New REW build: "Fixed: Coherent averaging did not work well for tones that were not locked to the FFT length"
https://www.avnirvana.com/threads/v5-20-14-early-access-build.11154/
https://www.avnirvana.com/threads/v5-20-14-early-access-build.11154/
I got a FiiO K5 Pro.
It has 2 inputs and one output so was pretty sure I would be able to use it with REW but Im having a hard time.
Im no seeing an input option. In REW when this is hooked up.
I do see a USB Input Codec when I plug in my Dats 2 unit though.
Any help to get this setup. My last option would to be to buy another DAC or sound card. Or figure out a way to use the internal mic jack on the laptop.
It has 2 inputs and one output so was pretty sure I would be able to use it with REW but Im having a hard time.
Im no seeing an input option. In REW when this is hooked up.
I do see a USB Input Codec when I plug in my Dats 2 unit though.
Any help to get this setup. My last option would to be to buy another DAC or sound card. Or figure out a way to use the internal mic jack on the laptop.
I tried Java and ASIO neither show an input in windows. Win7 and Win10.
FiiO has its own control panel app.
I have a USB sound card but it only supports a max input off 16 bits.
Datsv3 shows up an USB Audio in.
This is the Unit I am trying to get to work.
https://www.fiio.com/k5proESS
FiiO has its own control panel app.
I have a USB sound card but it only supports a max input off 16 bits.
Datsv3 shows up an USB Audio in.
This is the Unit I am trying to get to work.
https://www.fiio.com/k5proESS
It doesn't appear to have an ADC section. External signal input is analog, which is passed to analog amplifier. REW can't access that analog input as a digital signal, so many REW functions can't be used. REW may be able to output a test signal to the DAC, but there is no ability to loop that back to REW.
Been reading and going through this thread for what feels like forever. I finally got my setup working. Wanted to post my loopback test and then my first amplifier tested - ACA mini at 2.83 V. I think these look right and reasonable. I'm open to suggestions or thoughts.
Using Viktor's 1 khz oscillator, Akitika attenuator, Focusrite Scarlett 2i2 (2nd gen), into the ebay UXP/EHG resistors mentioned in this thread for a dummy load. These were taken with the oscillator plugged in but I have a battery supply as well that I have been using - I haven't seen any difference except in the lower part of the spectrum. It didn't seem to change the distortion readings however.
Thanks xrk971! And trobbins, ben mah, ItsAllInMyHead, whose posts were very helpful.
Using Viktor's 1 khz oscillator, Akitika attenuator, Focusrite Scarlett 2i2 (2nd gen), into the ebay UXP/EHG resistors mentioned in this thread for a dummy load. These were taken with the oscillator plugged in but I have a battery supply as well that I have been using - I haven't seen any difference except in the lower part of the spectrum. It didn't seem to change the distortion readings however.
Thanks xrk971! And trobbins, ben mah, ItsAllInMyHead, whose posts were very helpful.
Loop back looks fine, the amp not bad, but not impressive.It takes some experiments to find the sweet spots of such measurements. You should attenuate the input level while measuring the amp to the same -17db you used in loop back. Or do a loop back with the same input level as amp set up. Otherwise is is possible you measure the limits of your sound card.
It would be interesting to see whether nonlinear distortion of the amp depends on dummy load or not.
It would be interesting to see whether nonlinear distortion of the amp depends on dummy load or not.
Well done. REW certainly has the ability now to process and plot very broad spans of vertical signal range, although quick visual interpretation can be assisted by perhaps restricting max plot range to eg. 0dBFS and min to -200dBFS, as there is no information outside of those limits. Also you may want to bandwidth limit the assessment span to align to the plot bandwidth, as that can avoid differences between what is seen in the plot as 'Noise', and what is gathered up in the displayed calculation for Noise, and hence also for calculated THD+N.
I noticed the different input levels as well when I posted them. I tried for a few minutes adjusting the inputs and I got the lowest distortion at that input level for the amplifier. I have played with the loopback levels a lot more and get the best results somewhere between -17 and -20.
So is the best practice to find the best level for a loopback and then measure any DUT at the same level? I guess I'm asking whether you should adjust the levels while testing for the best result or just go with the settings from the loopback?
I have the parts express dummy loads as well I could hook up and compare. I'll try to post the two separate graphs later.
So is the best practice to find the best level for a loopback and then measure any DUT at the same level? I guess I'm asking whether you should adjust the levels while testing for the best result or just go with the settings from the loopback?
I have the parts express dummy loads as well I could hook up and compare. I'll try to post the two separate graphs later.
I recommend THD measurements displayed in dB instead of % for easier comparision.
Absolute noise levels can be measured after calibrating the input with a test signal of known amplitude.
THD measurements should be scaled in dBFS thus you can control how far you are from sound card sweet spot.
Absolute noise levels can be measured after calibrating the input with a test signal of known amplitude.
THD measurements should be scaled in dBFS thus you can control how far you are from sound card sweet spot.
Interesting, as I find % to be the easier metric to view.
I also aim to use coherent averaging rather than not, as it clarifies the harmonic levels better. I view Noise floor as equipment and setup dependent, and so imho it doesn't easily relate to anything tangible for others to compare to.
I prefer % too, as it's easier for my brain to comprehend and compare. I don't have to subtract the signal dB from the harmonic dB.
I also do not use coherent averaging as I also use the FFTs to assess the noise level of my builds. I have high sensitivity speakers so I strive for low noise builds. For comparisons purposes, I compare noise levels of my amplifier builds with the amplifier signal output at 1W into 8R and my preamp builds with the preamp signal output a 1Vrms into 10k.
I also do not use coherent averaging as I also use the FFTs to assess the noise level of my builds. I have high sensitivity speakers so I strive for low noise builds. For comparisons purposes, I compare noise levels of my amplifier builds with the amplifier signal output at 1W into 8R and my preamp builds with the preamp signal output a 1Vrms into 10k.
Appreciate the help and insight. I did some more tests. Turned off the coherent averaging and ran another self loop. Then left the input the same - they differ by a few hundredths I know, sorry- and checked the ACA mini into the UXG dummy load and then into the parts express dummy load (both are 8 ohm) - I do not see any difference.
Then I checked the ACA mini results when running the oscillator on battery supply. I still see a 60 hz and a 120 blip - i tried moving things, unplugging everything but the mini, putting the focusrite, the attenuator,and the oscillator in different positions - then all not touching, then touching, etc - no change. Computer is on battery power as well. Something I'm missing, I'll keep trying.
All are at 1 W into 8 ohms with coherent averaging off and other settings as in the self test drop down.
Here is my loopback with the coherent averaging off
Here is the aca mini on the UXP resistor dummy load:
Here is the ACA mini on the parts express style dummy load (still at 8 ohms)
And then here is the ACA mini with a battery supplied oscillator
Then I checked the ACA mini results when running the oscillator on battery supply. I still see a 60 hz and a 120 blip - i tried moving things, unplugging everything but the mini, putting the focusrite, the attenuator,and the oscillator in different positions - then all not touching, then touching, etc - no change. Computer is on battery power as well. Something I'm missing, I'll keep trying.
All are at 1 W into 8 ohms with coherent averaging off and other settings as in the self test drop down.
Here is my loopback with the coherent averaging off
Here is the aca mini on the UXP resistor dummy load:
Here is the ACA mini on the parts express style dummy load (still at 8 ohms)
And then here is the ACA mini with a battery supplied oscillator
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At those low levels the 60 /120 could easily be induced noise in the power amp. Any nearby mains transformers / fluro lights? I had similar induced noise and it turned out to be an isolating transformer some meters away. Even an SMPS can induce mains noise like that. As you've already considered, rotating a cable 90 degrees can make a difference to these setups. They are that sensitive.