![]() Nothing prepared me for the disaster that unfolded in front of me in test after test. Due to use of ESS DAC I thought the performance would be good. Going into this review I didn't think it would be exciting. are music to everyone's ears, mine included. The words on PS Audio website for Stellar Gain Cell DAC paint a super seductive picture of this DAC. Owner was anxious to see the measurements so here they are. Will perform tests and update the review later. I have to run out to our Audio Society meeting in half hour so no time for this. We can test the non-linearities by feeding the unit dual tones: one low frequency and one high and compute the "intermodulation" distortion relative to the level of input signal: There are voltage controlled amplifier ICs used in Audio/Video Receivers and they perform far better than this. The cure for potentiometer is far, far worse than the disease. Imperfect and non-matching transistors are in the circuit fed by noise and distortion that modulate them. The modulated ones are by definition not harmonic in nature so let's not have the argument that these are "good distortions."Īt any rate, no way, no how this pre-amp and its core circuit can be called "zero loss" or "pure." There is nothing pure about it. Put simply, we fed the Stellar Gain Cell one tone, and got dozens and dozens of unwanted tones and distortion product. Likewise, any power supply noise and spikes will also modulate our main signal creating sidebands on each side of our desired signal, creating that spray of spikes all around our 1 kHz tone we fed to the unit. Gilbert cell is also a modulator so any noise fed to its second input will modulate the primary (music) signal giving us what we are seeing. This indicates noise modulation of our signal much like can happen with DACs and jitter. The button of our 1 kHz tone has been broadened. The distortion is asymmetrical between the channels showing lack of precision that way too.īut look at what else is going on. Starting with the worst offenders, second and third harmonic distortions are way up at near 70 dB, resulting in SINAD (signal over noise and distortion) of just 68 to 71 dB. You are seeing what I am seeing? PS Audio, what the heck have you done to my pristine input signal? That is true, but PS audio goes further, saying this scheme puts nothing in the signal path and hence is "pure" in execution: ![]() PS Audio contrasts this with using a potentiometer which could have longevity issues. By controlling that DC unit using the front-panel microprocessor, you can now have control of the attenuation including the ability to have a remote control. Using 6 transistors in a clever differential configuration, you can either mix two analog signals together, or use DC on one pair of inputs and control the gain of the other. The Gain Cell is the PS Audio name for a differential mixer circuit called Gilbert Cell. This brings is up to the name of this product, "Gain Cell." So companies resort to an external analog variable gain output stage. Standard way of using the volume control built into the DAC chip (ESS in this case) doesn't obviously work for analog inputs. Inclusion of an analog pre-amp and switcher presents a problem for volume control though. ![]() In addition to usual set of digital inputs we also have a set of analog inputs! For people like me who have Reel to Reel deck and others who have turntables, being able to integrate everything into the DAC and thereby eliminating an external pre-amp, this is great!
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