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DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  "dying battery simulator" does nothing when pedal is first activated? 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: "dying battery simulator" does nothing when pedal is first activated?  (Read 1347 times)
joelindsey
Posts: 101



"dying battery simulator" does nothing when pedal is first activated?
« on: October 31, 2011, 11:54:20 PM »

So I added a pot across my DC jack on my Big Muff to simulate the dying battery effect. The pot is intended to serve as a voltage divider. From what I've read here it doesn't actually simulate a real dying battery (is voltage starving a more appropriate term then?), but I'm ok with that. I like the sound of it. It also cuts the volume significantly, which is fine.

The problem is, when I engage the pedal, for a few seconds the pot appears to do nothing, as if it isn't there. Really loud, different tone. The volume and distortion fades back down to whatever I have the pot set for after a second or two. This sudden surge of volume makes this quite impractical to use on and off. Is there anything I can do about this, or is it a problem inherent to slapping a pot across the DC input jack? Sound is always so difficult to put into words. Perhaps I could record a video of it? It seems as though this has worked for other people, so I don't know what it could be.
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artifus
Posts: 1742


dare to be na´ve


Re: "dying battery simulator" does nothing when pedal is first activated?
« Reply #1 on: November 01, 2011, 01:34:15 AM »

So I added a pot across my DC jack

http://www.beavisaudio.com/Projects/DBS/#Adding
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joelindsey
Posts: 101



Re: "dying battery simulator" does nothing when pedal is first activated?
« Reply #2 on: November 01, 2011, 09:13:48 AM »

I guess "across" was the wrong word to use. I did the same thing on the picture you linked to. It works, just not for the first second the Muff is switched on. It's the sudden volume boost (if I have the voltage set to something lower than 9v) that is giving me issues. I'll try actually hooking it up as a voltage divider, with lug 1 going to Vin, lug 2 Vout, lug 3 to ground and see if that helps.
« Last Edit: November 01, 2011, 09:19:20 AM by joelindsey » Logged
MikeH
Posts: 3087


Mike H - Ann Arbor, MI


WWW
Re: "dying battery simulator" does nothing when pedal is first activated?
« Reply #3 on: November 01, 2011, 12:03:27 PM »

My guess (and it really is a guess) is that it's due to the filter capacitors.  When you have the starve on and pedal off, voltage can trickle through the 'starve' control into the circuit and fill up the filter cap.  When you start putting signal through the circuit and the transistors start amplifying they draw more current than they do at idle, eventually draining that filter cap, and then you get your starve.  Try removing the filter cap, and putting it on the DC jack directly, before the starve control.

Again - mostly guessing here.

Also, you're not doing anything funky like switching the power on and off with your stompswitch are you?
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"Sounds like a Fab Metal to me." -DougH
joelindsey
Posts: 101



Re: "dying battery simulator" does nothing when pedal is first activated?
« Reply #4 on: November 01, 2011, 02:46:09 PM »

Also, you're not doing anything funky like switching the power on and off with your stompswitch are you?

Nope, the switching is normal.

You were right though. There were two 220uF filter caps in parallel on the board, so I removed them and put one across the DC jack before the starve pot, like you suggested. It worked! ...But the problem was reversed! Instead of being super loud when I switch the Muff on, it was quiet and quickly rose in volume. After toying with cap values, I settled for two 22uF caps on the board and a 220uF across the DC jack. They don't balance each other perfectly, as there is a short dip in volume when switch it on, but at least it doesn't blow my speakers every time I switch the Muff on!

I should have noted earlier that the sudden drop or peak in volume only occurs when I switch it on while I'm playing. If I turn it on without playing and wait a second it sounds normal.

Thanks for the suggestion Mike!
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