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How to defeating an Active EQ

9/11/2004 4:47 PM
Yannnick How to defeating an Active EQ
I have an active 3-band EQ block as shown in TUT2 and want to put in ON or OFF. I know some of you, with a passive EQ stack, are switching the connection to ground on and off to achieve this. Does doing the same thing on the inverting gain block of the active EQ will defeat it? And in doing so, the signal still will pass through it: does it will be attenuated or just transformed into a passive EQ?  
I don't want to use a relay or series-switch to select between the EQ or the bypass shortcut.  
Any with suggestion?  
9/12/2004 2:17 PM
Yannnick Re: How to defeat an Active EQ
Suggestions?? ideas??? Anybody?
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9/28/2004 4:39 PM

I assume you're using Fig 6-23. One way would be to add two resistors, maybe 470K, in series from Ein to Eout and then with a SPDT switch connect point A to either the junction of the two new resistors or the junction of R4, R8 and C4. You might need to add a 10meg resistor from point A to the junction of the new resistors to prevent switching noise.  
Another way would be to use a 3PST switch to short across the end pins of all the pots.
9/29/2004 8:51 AM
Thanks for that answer,  
Let's say the EQ is in a power amp chassis, the preamp in a another chassis.  
1) Defeating the active eq should be automated with channel switching, in other words, it is a preset mounted on the footswitch casing (exclusive 4 channel voicing with a preset on EQ on/of).  
The control line from the footswitch logic are plugged in the preamp chassis only. 2 of those control lines are shunting either output A or B (in the preamp). Input_A in the power amp connects to Eout while Input_B connect to Ein: will this method bypass the active eq effectively?  
Or maybe the input_A should connect to A? I'm really not sure about that one.  
Thanks again for your help.  
PS.: By the way, I'm effectivelly using fig 2-63 (it's preceding the power amp). The preamp channels (4-clean, od, crunch, lead) are control using fig.6-62 with a second 40175 for exclusive boost option.
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