Test Methodology:The configuration is loaded with a twin tone in the signal generator, with two high frequency tones (19kHz + 20kHz) at amplitudes of -7dBFS each, and separated in frequency by 1kHz. The analyzer measuring the first-order difference frequency at 1kHz using a highly-selective FFT-based filter.
Scope IMD 19kHz+20kHz.png
Test Results:- 2-Channel Direct DAC mode (https://analog-precision.com/forum/performance-and-measurements/dac-19khz-20khz-imd-test/msg362/#msg362)
- 2-Channel Preamplifier Mode using the ASRC (https://analog-precision.com/forum/performance-and-measurements/dac-19khz-20khz-imd-test/msg363/#msg363)
- IMD vs Ampltude (https://analog-precision.com/forum/performance-and-measurements/dac-19khz-20khz-imd-test/msg365/#msg365)
- DEQX PreMate, HF intermodulation spectrum from a Stereophile review (https://analog-precision.com/forum/performance-and-measurements/dac-19khz-20khz-imd-test/msg366/#msg366)
Conclusion:The following test results show that the IMD distortion of the Ultimate Preamplier is exceedingly low and betters the performance of the DEQX Pre-mate by a long margin !
IMD (19kHz+ 20kHz 30kHz BW Direct-2Ch).png
IMD (19kHz+ 20kHz 30kHz BW Preamp-2Ch).png
IMD(CCIF).png
Fig.12 DEQX PreMate, HF intermodulation spectrum, DC to 30kHz, 19+20kHz at 0dBFS into 100k ohms (left channel blue, right red; linear frequency scale). (https://www.stereophile.com/content/allnic-d-5000-dht-da-processor-measurements-0)
Note how the noise floor is lifted up by the two tones whereas this is totally absent in the UP spectrum above ! Again the UP wins hands down !
(https://www.stereophile.com/images/1214DEQXFig12.jpg)