Nothing New Under the AM Sun (Jan. 1977)--About high-fidelity AM radio

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In a previous article on AM high fidelity in Audio (Jan. 1975, pg. 28), mention was made of a 1936 E.H. Scott receiver. Many readers may not completely believe the assertion that it was a high-fidelity receiver. The trend towards modern component hi fi, however, actually began during that period, and E.H. Scott was the foremost manufacturer of custom high-fidelity component systems, being the Crown or McIntosh of his time. Custom is not an idle word either; Scott aligned tuners to work better for different geographical locations and added or subtracted controls to suit the purchaser.

Scott was born in New Zealand in 1887, orphaned at 14, and while in the Australian Army Corps, invented an automotive trouble shooting device which eventually brought him $46,000. After World War I, he migrated to Chicago where he wrote auto maintenance articles syndicated in 50 U.S. and Canadian newspapers.

His interest soon gravitated to radio, and he began to write articles on that subject too. On a holiday in New Zealand in 1924, he took with him a set specially constructed for the occasion, to receive U.S. broadcasts while there.

The feat of having received 117 programs from 19 stations, all at least 9,000 miles distant, with his World Record 9 receiver eventually put him into the radio manufacturing business.

His high fidelity receivers were bought the world over by those famous in musical circles. Scott owners included Sir John Barbirolli, Eugene Goosens, Tullio Serafin, Lauritz Melchior, Al Jolson, Eddie Cantor, Deems Taylor, Guy Lombardo, Rudy Vallee, and Arturo Toscanini. These names attest to the authenticity of the sound reproduced for that period. Other owners included Prince Otto von Bismarck, the Baron de Rothschild, and the Chicago Tribune's Colonel McCormick. The Hearst press used Scott receivers to monitor world news events. A Scott tuner was used to receive one of the earliest experimental television broadcast demonstrations during the early 30s in Chicago.

From his earliest receivers on, Scott emphasized good tone, realistic sound, and the custom look. There were always several different super crafted console cabinets available for both the receivers and speaker systems. All but the very first were sold directly from the factory to the customer. Each set was built to order by an individual technician, and all sets were "burned in" before final testing.

The Scott look lasted until the late 50s, that is, lots of chrome and massive construction. As the chassis and all coil and tube shields were heavily chrome plated, many owners bought only the basic component equipment, the tuner, power amplifier, and speakers. They would then, as now, proudly display their component equipment on shelves or table tops with the speakers mounted in the walls or in speaker enclosures, either custom built or made by Scott. This, by the way, was in the early 1930s.

But, what of the technical quality of the Scott receivers? How does this obviously archaic equipment compare with modern components? Well, first of all, Scott was initially bound to AM for radio reception, and he was forced to develop AM receivers to the technical limits of the period. His tuners, unlike most modern tuners, had an audio bandwidth that permitted the reception of everything being transmitted. For instance, my last $300 tuner had an AM response of a mere 1,500 Hz. My new. $400 tuner with a new IC AM circuit has an audio response of 4,000 Hz. However, my 1930 Scott Air-Wave 12 had a response of 4,000 Hz. I should add that the list price of the Scott was $600, during the Depression years to boot.

The early sets had a fixed, flat-topped i.f. response, and consequently fixed wide-band audio response, just like the modern solid-state super tuners. The use of a broad i.f. is fine for local stations which transmit wide-band information, but distant stations or limited bandwidth stations require progressively narrower i.f. bands. Soon Scott introduced a stepped i.f. bandwidth and later a continuously variable i.f. control. This allowed the user to adjust the i.f. to suit both the station and the atmospheric conditions. These controls are actually very simple to use.

Once on a station, the user opens up the i.f. with the "fidelity" control until the background noise and squeel become objectionable. This control permitted near perfect compromises between fidelity and selectivity. The only modern AM tuners with this 45-year old feature are the new McKay-Dymek line. One respected kit manufacturer is now making an AM/FM' tuner with a narrow, medium, and broad "bandwidth" switch. The control only operates a redundant treble cutoff and doesn't improve i.f. characteristics for better distant reception.

All pre-World War II Scott receivers had push-to-connect antenna terminals just like the modern Japanese sets.

Enter High Fidelity

The year 1937 saw the introduction of one of the best high-fidelity AM receivers ever built and, I imagine, to this day, unexcelled. To approximate it today you might purchase the following: a McKay-Dymek AM tuner, a DBX-119, a Burwen 1201 Noise Reduction unit, and an Audio Research tube amp.

The 1937 Scott 30-tube Philharmonic receiver came standard with features many of us are now seeing newly reintroduced and rediscovered.

This set had two tuned r.f. stages and four audio i.f. stages. The audio i.f. response was continuously variable and flat topped at all points but the narrowest, from between 4 kHz and 32 kHz wide, which permitted 16 kHz audio. Sensitivity was advertised as 0.5 µV. Just as with the latest Luxman $900 tuner, this set had effective AM muting, only it was continuously variable.

The i.f. was front-panel adjusted by a control mechanically linked to each stage and trimmed each transformer, primary and secondary, to accomplish stagger tuning.

The Philharmonic employed both i.f. AGC and delayed r.f. AGC. Each AGC voltage was separately derived by an extra tuned gain stage and rectifier. It could almost be said there were three i.f.s in the set, one for audio, one for r.f. AGC, and one for i.f. AGC. The use of tuned AGC amplifiers reduced the effects of modulation on the AGC voltage. That is, you do not hear the station breathe at you as the AGC voltage follows a broadcaster's voice. This problem just recently became apparent with another kit manufacturer's top-of-the-line receiver which boasted a super AM. So acute was its problem with r.f. AGC breathing, caused by rectifying wide band audio for AGC voltage, that this manufacturer just recently introduced "improved AGC." The improvement was to tie the r.f. amp's AGC gate to a fixed potential, leaving only i.f. AGC. It also saved two transistors and numerous other parts.

Noise Reduction System

Quite a bit of audio processing was employed in the Scott Philharmonic.

Besides the usual bass and treble controls and loudness compensated volume control, there was also a dynamic range expander and an automatic noise reduction system. The ±20 dB bass control, by the way, had a ganged 60-Hz notch filter to correspondingly minimize hum with the bass boost.

The dynamic volume range expander utilized a "Magic Eye" tube to indicate the degree of expansion, somewhat as its solid-state counterpart does on a DBX unit. It also had a continuously variable expansion control as does the DBX. The Scott noise reduction system is usually ascribed to H.H. Scott and is said to have been invented by him in 1946. This is not true. H.H. Scott (no relation) described in his 1947 Electronics article how he improved the time constants of the earlier 1937 E.H. Scott Radio Laboratory Automatic Needle Scratch Suppressor in developing his DNS. It has been suggested in AES literature that Burwen used the H.H. Scott DNS for inspiration in developing his now famous product.

This, of course, was a standard feature of the Philharmonic.

Other features of the Philharmonic were a 10-kHz audio notch filter, a 40 watt class-A power amp employing push-pull output devices, and a two-way speaker system employing a 15 in. woofer and two five-in. tweeters.

The set was constructed on two welded, heavy gauge, chrome-plated chassis, one for the tuner and control section and a second for the power amplifier/supply section. Later versions included a third chassis which contained an LC crossover network.

Dial calibration was advertised as 0.2 percent.

The 1937 Scott Philharmonic, then, was quite advanced even for 1977! However, it was missing one important feature which Scott had had in limited production in 1936 (and Sony and Crown in 1976)-tri-amplification. One channel was used for each of the following ranges, 30-125 Hz, 100-600 Hz, and 3-16 kHz. This set was the 40-tube, later 48-tube, and still later a 57-tube Quaranta. Besides employing an 18-in. woofer, two 12-in. midranges and three tweeters, some Quarantas came equipped with a disc-cutting lathe and ribbon microphone. At up to $5,000 in cost, its production must have been very limited.

Technical Competitors

E.H. Scott had several competitors. The most significant among them was a dashing young genius named McMurdo Silver. Silver was a continuous contributor of technical articles to Radio News magazine (the predecessor of Popular Electronics) throughout the 30s. He was a polo player, gun collector, and is said to have been quite a bon vivant. Formerly the president of Silver-Marshall, Inc., he set up the McMurdo Silver Corp. and began building custom high-fidelity receivers in competition with Scott. While good, his receivers were never quite the equal of Scott's. One of Silver's most famous owners was Dr. Lee De Forest, inventor of the vacuum tube.

DeForest owned a Silver Masterpiece V and praised it in the final chapters of his autobiography.

Throughout the 1930s, Scott's and Silver's advertisements would do battle trying to "one up" the other's in technical achievement. Features were stolen and lawsuits initiated. Finally, Scott won the battle and bought out the failing Silver in 1940. Scott then introduced a new, bottom-of the-line receiver and designated it as the Scott Masterpiece. I do not know if the gesture was meant as a tribute to his archenemy or to rub salt in the wounds. Silver eventually committed suicide in 1947.

Later Scott high-fidelity receivers came with 40 MHz FM, 100 MHz modern band FM, and push button, motor-driven remote-control tuning. By 1947, the last great Scott receiver was built-the AM/FM Model 800B, but the company was in advanced decline. Because of Scott being eased out of his company and the advent of post-World War II TV, Scott Radio Labs died in the early 50s.

Most audiophiles are skeptical about the concept of high-fidelity AM radio. An owner of modern "high-fidelity" equipment is almost guaranteed to get the mistaken impression of AM's potentialities because of archaic modern equipment. With a vintage Scott, however, one gets sibilant announcer voices, thunderous bass, the sounds of triangles and cymbals, plus wide dynamic range, low noise and distortion, and still excellent selectivity. One can also tune in a station 3,000 miles away without interchannel chatter.

I would like to point out to any owners of a vintage E.H. Scott receiver, that if it has not been overhauled recently, it is almost guaranteed to work extremely poorly. Almost any old Scott receiver required 15 to 30 capacitors, cleaning and lubrication, vintage tubes, and complete realignment. Sadly, almost no service technician has the knowledge, experience or patience to perform the kind of work required; besides the cost would be prohibitive. Probably the only way to tackle the problem is by yourself, given some technical knowledge and a good library. While a non overhauled set may appear to work well, it is only because of your point of reference.

(Source: Audio magazine, Jan. 1977; Michael N. Stosich)

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