Radio Broadcast (May 1928-Apr 1929)

RADIO BROADCAST ADVERTISER 307 A NEW SHORT WAVE ADAPTER FEATURING EASY TUNING AND SUPER SENSITIVITY RECORP LOWAVER The perfected "High Frequency" Converter for use with your regular radio receiver — any make. Plugs in. No change in wiring. Change back instantly. Hear around the world, telegraph, telephone, and television. Penetrates local electrical storms, day or night. Clear as crystal summer or winter. Model DC for all sets using A and B batteries or eliminators, and Model AC for sets using the new AC tubes, 226 and 227. This is a wonderful proposition for the technical dealer or professional custom builder. Sold completely assembled, unwired, nothing extra to buy, and with full directions. Price, two or more, $12.00. Sample, $13.00. Retails for $25.00. Post paid in U. S. Canada and Foreign, 60c extra. Also sent C.O.D. upon receipt of $1.00 deposit. Cash, money, or certified check. Literature upon request. Our dealers are our best reference. RICHARDSON ELECTRIC CORPORATION P. O. Box 2056 Fort Lauderdale, Fla. SILENCER SOCKET For anyone build No. 481-XS. 65c. ing short wave or regular sets, using sensitive detector or screen grid tubes, the Na-Ald 481-XS socket is recommended. This silencer socket prevents microphonic noises and preserves the life of these delicate tubes. Recommended in circuits elsewhere in this magazine, Na-Ald makes a socket for every purpose, as well as more than thirty different adapters. Write for new catalog just off the press. Alden Manufacturing Company Brockton, Massachusetts Build this Modern Amplifier! SANGAMO HIGH QUALITY AUDIO AMPLIFIER SANGAMO 00025 MFD MOULDED CONDENSER WITH GRIO LEAK CLIPS \ LIST 150 SANGAMO TYPE AJ AUDIO TRANSFORMS LIST I san6am0 type br push pull input transf" LIST t t. SO Dynamic FOR UK-210 on UX-II2 TuBCS LIST S6.S0 Push pull OUTPUT TRANSFORMER FREQUENCY INPUT TYPE 22 OCT EC TO movable coil on cone of oynamic Type of speaker connected 0irect to sangamo secondary gets the low notes The up-to-date radio is using "pushpull" for the last audio stage with two power tubes — the output going directly to the moving coil of a dynamic speaker. Thus ample capacity and energy for those low notes are available. Such an amplifier using good transformers gives a quality of reception never attained before. Little expense necessary Sangamo, manufacturers of precision electrical apparatus since 1899, have recently completed a line of audio transformers and impedances which match the various types of power tubes now available — and which sell at a price considerably lower than usual for apparatus of high quality. Included in this new "X" line is the "AX" audio transformer which has an extremely flat amplification curve over the entire audio frequency band. Two of these transformers and a Sangamo Output Impedance to match the power tube used form the basis for a remarkably efficient amplifier of the conventional type. Push-Pull Amplifiers The circuit diagram shown above is the latest and perhaps most satisfactory amplifier developed to date. It will be noted that the Sangamo Output Transformer is especially designed for the particular power tube used and for a dynamic speaker. That is, the primary has an impedance to match the tube and secure maximum energy transfer and the secondary impedance matches that of the moving coil of the dynamic speaker. The Sangamo Input Transformer has an accurately divided secondary to secure practically identical frequency curve characteristics for both tubes in the stage. Similarly in the "X" line are found Push-Pull Transformers to match power tubes but designed for use with speakers not of the dynamic type. The cost for the apparatus is shown in the diagram. The approximate cost of ' uilding the amplifier is only about $25.00. Latest Audio Hook-ups A free circular describing Sangamo apparatus and circuit diagrams of best types of audio amplifiers will be sent on request. SANGAMO aiffiSS Springfield, Illinois