CLC vs LC has benefits I never knew before

[Paul Barker]

https://apps.dtic.mil/sti/pdfs/ADA637782.pdf

Never too old to learn and change.

[JamesD]

Hi Paul,

Very interesting article and worth studying but I'm not sure how to assess it if you are not looking for peak efficiency but best sound...

Looking at the current graph over a charge cycle that compares capacitor input with choke input it is clear that the cap input has much steeper rise and fall times on the charging waveform and it is these edges that excite the ringing in the associated psu components that I associate with adverse sound... They also use a lot of capacitance on the cap input model...

I think I still favour a small value cap input rather than full choke input as it limits the voltage stress on the psu whilst only minimally increasing the slope of the charge curves... and I couldn't hear the difference when I tired it....

I'm surprised that Paul Joppa or Dave Sagle didn't comment on this on the asylum...

ciao

James

[Nick]

They also use a lot of capacitance on the cap input model.

Yep, but unlike the days past, there is not that much of a reason why you wouldn't use a lot of cap if you wanted. Combine with a CCS feeding a shunt reg and you can fix exactly the supply conditions you want. Thinking about it, given that constant and known load, you could use a CCS between the rectifier and first cap to manage the peak charging waveform. Add a driven mosfet bridge so even less switching issues.

Not that I have done all the above but it was just a thought.

[JamesD]

Interesting thought too... I'll have to play with that idea Gedankenexperiment of course... I like the MOSFET bridge with controlled switch on and off times idea...

[steve s]

Combine with a CCS feeding a shunt reg and you can fix exactly the supply conditions you want.

But apart from the advantage of reduced power supply modulation from the amplified signal, this method changes the operating point of the device to include the varied signal voltage
This may or may not be a disadvantage depending on the operating conditions
But in some conditions I would theorise that it could affect dynamics

So to put it simply, in a std supply we have the supply voltage + the signal volts, my measurements show a volt or so voltage drop under load

In a shunt reg we have the supply voltage and that is held constant
But that includes the signal, so the operating point of the device is changing constantly to include the signal within it. This is much more of change in operating point than a std supply, and the operating voltage drops more with musical peaks

Hopefully my understanding is correct... or I will soon be on a learning curve !!

[Nick]

I will be honest with you Steve, I think you were saying this to me at the last Owston, and I didn't understand what you meant then and I still dont.

[Paul Barker]

I’m far simpler minded. Back in the day I found choke input had better drive in se amps and didn’t see any reason to alter.

But clearly it’s much more complex. Though with my mind I’ll leave all the chatter to others.

[Nick]

I want to try and understand what you mean Steve. Can you describe a bit more, is this referencing a resistive or inductive load to (I assume) a triode stage? James if you see what I am missing please jump in at any time.

Also, Steve, I am unsure just what you mean in this context as "dynamics", I assume you mean more than just gain, maybe it relates to how linear the stage is?

[steve s]

I will be honest with you Steve, I think you were saying this to me at the last Owston, and I didn't understand what you meant then and I still dont.

Well I may well be missing something vital, I suppose the difference between regulated and none regulated supply is the operation point, which is held constant with regulation, as it absorbs the signals effect on it, by constantly changing the dc voltage to incorporate the signal volts effect on it, and has the big advantage of removing the signal from the supply, ie reduced power supply modulation that zero feed back amplifiers suffer.

Where as traditional powersupply is only a "nearly' fixed dc voltage modulated by the signal 'on top ' of the operation voltage.

To me that gives two slightly different operating scenarios.

I do totally appreciate the advantages of a regulated supply, its just in my mind a totally fixed operating point that includes the signal, is not how a valve was designed to operate... or is it ?

Hope that makes sense

[steve s]

I want to try and understand what you mean Steve. Can you describe a bit more, is this referencing a resistive or inductive load to (I assume) a triode stage? James if you see what I am missing please jump in at any time.

Also, Steve, I am unsure just what you mean in this context as "dynamics", I assume you mean more than just gain, maybe it relates to how linear the stage is?

Hope the last post made sense, in my mind I'm explaining logically as I can

But my brain sees things that I find difficult to explain !

[IslandPink]

The regulated supply is not trying to stabilised the operating point, it's stabilising the B+

( ps. there's quite a lot of difference between series-reg and shunt-reg in terms of what happens in the PS, to achieve that aim.)

[steve s]

The regulated supply is not trying to stabilised the operating point, it's stabilising the B+

( ps. there's quite a lot of difference between series-reg and shunt-reg in terms of what happens in the PS, to achieve that aim.)

But the b+ is the main thing that determines a valves operating point ?

[IslandPink]

How about the cathode resistor and the G1 voltage ?
But yes the B+ plays its part. Trouble is, without regulation, the B+ just fluctuated with the music signal, and it may or not be in phase with the music signal, too. Not ideal.

[Cressy Snr]

Deleted
I'm way out of my league in this one.

[steve s]

How about the cathode resistor and the G1 voltage ?
But yes the B+ plays its part. Trouble is, without regulation, the B+ just fluctuated with the music signal, and it may or not be in phase with the music signal, too. Not ideal.

On a std supply the b+ fluctuated with the load, a volt ir two in my experence

With a regulated supply the b+ is constant yes, but the dc supply is compensating for the peak voltage signal on the power supply from the signal
enough to suppress it, so in one of my typical amplifiers, that I have measured, the powersupply modulation,there could well be a 20 volt envelope the regulator is working within on the incoming dc b+ to keep the voltage constant when the signal is included.

Again I hope my logic is logical..