VOLUME 14 APRIL 1997 NUMBER 4
The Emerson Multivalve Tube and its ApplicationsBY RAY BINTLIFF
A.R.C. staff member, the "multi-talented" Ray Bintliff, recalls the development of the revolutionary Multivalve tube with some excellent examples of single tube Emerson Multivalve radios built in the 1920s. He cites the advantages of the early multi-element tube, which prompted the development in later years of an ever increasing number of elements in a single tube. (Editor)
As vacuum tube technology advanced, the number of tube types that had two or more functional tubes in the same glass envelope became quite common. But surprisingly enough, the use of multiple-element tubes began quite early.
Two sets using the multivalve tube seem to be the only ones manufactured in the early days of radio -- the Clapp-Eastham Baby Emerson and the Standardyne Multivalve. These are shown in Figure 1.
THE BABY EMERSON
Figure 1. The compact Clapp-Eastham Baby Emerson, the Standardyne Multivalve and the Multivalve tube.
The Baby Emerson "loudspeaker set" was manufactured by Clapp-Eastham, ca. 1927. At first glance this small set looks like a 1-tube radio with a Type 01-A tube protruding from the top of the metal cabinet. But how can a 1-tube set drive a loudspeaker? Easily -- the single tube contains three triodes with a common filament. One tube does the work of three.
The name Emerson refers to the Emerson Multivalve tube used in the radio and manufactured by the Emerson Radval Corporation, 25 West 43rd Street, New York City, N. Y., which should not be confused with the Emerson Radio & Phonograph Company.
The circuitry consists of a regenerative detector and two stages of audio frequency (AF) amplification. The front panel reads "Clapp-Eastham Co., Brooklyn, N.Y." rather than the earlier, and perhaps more familiar, Cambridge, Massachusetts, address. The Baby Emerson that I had the opportunity to examine seemed to fall short of the earlier Clapp-Eastham quality with wiring that looked very "homebrewish."
THE EMERSON MULTIVALVE TUBE
Before delving into the mysteries of Multivalve radios, let's consider the Multivalve tube itself. An advertisement from the March 1927 issue of Radio News, reproduced here in part as Figure 2, includes an illustration of the tube, along with some 1920s style hype. Despite some of the exaggerated claims, the Multivalve tube was an interesting concept -- three tubes in one. The use of a common filament (really three separate filaments in series) plus three grids and three plates resulted in a tube that functions like three tubes.
The tube's base is a modification of the UX-style, 4-pin base used for the Type 01-A and other similar tubes. A Bakelite ring, containing four binding posts, is mounted at the top of the base. The binding posts are used to make electrical connections to grids 1 and 2 and plates 1 and 2 (G1, G2, P1 & P2). The 4 pins in the base are configured like a 01-A -- two large pins for the filament (F- & F+) and two small pins for the grid and plate connections (G3 & P3). A schematic drawing of the base configuration is shown in Figure 3. The Emerson Multivalve has the same filament rating as the Type 01-A -- 5.0 volts at 0.250 amperes.
Figure 2. A 1927 advertisement for the Emerson Multivalve tube.
As other writers have noted, the schematic carries the notation "Illustration courtesy of Cleartron Vacuum Tube Co." The address of Cleartron was 28 West 44th Street, New York City, near the back door of Emerson Radval on West 43rd Street. Although both companies marketed the Multivalve tube, it appears that the tube was produced by Cleartron.
Figure 3. A schematic drawing of the base connections for the Multivalve tube.
In another advertisement (Radio News, May 1927), Emerson Radval described the tube as "a seven-element tube with 201A filament, three plates and three grids." This description seems to sum things up quite well.
The Emerson Multivalve was not the only vacuum tube to use the multiple-element concept. The Apco Twin tube was produced by the Apco Manufacturing Co. of Providence, Rhode Island, ca. 1925. Later in this article I will mention some European multiple-element tubes and radios. But for now, let's return to Multivalve radios made in the U. S.
THE STANDARDYNE MULTIVALVE
Another of the early Multivalve sets, the Standardyne Multivalve, was manufactured by the Standard Radio Corporation of Worcester, Massachusetts. Various publications date this radio as a 1925 model. The radio, a reflexed TRF, utilizes 2-dial tuning and a single filament rheostat. The Multivalve tube is employed as an RF amplifier, detector and AF amplifier.
This compact radio measures 12" wide x 81/4" high x 91/2" deep at the base. The sloping front panel results in a smaller top dimension of 73/4" deep. Of course, the use of the Multivalve tube contributes to the radio's small size, but the set's designers went one more step by making it a reflexed TRF.
In a reflex circuit the audio signal is fed back through an RF stage to obtain additional amplification. The use of a reflex circuit was used sometimes in very compact radios because it produced more amplification without the need to add another tube to the radio.
THE HAYNES DX-2 MULTIVALVE
The use of the Multivalve tube was not limited to factory-produced radios. The February 1927 issue of Radio News carried a construction article for the Haynes DX-2 Multivalve receiver. The circuit uses a Multivalve tube as an RF amplifier, detector and AF amplifier. Either a Type 112 or 171 was recommended as the audio output tube. The Cleartron Vacuum Tube Company was listed in the parts list as the source for all tubes.
THE LODGE "N" CIRCUIT
The famous Sir Oliver Lodge "N" circuit was also adapted to use the Multivalve tube. A construction article by the Precision Coil Co. was described in the June 1974 issue of the Old Timer's Bulletin. This circuit utilized a Multivalve tube as the detector and two stages of AF amplification. A Type 112 tube served as the audio output tube.
OTHER MULTIVALVE RADIOS
The McGraw-Hill Radio Trade Catalog, dated February 1927, contains a catalog page for the Emerson Radval Corporation in which Radval listed "examples of modern circuits practically built around the Multivalve." In addition to the radios described above, Radval claimed that the following circuits employed Multivalve tubes: the Haynes and Cockaday Univalve Receiver, Doctor Lovejoy's Multivalve Receiver, Browning-Drake, and Mignon Mastertone Senior Single Control. Did Browning-Drake ever produce a radio that used a Multivalve tube? Did the Mignon ever see the light of day? Many questions about Multivalve radios remain unanswered. Perhaps some A.R.C. readers have information that they can share with us.
EUROPEAN MULTIPLE-ELEMENT TUBES AND RADIOS
In addition to Emerson Multivalve and Cleartron, there were companies in Europe that offered multiple-element tubes. In 1925, Cleartron began producing conventional valves in Birmingham, England. However there is no evidence to indicate that Multivalves were ever produced there. In Germany, Loewe Radio AG specialized in multiple-element tubes and produced small radios that utilized its tubes. Another firm, TKD, produced 2-in-1 and 3-in-1 tubes.
In England, Ediswan produced its prototype ES220 tube and "One-Der" receiver. In addition, British Thompson-Houston (B.T-H) marketed radios that used 2-in-1 tubes produced solely for use in its radios.
A more complete description of these companies and their products appear in John Stokes' excellent book 70 Years of Radio Tubes and Valves.
Radios designed to use a multiple-element tube had a number of advantages. By eliminating two tubes, the cabinet could be made much smaller. Also, the A-battery drain was lower -- the Multivalve's filament operated on one-third of the current required for three Type 01-A tubes. The lower current requirement meant that the radio could be operated from dry cells as well as from a storage battery. From a cost standpoint, the Multivalve had only a marginal advantage at best. The Multivalve sold for $6.50 when 01-A tubes were selling in the $2 to $2.50 range. However, use of the Multivalve permitted the elimination of two tube sockets which resulted in a lower cost for material.
Why then did the Multivalve radios have such a short marketing life? Perhaps sales volume was not adequate to cover the start-up costs. Certainly the timing was poor because the Great Depression was just around the corner.
Even though these radios were not a commercial success, the idea of multiple-element tubes did not die. In 1933, the Type 19 twin-triode tube came on the market. The Type 19 is a twin power triode with a 6-pin base. These tubes were followed by more twin triodes, triodes with two diodes, triodes with pentodes, and on and on. The multiple-element tube wasn't such a bad idea after all.
Drakes Radio Cyclopedia.
McGraw Hill Radio Trade Catalog, February 1927, p. 120.
The Antique Wireless Association Old Timers Bulletin, June 1974.
Radio News, February, March & May 1927.
Stokes, John. 70 Years of Radio Tubes. Vestal, N. Y.: The Vestal Press Ltd.,1982.
Tyne, Gerald F.J. Saga of the Vacuum Tube. Tempe, AZ.: Antique Electronic Supply,1987.
Additional Information Credit:
Jeff Goldsmith and Robert Lozier, Jr.
(Ray Bintliff, 2 Powder Horn Ln., Acton, MA 01720)
Ray Bintliff, W1RY, holds an Amateur Extra Class license. A member of the A.R.C. staff and a retired RCA engineer, he enjoys repairing and restoring pre-1945 radios and test equipment. In addition to Amateur Radio, his interests include electronic equipment design and audio reproduction.