I did some measurements in single channel mode (with -70...):
- The frontend seems to be good to at least 100MHz.
- The displayed amplitude is a bit on the low side below about 20MHz
- The displayed amplitude is acceptable between ca. 20 and 45MHz
- The displayed amplitude is a bit too high beyond ca. 45MHz.
- Sine waves are displayed quite OK up to about 80 MHz - that's perhaps why HANTEK dares to issue the 2D82auto...
- Above 80MHz the sampling rate is too low, so aliasing effects become prevalent.
- Frequencies displayed correctly to above 100MHz!
And now for the brave - retrofitting the AWG using info gathered from YouTube videos, pictures of the PCBs and this thread.
But be aware: the parts nearly cost as much as the price difference between the 2Cx2 and 2Dx2 - so better give those few bucks to HANTEK, because
- they have put effort and manpower in designing this neat, little device
- you can't destroy your device with your plumbers soldering iron
- you keep your warranty
Anyway, here it is (see attached picture):
[disclaimer]Don't blame me, if anything is or goes wrong![/disclaimer]
- fit DAC902 at position U12
- remove R315
- R63, R70 = 50 Ohms (R63 was already fitted in my device)
- C70, C71 = 20 pF (C71 was already fitted in my device)
- fit R65 = 560 Ohm
- I did change R61 from 1,78 kOhm to 2,2 kOhm as the AWG amplitude of my device was too high with the stock resistor
In the frontend section (see picture from reply #56):
- fit EL5166
- fit BAV99
- change 0 Ohms resistor at the output of the OpAmp to 50 Ohms
- change 0 Ohms resistor at pin 3 of OpAmp to 150 Ohms
- change 0 Ohms feedback resistor (at OpAmp left side) to 560 Ohms
No software modification is needed!
But: the quality of the AWG is - uhmm - let's say: suboptimal. Clearly visible spikes and distortion everywhere.
I hope HANTEK will fix this in future versions or is it (only) related to overclocking the DAC902 (250 vs. the specified 165MHz = ~50% over)?
Btw. can someone confirm, that the +3,3V and -5V voltages are way too low (see attached picture)?
I have only 2,9V on the 3,3V rail, which is acceptable, as no analog circuitry seems to use it.
But the -5V rail delivers less than -4V which is not enough for the EL6155 in the AWG, which clipped at the negative half wave at full swing of 2.5V (EL5166 specs say +/-3,8V output at 5V Vdd and 150R Rload).
If your -5V rail also is too low, you can change the marked resistor to 27k which then gives about -4,7V (nominal for -5V would be 29,4k).
I guess HANTEK lowered the voltages to save energy - so I also only raised it bit, just enough to work...
And: don't forget - all modifications void your warranty...