UN-inverting an inverting boost.

[like Yeah!]

TL;DR: til that jfet buffers are not jfet boosts, and also that @Robert is a great human being.


Hi. I've read that single fet boosts invert the input signal.. and a way to uninvert it is to just use a single fet buffer along with it.

so i saw the jfet buffer board and i got one along with the fumble board ..for science!
i read in the docs for the buffer that it's literally a raw buffer and power protection/filtering are to be addressed by the installer (me).

Is this an acceptable way to provide power to the buffer board and connect it to the circuit as an input inverter that can be switched out of circuit?

[images removed]

 

[FiveseveN]

The voltage follower does not invert the signal.

 

[like Yeah!]

The voltage follower does not invert the signal.

ok, thank you.
what am i missing? do some single fet boosts not invert? or am i using the jfet buffer board wrong?
or both?

 

[vigilante398]

ok, thank you.
what am i missing? do some single fet boosts not invert? or am i using the jfet buffer board wrong?
or both?

Single FET boosts always invert, single FET buffers never invert. If you need a non-inverting boost or an inverting buffer, you need an opamp.

 

[like Yeah!]

Single FET boosts always invert, single FET buffers never invert. If you need a non-inverting boost or an inverting buffer, you need an opamp.

i see. ok thank you. i'd rather ask than go do it and be a dumb ass

 

[jubal81]

If you want an "inverting buffer," you can build it on a SHO PCB.

Replace the mosfet with a JFET and the boost control with a fixed resistor equal to the drain resistor.

 

[like Yeah!]

If you want an "inverting buffer," you can build it on a SHO PCB.

Replace the mosfet with a JFET and the boost control with a fixed resistor equal to the drain resistor.

i don't even really want the idea of a buffer in the circuit, i was just thinking to make what's already present ...invertable..
i just mistakenly thought a jfet buffer was the same as a jfet boost, but with gain of 1.
i guess i've got a spare buffer board now haha

 

[jubal81]

i don't even really want the idea of a buffer in the circuit, i was just thinking to make what's already present ...invertable..
i just mistakenly thought a jfet buffer was the same as a jfet boost, but with gain of 1.
i guess i've got a spare buffer board now haha

You can invert the signal on that PCB, but you'd need to cut a trace and tack on another resistor.

 

[phi1]

Kind-of explained above, but the key for JFETs is where the output comes out of.

For N-Channel JFETs (which basically all pedals use N-channel, not P-channel):
-If the output comes out of the DRAIN (top on schematic), it is an inverting boost.
-If the output comes out the SOURCE (bottom on schematic), it is a non-inverting buffer.

 

[like Yeah!]

You can invert the signal on that PCB, but you'd need to cut a trace and tack on another resistor.

..but i don't want to mistreat the board. it looks nice.
i'll just have to wait for the legitimare inverter board to be back in stock... the one with the opamp like vigilante398 suggested.. i saw it was out of stock, i just figured (wrongly) that a jfet boost was just a buffer with more gain..

Kind-of explained above, but the key for JFETs is where the output comes out of.

For N-Channel JFETs (which basically all pedals use N-channel, not P-channel):
-If the output comes out of the DRAIN (top on schematic), it is an inverting boost.
-If the output comes out the SOURCE (bottom on schematic), it is a non-inverting buffer.

TIL, thank you for the long version . the thing that got me was not realizing that jfet buffers never invert.

 

[Robert]

i'll just have to wait for the legitimare inverter board to be back in stock...

Look what I found... I'll send it your way.

 

[like Yeah!]

Look what I found... I'll send it your way.
View attachment 126909

Thank you so much @Robert, I appreciate you very much!