I recommend you REW FFT to measure the noise floor. You'll see something like this:any idea of those frequencies in upper region ?
Very nice!My last upgrade - dual E1DA Cosmos A-iso setup in mono mode driven from Topping D90SE
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not bed
I use a slightly modded frontend in ADCiso. Pls, try to search our discord regarding the powerbanks comparison, not too many but have some. Regarding the separated powerbank per unit, it is the best way to get the cleanest result, however, not necessary one, and it depends on your test room EMI conditions.Just out of curiosity, why does the ADCiso have typically 3 dB lower 3rd harmonic than the ADC classic, as mentioned by IVX a couple of pages ago?
About the low noise power pack Xiaomi PLM18ZM recommended by IVX, it does not seem to be available in Europe or is branded differently. It is listed on Aliexpress, but that shop does not ship it to Germany (btw, E1DA Ali shop also still does not ship to Germany, but to France).
What are people using in Europe instead of the PM18ZM? I was thinking may using an analog regulator fed from 2 Li-ion cells or a 12 V lead acid battery might even be better than a power pack with a switch mode converter? Is there a need to feed Scaler, APU and ADC from separate batteries or can they all use the same unit?
Yes, discord. I used to read there but haven't in about one year. It's only a few days ago that I started looking at your products again. However, with the link, if first get an invite from you and when I click join it keeps telling me the invide cannot be accepted. It has been like this for about a week on different computers.I use a slightly modded frontend in ADCiso. Pls, try to search our discord regarding the powerbanks comparison, not too many but have some. Regarding the separated powerbank per unit, it is the best way to get the cleanest result, however, not necessary one, and it depends on your test room EMI conditions.
Well somehow on both of the computers that I had used previously, logging into plain discord and accepting their updated conditions of use did the trick. The link now works. ThanksHmm, I tried right now this link, no problem..
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Sorry to ask, does it mean APU preamp can't measure Sweep IMD, Multitone, etc?I was waiting for the Cosmos Scaler because of the low input impedance of the Cosmos ADC, and while the Cosmos APU solves this issue for 1kHz signal, I wanted to measure IMD, Multitone, etc. I finally got the Scaler and did a quick test. Let me share the results.
https://www.audiosciencereview.com/...ts-and-measurements.37739/page-3#post-1328586
I measured two DACs with Cosmos Scaler and ADC (Grade B). One is TOPPING D30Pro (Balanced) which did not have any problem with the input impedance of Cosmos ADC. The other is an ES9023 based DAC board (SE), which had high level distortion at low input impedance. Below is a comparison of without Scaler, with Scaler 0dB, Scaler Auto and APU 1kHz notch (THD+N and 1kHz signal dBFS at 4.5V input range). The input range of Cosmos ADC was all 4.5Vrms, measured by Stereo mode of ADC (not MONO).
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As you see, Cosmos Scaler reduced harmonics of the ES9023 DAC drastically. Without Scaler (Red) vs with Scaler 0dB (Green).
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I was able to measure IMD (SMPTE 60Hz and 7kHz) either by 0dB or Auto settings of Cosmos Scaler.
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While the Auto setting of Cosmos Scaler was unstable when measuring multitone. 0 dB (or fixed gain) worked fine.
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I am satisfied with these results. Thank you @IVX for this nice variable gain input buffer.
It can, but only with low amplitude input signals as the preamp cannot be set to unity gain, only +34 or +60dB.Sorry to ask, does it mean APU preamp can't measure Sweep IMD, Multitone, etc?
As IVX answered correctly, the APU cannot be used for general multitone measurements. As stated in Cosmos APU's “Important notes”,Sorry to ask, does it mean APU preamp can't measure Sweep IMD, Multitone, etc?