An amplifier with a spare tube set is for sale. Built in-house and is made single end (SE) with 6N1P pre-amplification tubes and the final lamps are GU50. In the picture, there are still GU50 tubes on the amplifier, only the aluminum cover has been removed. the tubes from the preamplification are very good, you can see the quality on the catometer in the picture, and the final tubes are new. The amplifier works very well without suspicious noises.