LAB REPORT ROBERT KODA TAKUMIK-70 (£35k)

摘要

With its remote 350V/11A DC power supply and floating, DC-coupled output stage, the Takumi K-70 presents a potential hazard both for the enthusiast and, particularly, the test engineer! Precautions duly noted and implemented, the K-70 proceeded to develop closer to 40W/8ohm and 50W/4ohm rather than the specified "approx 70W, the output clearly in clipping at this point. A few more watts are available under dynamic conditions [see Graph 1, below] but with a maximum current delivery of only 3-4A, the K-70 is best suited to entirely passive, high sensitivity loudspeakers. Never connect an active subwoofer in parallel with the speaker terminals, for example. Limited power notwithstanding, the K-70 offers some intriguing numbers. With no fewer than 32 power transistors its output impedance is almost ruler-flat at 0.065-0.07ohm across the audio range before rising to 0.19ohm/100kHz. This is mirrored by the frequency response which extends down to -3dB/3Hz and is ruler-flat from 20Hz-20kHz before rising to +1dB/50kHz and +3dB/85kHz. The response into 8,4, 2 and 10hm loads follows this same trend. Distortion is low, typically around 0.02% at 1W/8ohm from 100Hz-40kHz, rising to 0.04% over the same bandwidth at 10W/8ohm. There is an increase at very low frequencies, rising to 0.12% at 5Hz/1 W and rising more steeply still at higher outputs. As promised in Kǒda's literature, noise is very low (-97dB, A-wtd re. OdBW) but power consumption is vast. At 800W drawn for 0-40W output, the K-70 is even less efficient than Musical Fidelity's AMS-100 [HFN Mar '11]. Readers are invited to view a comprehensive QC Suite test report for the Takumi K-70 amplifier by navigating to www. hlfinews.com and clicking on the red 'download' button.