Hello Gabriel,/\r\n//\r\n/do you plan an Hardware Update of the Xprotolab anytime soon? I have some proposals to make./\r\n//\r\n/The first concerns the AWG around OpAmp U3D. The way it is configured, it exhibits a first order R/C characteristic, whith its chracteristic poor shape (non-flat passband, slow roll-off). My suggestions is to modify this circuit to what is called an "Active Filter", in this case a "multiple feedback Filter - MFB". It just needs some re-wiring around the OpAmp, and comes at no extra cost (if I ignore one extra Cap and 2-3 R's)./\r\n//\r\n/I have attached: /\r\n/"01_schematic_MFB_filter.jpg": the proposed schematic of the modified filter./\r\n/"02_AGW_response.jpg": Spice Simulation comparing the repsonses of the original (red) vs. the proposed filter (blue). Note the much improved passband response, wider bandwidth and better supression above half the sampling rate./\r\n/"Sinus_Orig.png": Measurement of the AWG output Signal for 3 sinewave frequencies (16 kHz, 40 kHz, 125 kHz) with equal amplitude setting on the original Xprotolab AWG output. Note how the amplitude drops already at 40 kHz, as confirmed by the simulation./\r\n/"Sinus_Mod.png". Measurement of the same settings, after the new filter was implemented. Note that the amplitude drop toward higher frequencies has much improved. On the 16 kHz waveform (red) the sampling artefacts can still be ovserved, because the low sampling freq of 250 kHz cannot effectively be filterd, if higher frequencies up to 125kHz also need to pass. Can the sampling frequency not be increased like it is in the 40 kHz case (orange trace), which apart from less amplitude drop also has a much better sine-like shape than in the original./\r\n/"Rect_Orig.png", "Rect_Mod.png": compare similar scenarios, only with a square wave setting. Note that the improved bandwidth leads to a much better rectangular shape, even considering the small overshoot which is caused by the limited bandwidth of that ancient TL064 OpAmp./\r\n//\r\n/Talking about the OpAmp my suggestion is to replace that lame-duck TL064 at least with its sister part, the much faster TL074 which should be in the same ballpark concerning cost. Thanks to its much higher bandwidth and slew rate it should significantly improve the performance (at the cost of a few mA extra current). Even better and possibly interessting to guys who want to modify the existing Xprotolab is the TLC074, an improved version of the TL074./\r\n//\r\n/The analog inputs to the scope are likewise subjects of possible improvements. More about this later./\r\n//\r\n/BR/\r\n/Steve

Hi Steve! Thanks for the suggestions. I'll keep them in mind if I make another hardware revision. Can you also share the spice simulation files?

Hello Gabriel,/\r\n//\r\n/I am running my simulations on Keysight ADS, which is not a Spice Simulator in the conventional sense, but has its own proprietary data format. However it is possible to export a simulation setup into a Netlist file that might be compatible to a Spice simulator, though I never tried that./\r\n/See the attachment. Anyway, the circuit is very simple so it should be only a matter of a few minutes only for you to re-draw it into your favorite simulation environment from the sreenshot that I have provided./\r\n//\r\n/Regarding the distortion of the AWG output due to the too low sampling rate that I mentioned and that can be seen on the screenshots that I made, why don't you set the rate to the max. possible value of 500 kHz?/\r\n//\r\n/BR/\r\n/Steve

Hi Steve, I do send data to the DAC at 1Msps. More information about this can be found on section 4.3 of the manual.

Looking again at the measurement of the 16 kHz sinewave the distortion caused by the remainder of the DAC staircase output can clearly be observed with an effective rate of 125 kHz (see the attached screenshot)./\r\n/If the DAC update rate actually is 1 MHz then I suspect that the problem might be a too low amplitude quantisation of the sinewave approximation. /\r\n/This would mean in this case that each amplitude value is output 8 times in a row at a rate of 1 MHz, reducing the effective sample rate to 125 kHZ./\r\n/In that case a higher resolution would be desirable to cure this problem.

The TL081 is even lower noise Texas Instruments has a series of video?s on low noise and low distortion training.ti.com/ti-precision-labs-op-amp...on-design-1?cu=14685 for us audio guys. I know that a 15 volt supply is probably too much to ask for. i I just ordered the plain looking forward to using it.