
On the middle left is the ES9018 DAC. generating analog audio signal and then sending to the synwit processor below.
The Synwit chip will use onboard 12 bit ADC to convert that back to digital signal, and perform the FFT computation.
The FFT bin amplitude will be displayed on the screen as spectrum.
Right side is the I/V module and on the top is the output buffer for RCA using OPA1612.
The power supply is spread across the entire PCB. but below is the main one.
Here're the step down converters that generate +/-15V from the switching power supply. There're also mosfets/bjts that control the on/off of the power rails on the top.
the lower right is the headphone protection circuit, by detecting the sum of 4 (2 ch x 2 phase) outputs, so if any transistor fries, it should be able to prevent your headphone from being destroyed.
Here you see two I/V boards. Op Amps seem to be OPA1656.
I/V boards are dual sided and the front side can be seen as an improved op amp based on this patent.
once the circuit is simplified to equivalent circuit according to the patent,
what remains is a textbook I/V, identical to op1, r1, r2 and C1 in this article
The back side of the board is just the current source to support the differential pairs on the front side.
Below the I/V boards are the DAC chips and passive output stages.
Topping D50 III has the same board. but DX5 II has twice the I/V.
Each board computes the difference of L+/L-/R+/R- and Ref/2 per DAC.
D50III may omit the Ref/2 or just sum the L/R.
The middle part is particularly interesting. There're multiple transistor pairs. The output of those transistors goes to the I/V board's diff pair input.
So it's the reference voltage for the DAC chip. Based on the transistor counts I am pretty sure it's this patent.
D50 III has the same circuit, by the way. It's safe to assume both devices are designed at the similar time frame (2023).
On the right portion there's +/- 5.8V power rails (half of that shown in the photo), which power the op amps.
In kevin's diagram you can find the transistor pair model.
Finally the tiny PCB here is the HP Amp's input and VAS. BJTs are power source, similar to the I/V. The transistor pairs are the input stage (differential pairs).
The input signal is from the bottom motherboard's resistor group, which has the I/V output and HP amp feedback signal, with gain control / mute switches.
The Op Amp (looks like OPA1612) is the VAS. It finally goes to the heat sink on the right (not in the photo) for output.
The output stage is nothing special but a classic class B amplifier. Thanks to the global feedback and tons of compensation it doesn't show any signs of crossover distortion.
The efficiency of the amplifier is also how Topping can cram so much power inside this small box.
