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Delta Studio Amplifier KT88

"Audio Video" 6/2002

High power integrated tube amplifier with overaverage tone, taking advantage of highly valued by audiophiles stream tetrodes KT88

KT88 is the most expensive device in Delta Studio's tube amplifiers catalog. As regards of structure it looks similar to cheaper models, which were introduced in AV (12/01 and 4/02). Outwardly high price of this device finds complete justification in overaverage tone and high quality workmanship.


In comparison with previously tested amplifiers 6L6 and EL34, this device looks almost identical. Noticeable difference is the shape of power tubes. Other differences concern elements placed inside casing: metalized resistors, capacitors designed to work in high temperatures and a high quality ALPS potentiometr. Bigger speaker transformers enable power tubes to work in ultralinear configuration. Circuit conception is generally the same as in other models. Driver state is realized on 6N1P and 6N2P tubes, and output on high power stream tetrodes KT88 (Pa=42W), which work in AB class. In a practical side Delta Studio KT88 doesn't differ much from the other devices of this manufacturer.


Transmitted frequency band is wide and very well leveled. Timbre is showy and saturated with very audiophile style. With reference to natural sound we can't accuse anything but it's hard to resist the impression that there is lack of only one little step for complete satisfaction. The sound is decisive and clean. Shapes of individual tones have enough sharply outlined edges with good fill. Tone is drawed with a hard line of a very well changed thickness. The tone characterize by lightness, has moderate consistency, but if necessary it characterize with high energy and become powerful. In general terms the tone is rich, spacious, full, even, plastic, clear with a flourish and well joined. Although sometimes the amplifier tries "by force" to surprise the listener with showy phenomenons (commonly happened audiophile manner, which may be understood as the opposite of monitor sound). Range of middle tones falls gently, silky (you may say velvet). Timbre is very good and vocals have excellent timbre too. Bass: about it's high quality decides first of all power of impact and untied range of dynamic at this range. Grow and extinguish time is similar or even little better than in 6L6. Shape of bass is similar to natural with insignificant curvature with large dimensions. Regardless of part or underange his reproduce is categorical, just imperious. It doesn't mean exaggerated overwhelm, but pretty big dose of energy is secured. Trebles have solid support from upper middle and they are properly integrated with rest of the range and they doesn't go near sound (music). Space impressions are much better than this what is offered in other models. Both sizes, perspective and gradation of design decide about class difference, certainly on the advantage of KT88. Dynamics, especially in macro-scale is very good, also microdynamic represents standard much above average, although it has a little lack of sophistication. Impulses are transmitted with flourish, without embarrassment. The amplifier "is not afraid" of full orchestras and high volumes of sound. Temperament of KT88 as the only one of all three seems to be a good compromise or rather a golden mean which decides about real cohesion of music, what in my opinion undoubtedly is significant feature of every natural performance. Bravo!


Delta Studio KT88 is meant for all the people looking for universal high power tube amplifier with strictly audiophile tone. It doesn't mean that it will be liked by everyone - it concerns especially followers of sound of DHT-SE amplifiers (Direct Heated Triode - Single Ended).

Ludwik Igielski  

Delta Studio KT88
Category A
Rate High-end

Technical data
Output power 2 x 63 W (2 x 5 W in A class)
Band width 2,7 Hz-72 kHz
THD distortions < 0,06%
Intermodulation distortions < 0,1%
Signal/noise ratio > 90 dB
Dynamic > 125 dB
Weight 29 kg
Delta Studio Amplifiers - High End audio tube amplifiers