CAPI BT50 range mod

[rockprocess]

This may be opening a can of worms, but I’m wondering how one might implement the range switch in the 5500.  It changed the scale of the steps from X1 to x.5 or x.25.

Is anything like this possible with the BT50?

 

[TwentyTrees]

The pics I’ve seen of the 5500 internals show gigantic dual 3-deck grayhill rotary switches. Obviously they’re concentric, so I’m guessing three of the decks are for gain - I assume the gain range switch selects one of the three decks on each gain switch.

If that is how the 5500 does its gain range (and I’ve not seen a schematic), replicating this scheme wouldn’t be possible within the BT50 if keeping within the 500-series format, as there wouldn’t be enough space for an extra two decks per gain switch + range switch. If you rackmounted instead it would be possible, though difficult and expensive and requiring a whole new set of rotary switches to do properly. To do it improperly you could switch in resistors from the gain switch wipers to each end of the gain resistor ladder to reduce the overall range, but your taper would go crazy and it probably wouldn’t be that usable in practice.

Hope that helps!

 

[rockprocess]

Gotcha, thanks for the thoughts.  It’s a shame it takes large switches, etc. I kinda figured it was multi deck switches arrangement.  It is such a useful feature though.

 

[john12ax7]

How is the gain implemented? With some eq topologies you can limit the range by adding resistors at each end of the gain pot / switch.

 

[TwentyTrees]

Good point. I’ve not been able to find schematics for the 5500, but the 550B and 550A are in the Tech Docs section here for reference:

https://groupdiy.com/index.php?action=dlattach;topic=44738.0;attach=12753

https://groupdiy.com/index.php?action=dlattach;topic=44738.0;attach=7987

 

[emrr]

I believe Jeff said somewhere it would require a different resistor set on additional decks on the switch.

 

[[silent:arts]]

That range switch doesn't just add a resistor ...