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.RADIO BROADCAST ADVERTISER.
■57
. •
111 from ScifeetiGiritf Tiiftesf
ARE you getting full value from screenL grid tubes? Most likely not, for 99 out of every 100 radio men run these marvelous tubes at very low efficiency. Why?
The main reason is failure to bias the control grid at I 2 volt negative potential. Of course that's troublesome if you must use a dry cell in ground lead. Other methods are equally awkward. But now you can use a better way. And here's how: Try the Clarostat Hum-Dinger as a combination filament resistor and grid bias. Connect between negative A and filament, with center tap to ground side of antenna tuning unit. Adjust for proper grid bias by means of screwdriver, and leave it alone. Oh boy! What a difference! And if you want to know why, just look up the characteristic curves of the screen-grid tube.
Of course the Clarostat HUM-DINGER is primarily an improved hum-balancer. Use it with your A-C filament tubes, and forget hum.
M/7? ITJi for data regarding the Hum-Dinger and rr i\± ± l, other Qiaro5tat products. There's a Clarostat for every purpose — adjustable, variable; fixed and even automatic. Ask your dealer about Clarostats.
Potter
DYNAMIC SPEAKER
Filter
REDUCE the hum in A. C. operated dynamic speaker using low voltage rectifier
The installation of a Potter Dynamic Speaker Filter is easily made by connecting the two leads provided across the field of the speaker.
List Price $4*75
POTTER FILTER BLOCKS
T90nn Condenser Block for the single on nn ~Lo\j\3 250 type tube amplifier *p£U.UU
ToArn Condenser for the push-pull tfjoO; CA -LVOV 250 type tube amplifier «p££.DU
T 90,08 Condenser Block for single <£on aa -£UyO 210 tvpe tube amplifier <p£U.UU
Toon 171 Condenser Block for pow dj-io aa -£0U-H1 er pack with 280 type <plO.UU tube rectifier
The Potter Co.
North Chicago, Illinois
A National Organization at Your Service
GENERAL AMPLIFIER!
Model GA 20
List Price (less tubes) $225
A self-contained, rugged, all electric, three-stage power amplifier employing two UX-250, two UX-226, two UX-281 and one UY227. Will deliver approximately 14 watts of undistorted energy to the speaker. The use of dual push-pull makes for extremely quiet operation. Designed for 110-120 volt, 50-60 cycle alternating current operation.
The General Amplifier Company specializes in the design and manufacture of amplifiers to meet specific requirements. Your problems in the field of power amplification are solicited.
Bulletin RB-1 will be sent on request.
27 Conriimercial Avenue Cambridge,
Makers of High Grade Pouter Amplifiers
lass.
Stop that
tttft
RADIO ^TUBES
Uniform Quality
since
19 15
The high standard maintained in their manufacture is reflected in their quality performance.
Make every tube a Cunningham
E. T. CUNNINGHAM, Inc.
NEW YORK CHICAGO SAN FRANCISCO DALLAS ATLANTA
• may, 1929
page 53 •