LUXKIT A3550

Commentary

Stereo / monaural power amplifier kit with selectable beam tube connection and 3-pole tube connection.

The A3550 is based on a stereo power amplifier using a high-reliability and high-power beam tube 6550A developed by GE of the US.
As for the circuit method, while taking advantage of the advantages of the Williamson-type circuit characterized by a wide bandwidth and low distortion by reviewing the origin of sound production, we aim to improve sound quality by finishing it into a unique circuit that eliminates multiple NFB.
The basic form of the Williamson type amplifier is a high-feedback amplifier using a wide-band OPT (output transformer). However, the A3550 has newly designed and adopted the OY15 high-power type, which is well known for its OPT, and has a sufficient stagger ratio to enable stable NFB. By reducing the amount of NFB as much as possible, the transient response and dynamic characteristics are improved.

On the A3550, you can choose 8 modes with 3 selection points.
First, the connection of the beam tube and 3-pole tube can be selected at the time of assembly. After assembly, NFB and NON-NFB, stereo and monaural can be switched by the switch operation.

All transformers have been newly designed for the A-3550.
In addition to using non-magnetic acoustic resistors, Blackgate S block capacitors, oxygen-free copper wiring materials, MD-capacitors, etc. after controlling their polarity, it is equipped with a "Line Phase Sensor" which checks AC lines for the first time in a kit.

Copper plating is applied to the bottom plate and other parts necessary for sound quality.

Model Rating

Type	Bulb type power amplifier kit
	stereo				mono
	Beam tube connection		3-pole tube connection		Beam tube connection	Triode
	NFB	NON-NFB	NFB	NON-NFB	NFB
Effective power	50W		30W		100W	60W
Total harmonic distortion factor	Not more than 1%	Not more than 3%	Not more than 0.5%	Not more than 1%	Not more than 3%	Not more than 0.5%
Output impedance	8 Ω
Frequency characteristic	10 Hz to 40 kHz Within -1dB	30 Hz to 20 kHz Within -1dB	10 Hz to 30 kHz Within -1dB	30 Hz to 18 kHz Within -1dB	10 Hz to 40 kHz Within -2dB	10 Hz to 30 kHz Within -2dB
Input sensitivity	1.1V		1.0V	1.5V	1.1V	1.0V
Input impedance	80k Ω
SN ratio (IHF-A, input short)	106 dB or more	100 dB or more	105 dB or more	102 dB or more	107 dB or more	105 dB or more
Residual noise	0.3 mV or less	0.6 mV or less	0.25 mV or less	0.3 mV or less	0.35 mV or less	0.4 mV or less
Power consumption	200W
External dimensions	Width 465x Height 176x Depth 226 mm
Weight	18kg