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strobe sound

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Josh

New Member
hi. i want to make a guitar strobe sound effects pedal. i've made the 555 timer circuit and have an led pulsing, and i was going to run it through a 4066 to switch the audio with the pulses. it didn't work so i used the square wave to turn the whole IC on and off - and there is a loud click at the output every pulse. how can i make the audio strobe without interference? i would prefer not to use a relay.

Thanks

Josh.
 

Exo

Active Member
switching sound with a 4066 should work, do you have a scematic of your project?
 

Exo

Active Member
Also, make sure to put a buffer or amplifier AFTHER the 4066.
Don't drive a speaker directly with the 4066. The 4066's Ron is about 100ohm, wich is too much to drive a speaker directly.
 

Roff

Well-Known Member
It takes a lot of work to make a popless switch, especially when you can't really control the slew rate of the switch. DC biasing and AC coupling also are very tricky.

Take a look at Fig. 2 of LM13700. If you make +Vs and -Vs 9 volts each, change the gain control resistor to about 13k, and run the control voltage from -Vs to +Vs, the gain will go from zero to approximately 1. AC couple the input and the output. For the input, you'll need about 1uF. The polarity depends on the DC level of your source. On the output, your cap value depends on the input impedance of your amplifier. Pick a value that is close to 16/Rin, where Rin is k ohms and C is microfarads. In other words, if Rin=1k, pick Cin near 16uF (anywhere between 10uF and 22uF). Again, the polarity will depend on the DC level of your load. If your input is at zero volts, connect the + pin on this cap to the input of your amp.
 

spuffock

Member
There will be all sorts of problems with pops and thumps. Some of the switching signal will be coupled to the audio, and it may give rise to pops and clicks if you feed a low level signal from a guitar directly to the 4066.
It would be a good idea to amplify the signal to a volt or so first. Secondly it would be a good idea to arrange that the switch always operates as the audio crosses zero going positive, to avoid clicks from sharp edges and thumps from dc level shifts. I,ve got someone worrying me for one of these, so I,ll be developing the circuit shortly, and I'll be able to send you the circuit privately in a couple of weeks. I think it might use a couple of 7555's , a tl082 and a 4013.
 

Josh

New Member
cheers guys. sounds pretty tricky to do it properly. maybe i'll settle for a relay. no-one's gonna hear it in a concert or anything.

Thanks again

Josh.
 
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