CLC vs LC has benefits I never knew before

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Nick
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#31 Re: CLC vs LC has benefits I never knew before

Post by Nick »

if the ps is stable enough not to sag under changing conditions then there is no change in the dynamics, or the op point if you will.
Yes, this is my point, the op point as it seems to be used here will not change with a regulated (or non sagging) supply. Steve seemed to be suggesting the opposite.

The result will be different in the two cases, but the issue then as always changes from a discussion as to whats actually happening into an exchange of preferences.
it seems so much easier to discuss the current instead...
Agreed, as I have been trying to, but as the change in the current is created by the signal, so its hard to keep the two apart.
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Nick
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#32 Re: CLC vs LC has benefits I never knew before

Post by Nick »

I'm on the fence...
I've always perceived a (very slight) change in dynamics with what I've heard from regulated supplies, a small price to pay for the advantages it brings. My understanding could explain that. ? Or not !
But in reality you are not on the fence, you hear a change, and decide that one way is a price. This is exactly not being on the fence. Price is a vector not a scalar, it has a direction. However there are good and bad regulated supplies so I cant say if what you perceive in a particular example as a "price" is the result of increased or decreased accuracy.
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#33 Re: CLC vs LC has benefits I never knew before

Post by Nick »

In the case of a series-reg supply , there is a reference voltage provided either by a VR tube, or Zener(s). This is a reference , it's not affected by ( or including ) the music signal.
But that's where the mirrors come in, in most cases the supply to the voltage reference will be the same non zero impedance B+ supply that's supplying the regulator, so to say even that is not affected by the signal is not entirely accurate.
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#34 Re: CLC vs LC has benefits I never knew before

Post by steve s »

Nick wrote: Thu May 19, 2022 5:09 pm

But in reality you are not on the fence, you hear a change, and decide that one way is a price. This is exactly not being on the fence. Price is a vector not a scalar, it has a direction. However there are good and bad regulated supplies so I cant say if what you perceive in a particular example as a "price" is the result of increased or decreased accuracy.
If I was certain about my view you would be absolutely spot on, but I never really trust what I've learnt so far to be the complete story..
I go through life trying to understand lots of things.. yet I only skim the surface in reality..
But I'm taking what you said as a compliment .. and thanks for your input
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#35 Re: CLC vs LC has benefits I never knew before

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Nick wrote: Thu May 19, 2022 5:12 pm the supply to the voltage reference will be the same non zero impedance B+ supply that's supplying the regulator, so to say even that is not affected by the signal is not entirely accurate.
To be rigorous , yes, but I think we'd agree it's a second-order effect, since the gradient of Vref vs. current is usually pretty shallow.
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#36 Re: CLC vs LC has benefits I never knew before

Post by JamesD »

Sorry for the delayed response - I had a long sleep this afternoon - still no energy or stamina...

My take on Steve's response - with apologises for repetition of what others have said:

1) if we consider a triode (internal resistance ra) sitting on a cathode resistor (Rk) and with an anode resistor (Rl) load then, with no signal present, the B+ voltage divides between Rk, Rl and ra according to their values such that B+= Ia(Rk+Rl+ra) where Ia is the anode current supplied by the psu. And with no signal we can regard Rk, Rl and ra as constant. As soon as we introduce a signal ra will vary but Rk and Rl will stay the same valve and this results in Ia varying so the voltage division between Rk, Rl and ra changes responding to the applied signal. It is the varying of anode current across Rl that is normally taken as the production of output voltage signal although for a cathode follower it is the varying of the cathode current (= anode current) that produces the voltage varying across Rk that is taken as the output.

This is independent of the psu as it assumes constant B+ and an infinite current delivery ability from the psu i.e. the psu internal resistance is = zero...

In practice the psu internal resistance is finite and hence the varying anode current supplied by the psu causes the psu voltage to vary by a small amount (for a well designed psu) and it is this mechanism that causes some small value of signal voltage to appear across the psu. Regulated psu exploit the dynamic characteristics of the active devices to lower the apparent psu internal resistance as seen by the signal circuit and hence reduce the amount of signal driven variation in the B+ voltage.

I hope that helps clarify what is happening - this is simplified but is the essential mechanism as I understand it...

ciao

James
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