Why the dislike of external power supplies?

[IPunchCholla]

I’m in the (very slow) process of building a DIY amp. One of my goals is to keep the footprint of the amp as small as possible. Towards that, I’m considering building an external power supply (linear).

In various amp reviews, people seem to really dislike external supplies. Mostly it seems they dislike the aesthetics (which is cool, but it doesn’t bother me). I was wondering, though, what some technical issues might be that would make external an issue.

I’m using an ICL combined with a relay to limit inrush current, as well as a relay to only turn on the +-12v and 55v after the capacitor bank is charged. I’m also planning on two switches: one to disable the psu completely, and one that is effectively a standby switch ( turns off the voltage outputs, but not the AC)

What else should I be taking into consideration?

 

[fpitas]

I use external supplies professionally. The real trick is a good connector. The little barrels are cute and easy, but not real reliable.

 

[MRC01]

... In various amp reviews, people seem to really dislike external supplies. Mostly it seems they dislike the aesthetics (which is cool, but it doesn’t bother me). ...

The reasons people don't like them aren't limited to aesthetics.
They waste energy, always powered up and warm even when not in use.
They are usually big and blocky, hogging multiple sockets on the wall.

 

[fpitas]

The reasons people don't like them aren't limited to aesthetics.
They waste energy, always powered up and warm even when not in use.
They are usually big and blocky, hogging multiple sockets on the wall.

I use the type that power laptops when I need a good size supply. An AC cord to a brick, then a DC cord out. I agree the aesthetics aren't the best. But it gets the noisy stuff away from the sensitive stuff.

 

[anotherhobby]

I love external power supplies for gear on my desk. The tuck nicely into a cable tray on the underside, and on the top side I have a nice, compact, stack of equipment that actually fits on my desk. For my home theater system, I'd find it annoying to have all the extra cable, and I'd prefer to have internal power supplies. This isn't speaking to any technical merits, just the physical property of the power supply being separate.

All of these 4 devices have external power supplies:

 

[IPunchCholla]

The reasons people don't like them aren't limited to aesthetics.
They waste energy, always powered up and warm even when not in use.
They are usually big and blocky, hogging multiple sockets on the wall.

Aren’t internal supplies always on if plugged in? All my devices that use them (barring our infrared toaster oven) are.

 

[IPunchCholla]

I use external supplies professionally. The real trick is a good connector. The little barrels are cute and easy, but not real reliable.

I was thinking of using DIN? Connectors. Barrel connections always seem to fail over time. Any connectors you recommend?

 

[fpitas]

Aren’t internal supplies always on if plugged in? All my devices that use them (barring our infrared toaster oven) are.

My experience of external switchers like for a laptop is they draw very little idling. But I can't say that's the rule.

 

[fpitas]

I was thinking of using DIN? Connectors. Barrel connections always seem to fail over time. Any connectors you recommend?

DIN, maybe multi-pin XLR. I'd look through DigiKey to see what looks likely

 

[IPunchCholla]

My experience of external switchers like foir a laptop is they draw very little idling. But I can't say that's the rule.

My skills aren’t up to an external SMPS. But I am trying to be careful about idle current.

 

[Geert]

External power supplies are a mess, that's my take on it.

 

[Doodski]

The conductors from the power supply smoothing caps should be as short of a distance from the output transistors as is possible. Putting the supply externally is the opposite of this.

 

[IPunchCholla]

External power supplies are a mess, that's my take on it.

They are. But they are also a mess in what is otherwise… a mess. With the number of AC cords running around my setup (two monitors, computer, amplifier, external storage, sewing machine, record player, phono amp, two power strips, sub woofer, maybe more) the cords themselves are an eyesore. Best solution aesthetically is shoving them behind a rolling cabinet. What’s a couple extra PSUs behind there?

 

[fpitas]

The conductors from the power supply smoothing caps should be as short of a distance from the output transistors as is possible. Putting the supply externally is the opposite of this.

Yes, but. You also put caps right at the point of load. Then, the impedance in the power feed actually helps with EMI.

 

[IPunchCholla]

The conductors from the power supply smoothing caps should be as short of a distance from the output transistors as is possible. Putting the supply externally is the opposite of this.

I’m not sure I understand the output transistors part. Which output transistors are you referring to?

I’m locating the smoothing capacitors for the regulators as close to shorting as possible.

 

[Doodski]

Yes, but. You also put caps right at the point of load.

How about putting the transformer externally and having the power supply caps near the output transistors?

 

[fpitas]

How about putting the transformer externally and having the power supply caps near the output transistors?

I like to put some caps ASAP after the transformer to stop noise as soon as I can. If you put them far away, the huge, non-linear charging currents might just radiate.

 

[PHD]

Are you building a class-D power amp? If so, it makes no sense to use a linear power supply. Linear PSUs are inferior to SMPSs almost in every aspect, provided that a good quality SMPS is used. Especially if you want a small form actor. You also want to avoid long connection cables which will pick up more noise and may cause instability due to parasitic inductances.

 

[Doodski]

I like to put some caps ASAP after the transformer to stop noise as soon as I can. If you put them far away, the huge, non-linear charging currents might just radiate.

So conducting high current DC through 3 conductors is the way to go from the power supply to the amp?

You also want to avoid long connection cables which will pick up more noise and may cause instability due to parasitic inductances.

This?^

 

[fpitas]

So conducting high current DC through 3 conductors is the way to go from the power supply to the amp?

What's wrong with lots of DC current? Alternatively, your power cord to the unit would have had lots of AC current. And I have never had problems picking things up, because I filter the crap out of things.