Alembic F-2B info

[PRR]

I have not seen such "old looking" information for Alembic F-2B before.

I do think there must be a filter-cap at the "X" nodes?

[AlNewman]

I find it interesting how in their write up they stake claim to fender's input switching as the latest and greatest thing.  Does the x node not have filtering already, or does the voltage divider somehow cancel it out?

[kagliostro]

From a very old thread at DIYItalia


Franco

[tubeswell]

  Does the x node not have filtering already, or does the voltage divider somehow cancel it out?

On that schematic there is no filter cap decoupling the X node. Which means that all the preamp stages will get unwanted crosstalk from each other. (The voltage divider output will only set an 'average' supply voltage for all four stages, leaving them to feedback any signal at each of the plates to all the other plates - and vice versa- through the power supply rail). There probably wants to be a filter cap there in reality.

[AlNewman]

  Does the x node not have filtering already, or does the voltage divider somehow cancel it out?

On that schematic there is no filter cap decoupling the X node. Which means that all the preamp stages will get unwanted crosstalk from each other. (The voltage divider output will only set an 'average' supply voltage for all four stages, leaving them to feedback any signal at each of the plates to all the other plates - and vice versa- through the power supply rail). There probably wants to be a filter cap there in reality.

That's actually pretty crazy.  So  that point, could the problem be solved with a coupling cap?

Never mind, stupid suggestion

[HotBluePlates]

I find it interesting how in their write up they stake claim to fender's input switching as the latest and greatest thing. ...

Mostly, they were just explaining the different function of using "Input 1" vs "Input 2" vs "Both Inputs used."

But also look again:  plugging into Input 1 only uses the switched contact on Input 2 to bypass the 68kΩ resistor & connect directly to the tube grid.  So reminiscent of Fender, but not Fender's plan.

[AlNewman]

Mostly, they were just explaining the different function of using "Input 1" vs "Input 2" vs "Both Inputs used."

But also look again:  plugging into Input 1 only uses the switched contact on Input 2 to bypass the 68kΩ resistor & connect directly to the tube grid.  So reminiscent of Fender, but not Fender's plan.

Good catch.  I stand corrected, again.  That's why I'm here.