At the beginning of this year, I ordered transformer steel of the Z11 type for the manufacture of new SW4 and SW9 amplifiers. I have never worked with this steel, I knew only from reviews and rumors. When I had a little time, I decided to conduct comparative tests of steel of the M6 and Z11 types. To begin with, I put together a magnetic circuit measurement unit from an electrical engineering textbook. Then I assembled two transformers on different magnetic cores, but with the same coils. The left transformer with a dark core is with a Z11 magnetic core, the right transformer with a light core on a M6 magnetic core The first tests. Measurement of the inductance of the core without a gap. - Z11 - 20,68 H - M6 - 12,35 It can be seen that the initial magnetic permeability of Z11 is noticeably greater. The second test. We visualize the hysteresis loop in the core without a gap. - Z11 steel hysteresis loop - M6 steel hysteresis loop It can be seen that the coercive force of M6 steel is greater, which means there are more losses in it. But not much. The next test, visualization of the hysteresis loop with a gap in the magnetic circuit of 0.1 mm. For this purpose, the transformers were disassembled and paper with a thickness of 0.1 mm was placed between the plates E and I - Z11 (0.1mm) Zoom in horizontally - M6 (0,1mm) Zoom in horizontally The characteristics have become very similar. But the initial inductance of Z11 turned out to be greater, 12.7 H (Z11) versus 8.75 H (M6) From this I concluded that both brands of steel are suitable for a high-quality transformer, but the Z11 is still better.