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How important is it to decouple the power supply with an RC section for my driver/phase splitter in a push pull amplifier?
does common mode rejection help here? are there any major benefits to have the decoupling RC stage? in particular I am using a differential pair input with a CCS in the tail.
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longer answer, it can help a lot.
We run a separate power supply, complete with separate power transformer, for our driver circuits. No matter what happens in the output section, power supply perturbations that result cannot affect the driver. The result is less IMD, both audible and measurable.
You'd think that a good CCS is all you need, but cleaning up the supply helps! BTW, the CCS should be a 2-stage circuit or you are missing a bet- a single stage CCS just isn't.
I would add a shunt reg. to that CCS equation.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
Few years ago, I scored a small lot of military choke, it is 4.5 H/30ma, 350 ohm. I use it to de-couple the driver tube from the B+, the change and improvement is very significant. I notice the different immediately, much darker background and smoother sound. Give it a try if you have room. I think Hammond have small choke can fit such use.
Doesn't everyone decouple every stage? If not with a choke, at least a RC network? I never power two stages from the same bypass cap, that's just asking for trouble.
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Buy Chinese. Bury freedom.
Edits: 01/27/15
"Doesn't everyone decouple every stage?"
Hell, I usually build a separate power supply for every stage.
!
The Mind has No Firewall~ U.S. Army War College.
true. I found LC is definite better than RC decoupling, especially on preamp.
A differential pair with CCS tail should have high PSRR. And it does. But is that good enough? The driver stage in my fully differential transformer coupled mono-blocks had RC decoupling. Was adding a CCS fed shunt regulator just gilding the lili? No! It provided for a nice jump in sound quality. Don't let conventional wisdom stop you from trying new things.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
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