[Ron Ramirez]

Whilst it seems like tube stuffing a chassis on brand Zs part having separate oscillator and mixer tubes is actually a meaningful improvement to a radio. Having separate tubes for the mixer/detector and local oscillator reduces noise and allows more stable operation at higher frequencies then a pentagrid converter like a 6A8 or a 6A7.

Acked, and agreed. Philco did their own cost-cutting, though, and from 1932 on it usually involved combining mixer and oscillator functions in one tube, poorly at first (the infamous autodyne circuit first used in the late versions of the 70 and 90, then the 51, 52, 15, 71, 91 and most infamously, the 19 and 89). The 6A7 was a big improvement over using a 36 tetrode. But, yes, separate mixer and oscillator is always better. So Brand Z gets points for that.

But I take away points for connecting a 6H6 as a single diode (both plates and both cathodes are connected together, making it a single diode). Again, a 6Q7G could have done the same job as separate 6H6G and 6F5G tubes did.

Oh well, a 9 tube radio sounds more impressive than an 8 toober, right?

[morzh]

Ron

What's wrong with single diode?
Oh....do you want separate AVC and Signal paths? Philco in 38-15 separated them at some point, before they had them together.

Does this really improve sound?

[Arran]

Whilst it seems like tube stuffing a chassis on brand Zs part having separate oscillator and mixer tubes is actually a meaningful improvement to a radio. Having separate tubes for the mixer/detector and local oscillator reduces noise and allows more stable operation at higher frequencies then a pentagrid converter like a 6A8 or a 6A7.

Acked, and agreed. Philco did their own cost-cutting, though, and from 1932 on it usually involved combining mixer and oscillator functions in one tube, poorly at first (the infamous autodyne circuit first used in the late versions of the 70 and 90, then the 51, 52, 15, 71, 91 and most infamously, the 19 and 89). The 6A7 was a big improvement over using a 36 tetrode. But, yes, separate mixer and oscillator is always better. So Brand Z gets points for that.

But I take away points for connecting a 6H6 as a single diode (both plates and both cathodes are connected together, making it a single diode). Again, a 6Q7G could have done the same job as separate 6H6G and 6F5G tubes did.

Oh well, a 9 tube radio sounds more impressive than an 8 toober, right?

Ron;
  I always figured that Philco's use of autodyne circuitry was the company's attempt to circumvent RCA's patents, at least on their higher production models. The arrangement with an RCA licensee was that they would have to pay RCA so much in royalties per set they built, so less money going to RCA meant more money going to Philco. I've read about the non stop patent wars that went on in U.S courts for decades, and the rivalries and conflicts they created, and public enemy #1 was RCA since they held so many patents exclusively, so many manufacturers went out of their way to circumvent or work around them. Some are borderline idiotic, like the tube shield bases Philco use in their 1938 model sets, purposely designed to prevent the use of anything but G style octals being used, it seems like a childish and vindictive attempt to control what style tubes a Philco owner used as replacements.
 In Canada, on the other hand, all the manufacturers were involved in a patent pool called "Canadian Radio Patents Ltd", no doubt that you have seen this posted in the back of some of your Canadian built Philcos. In exchange for the control of the patents from various companies they were issued shares in Canadian Radio Patents and could use whatever patents they wanted, they paid royalties to the patent pool, and the pool would pay them back in dividends. This is why you see things like Canadian Philcos with factory fitted RCA phono jacks, and Canadian RCA sets with 5Y4s, they could pretty much use whatever they thought best, it all worked out the same in the long run.
Regards
Arran