Radio Broadcast (May 1928-Apr 1929)

.RADIO BROADCAST ADVERTISER. Tke Peer of All Theatre or Stadium Sound Amplifiers Now Offered to the Public for the First Time For the Smaller Theatre, or the Home — The new 2-stage S-M 678PD Phonograph Amplifier is priced so low that, while particularly adapted for dance halls and small theaters, it is ideal for the home also. Used with any 110 volt D.C. dynamic speaker, it takes input from any magnetic phonograph pickup, or from the detector tube of a broadcast or short-wave receiver, and, by means of its S-M Cloughsystem audio transformers, supplies to the speaker undistorted the full power output of its 250-type tube. Tubes required are: 1 — 226, 1 — 280, 1 — 250 type. All input power is taken from the 110 volt A.C. houselighting mains. Price (less tubes), WIRED, $73.00; complete KIT, $65.00. EVER since the revolutionary improvement in tone quality created by the Clough audio system when first demonstrated to the trade last June, the S-M laboratories have been working day and night to make this discovery available for the largest theatres, auditoriums, football stadiums, and such assemblages at a low cost. As the culmination of these labors, S-M takes the greatest pride in announcing the 690 Super-Power Amplifier. Three stages — Uvo of them push-pull — microphone, radio, or single or double record input — two 250 type tubes in the last push-pull stage giving 15,000 to 16,000 milliwatts output, with uniformly high tone quality down to 50 cycles such as only S-M Clough Audio Transformers can produce — the same quality that is drawing crowds into S-M-equipped movie theatres throughout the United States. With such a unit available completely wired at $245 list price, less tubes — knowing as you do the tremendous present demand for sound amplifiers of the highest grade — you as a setbuilder or service man afford to neglect the installation opportunities ^hich this new S-M amplifier offers you? These New S-M Transformers Make It Possible Built on the Clough System, with curves flat from below 50 cycles to well above 5000 — these transformers give to "push-pull" a new and really startling significance. And their prices, like their quality, are unbeatable! 257 Push-Pull Input Transformer, to operate from one amplifier tube into two 171 A, 210, or 250 tubes. Price, $7.00 227 Push-Pull Interstage Transformer, to feed from two 112A, 226, or 227 tubes into two 112A, 226, 227 or 171A, 210 or 250 tubes $8.00 258 Tapped Output Impedance, to feed from two 171A tubes into any standard speakers $5.00 248 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. .$7.00 228 (248 in case like 227) $8.00 Type 257 Get 250 Tone Quality in Your Present Receiver Or you can get 250-tube power rig/it in your present set by inserting a 250 tube (with an adapter) in the last socket of the set, and using the S-M 675ABC Power Supply. Presto! — the 675 supplies all ABC power to the new power tube (without a single change to the set) and replaces all B batteries or other B eliminators as well. (It will also supply A and C power to A.C. tubes). # Add a 675 to your set and you have all the advantages of the fine, full sonorous tone the super-power tubes bring — tone you find only in $300.00 to $500.00 factory-built sets — yet you can add it to your set for $54.00 plus two tubes! The 675ABC power supply is priced at only $54.00 for the kit, or $58.00 fully wired with adapter. Type 227 Remember — S-M guarantees these push-pull trans formers to have a finer frequency characteristic than any and all competitive types — bar none. 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, at 2c each: No. 1 . 670B, 670ABC Reservoir Power Units .No. 2. 685 Public Address Unipac No. 3. 730, 731, 732 " Round-theWorld" Short Wave Sets No. 4. 223, 225, 226, 256, 251 Audio Transformers ... .No. 5. 720 Screen Grid Six Receiver No. 6. 740"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 Name Address 1 Ave you getting The RADIOBUILDER regularly? No. 9 (Jan. 1929) describes these new push-pull transformers, and the 690 Amplifier, as well as the new (and different!) S-M Dynamic Speakers. No. 7 (Nov. 1928) described in detail, with complete circuits, a 750-volt rectifying system. Sample copies may be had without charge as long as they last; use the coupon. If you build professionally, by all means ask for information on the S-M Authorised Service Station proposition; its money-making opportunities are greater than ever. SILVER-MARSHALL, Inc. 838 West Jackson Blvd., Chicago, U. S. A* a me II ress I Radio Broadcast. February, 1929. Published monthly. Vol. XIV, No. 4. Published at Garden City, N. Y. Subscription price $4.00 a year. Entered at the post office at. Garden City, N. Y., as second class mail matter. Doubleday, Doran & Company, Inc., Garden City, N. Y