HankMcSpank
New Member
Got a little problem, that's driving me potty!
I've a guitar with it's output signal 'Y'ed off ....1 leg into an opamp preamplifier - the other leg has original guitar signal travels unabated onwards to a high gain guitar amp.
Here's the problem - when the preamplifier circuit is powered on/off (it's battery operated so can't be left on - and worse still needs to be switched on/off a lot), I get an annoying click out of the guitar amp.
Now I know what causes such clicks - sudden inrush current on power up (note: The circuit is required operate from a single 9V battery.). The transient in this case is the result of the opamp input pin biasing/ramping up to VCC/2 (virtual ground) too quickly - this small level surge finds it's way back out of the circuit input connection (in other words the transient travels in reverse trough the opamp input decoupling cap & back into the Y'ed off raw guitar signal travellling onwards to the high gain amp.
CLICK!
So, I then brought in a 7660 switched cap inverter .....to make the opamp supply bipolar thereby removing this sharp dc level at the input on power up - sure enough, click is virtually eliminated, but would you believe that on power off, I can hear the 7660 oscillator collapsing down out of my guitar amp! (like a peeeeuwwwww sound - only discerible upon switch off - & it's definitely the 7660!)
Any ideas on how to approach this, to rid myself of the click or other nasties as heard out of my hi gain guitar amp?
I've a guitar with it's output signal 'Y'ed off ....1 leg into an opamp preamplifier - the other leg has original guitar signal travels unabated onwards to a high gain guitar amp.
Here's the problem - when the preamplifier circuit is powered on/off (it's battery operated so can't be left on - and worse still needs to be switched on/off a lot), I get an annoying click out of the guitar amp.
Now I know what causes such clicks - sudden inrush current on power up (note: The circuit is required operate from a single 9V battery.). The transient in this case is the result of the opamp input pin biasing/ramping up to VCC/2 (virtual ground) too quickly - this small level surge finds it's way back out of the circuit input connection (in other words the transient travels in reverse trough the opamp input decoupling cap & back into the Y'ed off raw guitar signal travellling onwards to the high gain amp.
CLICK!
So, I then brought in a 7660 switched cap inverter .....to make the opamp supply bipolar thereby removing this sharp dc level at the input on power up - sure enough, click is virtually eliminated, but would you believe that on power off, I can hear the 7660 oscillator collapsing down out of my guitar amp! (like a peeeeuwwwww sound - only discerible upon switch off - & it's definitely the 7660!)
Any ideas on how to approach this, to rid myself of the click or other nasties as heard out of my hi gain guitar amp?
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