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Balanced Phase Inverters...and you


bmast160

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i know this is hotly debated...the only balanced tube id consider getting for my amp is a phase inverter...what you think of balanced phase inverters...has anyone tried a balanced PI vs an standard PI of the same brand?

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not necessary. look at any push pull amp, and you'll see that the plate resistors on the PI are different values. this is because the typical long tail pair PI is not a perfectly balanced circuit. even with the different plate load resistors and a balanced tube, the circuit is not balanced. it doesn't need to be.

 

but whatever you want to do with your money ain't gonna hurt me a bit.:thu:

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so basically its use a possibly unbalanced tube...with unbalanced plate load resistors....and get an unbalanced result

or

use a balanced tube with unbalanced plate resistors and get an unbalanced result...

i guess the only way that it would work out balanced is if the tube was unbalanced in a way that was opposite how the plate resistors were unbalanced...then they would cancel out and i could take a nap

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you're missing the point.

 

the PI doesn't need to be a balanced circuit, which is a good thing because it's not a balanced circuit. the different value plate resistors are a bandaid to help get the circuit closer to being balanced. if you REALLY wanted to have balanced output from your power section, you'd be better off having a bias adjustment for each side (or each tube).

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okay, heres what i've found. Yes it doesnt really matter if its a little off balance or not.

 

But if the tube you use is WAY off spec (and really off balance) which is rare, then it will create noise just like having a bad bias will create noise. This is why some amps let you bias the pairs of tubes: so one side isnt way off of the other.

 

but yeah, typically it doesnt matter.

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