Radio Broadcast (May 1927-Apr 1928)

RADIO BROADCAST ADVERTISER 183 SM Any Bird Can Twitter — BUT— It Takes a Bull to Bellow We Could Charge More But — A Better Transformer Can't Be Made That's a cold statement about the S-M 220 audio transformer, but it takes steel and copper to ma\e the best transformer. The size and weight of the S-M core — the countless turns of wire — these are the things that produce real transformer quality. And where will you find a heavier or higher grade silicon steel core — where will you find more copper than in the S-M 220? The 220 has from 2$ to $0 per cent more steel and copper in its construction than any other transformer on the market. We could charge from 25 to 50 per cent more for them than we do, but at no price can you get a better transformer. Do you wonder why it's sold on an unconditional guarantee to give you better tone quality than any other audio amplifying unit available? The 220 audio is $8.00, and the 221 output is $7.50. They are priced low, not merely made to sell at a low price. We can't make the 22o's cheaper but if you desire a transformer somewhat lower in price: td^mg up a little less room, and with a little less core and wire, the new 240 audio and 241 output transformers are superior to most other transformers, and are far superior to anything in their price field. They have the same general characteristics as the famous 220 s and 221V, but provide slightly less accentuation of frequencies below So cycles. They have the same yooo cycle cuuoff for which 220's are famous, eliminating many of the objectionable whistles and heterodyne squeals. The 240 audio sells for S6.00 and the 241 output at $5.00. Hard to beat at any price. Impossible to equal at these prices. S-M audios have outsold all other transformers. They are specified in more prominent circuits than any other. The answer is obvious — they are better — that's all. IT takes real power output — real voltage — for a power amplifier to reproduce the lowest note on a bass viol or the beat of the kettle drums so that it is really recognisable. The 660-210 Unipac is a combined last stage amplifier and full 425 volt power supply. Its amplifier consists of a stage of transformer coupled audio, in push-pull arrangement, employing two 210 super power amplifying tubes. Its undistorted power output is three or four times greater than that of any amplifier yet developed. And, this does not necessarily mean that the volume delivered is such that an auditorium is needed to keep tone values within reason — the volume is under control — but it does mean that the tremendous power required to reproduce tones in the lower frequencies — below 100 cycles — is there at all times. The 660-210 Unipac is entirely self-contained — it connects to any 105-120 volt, 60 cycle alternating current. It furnishes its own A, B and C power — and supplies B current to the entire receiver as well. 1.5 volt filament current is also available for first stage audio A. C. tubes. The 660-210 Unipac in kit form is $83.25 or $93.25 completely wired. While the 660-210 Unipac stands alone for its undistorted power output and handling capacity, other models are available covering practically all requirements in the audio amplifying and power fields. The 660-171 Unipac with its two 171 tubes in push-pull arrangement, possessing of course less amplification than the 660-210, will furnish ample undistorted output for the average home — more than any single tube 210 amplifier that is on the market. It delivers all ABC power to the amplifier and 45 and 90 volt potential to the receiver as well. The 660-171 Unipac kit is $64., or $74. completely wired. The 660-171 A Unipac, similar to the 660-171 will, in addition, furnish complete A power to the receiver when new A.C. tubes are employed. The 660-171A Unipac kit is $66., or $76. completely wired. Various models may be built up as phonograph amplifiers — as complete two-stage amplifiers — in fact, the constructor can build up practically any combination of audio amplifier system and power supply that he demands. All are described in the Unipac booklet which we will gladly send. An outstanding example of Unipac flexibility is the LC-a8 Unipac, developed for Laurence Cockaday, a two-stage amplifier and power supply for the LC-28 receiver, employing the new S-M 240 and 241 transformers. A similar model has been specified by Glen Browning as the official amplifier for the new Browning-Drake Two Tube Tuner. Complete parts for the LC-28 Unipac, $81.25. SILVER-MARSHALL, Inc. 838-A West Jackson Blvd. Chicago, U. S. A. We can't tell you here the full Unipac story, nor of the new developments in audio amplification and complete A. C. operation, but if you'll send in the coupon we'll send you complete data. SILVER-MARSHALL, INC. 838'A West Jackson Blvd., Chicago. Please send me all data on the Unipacs, Improved Shielded Sis, new transformers, ABC power units, etc. Enclosed is 10c to cover postage. The A new ie A. C. Improved Shielded Six is ready — a completely light socket oper ted batteryless set A. C. tubes. It's illustrated above, with its comp'ete dry ABC power unit — less than 7 incl Address . . using the :hes square.