1931-32 big chassis output tube changes ? - Printable Version

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+--- Thread: 1931-32 big chassis output tube changes ? (/showthread.php?tid=819)

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1931-32 big chassis output tube changes ? - Drew - 11-04-2007

I was wondering what the performance differences were with the change mid season in the 1931 Model 112, from the 45 output tubes to 47's. Then the following year the big 11 tube chassis made another change to the 42's for the output (model 15). Which of these three is considered the "Better" tube with best sound ?

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- Ron Ramirez - 11-04-2007

With the understanding that "better" and "best sound" can be quite subjective, here goes my two cents' worth:

The Type 47 tube offered a higher power output than did the Type 45. I don't have a tube manual in front of me and am, frankly, too lazy to go look it up right now; but the power increase of using two 47 tubes in push-pull was substantial over the Type 45.

Type 42 tubes are very similar in electrical characteristics to Type 47, yet offer the advantages of slightly higher power output, an indirectly heated cathode, a 6.3V filament, and the ability to handle higher plate and screen voltages (thus giving the slightly higher power output over Type 47).

On paper at least, one would believe that Models 15X and 15DX would have quite an advantage over Model 112. Better, more efficient tubes, two speakers instead of one, and the most refinements of the large chassis Philco sets.

I've listened to 112 sets with Type 45 and Type 47 output tubes, and have owned a 15X in the past. I couldn't really tell much of a difference in the sound qualities of the various models. The twin speakers used in Model 15 do not really seem to give it an advantage in fidelity; after all, these are AM-only receivers, and the fidelity was thus limited even back in the days before NRSC.

Model 111 does not count, as these sets use the older Philco speaker with the stiff center spider, which severely limits its fidelity. Recone one of those speakers and use a better spider, and you will unleash its true potential - sound quality equivalent to Model 112.

I suppose this doesn't really answer your question, but it is one man's opinion. That's all.

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- Drew - 11-05-2007

Thanks Ron, that actually does ansear my general question. Looks like philco was going for a power increase with the tube changes. My 112 lowboy has the 47's and I enjoy it's performance...it helps that WNBP 'The Legends' is very close to me and comes through very strongly.

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