Supreaux power section(s)

[matopotato]

I am about to build a Supreaux based on @Aion FX PCB.
It can be done in 2 versions: The 9V Supreaux or 18V JHS Superbolt.
Looking at the schematics in the doc it seems possible to actually build both in one enclosure with toggles to shift.
My thinking is that the three trimmers would need to be doubled up on a breakout board (their settings vary quite a bit during BB testing) along with R1/C1, R5 and R9. This all seems feasible on 2 x 3PDT switches.
The power section can be changed by:
"IC1: Omit
D3-4: Omit
Connect 9V jumper pads
C12-15: Omit"
according to the documentation.



IC1, D3, D4, R12 (!) and C13 will get bypassed with the 9V jumper, but
C12, C14 and C15 will be "dangling" unless they are omitted.

What would be the impact on leaving C12, C14 and C15 in there when 9V jumper is used?
My thinking is that if the impact is mainly to keep DC ripple out and the downside is negligible, then only a switch for the 9V jumper is needed and using a 4PDT instead of one of the 3PDTs would give the switch points needed.

[antonis]

I don't know if it's safe to switch from +18V to +9V in such an abrupt way..

1044 charge-pump pin 8(V+) input is rated up to +12V so, IMHO, C14 should be partially discharged prior to switching..
(maybe circuit's time constant for "excessive" voltage is shorter than lug-to-lug switching time, but..)  

[matopotato]

I don't know if it's safe to switch from +18V to +9V in such an abrupt way..

1044 charge-pump pin 8(V+) input is rated up to +12V so, IMHO, C14 should be partially discharged prior to switching..
(maybe circuit's time constant for "excessive" voltage is shorter than lug-to-lug switching time, but..)  

Ok, so if stomping off, swich power and stomp back on would be ok. Or should I unplug first?

I tried this during breadboarding and it "worked", but was not thinking of what kind of damage it might cause. Right away or over time?

[antonis]

I should "sacrifice" a couple hundrend mV by placing another Schottky diode between pin 8 and 9V jumper..

To be honest, it might be overkill (pin 8 permanently sits on 9V so instant voltage difference shouldn't be higher than 9V) but..   

[matopotato]

Thanks, will add the Schottky.

Is it a problem to leave C12, C14 and C15 as they are in 18V when changing to 9V mode?
Doc say "omit" but I am not sure if it is to save parts or if it has any impact.

[drdn0]

Thanks, will add the Schottky.

Is it a problem to leave C12, C14 and C15 as they are in 18V when changing to 9V mode?
Doc say "omit" but I am not sure if it is to save parts or if it has any impact.

Yep, totally safe

[matopotato]

Thanks, will add the Schottky.

Is it a problem to leave C12, C14 and C15 as they are in 18V when changing to 9V mode?
Doc say "omit" but I am not sure if it is to save parts or if it has any impact.

Yep, totally safe

Thanks!

[matopotato]

I should "sacrifice" a couple hundrend mV by placing another Schottky diode between pin 8 and 9V jumper..

To be honest, it might be overkill (pin 8 permanently sits on 9V so instant voltage difference shouldn't be higher than 9V) but..   

In practice, does it matter if I put the diode between pin8 leg and pcb eyelet for pin8, vs adding as part of the jumper? Latter probably easier fit.

[antonis]

Any place inside Green line..

[matopotato]

Any place inside Green line..

Many thanks!