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Re: Hey Max


 :
12/6/1999 3:13 AM
Stokes
Re: Hey Max
I have a question for Gil.I wired a switch to change the bias from cathode to fixed.What I would like to know if you know,is it safe to switch bias modes on the fly,or should I put the amp on standby before switching?Thanks for your help.  
Stokes
 
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12/6/1999 6:32 AM
Gil Ayan

quote:
"I have a question for Gil.I wired a switch to change the bias from cathode to fixed.What I would like to know if you know,is it safe to switch bias modes on the fly,or should I put the amp on standby before switching?Thanks for your help.  
Stokes"
 
 
You mean cathode SELF bias or a fixed bias amp with a cathode resistor, like the Boogie Simulclass? IF the former, I would probably put the amp on standby first; if the latter, if it probably not that critical.  
 
Gil  
 
PS: you should ask the guys that know amps, like R.g., K.G. and R.A.... I am just a guitarist with an adventuresome spirit. :/
 
12/6/1999 3:02 PM
KG
No matter how hard you try, I really doubt you would be able to syncronize the application of one bias method while simultaneously removing the other. This will create a large transient in effective grid bias voltage, which will cause a pretty large bump in the plate current. Since the amp is a differential amp (ie it is a push pull output stage) then it will not be quite as sensitive to this common mode input, but I still suspect that there will be a quite loud transient output from the amp.  
 
I would certainly not want to do this while actually PLAYING something through the amp... that would create a whole new level of complexity in terms of what's going on. So you might as well switch the amp on standby while you're switching modes. It is certainly safer.  
 
You COULD get really fancy and rig up a circuit to lift all of the output stage's cathodes from ground while the switching takes place. This would interrupt plate current, like the other methods may do as well, but it would eliminate the possibility of creating a SURGE in plate current, which is of course far more detrimental.  
 
As stated earlier though, I can't really imagine a way to switch this on the fly without creating a transient signal.  
 
Good luck,  
KG  
 
12/6/1999 11:16 PM
Max

Hi guys.  
And thanks a lot for all the info.  
I'll contact Boogie soon.  
Best regards.  
Max.  
=:o)
 

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