Is it silly to wire in a dying battery simulator while using just a battery?

[Dom D]

I want to use this layout by Beavis Audio:


My fuzz face has no LED and no adapter. I would be using a 9v battery and wiring the black lead to the pot. Just wondering if it's senseless to simulate death in a battery already fated to die and would this simulator become useless once the battery inevitably loses juice? I would think that the low current draw of the fuzz would make the battery last pretty long and thus justify the simulator. assuming this even leads to useful tones, then, I could simply just turn the voltage back up to 100% if the battery starts to die and none of this would matter, right?

[Dom D]

Good lord, I haven't even realized that I have a PP2+ with those battery adapter things and votlage sag that I could try out. silly me.

[amptramp]

This is a perfectly good way to stabilize the performance of a fuzz face against battery aging.  You will have to experiment to find the best setting as the battery ages.

[Mark Hammer]

IS it an effective compensation for battery aging?  The diagram shown essentially limits the current available to the circuit.  While older batteries do ted to lose the ability to deliver nice healthy zaps to one'stongue (and circuits), they also decline in voltage.  My sense, maybe naively, is that the control will adjust for current delivery changes, but not for voltage changes...at least with the circuit shown.  I would think that if one wanted to have the lovely pure DC of a battery, and make any necessary internal adjustments for a given supply voltage, then perhaps the optimal would be to use zeners, or other diodes, to achieve a supply voltage below that of the battery.  Hopefully, it would be far enough below that it would take a while for the battery to hit the threshold of the diodes.

[Dom D]

Thanks for the replies. Unfortunately, Mark, you're speaking well above my level of expertise. My interests/experiences in pedal building do not stray far from simple germanium fuzz. I'm always down to learn more though. Something I like to do is use a hunk of vero with a bunch of trimmers mounted inside the enclosure for all kinds of fiddling like blending caps, etc. A fun build was a knobless fuzz factory, which I replaced all the pots besides volume with trimmers.

You're saying I can reduce the voltage down to a fixed voltage using diodes. I would first have to decide which voltage I wanted to reduce to right? Or experiment with diodes on a bread board?

[amptramp]

Two things happen when a battery ages: the voltage goes down and the internal resistance goes up.  For a fuzz face, the voltage is of less importance than the resistance because the fuzz face has DC negative feedback to partially stabilize transistor bias but no bypass capacitors and the internal impedance of the battery creates an unintended feedback path, which does make a difference.  The variable resistor does this, but dropping the voltage via a regulator leaves a low impedance and adding a series diode adds an impedance of 26/i ohms where i is current drain in milliamps.  You may want to see if you like the performance with a bypass capacitor across the battery or across the terminals of the fuzz face circuit board with the variable resistor still in there.  If you do and you add it, then battery aging is less critical.

[Dom D]

Thanks. I need to Google some stuff to completely understand. I'm completely swamped in my studies right now and will hopefully have some time to screw around this weekend or the next.

[kaycee]

Whatever the pro's and cons of the Beavis sag method, it is a nice extra to add to a fuzz face. You can take the edge off of the fuzz and its different to an external bias control.

Does this info also apply to sagging power from a PSU by this method I would like to ask? Some interesting info there, much more to it than I thought, thanks guys for sharing. 

[Mark Hammer]

Anything that produces a musically useful tone variation that is reliably audible (as opposed to things which are hypothetically different but don't sound any different once the volume level goes up) is alright with me.

The so-called sag control does not flawlessly mimic a weakened red Eveready Classic (which will provide a short burst of current in response to pick attack but give up and retreat to lower current very quickly).  But so what, right?

As always, I encourage people to take a peek at this older construction article from Electronic Musician: http://www.generalguitargadgets.com/tech-pages/46-articles/36-em-fuzz   It demonstrates an interesting, and under-utilized, way of imposing current limitations on a distortion circuit.