RCA BA21 build

[emrr]

And I'm guessing here, but maybe RCA was trying to reduce the cost of the transformers going from the no-feedback of the early BA-2 and console amps with the larger can transformers (i.e. similar to UTC LS series) to these smaller square can transformers (i.e. similar to UTC A series), with 20 dB of negative feedback.
Though I haven't had time yet to really compare the sound of this preamp yet with the BA-2 I built with original transformers.

Everyone was trying to reduce the cost of transformers, it’s across the board post-war.

 

[dmp]

I was looking through the UTC 1949 catalog, and the LS-10 was $25, while the A-10 was $15
For the outputs, the LS-27/LS-50 was $24, while the A-24/A-25 was $15/$14
But I don't see a single off-the-shelf transformer with a tertiary winding. Would think that would add some cost and shrink the difference.
Adding feedback would make the whole thing more forgiving I would think, build quality, etc... but as designed it doesn't account for the input transformer
BTW, $25 in 1949 is $311 today using the CPI inflation calculator.

 

[fazer]

BTW, $25 in 1949 is $311 today

That puts things in perspective

 

[emrr]

No stock UTC with feedback windings, some other manufacturers did, but frequently power outputs. Not a lot to choose from off the shelf, plenty of customs.

 

[heatwalk]

Anyone seen this before? Long gone reverb listing from a couple years ago showcasing a passive EQ, described as akin to UA1008 off feedback winding?

 

[emrr]

Interesting, though it’s not an RCA EQ and there’s no way to strap that into an RCA like UA does without rewiring. If it was auctioned that way it was a misdirect or wishful thinking.

 

[heatwalk]

Guess I should have realizdd that based on package size compared to the RCA stuff. Glad I wasn't the one fooled who bought it...