Originally Posted by goodvibes
The diagrams are not using the same block setup and the Fiio one actually doesn't make sense coming off the last stereo 1612. iBasso shows the separate channels of a single chip as independent blocks and Fiio shows entire chips as blocks. Either is fine but not directly comparable pictures. Fiio improperly has the last 1612 as a single channel out becoming stereo again.
The DAP's 2 paths are very much the same in practice except for summing in the LPF of the iBasso with only parts selection and voicing being different. There is no material advantage to either unless the new Sabre DAC chip proves to be one.
Afraid you are quite wrong, both the diagrams actually show exactly how many opamps the x5 and dx90 use. The x5 uses a single dual channel opamp for LPF and another for AMP, while dx90 uses two single channel opamps for each, the dx90 is technically the better design, using two extra opamps over the x5 to completely separate the channels.
The reason why the x5 and dx90 have two dual channel opamps after the dac is because both dacs output a 2 channel current for each left and right channel (so 4 channel total), so either 2 dual channel opamps are needed, or 4 single channel opamps, after this the signal is converted to 2 channel and you need either 1 dual channel opamp or 2 single channel op amps the rest of the way down the chain.
The only thing the x5 does better than dx90 in the schematic is x5 can be said to have a better IV stage than the DX90 (the two chips after the DAC) purely because the x5 uses two better opamps than the dx90 (x5 uses opa1612, dx90 uses opa1602), all the rest of the schematic the dx90 is much better than the x5. I do wish that the dx90 used the same IV opamp as x5, then the dx90 would have been faultless.
It is right after the DAC where ibasso went with slightly lower end chips, so that affects the rest of the chain. I would have thought it was a no brainer for ibasso to use the opa1612 instead of the 1602. In the rest of the line up ibasso use the opa1611, which is a high end, high power consumption chip, it doesn't make sense to go with a lower power, lower end chip for converting the dac signal!
Edited by T.R.A.N.C.E. - 4/9/14 at 7:37am