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Re: Paraphase inverter questions

11/9/2004 1:12 PM
Re: Paraphase inverter questions
"Thanks Dutch, "
You're welcome....  
"I also think I'll try what you recommend with the 50k pot. The balance would change with a different tube in the PI slot however right? "
Yes. The pot should hopefully allow enough leeway to get anything from a 12AU7 to a 12AX7 relatively balanced, though. For a bit more range, you could replace the 470k feeding the second triode with a 390k and instead use a 100k pot. That would keep the 7868's grid resistance relatively within bounds (too high and the tube can "run away" and red-plate) but gives you a larger range of voltage division ratios to work with....  
"I may have room to fit a balance pot as you suggest permanately on the power amp chassis, so I could take care of that if the balance goes off when I change a tube. "
It'd be a nice tone tweek, as I'm sure there'd be a sweet spot where it wasn't *perfectly* balanced, but sounded *real* good....  
Have fun!  
C ya,  
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11/10/2004 6:13 AM
Greg Simon
Thanks again Dutch! I'm in the process up wiring up the preamp chassis now that I corrected the layout. (had it backwards, was getting very confusing!)As soon as that is done, I'll test things to make sure they work, then start in on the power amp chassis. So thats when I'll be playing wih the inverter, and I'll take your suggestions there. I definitly would like "some" clean headroom out of the thing and your suggestions seem like a step in the right direction.  

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