Phase questions...

[Sensei Tim]

So I built a blueberry bass od with and amz mosfet boost

The thing is that I let a friend borrow it to,try out and he's saying that the output from the bbbod is out of phase with some other stuff that they are running yet when the amz is on it is in phase.

I don't run effects in parallel so I can't really comment on this

Anyone?

[Travis]

The AMZ inverts the phase, but judging by your description either circuit will be out of phase in their rig when used independently.

In order to make it work in their rig, you would need to add a phase inverting stage in series with each circuit. That way neither circuit inverts phase and they can be used independently or together without issues

This can be done a few different ways, but if you don't want to add another gain stage to invert phase, you can use an inverting buffer like the one at the bottom of this page

http://www.muzique.com/lab/buffers.htm

Of course you could use a dual op amp to do both buffers with one IC

[Sensei Tim]

that's awesome! thanks!

i'm assuming that for bass i'd probably drop the input cap to 10n from 100n and maybe drop the output cap as well?

would i need a pull-down resistor on this to prevent popping when switching it on or off if I'm not going to be using an LED with it?

also,  what voltage is Vr?   is it just Vsupply/2?

[Travis]

For bass you typically want to INCREASE the input/coupling cap values. 100n should be fine but if you wanna up it for good measure 220n would be safe.

You could do an LTspice sim to see what the frequency response of the stock circuit would be but I'm too lazy to download that and figure it out lol

If you're switching with toggle switches I wouldn't bother with the pulldown resistors really since you're not gonna be toggling it mid song as an effect or anything.

Vr is a voltage reference. You make that with a voltage divider and give it a filter cap. I can draw a little layout for you no prob. Will post it shortly

[Travis]

[induction]

Sensei Tim wrote

what voltage is Vr?   is it just Vsupply/2?

This is the first image on the page you linked.


A 100n input cap will give you a flat response at all frequencies of interest. No need to change anything to let more bass through.

[Sensei Tim]

+1 for reading ;)

thanks travis!

[Sensei Tim]

Hey Travis,

Just noticed that none of the jumpers in the 2nd image align with the first image

[Travis]

oops not sure how I missed that. edited the post with the links moved into place

[Sensei Tim]

Heybtravis, I finally got around to building this and think I spotted an error:

The 1m resistor to thenleftmof thenop amp needs to connect to pin 1, not pin 2 and the jumper beside that 1M needs to connect to pin 2 of the opamp, not pin 1.

Cheers

Tim