Is this a well designed power supply?

[Hailey]

Popped the cover off this PSU to install a new wiring harness. Here's what I saw: A forest of capacitors and a transformer smaller than Donald Trump's...hands.

 

FYI, its output power rating is 25 w (15 v, 1.7 amps.)

 

"Typical output noise" is said to be < 400uVpp

 

Internal capacitance: 85,000 uF

 

Any thoughts anyone?

[esldude]

The 400 microvolts looks pretty good. As for whether it is good depends upon what it is powering.

[Hailey]

The 400 microvolts looks pretty good. As for whether it is good depends upon what it is powering.

 

This is the external PSU for the Exogal Comet Plus.

[sandyk]

Popped the cover off this PSU to install a new wiring harness. Here's what I saw: A forest of capacitors and a transformer smaller than Donald Trump's...hands.

 

FYI, its output power rating is 25 w (15 v, 1.7 amps.)

 

"Typical output noise" is said to be < 400uVpp

 

Internal capacitance: 85,000 uF

 

Any thoughts anyone?[ATTACH]28460[/ATTACH]

 

Despite the massive output filter capacitance, it's still powered by a cheap and nasty SMPS which will send back quite a bit of RF/EMI into the A.C. mains sewer to get back into other sensitive gear.

It will also almost certainly have a measurable A.C. voltage of up to half the A.C. mains supply voltage between it's output and mains (real) earth !

[Hailey]

Despite the massive output filter capacitance, it's still powered by a cheap and nasty SMPS which will send back quite a bit of RF/EMI into the A.C. mains sewer to get back into other sensitive gear.

It will also almost certainly have a measurable A.C. voltage of up to half the A.C. mains supply voltage between it's output and mains (real) earth !

 

Interesting. I'm a PSU newbie. Would you mind unpacking this a bit? So it's actually a switching power supply filtered to a fare-thee-well by capacitors?

 

That's why the transformer is so tiny?

 

Thanks for helping this electro-ignoramus understand...

[sandyk]

Interesting. I'm a PSU newbie. Would you mind unpacking this a bit? So it's actually a switching power supply filtered to a fare-thee-well by capacitors?

 

That's why the transformer is so tiny?

 

Thanks for helping this electro-ignoramus understand...

 

Yes, that is why the transformer is so tiny. Cheap commercial SMPS also have a low value high voltage capacitor between primary and secondary sides to help meet mandatory RF/EMI regulations, which is how it ends up with up to half the AC mains supply voltage between it's output and earth, albeit at low current.

[Hailey]

Yes, that is why the transformer is so tiny. Cheap commercial SMPS also have a low value high voltage capacitor between primary and secondary sides to help meet mandatory RF/EMI regulations, which is how it ends up with up to half the AC mains supply voltage between it's output and earth, albeit at low current.

 

I keep reading that switching power supplies are more complicated and, therefore, expensive than linear power supplies at equivalent levels of performance. So if they're trying to save money, why not go linear?

[sandyk]

I keep reading that switching power supplies are more complicated and, therefore, expensive than linear power supplies at equivalent levels of performance. So if they're trying to save money, why not go linear?

 

An SMPS as shown in the photo is mass produced at perhaps several $ each !!!

[Superdad]

This is the external PSU for the Exogal Comet Plus.

 

Actually, that is a hybrid supply. They are using the high frequency switching side to feed a linear regulator chip on the right side (that LT1764A).

[Hailey]

Actually, that is a hybrid supply. They are using the high frequency switching side to feed a linear regulator chip on the right side (that LT1764A).

 

Interesting analysis of pros and cons of hybrid supplies.

 

http://www.digikey.com/en/articles/techzone/2012/may/hybrid-power-supplies-deliver-noise-free-voltages-for-sensitive-circuitry

[mansr]

What are the advantages of such a design over a linear power supply? It doesn't get very hot? Anything else?

You don't need a heavy, expensive transformer.

[Hailey]

You don't need a heavy, expensive transformer.

 

So cheaper to ship

[sandyk]

So cheaper to ship

 

Although Pro grade SMPS can be very good, don't forget that most consumer grade SMPS inject a lot of rubbish back into the A.C. mains supply, as well as having that A.C. leakage voltage to earth.

[sockpit]

This supply lists separately for $600 last time I looked. Is bundled with the DAC for $500 think. I own one.

[Hailey]

This supply lists separately for $600 last time I looked. Is bundled with the DAC for $500 think. I own one.

 

The WyWyres DC cable upgrade makes a huge difference. Hence my inquiry into the design of the power supply.

[sandyk]

The WyWyres DC cable upgrade makes a huge difference. Hence my inquiry into the design of the power supply.

 

To put the price of this PSU into perspective.

 

They could have fitted a 15-0-15V 50VA toroidal transformer and the attached module into a similar case for a cost of < $60 retail for the transformer and the PSU PCB , and ended up with a PSU with a tenth of the noise output, and a max. 1.5A continuous output with a much lower level of RF/EMI injected back into the A.C. mains supply.

 

$600 , or even $500 bundled, for the hybrid version is a ripoff !

 

Ultra LOW Noise 40ÎœV Adjustable Voltage Regulator Module 1 25 20V 1 5 AMP | eBay

[Hailey]

To put the price of this PSU into perspective.

 

They could have fitted a 15-0-15V 50VA toroidal transformer and the attached module into a similar case for a cost of < $60 retail for the transformer and the PSU PCB , and ended up with a PSU with a tenth of the noise output, and a max. 1.5A continuous output.

 

$600 , or even $500 bundled, for the hybrid version is a ripoff !

 

Ultra LOW Noise 40ÎœV Adjustable Voltage Regulator Module 1 25 20V 1 5 AMP | eBay

 

Holy mackerel.

[sockpit]

The Wywires upgrade, by contrast, is a steal for $199.00!

[Hailey]

The Wywires upgrade, by contrast, is a steal for $199.00!

 

I get the snark and, yeah, the guy is making a profit but he does deliver the goods.

 

Is it a "steal" at $199?

 

Definitely not.

 

Is it worth $199?

 

Definitely.

[sockpit]

Sorry. Meant in jest. My view is that a $600 power supply upgrade should not require $200 more for a top notch umbilical. What is worse, the Comet's warranty says that upgrading the umbilical voids the entire warranty. So it goes in this industry . . .

[Hailey]

Sorry. Meant in jest. My view is that a $600 power supply upgrade should not require $200 more for a top notch umbilical. What is worse, the Comet's warranty says that upgrading the umbilical voids the entire warranty. So it goes in this industry . . .

 

Well, Exogal urges the WyWyres upgrade on its website and provides illustrated, step-by-step instructions on how to carry it out, so I don't see how they can then claim the warranty is voided.

 

That said, I do agree with you that a $600 (or $500) power supply upgrade should not then require an additional $200 to make it "just so."

 

THAT said, the Exogal Comet punches so far above its price class that the additional $200 hardly changes the value proposition, imho.

 

But, yeah, why on earth didn't they just include it in the first place. What would the additional marginal cost have been? Twenty dollars?

[sockpit]

Well, Exogal urges the WyWyres upgrade on its website and provides illustrated, step-by-step instructions on how to carry it out, so I don't see how they can then claim the warranty is voided.

 

That said, I do agree with you that a $600 (or $500) power supply upgrade should not then require an additional $200 to make it "just so."

 

THAT said, the Exogal Comet punches so far above its price class that the additional $200 hardly changes the value proposition, imho.

 

But, yeah, why on earth didn't they just include it in the first place. What would the additional marginal cost have been? Twenty dollars?

 

I wrote the Exogal CEO, Jeff Hagenstad, a couple months ago and pointed out the fact that their website has links to umbilical upgrades (and detailed instruction about how to do it), while their warranty proscribes any such tampering. He acknowledged the anomaly, but went on to give a very thoughtful and long explanation of this apparent contradiction. I too wish they'd do it right and save the consumer the expensive upgrade. They could even boast about how good their umbilical is, and it probably wouldn't cost them $25, if they designed it themselves. It wouldn't satisfy every "tweaker," of course, but it would have been good enough for me,--or at least kept me from wondering how it would sound if they had only put a great umbilical on the PSU in the first place.

 

In any case, I've exchanged emails with Jeff on a number of occasions: he strikes me as a a straight shooter, I'm totally happy with my Comet, and I wish the new company, made up of a couple industry vets who want to do a few things differently, much success in such a competitive market. I have only one DAC to compare my Comet to, but it has gotten stellar reviews, I like its sound, and I plan to keep it a long time, and take advantage of FPGA upgrades. We'll see if that plan gets nixed by tech advances . . .

[Hailey]

I wrote the Exogal CEO, Jeff Hagenstad, a couple months ago and pointed out the fact that their website has links to umbilical upgrades (and detailed instruction about how to do it), while their warranty proscribes any such tampering. He acknowledged the anomaly, but went on to give a very thoughtful and long explanation of this apparent contradiction. I too wish they'd do it right and save the consumer the expensive upgrade. They could even boast about how good their umbilical is, and it probably wouldn't cost them $25, if they designed it themselves. It wouldn't satisfy every "tweaker," of course, but it would have been good enough for me,--or at least kept me from wondering how it would sound if they had only put a great umbilical on the PSU in the first place.

 

In any case, I've exchanged emails with Jeff on a number of occasions: he's strikes me as a a straight shooter, I'm totally happy with my Comet, and I wish the new company, made up of a couple industry vets who want to do a few things differently, much success in such a competitive market. I have only one DAC to compare my Comet to, but it has gotten stellar reviews, I like its sound, and I plan to keep it a long time, and take advantage of FPGA upgrades. We'll see if that plan gets nixed by tech advances . . .

 

So what's the gist of his "thoughtful and long explanation"?

 

My thoughtful and short response would be that if something goes wrong, swap the wires back out and pretend you never did anything.

[sockpit]

The gist was that the warranty is written that strictly to protect the company from claims lodged by tweaks who go into the supply and start replacing capacitors, etc. I wouldn't sweat it. The response was long because he gave some examples of to what length some customers go to to upgrade their stuff--and then return it for warranty service when things go south with the upgrades. That still doesn't resolve the contradiction, but my sense is that they'll stand by any reasonable warranty claim regardless of whether you installed an umbilical or not.

[Hailey]

The gist was that the warranty is written that strictly to protect the company from claims lodged by tweaks who go into the supply and start replacing capacitors, etc. I wouldn't sweat it. The response was long because he gave some examples of to what length some customers go to to upgrade their stuff--and then return it for warranty service when things go south with the upgrades. That still doesn't resolve the contradiction, but my sense is that they'll stand by any reasonable warranty claim regardless of whether you installed an umbilical or not.

 

That makes sense.

 

In any event, it's a fantastic DAC.