After the main tests I noticed that I could make the sound more comfortable and increase the depth of the scene by lowering the sound card’s volume and increasing the volume on the amplifier. As a result, the KamaBay Amp delivered a confident, crisp bass, good dynamics, and a huge reserve of volume. Therefore I can recommend it for headphones with low sensitivity. The 32Ohm headphones squeeze rather too many distortions from that amplifier whereas high-sensitivity headphones don’t need such a high gain setting. Formally, the KamaBay Amp supports 16Ohm headphones, but you shouldn’t expect good sound then.
Next I tested the amplifier with a speaker system that had an impedance of 4 Ohms. To remind you, Scythe never mentions the allowable load impedance for the digital amplifier although the chip manufacturer says about the need to use speakers with a resistance of 7.5 Ohms or higher in stereo mode. This is half true. The KamaBay Amp could actually work with a 4-Ohm load until a certain level of output power as determined by its protection. The level was higher than what I could get from the C.E.C. HD53R-80 which is specified to deliver 2x10W with such load. So, it is quite possible that the KamaBay Amp was just limited by its power adapter’s capabilities. Anyway, the sound quality of both amplifiers was far from perfect, even though the C.E.C. produced a clearer sound. On the other hand, the Scythe was colder. Its case did not heat up even when working for long at the maximum volume.
To go on with my experiments I needed speakers with an impedance of 8 Ohms. After some deliberation I selected the popular multimedia speaker system Microlab Pro 3 with dedicated amplifier. It is with this system that the KamaBay Amp had the final battle. I installed the new Microlab Pro 3 in the part of the office room that was free from furniture and placed the speakers in such a way that they formed an equilateral triangle with the listener. Each side of the triangle was no shorter than 1.5 meters, and the distance from the nearest wall was over 1 meter. The speakers were set at a height of about 80 centimeters above the floor at the edges of two office desks. In other words, I had to achieve a more or less correct sound staging with what I had at my disposal since I had no special room to perform the test in. And I guess I achieved my goal well enough. The signal source and player remained the same, and I used a Dali Stereo Demonstration CD as the test material.
When I turned the KamaBay Amp on, I realized that it was not inferior to the Microlab Pro 3 amplifier in terms of output power. Both easily delivered sound volume above the comfortable listening level. Overload would show up on the KamaBay Amp as wheezes at low and medium frequencies whereas the Microlab amplifier cut the ear with high frequencies even at medium volume level and it was too much for me to bring the latter to obvious overload. The KamaBay Amp had stiff high frequencies (perhaps, it is a peculiarity of the Microlab speakers) but they were not that irritating. The KamaBay’s tonal balance seemed truer to me but the Microlab amplifier had less distortion in medium frequencies because even the most excellent vocals provoked no excitement on the KamaBay Amp. Both amplifiers coped so-so with the piano but I just could not listen to Deep Purple on either of them. There were differences in terms of sound staging: it was washed-out on the Microlab while the KamaBay lacked any echeloning.
Summing it up, the KamaBay shows nothing extraordinary as a speaker system amplifier, but its sound quality is on the same level with amplifiers of multimedia speaker systems. Since it delivered dry stiff sound with a flat scene in the headphones too, I can guess that this is not the digital amplifier’s fault. The problem is in the passive analog components accompanying the chip or the input cascade that is set for too high amplification.
As for the Microlab amplifier, it seems to be let down not by its LM4766 amplification chip but by its low-quality digital volume/timbre regulator because I have a similar amplifier with a passive volume control and a disabled timbre unit which does not produce such obscenities with high frequencies.