Thanks Pavel, but I think my concern was related to the low input impedance of the Cosmos ADC when used in unbalanced operation.Absolutely no problem, just make a 3- wire RCA to XLR cable. Low distortion remains same.
Thanks Pavel, but I think my concern was related to the low input impedance of the Cosmos ADC when used in unbalanced operation.Absolutely no problem, just make a 3- wire RCA to XLR cable. Low distortion remains same.
You are right, in some cases I have to use a buffer in front of E1DA Cosmos. It is not a universal unit and needs qualified operator. But it is good for measurements of power amplifiers, as they have extremely low output impedance and in parallel with usual 4 or 8 ohm load the input impedance of Cosmos is negligible and low impedance dividers can be used.Thanks Pavel, but I think my concern was related to the low input impedance of the Cosmos ADC when used in unbalanced operation.
Hi @IVXTHD+N 6db mismatch at 1kHz -116db. BTW, REW seems adjusted only for 1k THD+N and >1k or <1k THD+N are also wrong, at 100Hz AP2700 6-7db better! I gonna test Arta at 100Hz and 6kHz.
PS: no, regarding REW it was my mistake because FFT was 64k and spectral leakage made 100Hz THD+N so bad. At 6kHz REW shows 1db less THD+N vs AP2700, similar to Arta.
Ah yeh I am blueYou should also see that the signal LEDs next to the XLR inputs light up blue when a signal is present. Blue=Mono, Green=Stereo.
please read the product description https://e1dashz.wixsite.com/index/cosmos-adcAh yeh I am blue
Thanks
I remember the measurements are a little more accurate in mono mode, correct ?
Mono mode increases the Cosmos' SNR by 3dB.Ah yeh I am blue
Thanks
I remember the measurements are a little more accurate in mono mode, correct ?
Ive been doing measurements with only 1 channel connectedMono mode increases the Cosmos' SNR by 3dB.
Keep in mind that in Mono mode, you have to connect One output channel of your DAC to both inputs on the Cosmos.
Also keep in mind that doing so will halve the load impedance that your DAC has to drive. That can cause issues depending on the DAC.
Mono mode increases the Cosmos' SNR by 3dB.
Keep in mind that in Mono mode, you have to connect One output channel of your DAC to both inputs on the Cosmos.
Also keep in mind that doing so will halve the load impedance that your DAC has to drive. That can cause issues depending on the DAC.
With the Cosmos in Mono and signal only present on R input, the R output is identical to if the Cosmos had been set to Stereo. See here:Ive been doing measurements with only 1 channel connected
So i have not been betting the true benefit of mono mode?
in other words, same performance as stereo mode?
there is some trick to measure SN/DR at a lower level than Cosmos ADC may offer i.e. subresidual noise.Exactly this. I only use mono mode for dynamic range measurements as you often end up with worse results than stereo mode if making full scale measurements as many DACs do not like halving the already low input impedance caused by the splitter.
I've found that when making full scale THD+N measurements there is often a sweet spot. For noise performance you want to use the lowest sensitivity as possible but this also results in the lowest input impedance which is bad from a distortion standpoint. I've often found that a slightly higher sensitivity gives the best results as distortion is reduced while not compromising noise too much.
Michael
mdsimon was talking about full-scale THD+N measurement and the challenge of high load impedance with the Cosmos, especially in Mono.there is some trick to measure SN/DR at a lower level than Cosmos ADC may offer i.e. subresidual noise.
I understand, but as I see he's a smart user so I like to disclose that idea to himmdsimon was talking about full-scale THD+N measurement and the challenge of high load impedance with the Cosmos, especially in Mono.
there is some trick to measure SN/DR at a lower level than Cosmos ADC may offer i.e. subresidual noise.
Thanks !With the Cosmos in Mono and signal only present on R input, the R output is identical to if the Cosmos had been set to Stereo. See here:
View attachment 273784
The L output will have 6dB lower signal and 3dB lower noise, so in total 3dB less SNR.
With the signal only present on L input, the L output will have 6dB lower signal and 3dB lower noise, so in total 3dB less SNR.
And R output won't output anything regardless of Mode.
At the moment I am measuring from my headphone amps XLR-4 outputKeep in mind that in Mono mode, you have to connect One output channel of your DAC to both inputs on the Cosmos
Nobody's talking about the DAC to AMP connection.In this case I can't really connect DAC left output to AMP L+R output ?
Yeah I think you didUnless I misunderstood what you wrote here (quoted)
No. If you want to do Mono measurement with the Cosmos, then don't connect L out to L in and R out to R in.I can connect both left and right to Cosmos and can play L+R signal at the same time from REW - will that achieve what you wrote or not really? For optimising mono measurement
I am measuring my DAC output from the output of my amp. So measuring the combinationNobody's talking about the DAC to AMP connection.
Not really possible with XLR-4 to dual XLR3 adapter right?Instead, you should connect L out to L in and L out to R in. One output (L) to both inputs (L+R).