amz presence control in a tube screamer

[ninjadave7]

Hey everybody, I built an eternity ( a tubescreamer...) and i spent the afternoon yesterday trying to get the amz "version 2" big muff tone controls to work with it.  i built it the amz presence control on a 2nd vero and just wired it out pin 7 and in pin 3 on the opamp, and grounded it, inserted right between the 1k that follows the 1st stage of the opamp, and the non-inverted input of the 2nd opamp stage.  the 1k resistor between the 2nd inverted input and output stayed, so basically the original circuit is there except the cap to ground right before the 2nd stage and the original tone stack.

my problem is that it doesn't do anything... neither the tone nor body pots seem to do anything at all, certainly not like the graphs shown on the amz page.  I am very confident (1st mistake...?) that i've built the presence control correctly, there's not much there, but did i put it in the wrong spot?  does it not do much in that circuit anyways?  any suggestions?

i like the existing tone stack, i mainly just wanted the body control, which pulls/pushes mids.

thanks!

[ninjadave7]

btw, here's the vero i used.  maybe it's the problem??

[slacker]

The 2 pins of the body pot that are connected together need connecting to ground, otherwise the pots won't have any effect.

[ninjadave7]

oops, i actually did do that, just didn't put it on the layout... sorry bout that

[slacker]

I should have read your post properly instead of just looking at the layout, I think you need a couple of tweaks to get it to work.
I've never seen an eternity but if it's exactly like a Tube Screamer then you'll probably have to remove the 10k connected to the non inverting input of the second stage. The Big muff style tone control need a high input impedance after it too work properly and 10k is too low. Then connect the bits you've got going to ground to 4.5 volts instead that should work.

[ninjadave7]

sweet i'll try that!  thanks!

[askwho69]

mmm interesting!

[ninjadave7]

the eternity is basically a tubescreamer with no buffers.  but it actually doesn't have the 10k to ref that the ts9 does, so i'll try to send the ground connections from the amz tonestack to ref and see what happens.

[ninjadave7]

here's the schem i followed.  i put the new tonestack inbetween 7 and 3, then 7 and 2, but still no difference.  i kept the connection between 7 and 3 in place with a jumper because the circuit didn't work without it, so basically where the eternity tone is is where my new one is, but i also tried going into non-inverting input.  ideas?

[slacker]

Remove the 1k resistor, the 0.15 cap the tone control and the other cap and resistor and connect the tone stack between pins 7 and 3 with the "ground" connections going to 4.5 volts, that should work.
You might want a resistor from pin 2 to Vr, to give the second stage some gain to make up for any volume loss from the tone stack, 200R - 1k or something in that range.

Don't forget the pedal doesn't have much bass to start with so you aren't going to get a big mid scoop or bass boost from the tone control. If you want that you'll need to replace the 0.22 cap off the first stage with something much bigger.

[ninjadave7]

ended up sounding amazing, thanks for all the help!

[Levispeights]

Could you post a schematic of your final circuit?

[ninjadave7]

sorry, been out of the country till last night.  i'll try and work one up in the next couple days for you.

[Levispeights]

Thanks!

[Levispeights]

Bump?

[jstbrowsin]

Bump I'm very interested in this too thanks