freestompboxes.org

Hello everyone, I am confused by the power switching scheme, or am I mistaken, or does the voltage change only in the second half of the VB circuit, explain how in fact the voltage changes, on the whole circuit or only the second part of it?

VA and VB are both switched between 9v and 18v - They are connected at the node that links to the two 47ohm resistors that feed these points,so both VA and VB will either provide 9v direct from the supply, or 18v from the charge pump. The only difference between VA/VB is that they have separate power filter caps and resistors.

Nocentelli wrote:VA and VB are both switched between 9v and 18v - They are connected at the node that links to the two 47ohm resistors that feed these points,so both VA and VB will either provide 9v direct from the supply, or 18v from the charge pump. The only difference between VA/VB is that they have separate power filter caps and resistors.

Thanks.

OK,
Here's the (I hope) last post in this thread, so folks can find the correct schematic without going through all kinds of confusion getting the correct schematic.

I made it a bit easier to read and cleaner, the last schematic was already correct.

mr coffee

Long time listener, first time caller...

I built this off of Bugg's PedalPCB Marble Drive, which I'm assuming is based off of this schematic. I'm getting a whine from the TC1044S when I'm in 9V mode. Everything's good in the 18V mode. I've tried two different chips with the same result. Any ideas why this might be happening? Obviously it goes away when I pull the chip.

https://www.pedalpcb.com/product/marbledrive/

Any help would be appreciated, thanks!

I'm getting a whine from the TC1044S when I'm in 9V mode.

I think that the whine is not caused by the TC1044S in the 9V mode, but rather by means of bias point shifting on the FET stages.
Remove the chip and run the circuit using a 9V battery to see if the whine is still there.

Manfred wrote:

I'm getting a whine from the TC1044S when I'm in 9V mode.

I think that the whine is not caused by the TC1044S in the 9V mode, but rather by means of bias point shifting on the FET stages.
Remove the chip and run the circuit using a 9V battery to see if the whine is still there.

The whine is gone when I pull the chip and run it at 9V (with my PP2+, no battery).

JabboWookie wrote:I built this off of Bugg's PedalPCB Marble Drive, which I'm assuming is based off of this schematic. I'm getting a whine from the TC1044S when I'm in 9V mode. Everything's good in the 18V mode. I've tried two different chips with the same result. Any ideas why this might be happening? Obviously it goes away when I pull the chip.

Add a 10K resistor from the bottom lug of the SPDT to ground, should clear up the whine. This is happening with some charge pumps.

I built this off of Bugg's PedalPCB Marble Drive...

https://www.pedalpcb.com/product/marbledrive/

Even though this is not an issue for me, I still can't decide why pedalpcb does not specify the bias voltage in his manual. How on earth would a newb decide on a bias voltage (which should not necessary be 1/2 of the VCC)?

plush wrote:

I built this off of Bugg's PedalPCB Marble Drive...

https://www.pedalpcb.com/product/marbledrive/

Even though this is not an issue for me, I still can't decide why pedalpcb does not specify the bias voltage in his manual. How on earth would a newb decide on a bias voltage (which should not necessary be 1/2 of the VCC)?

I think you unknowingly answered your own question.

J0K3RX wrote: I think you unknowingly answered your own question.

Oh, wow, this was unintentional
Lmao