One more VariMu question - common cathode resistor

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rafafredd

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You guys probably noticed I'm messing with VariMu variations a lot lately. I am really in love with these tube comps for years, and I just got back to DIY, so I am excited and starting lots of new experiments on breadboard... I mean, breadpoint...

So, is there a reason why I've never see a common cathode resistor for both plus and minus sides in a balanced varimu compressor circuit like this?

This is an example circuit. one could use small trimmers on the plates for balancing operantion.

cathodes tied together would easy CMRR of thumps and noise, and save on a big capacitor for AC coupling the cathodes like Ive seen on some compressors.

Also, not sure, but impedance would be lower on plates, wouldn't it?

So, is there anything wrong or bad about getting the cathodes on a compression stage tied together like this?

Thanks for any inputs!
 

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Primarily about balance, metering, or hum control.

It's common in the Gates SA-39.  It could be common in many others, if not for individual tube current metering that's built in with a need for separate cathode resistances. 
 
EmRR said:
Primarily about balance, metering, or hum control.

Yes, I though so...

But these can all be done in the plate circuit, like in my drawing... Even the metering.

So... for the next build, common cathode here I go.

And I'll check SA-39, thanks!
 
None of the schematics I have show it, but I've seen several General Electric Unilevel with common cathode 6386.  I would assume the earlier versions. 
 

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