Re: OT Variable Power Supplies for Stomp Box Pedals

[andy butler <akbutler@tiscali.co.uk>]

andy butler wrote:
> Rick Walker wrote:
> 
> 
>> Anyway,  I told him that I keep a bunch of old used 9 volt batteries 
>> (in various
>> short lengths of time before their battery death) and that , 

> The resistor you need ...well I don't know what would work best...
> ...you could try starting with a 1k log pot then turn the spindle
> till the desired artefacts appeared.
> 
> andy
> 
> 
> 
> 

ahh, I guess that's about right:-

“put a 5k linear pot in series with the positive terminal to the circuit. 
that's all you need to simulate a typical dying 9V battery. the resistance 
range is almost identical to the chemical build-up over time using a pedal 
that draws around 5mA. if you don't believe me. try it, and then 
substitute a dead/dying battery and listen for a difference with the pot 
shorted. batteries can't die without building up series resistance. 
likewise, the reason for voltage drop is a result of the increased series 
resistance! i put it to you... the lowering of battery voltage is a result 
of exactly the same mechanism as increased series resistance. a pot in 
series with a battery will most certainly simulate the dying of a 
battery.” – Zachary Vex