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334
RADIO BROADCAST ADVERTISER
oA NEW
AMPLIFIER UNIT
that provides for Sxtremely Faithful ^production
SCHEMATIC DIAGRAM FOR COMBINATION 2 STAGE DOUBLE IMPEDANCE COUPLED AND I STAGE TRANSFORMER COUPLED AMPLIFIER WITH SPEAKER FILTER
373 373 285D 387A
CBATT.
A BATT.
While the use of double impedances is not new in principle, the General Radio Type 373 Double Impedance Coupler is unique in design and performance. To facilitate installation the complete unit, consisting of two impedances and a fixed condenser, is contained within a metal shell. It is connected in precisely the same manner in an audio amplifier circuit as a transformer.
(Announcing a NEJV Single Hole Mounting Rheostat
The Type 410 rheostats are similar in general appearance and construction to the well known Type 301 rheostat, except that they have the single hole mounting feature, and a flanged knob with engraved pointer of moulded Bakelite. Furnished with resistances of 6, 12 and 25 ohms.
Type 410 Rheostat #1.25
The extent of its range of even amplification is from appreciably below 100 cycles to over io,COO cycles, with a gradual downward deviation of slightly less than 7% between 100 to 400 cycles. This deviation in an otherwise perfect amplification curve is so slight as to be practically negligible, because the ear of the average individual can not detect a variation of intensity of much less than 25%.
The amplification curve, in fact, compares favorably with that generally obtained with resistance coupled systems which have the disadvantage of large sacrifices of plate voltages.
The General Radio Double Impedance Couplers have the further advantage that when connected as shown in the above diagram, with one transformer coupled stage, they may be used with a properly designed Plate Supply Unit.
Type 373 Double Impedance Coupler $6.50
The following parts are used in the General Radio Laboratory Amplifier:
2 — Type 373 Double Impedance Couplers $13.00
I — Type 285-D Audio Transformer 6.00
I — Type 387-A Speaker Filter 6.00
3 — Type 349 UX or CX Sockets 1.50
I — Type 410 or 301 Rheostat 6 ohms 1. 25
Complete cost of amplifier parts $27.75
If your dealer is unable to supply you with any of the above items, we shall be glad to send them to you prepaid upon receipt of list price.
PARTS and ACCESSORIES
"'Behind the Panels
of Better Built Sets"
February, 11
Published mmithlv. Harden City, N. V.
X, No. gecond cli
1. l'llbllslH'il I
ss 1 11 11 1 1 matter.
Garden Citv, N. Y. Doubleday, Page & C(
Subs
mpans
•rlin imi price H.no i , Garden City, N. Y.
Entered at (lie post oflioe at