30W Tube Amplifier Output Transformer Single-ended Z11 Annealed Silicon Steel EI 300B 2A3 2A3EL156 KT88 FU13 Audio HIFI DIY 50w tube amp output transformer single ended z11 silicon annealed steel 0 4 8ohm for 2a3 300b el156 kt88 fu13 el34 6p3p hifi