(a summary translated from a post on 2019/09/01 23:50 at
https://bbs.kakaku.com/bbs/K0000579959/SortID=22884769/ )
ES9038PRO has 8 channels, which makes the output current too large to I/V conversion by a single OPamp, if the 8 channels are wholly utilized. People have been coping with this challenge by, for instance, coupling an OPamp with a current buffer, using two parallel OPamps, or using a discrete I/V converter instead of OPamps. One such example is an implementation by the Japanese boutique AIT Labo
http://aitlabo.net/ . There are pictures on this page of their DAC implementation using ES9038PRO. Compare this with the Sabaj D5 circuit board
http://www.sabaj.com.cn/en/productshow.asp?id=79 . It uses two OPamps per channel for I/V conversion and post-filtering. That means it only uses a single OPamp per channel for I/V conversion. As said above, it is not enough to handle the output current of the all eight channels from this high-end DAC chip. The chip is like an American V8 engine, which requires an extraordinary power train. An ordinary one cannot handle the enormous torque and its drive shaft would break. This probably means D5 only uses two channels out of the 8 available on the chip. Of course, this is nowhere explained in the Sabaj D5 page. The blurb reads "its official dynamic range is up to 140" about ES9038PRO. Why say anything about the "official" dynamic range of the chip, rather than their implementation? It even mentions the price of the chip! They emphasize how great the chip is to cover up their cheap implementation of the set. The D5 is like a car with a huge V8 engine that uses only two cylinders because of its weak power train, advertised emphasizing the engine, without mentioning anything about the power train.