Ultimate Preamp vs DEQX

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Introduction:

Whilst we don't actually have a DEQX in front of us to test and compare with, we can still leverage the test results from a recent Stereophile review of the DEQX Pre-mate  which apparently is the same hardware used in all of their models with some changes to the I/O and software capability otherwise it is the the same old hardware except for the cheaper models which apparently use a switch mode power supply instead of the linear power supply used in the more expensive models. Of course the UP uses a linear power supply in all of its models

For a detailed comparison between DEQX and the Ultimate-Preamplifier please click here to refer to our comparison table

Test Results:

• Spectrum of 50Hz sinewave, DC–1kHz, at 0dBFS into 600 ohms
• 16 bit Jitter Test using J-test
• DAC (19kHz + 20kHz) CCIF IMD test
• Waveform and Spectrum of undithered 1kHz sinewave at –90.31dBFS

Conclusion:

We can see a pattern emerge here and that in all tests shown below the Ultimate Preamplifier displays superior performance over the DEQX in all cases. Not just a small improvement but a major improvement !

DEQX claim the following from their own website but the measurements from Stereophile review don't really support these claims !

Audiophile-grade engineering

Every aspect of a DEQX is carefully engineered for optimum audiophile performance. For example: countless design, development, and auditioning iterations were put into the latest A/D convertor circuit and the DAC's I/V (current to voltage) convertor circuits. Over a decade of constant refinement and attention to detail has paid off in superlative performance.

Now add in superb digital coding and algorithms: a −140 dB digital processing noise floor and a precision digital volume control. The end result? A truly transparent component with zero digital artifacts. An "analog" sound for all combinations of input to output: analog to analog, digital to digital, and any combination of the two.

DEQX also claim in one of their reviews of "'first do no harm' transparency" but the measurements from Stereophile compared to our own measurements of the Ultimate Preamp show anything but transparency. Add to this an antiquated DSP platform with very limited FIR capability shows that this product is trying to be all things to everyone but succeeding at none of them.

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Fig.11 DEQX PreMate, spectrum of 50Hz sinewave, DC–1kHz, at 0dBFS into 600 ohms (left channel blue, right red; linear frequency scale).



Shown below is the output from the UP which shows at least an order of magnitude less noise and distortion compared to the DEQX whilst approaching the bottom limit of what the analyzer is capable of measuring !

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Shown below is the J-test Jitter spectrum of the DEQX Pre-mate as reviewed by Stereophile. Noise floor modulation, spurious artifacts and poor jitter performance shows some issues with this design.



By comparison the resulting spectrum from the Ultimate-Preamplifier below is much cleaner even for 16 bit Red-book standard and does not suffer from noise floor degradation like the DEQX does above. We can see that the DEQX above needs a lot of work to match the outstanding performance of the Ultimate Preamplifier even for Red-Book 16 bit playback



For the 24 bit J-test Jitter Spectrum the news is even better for the UP which is bad news for DEQX with vanishing low levels of jitter artifacts from the UP !

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Fig.12 DEQX PreMate, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 0dBFS into 100k ohms (left channel blue, right red; linear frequency scale).

Note how the noise floor is lifted up and modulated by the two tones whereas this is totally absent in the UP spectrum ! Again the UP wins hands down when it comes to transparency !



The following test results show that the IMD distortion of the Ultimate Preamplifier is exceedingly low and betters the performance of the DEQX Pre-mate by a long margin !

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Fig.10 DEQX PreMate, waveform of undithered 1kHz sinewave at –90.31dBFS, 24-bit data (left channel blue, right red).
 


Fig.8 DEQX PreMate, filter operating for Bryston Model T, spectrum with noise and spuriae of dithered 1kHz tone at –90dBFS with: 16-bit data (left channel cyan, right magenta), 24-bit data (left blue, right red) (20dB/vertical div.).



Below is the real time capture of the Left and Right Channels of the Ultimate Preamplifier at -90.31dBFS @ 1kHz 24 bit WL. Compared with DEQX above the output of the UP is significantly cleaner !



Below is the FFT Spectrum of the Ultimate Preamplifier output. Compared with the DEQX above the noise floor is much lower on the UP !