cap multiplier or not?

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Hi there!

Really like this forum, lot´s of knowledge here!

Would like to ask u psu-gurus this:

Do u consider this circuit to be some kind of a cap multiplier?
(only showing the positive side of the psu)
That´s what I am wondering about...and if it wouldn´t be for the zener I would have been sure about it, but...??
Could u please enlighten me please?
And if it is a CM are there anything that can be improved there?

It´s a break out from a psu to a bass preamp.

thanx! /Peder
 

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I really often wonder what is the function of Cap multiplier. Is it to give cleaner supply to the CCT? Have tried this, it gives ultra clean sound (is it good or bad? Some people say it is sterile).

Mr. Curl, the example of Cap multiplier is in the Parasound HCA 1200 schematic, right?

Why do you consider this example cct is only zener regulated? Inspite of there is zener to ground, there is also cap to ground (both connected to base). The cap effect got tobe multiplied too?
 
lumanauw said:
I really often wonder what is the function of Cap multiplier. Is it to give cleaner supply to the CCT? Have tried this, it gives ultra clean sound (is it good or bad? Some people say it is sterile).

Mr. Curl, the example of Cap multiplier is in the Parasound HCA 1200 schematic, right?

Why do you consider this example cct is only zener regulated? Inspite of there is zener to ground, there is also cap to ground (both connected to base). The cap effect got tobe multiplied too?

You know... if you look at Rod Elliots page, his "cap multiplier" circuit looks just like this circuit, well with a protection diode.

I really wonder if either of these actually "multiply" the capacitance at all or just have a regulating effect like IF an equivelent sized capacitor XXX was there.

The truth is, if you take both circuits and flip the transistors into standard vertical alignment you'll see easily that they are EF buffers on fixed voltage source. What happens is that the main source of their filtering has to do with the diode voltage vs current. The base is being fed by a resistor which buffers it from the voltage ripple and instead converts this to current ripple. Diode voltages are quite resistant to current ripple being 1/sqrt(x) kind of nature. I think that's where the regulation is coming into play.

--
Danny
 
Zeners cannot be effectively directly bypassed by caps. Why is this? Zeners are good, IF you have enough extra voltage to throw away. The JC-1 power amp, for example, uses zeners and buffered caps in the driver power supply, because we have extra voltage. The 1200 had NO extra winding on the power supply, SO we had to use a multiplier. Also, it tracks the main power supply, so even with low line voltage, it still works.
 
Adding the transistor shown in the diagram below makes it a zener pre-regulated capacitance multiplier.

Your schematic I would describe as a "reference follower" - in your case you have a reference voltage provided by the zener that is effectively low-pass filtered by the RC network. An emitter follower circuit is then used as a current amplifier to feed the following circuitry.

Does this help?
 

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Just want to ask u regarding ur first answer:
"No, it is a zener filtered power supply. This is better."
By that U mean that it´s a better regulator this way over all or do u mean that the "cap multiplier" is working better this way?.. no that couldn´t be it, right?

Thank u for answering my questions mr Curl!

/Peder
 
The performance of each circuit, i.e. the cap. multiplier and the zener follower depend on components used.

I can't say which works best without some prior simulation/testing although both have different characteristics and can therefore prove to be better in a given situation.

I did state that original circuit you posted was not a capacitance multiplier although I did not actually tell you what it is. I simply told you how to make it a capacitance multiplier (albeit a slightly modified one) - the original circuit you posted is just a zener follower with the zener reference voltage filtered with a simple RC lowpass filter. A darlington pair is used so as to limit the effect of the current draw on the output voltage.
 
Zener referenced regulators are noisy. Cap referenced regulators have poor DC stability. A combination of the two, or even better: One zener referenced regulator (IC can be OK) and then a cap multiplier to smooth noise and give good high frequency performance is even better. Be careful NOT to share cap multipliers with different channels. They can xtalk. Best to use a separate cap follower with each circuit or at least, each channel.
 

Zener referenced regulators are noisy. Cap referenced regulators have poor DC stability. A combination of the two, or even better: One zener referenced regulator (IC can be OK) and then a cap multiplier to smooth noise and give good high frequency performance is even better. Be careful NOT to share cap multipliers with different channels. They can xtalk. Best to use a separate cap follower with each circuit or at least, each channel.

I agree - probably the best method if using a circuit with multiple op-amps/stages is to use a zener reference follower as the first global regulator, then to use a cap. multiplier for each op-amp/stage as a local regulator.

This way you should achieve a good DC performance whilst satisfactorally isolating each stage.
 
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