Dying battery simulator

[Rob Strand]

It is noteworthy that the FuzzFace's bias is stable many ways, but the drop across Rc2 is nearly fixed (Rc*Vce/Re) so supply voltages have a large effect on Vc2 and on clipping (a)symmetry.

In the old germanium days there was a lot of unit to unit variation due to leakage.   The root cause was usually a mis-biased Q2 voltage.   You had a lot of pro players gathering up "good ones".

I think a lot of the flat battery stuff come about because it fixed the biasing of some of the poorly biased units.  That being said there's people who like the misbiased sound ...     IIRC there was an Eric Johnson Fuzz-Face produced and it doesn't bias Q2 to 4.5V.

[zbt]

Has anyone tried using a battery? In Series using One 1.5V AA or Two.
With less than 1mA, I think the battery will not be able to survive. 
Output voltage range around 7.5V for one battery, or around 6V if two.

[yeeshkul]

How does it actually work that a signal that goes through FF loads the dying battery so the DC level swings?

[zbt]

As replacement for RBat, the circuit I try (Fuzz Face) still work.

[yeeshkul]

Dying battery becomes softer DC source. I am not sure you can simulate it by a fresh battery of lower voltage.

[zbt]

My battery is no longer fresh, I measure about 2.763 volt

[zbt]

I short circuit the battery

Battery  Output   
2.526    6.59     
2.14     6.83
1.87     7.04     
1.16     7.92     One Battery

It's weird if the fresh battery tastes sour like tom yum
The lower the Output voltage (6.59) sound like a coughing bear
the high is softer, less spicy but like too much pepper I guess. 

Is this sound of dying battery? hahaha 

[iainpunk]

Has anyone tried using a battery? In Series using One 1.5V AA or Two.
With less than 1mA, I think the battery will not be able to survive. 
Output voltage range around 7.5V for one battery, or around 6V if two.

i think different Zener diodes or LED's would be a safer/cheaper/better option.
some home audio tube amps used batteries to provide bias to the cathode, but those needed replacement every so often because they would over-charge and bad things can happen.

How does it actually work that a signal that goes through FF loads the dying battery so the DC level swings?

when the Fuzz Face puts out full volume signal, internal bias shifts, this means the circuit tries to pull more current, and this higher current makes a larger voltage drop over the batteries internal resistance, dropping the voltage a bit.

cheers

[Mark Hammer]

Again, let's go back to original source-context: a Fuzz Face and a carbon-zinc 9V battery.  What one measures at the output of the battery is certainly reflective of what is happening at the junction of the 6 internal cells, but I think that is unlikely to be mimicked by individual AA cells, whose "junction" is nice shiny metal.  Keep in mind that alkaline 9V batteries are not reputed to yield the legendary "dying battery" effect, and they consist of 6 sub AAA cells internally, spotwelded to each other in a manner more like a clip of multiple 1.5V batteries.

[zbt]

Yes, Sir.

I also try to understand the purists, or at least my friend.
I use this 9Volt battery, and my current circuit is silicon fuzz face, without diode protection and filter capacitor.



My first introduction to voltage sag came from beavis board.
I tried it while trying the treble booster circuit, with a 10K resistor, and it didn't sound good to me.

Then I read about using batteries, interested in the difference between zinc and alkaline, for me batteries are wasteful and expensive,
so I also tried with a 12V motor battery, and lowered the voltage to 9V, used a regulator and it worked fine, enough for a year.
The only think I like about using battery is less noise.

My curiosity reappeared after reading this article https://www.analogman.com/fuzzface.htm There is you Sir.

No nice fancy led, is this what makes the guitarist legendary? even i'm starting to think they practice with their eyes closed. ahah.

And why a dying battery, isn't a fresh battery better?
Then I read this Amazing Spider Keen http://geofex.com/article_folders/oldspyder/oldspyder.htm and that I know that Rbat is for simulating dying battery.
if it's already in the design, there's definitely something useful.

I just don't know how to use it, even in this realm there are myths also  .

Last time

Using dead 9Volt battery sound bad, and then silence, recharge a little, sound bad then stop.
Set PS to 8Volt, 7Volt, 6Volt the lower sound just like lower gain  Using Red Led, same as lower the supply
Find resistor value, 3K9 around 7volt sound like piezo, the fizz gone. below 3K9 sound different from 1.5 AA Battery.

I prefer to use two 1.5 AA batteries, the fizz still there but much softer, while overall sound more low.
May be is not the same as actual dying sound, but now I know the battery can make the fizz softer.

[iainpunk]

yes, that might work, but using batteries like that is an
> UNSAFE
idea, since they don't really like being over-charged.
maybe put a huge capacitor from the new, lowered vcc to ground when using LED's, resistors or lower power supply voltages, this will soften some of the harsher overtones.

cheers

[Mark Hammer]

What would help a LOT is if the experts who swear by dying 9V carbon-zinc batteries would either describe, in words, what the impact is on the behaviour of their fuzz, and also measure the actual voltage of what "dying" is.  It certainly isn't dead.  Maybe it's just really exhausted, in the sense of able to walk but not ready to run up the stairs.

And as I hasten to remind people, a stable voltage or current-limited supply isn't necessarily a bad thing or a musically useless thing.  Even if all the simpler "supply degraders" do not accurately mimic a dying battery, that does not mean they can't do something that pleases us.  They just don't do EXACTLY what an exhausted carbon-zinc battery might do for a Fuzz Face

[zbt]

I measure the current is about 600uA the battery voltage at 2.661V so the R = 2.661/0.0006 = 4435, I replace it with 4K7 resistor, still sound different.
I measure the current again with signal, it raise about 50uA and voltage drop at about 1mV, 2.660/0.0065 = 4093, around 340  ohm different.
At this time, I feel RBat is like spring or variable resistor, the more fresh battery like ps, is hard to pull, at dying process it weaker.

measure the actual voltage of what "dying" is.  It certainly isn't dead.  Maybe it's just really exhausted, in the sense of able to walk but not ready to run up the stairs.

If the capacitor is tumbler, I just give a fuzz a drink a little, may be a cup, just to make refresh a bit.

                            R
---[ RBat ]----*----///----
               |
              ===  C
               |
               V


RBat = 4K7, R = 390, C = 470nF close enough,
adding diode the string is like rubber, and sound like boing! boing! at single note 
same like make RBat bigger but more tight rubber
I like RBat = 6K8, R = 390, C = 470nF, too mantain the fizz.
The bigger the C, good if used a ripple supply.

RBat work, put again using POT 10K, RC just make softer, diode also nice

yes, that might work, but using batteries like that is an
> UNSAFE
idea, since they don't really like being over-charged.
maybe put a huge capacitor from the new, lowered vcc to ground when using LED's, resistors or lower power supply voltages, this will soften some of the harsher overtones.

cheers

Everyone try this 1.5V battery, please be careful

Isn't it interesting that as we "modernize" some circuits by fixing the bias and adding power supply filtering, that we have engineered much of the character out of it. Many times the "mistakes" make the magic. 

And as I hasten to remind people, a stable voltage or current-limited supply isn't necessarily a bad thing or a musically useless thing.  Even if all the simpler "supply degraders" do not accurately mimic a dying battery, that does not mean they can't do something that pleases us.  They just don't do EXACTLY what an exhausted carbon-zinc battery might do for a Fuzz Face

[acquiesce808]

here we go - an external DBS 

hey, old topic but, did this work?  what's the value of the potentiometer? and is that a 100uF capacitor?
thanks!
al b