Linear Power Supply for Class D amps - Issues? Idle loss? Efficiency? Benefits?

[Guddu]

What are the issues in using linear power supply (transformer + bridge rectifier assembly etc.) with class D amplifiers?
Idle energy loss too high?
Efficiency?
Magnetic field interferences?
Price?

Almost every established traditional brand (like Denon, Marantz, etc.) used linear PSU in their class D amplifiers.
Are there any benefits to do this?
Head room?
Dynamic performance?

“Let us learn from what you’ve learned”

 

[pma]

What are the issues in using linear power supply (transformer + bridge rectifier assembly etc.) with class D amplifiers?
Idle energy loss too high?
Efficiency?
Magnetic field interferences?
Price?

The only issue, from my point of view, is heavy weight of big transformers if you need high power.

Idle loss is fine.
Efficiency is not that bad.
Magnetic field interference is an issue only for poor designs (PCB design and wiring). Below see Purifi with linear PSU:
there is no trace of mains components.
Price depends.

Linear PSU usually gives more power at low frequencies.

 

[sq225917]

As ever implementation is everything.

 

[BeeKay]

Some occasional hum

Also:

Mode	SMPS Efficiency	LPS Efficiency	SMPS Heat	LPS Heat	Notes
Standby	High	Low	Very Low	Moderate	SMPS excels in low power modes
Idle (light)	Moderate–High	Very Low	Low	High	LPS still wastes much power
Full Load	High	Low–Moderate	Moderate	High	LPS less practical above ~20W

 

[DVDdoug]

Efficiency?

Most of the efficiency is in the regulation . Linear regulators are inefficient. An unregulated linear power supply* can be almost as efficient as a switching supply. (Regulation is inherent in switching supplies.)

every established traditional brand (like Denon, Marantz, etc.) used linear PSU in their class D amplifiers.

I didn't know that. ...It seems like almost all power supplies are switching these days.

Switching power supplies have a lot in common with class-D (switching) amplifiers.

Linear PSU usually gives more power at low frequencies.

As long as the power supply can supply the voltage & current it doesn't matter. Power supplies put-out DC and they don't "know" anything about the frequency coming out of the amplifier. If the voltage can't hold-up for the duration of a half-wave of a low-frequency signal it will clip at lower output. Linear power supplies DO require bigger capacitors to hold the voltage and supply current during the full 50/60Hz cycle but there's no reason a switching supply can't have big capacitors or otherwise hold-up the voltage & current continuously.

* P.S.
As far as I know, all good amplifiers have regulated power supplies. Besides making the voltage independent of line-voltage and load, they provide additional filtering and the regulator can kill that last-bit of hum.

 

[Chr1]

Question1 : Are there any disadvantages to a SMPS?

Question2 : Why are they not used more in Class A/B, H?

Thanks.

 

[voodooless]

Almost every established traditional brand (like Denon, Marantz, etc.) used linear PSU in their class D amplifiers.

Citation needed. Specifically to Marantz: AMP 10 (Ice), Model 10 (Purifi), Model 30 (Hypex), all use an SMPS.

 

[antcollinet]

Question1 : Are there any disadvantages to a SMPS?

Question2 : Why are they not used more in Class A/B, H?

Thanks.

Q1 - No
Q2 - Audiophiles. But see also the AHB2 - one of the best perfomrming AB (H) type amp on the market. Uses a switching supply.

 

[Chr1]

Thanks.

Was always of the impression that a big hefty torroid was a desirable feature of a power amp.

Why were SMPS not used more then? Seems odd if there is no downside...
Presumably they are cheaper to make too?

Wonder if earlier ones were prone to failure.

 

[antcollinet]

They are relatively easy to design/make now at high power due to the ready availablity of SMPS control IC's.

These were not available in the early days of audio.

 

[Guddu]

Citation needed. Specifically to Marantz: AMP 10 (Ice), Model 10 (Purifi), Model 30 (Hypex), all use an SMPS.

‘almost’

 

[voodooless]

‘almost’

Yeah, almost none..

 

[solderdude]

Question1 : Are there any disadvantages to a SMPS?

Longevity.

Question2 : Why are they not used more in Class A/B, H?

Thanks.

Most SMPS do not like to 'see' a dynamic load.
The SMPS used in the more expensive power amps work different from the usual power bricks and are designed to handle dynamic loads.

 

[mcochris]

As noted earlier, linear power supplies (LPS) tend to be larger and less efficient than switch-mode power supplies (SMPS), especially when handling higher current loads. Maintaining stability in an LPS circuit may require large heatsinks, which increases the need for a more robust (and costly) enclosure.

-- edit --
I should have been clearer — I was specifically comparing regulated LPS and SMPS power supplies. A non-regulated LPS, such as those often used in power amplifiers, can be relatively efficient in comparison. Most LPS power amps use unregulated supplies, while most SMPS designs are regulated by nature.

 

[Cogito]

When it comes to power amps, LPS all the way. Go heavy iron or go home! As for you SMPS advocates? LOL You guys kill me...

 

[DVDdoug]

As for you SMPS advocates?

Your post is the 1st one advocating either way. Everybody else is discussing the pros/cons/characteristics.

...Your Gramophone probably runs off of a spring. Very efficient!

 

[pma]

You know guys - I prefer facts and I prefer facts over opinions. That said, below please see measurement of efficiency of my UcD180 implementation with linear power supply. Power consumed at idle is 8W.

Note: “total output power” on X-axis is in fact power delivered into 4ohm load at amplifier output.

 

[Count Arthur]

Early on Hypex supplied linear power supplies and toroidal transformers for use with its UCD amplifier modules, before moving to SMPS.

 

[pma]

Interesting. I have my own PSU.

 

[voodooless]

Early on Hypex supplied linear power supplies and toroidal transformers for use with its UCD amplifier modules, before moving to SMPS.

View attachment 448730

Yup, still have one:

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