Regulated Power Supply for power amp

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By big capacitors, if you mean the large electrolytic supply smoothing caps after the rectifier, then they go before the regulator. A regulator needs a relatively steady supply voltage to get the best out of it.

What sort of power supply do you need? Split rail? What voltage and current rating?
 
Hi,
many do not recommend a regulated PSU for a power amp. Partly due to the PSU cost being greater than the amp cost. But mostly due to interaction between the reg. active stages and the amp. active stages. Quite difficult to eliminate all the little (or big) instabilities.

A regulated front end and unregulated output stage is often popular, much cheaper and very much easier to debug.
 
AndrewT said:
Hi,
many do not recommend a regulated PSU for a power amp. Partly due to the PSU cost being greater than the amp cost. But mostly due to interaction between the reg. active stages and the amp. active stages. Quite difficult to eliminate all the little (or big) instabilities.

A regulated front end and unregulated output stage is often popular, much cheaper and very much easier to debug.

Loop stability is mostly a problem for low dropout regulators in which the output capacitor is part of the feedback loop -- if mama bear isn't happy, papa bear ain't happy either.

In one of the Nelson Pass "Audio Amateur" (predecessor or AudioXpress) designs he recommended regulation as the particular circuit had poor power supply ripple rejection (PSRR). There is an article on the PASS DIY website which describes MOSFET regulators for this amp.

I did some testing of LM3875 and LM4780s with regulated and unregulated supplies -- my observation (measurements) was that at low levels the THD was about 0.001% lower for the regulated version, but about 0.001% higher at the high end. At high output levels there was no difference except that power was consumed by the regulator. YMMV
 
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Hi,
overall regulation has good and bad points.
It's more expensive to regulate and peak power is more limited.
On the other hand, it seems to give the bass more oomph.

If possible, regulating only the first couple of stages (input and voltage) is useful and much less expensive.
 
I fiddled around with a reg circuit for a project in the works, running off of a +/-72V, half wave rectified source. It functions pretty well and has very little noise, and good load rejection. I was worried about zener noise due to very small current in the 25V ones, but the circuit seems to correct for it, being inside the loop. Output is adjustable from like +/-55V to +/-65V, with about 30mA max. The circuit can be switched on and off with +5V logic. The only transistors that are not SOT-23 SMD’s are 2N6038/35(TO-126) and 2N2716/27(TO-237). 2N6038/35 are Darlington. All resistors except the two 6.8K on the collectors of the voltage source for the op-amp chip are also SMD. This way it can all be squeezed onto a small PCB. The SMD components are pennies a piece, so cost isn’t as high as it seems from the schematic. I’m sure there can be many variations of this circuit, but that depends on who is making it I suppose.


EDIT> Although it works quite well, any suggested improvements are always welcome.
 

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Placing the main storage capacitors before the regulator reduces the amount of voltage ripple that the regulator has to reject, but forces it to deal with big AC currents. On the other hand, placing most of the capacitance after the regulator increases input ripple voltage but reduces current requirements dramatically.

Nevertheless, I prefer splitting the latter option, or at least, splitting the capacitance equally between both sides.
 
At this website you will find several different regulated supplies for LM3886.
Also very nice pictures showing 4 different Gainclone projects, like paralleled LM3886 for 100 Watt..
I recommend all interested in Chip Amps to visit
:)
Monster's Gainclone

Supply using LM1083. LM1083 can provide max 8 Ampere.
reg_PS.gif


Supply using LM317 and bypassing power transistor.
pa100_supply.gif


Gainclone version 2 ( GCv2 ) amplifier with LM1083 regulator card.
GCv2_inside.jpg
 
I have built several LT1083 based regulated power supplies for both class A and AB (MOSFET) amps, and I can tell you it makes subtle, yet huge differences.

The bass is significantly cleaner and tighter, the highs is smoother and not as edgy, and female vocals sound more liquid.

You don't need huge caps - I'm running my JLH class A at 2.4A total quiescent current, with only 10000uf/4700uf total supply caps, but you do need a regulated power supply.
 
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I have built several LT1083 based regulated power supplies for both class A and AB (MOSFET) amps, and I can tell you it makes subtle, yet huge differences......
You could also be describing the effects of a reduced HF response there. First, I would want to see a squarewave and frequency response plot of the complete amplifier before and after regulation. This is essential for evaluating the effects on class AB amplifiers in particular.

Subjective assessment is fine for personal tastes but my experience with regulated supplies has not been as rewarding. Music has often indeed sounded different, sometimes nicer but not always better in actual fidelity.
 
Akitika GT-101 and GT-102 with regulated power

LM3886: Akitika GT-101 and the new GT-102 have the same regulated power.



Akitika Preamp and Power Amp Kits

Class AB with a Regulated Supply...Approaching Class A?

The GT-102 has an electronically regulated power supply. That makes it unusual among audio power amplifers. But in some ways, it offers an advantage similar to class A operation.

Class A amplifiers can be among the most linear of amplifiers, and the least efficient. They draw a constant current from the power supply, no matter what signal is being delivered to the speaker. That says that a Class A amplifier doesn't modulate the supply rails..constant current drain produces a constant load on the power supply, and hence a constant voltage.

Is a Class AB amplifier with an electronically regulated power supply almost as good in that respect? If the power supply's output impedance is low, then the output signal minimally modulates the rails. That should cause less distortion at the output. In that sense, the Class AB with regulated power supply should be about as blameless as a Class A amp.

The one way that the Class A amplifier still has it over the Class AB is that at low listening levels, the output device has nearly constant current. That is, its operating current is the large class A bias current with the small signal modulations. Of course, at high output levels, the Class A advantage diminishes, as the output device then experiences wide swings in operating current.
 
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