Philco Model 37-670B Tombstone Radio (1937)
This big, boxy model 37-670 Baby Grand (37-670B) tombstone
radio was Philco's top of the line table set for 1937. It was
introduced in June of 1936 for the 1937 model year at a list
price of $99.50.
The styling of this set to some extent mimics that of the prev-
ious season's late 116B version and as with that model, it uses
an 11-tube chassis. As such, the 37-670B might be regarded
as a continuation of the highly successful and respected
16B/116B line. Despite these similarities, however, the circuitry
of the 670B differs markedly from that of the earlier 16B and
116B sets. For starters it adopted the new Octal tube types.
Moreover, it dispensed with the second IF amplifier and
separate local oscillator, leaving an RF/IF front-end built
around just 3 tubes. Much of the balance of the tube count was
devoted to the AF section, which comprised an AF amp, phase
splitter, push-pull drivers & a 10W push-pull triode-connected
class A output stage - a total of 6 audio tubes! Upon first
glance, the circuit philosophy has more likeness to that of a
contemporaneous Zenith set than to a Philco!
The 37-670B's 11-tube chassis tunes 5 frequency bands:-
530-1600kc (standard broadcast), 1.58-4.75mc (police),
4.7-7.4mc (shortwave 1), 7.35-11.6mc (shortwave 2) and
11.5-18.2mc (shortwave 3). The tube complement is:- 6K7G
(RF amp), 6A8G (LO/mixer), 6K7G (IF amp), 6J5G (2nd
detector/AVC), 6J5G (1st AF), 6J5G (phase inverter), 6J5G * 2
(push-pull drivers), 6F6G * 2(push pull audio output) and 5X4G
(rectifier). The model uses a shadowmeter visual tuning aid & a
4-point tone control. The schematic may be found here.
Was the 670B a Better Buy than Zenith's top-of-the-line 10-S-130?
When I compare this 11-tube Philco 670B, which sold for $99.50, with the
contemporaneous 10 tube Zenith model 10-S-130, at $84.95, I cannot
help but ponder this question. Both were their respective companies top-
of-the line table sets for 1937. To me, the Zenith certainly has the more
attractive styling, but what about comparative performance?
Both sets use an 8" speaker and produce a comparable push-pull audio
output power (12W for the Zenith versus 10W for the Philco). The Philco
uses Super Class A triode-connected 6F6G output tubes compared with
beam power 6L6 outputs for the Zenith. The Philco employs an additional
stage of push-pull audio amplification (6 audio tubes in all, compared
with 4), so perhaps overall it should have the sweeter sound, though I
haven't conducted a side-by-side test (my 37-670B is as yet unrestored).
Both sets feature shadow tuning and have RF front ends built around the
same 3 tubes. An inspection of the schematics however, reveals a higher
degree of sophistication for the Philco. In particular, it uses separate coils
for each of its 5 bands (23 Tuned Circuits), rather than the simpler, tapped
coils used by the 3 band Zenith. This should certainly make for better RF
sensitivity and selectivity from the Philco when correctly aligned, although
for sure, both sets do perform well.
All in all, I would judge that the Philco has the edge as far as circuitry &
performance are concerned but that it has the plainer cabinetry. It would
have likely cost more to manufacture the Philco, if not the least because of
the additional costs to wind, install and align all of those tuned circuits!
So would the relatively affluent buyers of these high end sets in 1936/37
have gone for beauty or performance? The Philco 670B is not a common
set (less than 9500* were sold) and the Zenith is even less common (less
that 6000* sold), so perhaps we'll let the last word on this matter be told by
*sources: philcoradio.com and Zenith The Glory Years Illustrated Catalog, Cones & Bryant, for Philco & Zenith
Philco Spread Band 37-670B ...possesses a distinction all its own!
|"A baby Grand that has that simplicity of design
which possesses a distinction all its own! The
center portion of the instrument is of figured
walnut... while a wide band of butt walnut enriches
the base. This effect is repeated at the top of
the pilasters by the use of narrower strips of
butt walnut. Base and top mouldings are of
slightly darker contrasting tone"
"American and Foreign...5 tuning ranges with
Glowing Beam Tuning Range Indicator... Super
Class A audio system... 11 Philco high-efficiency
tubes... Spread Band dial with foreign stations
spaced 5 times farther apart... 23 Tuned Circuits
with the Philco High-Efficiency Aerial... Shadow
Tuning... Philco Foreign Tuning System... Four Point