Zombii mods to allow full input level to the circuit?

[Om_Audio]

Hi,

I LOVE my Zombii, but it is a bit frustrating to have to turn the guitar down and back up every time I use it. Also I love using it with my Macheen but same issue but even harder because the Macheen LIKES full output from guitar but then the Macheen overloads the Zombii.

Are there any mods that could change this? It is like the circuit does not like the "normal" output level of a guitar but more like half the output. or is it an impedance issue? Heck if I know. I just know as wild of a fuzz it is it is also the best transparent dirt pedal I have right now.

Thx,
C

[jtn191]

yeah you could solder a resistor between the middle lug of the 3pdt and the input on the pcb. I'd guess the value would be about 25k (strat) to 50k (humbuggies).

Alternately, you could wire a pot as a variable resistor and have a "pregain" pot

[stecykmi]

ya a pre-gain pot seem pretty reasonable.... anything from 25k to 250k would probably work

[Om_Audio]

Cool, thanks guys! Maybe I could use a trimmer and tuck it inside! I'm excited to try it.
C

[GrindCustoms]

That's something i never had problem with......., i built couple Fuzz Factory type pedals and all my guitars have pretty high output pickups (16K to 21K).......and i never had to turn down the volume on them to get a nice sound out of that box....

Could you explain me what are the symptoms you get? It's just simple curiosity......

[Om_Audio]

Hey Rej,
The Zombii sort of "over compresses" and stops producing a signal. Oddly, if I turn on the Macheen (in front of the Zombii) I can leave the guitar volume up. The Zombii settings in the demo are not really my norm settings but no matter the result is same. I forget who told me to turn the vol of the guitar down, might have been JakeFuzz (Paul) whom I bought the pedal from and got me into this whole DIY fiasco. Blame him!
 
Thanks-
C
[soundcloud]http://soundcloud.com/clifford-novey/zombii-guitar-volume-test[/soundcloud]

[Om_Audio]

yeah you could solder a resistor between the middle lug of the 3pdt and the input on the pcb. I'd guess the value would be about 25k (strat) to 50k (humbuggies).

Alternately, you could wire a pot as a variable resistor and have a "pregain" pot

I need some clarification por favor~
I tried a 47K just from center lug to lug w input wire- no luck. See example in red.
Do you mean the resistor should be in series between the input and the 3pdt like the green shows? Not in that spot but you get the idea.
Thx,
C

[JakeFuzz]

Hey Cliff. Man its been a while since I've seen the inside of that thing! I agree that a pre-gain pot is probably an easy fix. To me it sounds like some kind of impedance matching issue. I've tried to run buffers in front of a lot of different fuzz pedals (especially the TB and FF variety) and they never like it. The zombie has a similar structure to both of these fuzz circuits. The output impedance of the macheen is probably providing a better match to the zombie than the guitars pickups. Also if you didn't want to drill a hole in that enclosure you could build an external box with just two jacks and a pot to do it for you.

[Om_Audio]

Hi Paul,
Ya I'd like to just use an internal trimmer- I don't care about drilling another hole I just don't see why having it avail on the outside would be needed, kind of set it and forget it, no? On the other hand you still have the same issue I suppose that what you are throwing at it changes regardless and once the pre gain pot is in there now you may have the opposite issue of it working good with just guitar at full volume but not so good with Macheen?
If you fix the impedance with a resistor or pot, but then change it with what you throw at it does it matter?
I gues maybe you just change what the circut sees to behave more like most other pedals so it would generally work more like I want it to. Hmm, my grey matter is churning.
In any event, could you tell me how it would be wired specifically? My guess would be in series with the input to the circuit.
thx
C

EDIT: Interesting discussion on impedance I found while trying to see if I could measure impedance at varios points to learn like what the Macheen is creating vs the guitar output.
http://www.tdpri.com/forum/just-pickups/95648-how-do-you-measure-pickup-impedance.html

[JakeFuzz]

Your wiring diagram should be right. Just wire it in series with the input.

You could find the DC resistance of the macheen output. We usually use a spectrum or network analyzer here at work to get a Smith chart for impedance. We also have an Agilent LCR meter that might get the job done. Never hooked it up to one of my pedals though (most of the NA's we have start at 10MHz!)

[Om_Audio]

Thanks Paul, will try it tonight!
C

[Om_Audio]

So results were interesting.
Tried a 50k and a 100k pot.
None of the results take care of all the issues and also creates different issues:

- Adding the pot and increasing the resistance does allow chords to be played (there is a BUT...)
- (BUT) with pot single notes no longer hold- so you solve the chord issue but sacrifice single notes.
- The response and character of the pedal is different with the pot vs backing the guitar volume off- cannot offer any more description other than the results are significantly different with each method.

So-
-a pre-gain pot or resistor is NOT the same as backing off the guitar volume- they create different results.
-I clearly need to spend some more time with the stock pedal to learn its behavior/limits and have a better "control" reference in my head before experimenting with the pot/resistor.

This is fun!

C