Question about the Roland Micro Cube Effect Loop add-on by Thomeeque

[Kekke466]

Hello,

I am confused about the buffer and trying to understand more about effect loops.
What I am trying to recreate is the voltage follower used in the schematic of Thomeeque.

When I look at the schematic, I see that the dual opamp (TL072) is fed single supply.
But only one amp, (in the return) receives Vbias on the non-inverting input.

Can voltage followers output AC when they don't have a Vref or Vbias?
I don't understand why the buffer doesn't need a Vbias at the non-inv. input.



Link to the thread: https://www.diystompboxes.com/smfforum/index.php?topic=123179.0

[idy]

I think because

add-on replaces decoupling capacitor C32

there is no need: A decoupling cap stops DC  from going through as path. By removing it you allow the bias of the last stage to continue on into the + input.

[Kekke466]

I think because

add-on replaces decoupling capacitor C32

there is no need: A decoupling cap stops DC  from going through as path. By removing it you allow the bias of the last stage to continue on into the + input.

Hi idy,

I took a look at the schematic of the Micro Cube and the opamps inside there are fed with a Dual supply (LM7808 positive - LM7809 negative combo).

If I am correct, there was never a Vref or Vbias introduced at any point before because the opamps inside are fed dual supply.

I still don't understand how any voltage swing for audio can be produced at the output, looking at just the schematic.

I guess there is enough DC present from previous stages. It is clear for me at this point.

[PRR]

.... When I look at the schematic, I see ..... Link to the thread: https://www.diystompboxes.com/smfforum/index.php?topic=123179.0

There's many schematics in that thread. I wonder what one you are looking at?

However, maybe this clears it up?

[Kekke466]

.... When I look at the schematic, I see ..... Link to the thread: https://www.diystompboxes.com/smfforum/index.php?topic=123179.0

There's many schematics in that thread. I wonder what one you are looking at?

However, maybe this clears it up?

The schematic Roland MircoCube FX Loop
Revision 1: R5, R6, C10 (bias fix)

There is DC bias at that point.  I have been overanalyzing this.