Radio Broadcast (May 1928-Apr 1929)

.RADIO BROADCAST ADVERTISER. 1950 Reception Will be Different! Try It NOW and See — in the New S-M 72oAC All-Electric Screen-Grid Six Know How Next dear's Best Will Sound A SCREEN-GRID tube with A.C. heater-type filaA\ merit, nearly twice as good as the wonderful UX222— and the '22 in S-M 1929 sets is enabling S-M setbuilders to get station after station never heard with common factory-built sets. . « A power tube with more than sufficient undistorted output capacity to fill the best dynamic speaker — yet without the high plate voltage required for the 250. . . Every refinement of precision manufacture as built into the tremendously successful 720 (D.C.) Screen-Grid Six — plus improvements which make the new 720AC All-Electric a set capable of far better reception, both as to distance range and selectivity, and tone quality as well, than even the original, never-yet-equalled, 720. . . Be the first on the ground with it! Get your order in at once to your S-M jobber or dealer. Tubes Required 3 UY224 (C324) (The new A.C. screen-grid lube.) 2 UY227 (C327) (The present popular heater tube.) 1 UX245 (CX345) (The new super-power moderate voltage output tube. Used with the new S-M 669 power supply, the 720AC is a complete all-electric receiver designed especially to bring out the extreme possibilities of these new tubes. Price, completely WIRED in 700 two-tone shielding cabinet, less tubes and power unit, $117.00. Component parts total $78.50; cabinet $9.25 additional. S-M 669 Power Unit, WIRED, $57.50. S-M 720 receivers can be changed over at slight cost to the 720AC circuit. S-M And ios-Positively Guaranteed Superior That same unchangeable purity and fidelity of tone, which has established S-M supremacy even more firmly this year than ever before, can be built into any receiver or amplifier by using the new S-M. Clough -system audio transformers. Guaranteed absolutely and unconditionally to surpass, in their uniform amplification of all notes from 5000 down to 40 cycles, any other transformers obtainable on the American market at any price, these unique instruments make use of a principle totally different from anything used in standard transformer construction— built-in resonance to even out the amplification curve in the critical range which ordinary transformers weaken— and a circuit which keeps D.C. plate current entirely out of the transformer winding and thereby avoids the common injurious effect of hysteretic distortion. Amplification obtainable — running as high as 4Vz to 1 — is far higher than with any standard transformers of comparable tone quality. S-M Clough system audios are now obtainable in a complete line, for both single and push-pull amplification, as follows: 255 and 256, for standard use in first and second stage respectively. Each. . . .$6 225 and 226, similar to 255 and 256, but larger and slightly more perfect in both frequency characteristic and amplification ratio. Each $9 257 Push-Pull Input Transformer, to operate from one amplifier tube into two 171A, 210, or 250 tubes. Each. .$7 227 Push-Pull Interstage Transformer, to feed from two 112A, 226, or 227 tubes into two 112A, 226, 227 or 171A, 210 or 250 tubes. Each $8 258 Tapped Output Impedance, to feed from two 171A tubes into any standard speakers. Each $5 248 Universal Output Choke to feed out of two 210 or 250 tubes into one to six or more standard speakers; provided with several impedance-matching taps. It will handle over 20 watts without core saturation. Open-mounted. Each $7 228 (248 in case like 227). Each $8 ■For the New Tubes: S-M 335 Power Transformer" This is the transformer used in the new S-M 669 power unit. It contains one 105 to 120 volt primary; one 5 volt, 2 ampere, rectifier filament winding; two 2.5 volt, 6 ampere, filament windings. Plate voltage with one '80 tube, 300 volts at 100 m.a. Provided with iron end terminal mountings, or (335U) in open mounting; either type $15.00. Are you getting the Radiobuilder, a monthly publication telling the very latest developments of the S-M laboratories? No. 11 (Mar. 3929) gives further details of the new 720AC. Send the coupon for free sample copy, or to enter your subscription if you want it regularly* If you build professionally, but do not have as yet the S-M Authorized Service Station appointment, ask about it. SILVERMARSHALL, Inc. 838 West Jackson Blvd., Chicago, U. S. A. Silver-Marshall, Inc. 838 W .Jackson Blvd., Chicago, U. S. A, Please send me, free, the complete S-M Catalog; also sample copy of The Radiobuilder. For enclosed in stamps, send me the following : .... 50c Next 12 issues of The Radiobuilder .... SI .00 Next 25 issues of The Radiobuilder S-M DATA SHEETS as follows, a 1 2c each: No. 1 . 670B. 670ABC Reservoir Power Units No. 2. 685 Public Address Unipac No. 3. 730. 731, 732 "Round-the-World" Short Wave Sets No. 4.223, 225. 226, 256, 251 Audio Transformers No . 5 .720 Screen Grid Six Receiver . . . .No . 6 . 7 40" Coast-to-Coast" Screen Grid Four . . . .No. 7 .675ABC High-Voltage Power Supply and 676 Dynamic Speaker Amplifier . . . No. 8. Sargent-Rayment Seven . . . .No. 9. 678PD Phonograph Amplifier No. 10. 720AC All-Electric Screen-Grid Six. Name. n • april, 1929 . . . page 363 •