* Single Ended
* U$840
* One of the best sounding and best parts at this range
* One of the amplifier with largest power transformer at this range (EI 114-60)
* One of the amplifier with largest output transformer at this range (EI 86-50)
* One of the amplifier with best ripple filtering (double choke filter) at this range
* One of the amplifier with sturdiest chassis at this range (double layered stainless steel that can take 70KG load without deforming
A20 (KT88 single ended class A amplifier) - one of Boyuu's cost no object creation, with high quality oversized output transformer and power transformer.
The circuit is evolutionized from WE 91 amplifier, taking the gist out of this design and make it even better. It uses 6J8PG as voltage amplifier (equivalent to US's 6SJ7, direct drop in), with gain of ~60 that is sufficient to drive KT88 to full power. It uses aerospace/medical grade Shuguang 5Z3PAT as rectifier (5Z3PAT is a few grades higher than 5Z3PJ in terms of stability or sound). Shuguang KT88-98 or PSVANE KT88 is used as the output power tube, not to mention localized feedback is used.
A20 specialty
* High single ended output power, reaching 18W
* Output stage uses specialized localized feedback technique for better sound
* 0.35mm SiFe core as power transformer
* Has output tube current monitoring for easy observation and tube change
* Medical grade 5Z3PAT rectifier
* Potted output transformer for vibration prevention, moisture prooving and protection
* Double layer chassis design, using 1.2mm stainless steel, with 2 U-shape bracing for strengthening, totaling 2.4mm thickness, capable of withstanding 70KG of load
* Output transformer uses imported 0.35mm SiFe core specialized for audio usage, EI 86 with 50mm stack, with Gauss capacitor reaching 13,000, much better than the general 7000 range
Technical specifications
* Output power: 18Wx2 (Ultra-linear)
* Frequency response: 20Hz - 35kHz
* Output impedance: 4 Ohm, 8 Ohm
* THD: <= 1% (1kHz)
* Input sensitivity: 750mV
* Input impedance: 100k Ohm
* Sze (WxDxH): 366x300x185mm
* SNR: 89dB
* Net weight: ~16.5KG (EI 114 power, export version)
Product details
* Driver tube: Shuguang 6J8PJ x2
* Power tube: Shuguang export KT88-98 x2
* Rectifier: 5Z3PAT x1 (not the same as 5Z3P, do not mix up)
* Power transformer core: imported 0.35mm, EI 114-60 stack
* Output transformer: high SiFe imported 0.35mm EI86-50 stack
* Chassis: imported stainless steel chassis
* Face plate: CNC ALU plate, annodized
* Output: high grade binding posts
Design details
* Potted output transformer for stability and reliability, especially for moist/wet area
* High grade pure copper magnet wires are used for winding, with layered and segmented winding method for best bandwidth
* High grade transformer casing are used, with powder coated wrinkled finishishing
* Imported 0.35mm core for power transformer - ensure sufficient power and low operating temperature
* Optional tube cage, purchased separately
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