[HBR] 6SN7 infinite-impedance upgrade for HBR-14

[Tim Shoppa]

The HBR-16 uses a 12AU7 for the infinite-impedance
detector and AVC.

There was evidently an upgrade for the HBR-14 which
added these features using a 6SN7.

Is the upgrade for the HBR-14 identical to the HBR-16
section except for the transliteration of a little bottle
with a big bottle?

Does this upgrade necessitate replacing the 6SQ7 with
the 6BE6 too, or could it be done in two steps?

Tim. (KA0BTD)