[MrFixr55]

Many moons ago (1963), Dad bought Mom a V-M (Voice of Music) Stereo phono that had a 3 tube "SE" Amp2 50L6s and a 12AX7, 2 detachable speakers, each containing 2 6" speakers.  The VM Changer contained an Astatic ceramic cartridge.The power came from a voltage doubler circuit and the output transformers were larger than normal.  This set sounded rather nice. Unfortunately, when the family house changed hands, the stereo, which had deteriorated and was relegated to the basement, was lost. The large output transformer, large speakers and about 160V on the plates of the 50L6s was the key. A similar formula (About 130V on the plate, 8" speaker and more iron and copper than normal in the OPT) contribute the great sound of your Zenith. I have an RCA 1R81 "Livingston" with power transformer and 245V on a 6V6 output tube and an 8" speaker. This does not sound much better than the Zenith H725 at a reasonable volume. Only at high volume toes the Livingston outperform the H725.