Replacement Wall-Wort for DAC

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Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 12:15 am

I bought a cheap chinese DAC about a year ago. I have read in many places that the power supply that comes bundled with the DAC is very low quality and quality would be improved if replaced. The bundled power supply is 15v 1A.

Would a replacement power supply also need to be 15v 1A or could I use something different? I have a couple of ersatz powers supplies that are 12v 2A that I thought I might try out to see if there was any improvement. I'm not really looking to spend money on this as the system itself is not high enough quality (approx. $500) to really worry about things like the condition of the power.

I've tested it and the DAC functions with one of these 12V 2A power supplies, but I don't know if there are any long term negative effects. I'm much more familiar with computer PSU's than those for audio equipment and would appreciate any answers or explanations.
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 12:30 am

You want to replace it with EXACTLY the same voltage and amperage. You can and will damage the device otherwise. Amazon or Frys should have plenty of universal DC adapters available. They usually come in a set amperage, and then have a selector switch for the voltage. From there, you snap in the plug connector that fits in your device, making sure to have to polarity correct.
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 12:40 am

The Egg wrote:You want to replace it with EXACTLY the same voltage and amperage.


Not true. With power supplies only voltage matters as the attached device will draw only the current it needs, no more. Just make sure the replacement power supply is rated to supply at least as much current as the original.
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 12:53 am

Unless the factory power supply is doing something definitely objectionable, like introducing high frequency noise into the system, an alternate supply won't make any difference. There appear to be several DC-to-DC conversion circuits inside the chassis, along with a good deal of filtering.

However, the 12V/2A supply is probably capable of supplying adequate power to operate reliably.
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 1:31 am

ludi wrote:Unless the factory power supply is doing something definitely objectionable, like introducing high frequency noise into the system, an alternate supply won't make any difference. There appear to be several DC-to-DC conversion circuits inside the chassis, along with a good deal of filtering.

However, the 12V/2A supply is probably capable of supplying adequate power to operate reliably.


Thanks, I kind of imagined that focusing on the power supply was kind of like focusing on the quality of the cabling (i.e., any perceived effects are the result of marketing).

Can you point me to any resources where I could read a little bit more about this? I assume this is just basic electrical engineering, but I don't know enough to isolate the keywords I would use to run a search.
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 9:20 am

If you're semi-paranoid, hit Guitar Center or Musician's Friend and look for a pedal power supply with the specs you need. Those intended for such uses tend to be of much higher quality than the usual knockoffs.
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 9:32 am

Not one for audio equipment but coming from using a Raspberry Pi making sure that the wall wort is providing the full power required can be a big deal, especially under draw.

+1 for making sure you have a decent power source, especially if it is suspect to you already.
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 7:17 pm

Arvald wrote:Not one for audio equipment but coming from using a Raspberry Pi making sure that the wall wort is providing the full power required can be a big deal, especially under draw.

+1 for making sure you have a decent power source, especially if it is suspect to you already.


Yes, but it should be pointed out that the Raspberry Pi is unusually sensitive to power supplies due to its awful power circuitry. It's basically just cheap and nasty and a pain in the ass to deal with.
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 8:24 pm

Unless you're getting audible noise or static on the outputs of the DAC, changing the power supply probably isn't going to make much (if any) difference. Even if you *are* having audible problems, there's no guarantee that the existing power supply is to blame. If you do decide to swap it, rephlex got it right - you want one with the same voltage, and the same or higher current rating.
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 10:14 pm

Technically, a higher voltage psu will allow the DAC to perform better.
I was going to suggest a linear regulated psu from Jameco, but they don't have one in 15V.
You can build your own high(ish) quality DC psu for not that much (Maybe $40 including shipping and the case).
here's a basic schematic:
Image
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 10:27 pm

chµck wrote:Technically, a higher voltage psu will allow the DAC to preform better.

No. Over-volting a DAC isn't going to accomplish anything useful other than maybe damaging it (if its power circuitry isn't designed to handle the higher input voltage). It's not like we are trying to overclock a CPU here; more voltage doesn't help. If it did, the vendor would've speced a higher voltage wall-wart in the first place.

chµck wrote:I was going to suggest a linear regulated psu from Jameco, but they don't have one in 15V.
You can build your own high(ish) quality DC psu for not that much (Maybe $40 including shipping and the case).
here's a basic schematic:
(image)

Unless the existing wall-wart and/or power regulation circuitry in the DAC suck pretty badly, all this will do is waste power. Linear supplies are very inefficient, and the operating frequencies of modern switchmode wall-warts are far beyond the audible frequency range anyhow.
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 11:21 pm

just brew it! wrote:
chµck wrote:Technically, a higher voltage psu will allow the DAC to preform better.

No. Over-volting a DAC isn't going to accomplish anything useful other than maybe damaging it (if its power circuitry isn't designed to handle the higher input voltage). It's not like we are trying to overclock a CPU here; more voltage doesn't help. If it did, the vendor would've speced a higher voltage wall-wart in the first place.

you're right, i was aiming this comment at him using a 12v psu instead of the included 15v one.
just brew it! wrote:
chµck wrote:I was going to suggest a linear regulated psu from Jameco, but they don't have one in 15V.
You can build your own high(ish) quality DC psu for not that much (Maybe $40 including shipping and the case).
here's a basic schematic:
(image)

Unless the existing wall-wart and/or power regulation circuitry in the DAC suck pretty badly, all this will do is waste power. Linear supplies are very inefficient, and the operating frequencies of modern switchmode wall-warts are far beyond the audible frequency range anyhow.

High performance demands inefficiency!
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Re: Replacement Wall-Wort for DAC

Postposted on Mon Feb 24, 2014 11:26 pm

chµck wrote:you're right, i was aiming this comment at him using a 12v psu instead of the included 15v one.

Ahh, OK. That makes more sense!
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Re: Replacement Wall-Wort for DAC

Postposted on Wed Feb 26, 2014 12:14 am

I tried to find a picture that showed the part number of the internal regulator -- to no avail. I can say with about 99% certainty that there is not a switching regulator inside the case. The only inductors visible on the board are not a switching inductors. They look more like a ferrite bead filters, probably to keep high frequency digital noise from feeding back into the raw power rails. Secondly, the heat sink just shouts "linear" regulator. If I had to guess, it is probably something like a power op amp configured to give a virtual ground for the audio side of the circuit, probably as a +/- 5V supply are so. It is also possible that it is simply a big 5V regulator that is burning a lot of power. It would be feeding the audio side directly and then the digital side would be through their individual regulators which are probably 3.3v low drop out jobs so they won't dissipate much heat since the first regulator would do most of the work. In this case, a couple of the big capacitors would be used to create a floating ground for the output. In either case, I found at least on place where there is reference to a warning that the line level ouputs cannot be connected to ground. This would certainly be the case if it were using a floating/virtual ground.

Looking at the picture of the power supply, it appears that it may be a simply transformer wall-wort, not a switch mode supply. The filter caps inside the D20 certainly look like they were designing for a high ripple input. Using a high input voltage and a big linear regulator to drop down to 5V would ensure that the internal power supply was way below the normal ripple of the input. If it wasn't, you would get a 60/120hz hum (different from ground loop). A 15v SMPS might give you "better" sound. It might also give worse sound depending on the switching frequency and quality of the supply. So long as it is rate at 15V or so, and at least 2A, it will not cause damage (check the polarity of the plug). I would not go above 16V, or below 14V. Some people have reported that 12V supplies work, and they probably will, but you might actually get more distortion on very high signal depending on the internal power layout. The problem with a cheap switching supply is that they tend to have high frequency noise that big filter capacitors won't necessarily address. If this noise makes it into the analog supply, you may not hear it directly, but it will contribute to the measured THD of the output.

Whether you can hear the difference of a new suuply or not probably depends on your ears and how much you want to justify the purchase. A bench qaulity supply will certainly give you cleaner power but it will cost nearly as much as you paid for the DAC and be bigger. A $15 replacement laptop supply? Probably not.

How much do you want to spend money? :wink:

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Re: Replacement Wall-Wort for DAC

Postposted on Wed Feb 26, 2014 3:22 am

SecretSquirrel wrote:Looking at the picture of the power supply, it appears that it may be a simply transformer wall-wort, not a switch mode supply.


Not likely. A 15 watt (around 20 VA) transformer is about 32 mm (height) x 70 mm (diameter) if it's a toroidal. See here for an example. The wall wart looks too small to contain one.
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Re: Replacement Wall-Wort for DAC

Postposted on Wed Feb 26, 2014 5:54 am

SecretSquirrel wrote:Whether you can hear the difference of a new suuply or not probably depends on your ears and how much you want to justify the purchase. A bench quality supply will certainly give you cleaner power but it will cost nearly as much as you paid for the DAC and be bigger. A $15 replacement laptop supply? Probably not.

How much do you want to spend money? :wink:


I was thinking of spending around $15, but I'm not willing to take the plunge into $150 PSU. At this price point I feel like if I want to spend $150 I should just put it toward upgrading my audio equipment generally. Maybe if I had a $1500 Benchmark DAC.
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Re: Replacement Wall-Wort for DAC

Postposted on Wed Feb 26, 2014 10:23 am

kumori wrote:
SecretSquirrel wrote:Whether you can hear the difference of a new suuply or not probably depends on your ears and how much you want to justify the purchase. A bench quality supply will certainly give you cleaner power but it will cost nearly as much as you paid for the DAC and be bigger. A $15 replacement laptop supply? Probably not.

How much do you want to spend money? :wink:


I was thinking of spending around $15, but I'm not willing to take the plunge into $150 PSU. At this price point I feel like if I want to spend $150 I should just put it toward upgrading my audio equipment generally. Maybe if I had a $1500 Benchmark DAC.

Aren't the benchmark DACs considered obsolete now? There appear to be several products under the $1k mark that come very close or are indistinguishable from it.
I haven't heard the DAC1, but my gamma 2 is supposed to be on par with it.
The pico DAC is also supposed to be very good.
And Schitt audio has highly praised DACs like the Bitfrost.

Back to OPs post: A high quality PSU will improve DAC performance, but the money would be better spend on better headphones or and amp if your current one is insufficient.
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Re: Replacement Wall-Wort for DAC

Postposted on Wed Feb 26, 2014 12:36 pm

SecretSquirrel wrote:I tried to find a picture that showed the part number of the internal regulator -- to no avail. I can say with about 99% certainty that there is not a switching regulator inside the case. The only inductors visible on the board are not a switching inductors. They look more like a ferrite bead filters, probably to keep high frequency digital noise from feeding back into the raw power rails.

Big inductors are characteristic of high-current supplies, and even then, modern SMT packages may not show an inductor in the form you're accustomed to seeing. FWIW the device on the heatsink is TO-220 but with a five-pin interface -- slightly better view angles here. Could be something like this, with L1 from the "typical application" schematic replaced with more aggressive RC output filtering to save money.

However, your comment about the ferrite bead filters seems correct and it looks like there might be a couple SMT linear regulators for specific subsections. One way or another, everything here appears to be running from a 5V internal supply and using a floating earth to obtain a suitable output voltage swing. So there is almost certinaly nothing to be gained electrically from changing out the external power supply, although I can't speak to whatever psychic benefits chµck has apparently discovered.
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Re: Replacement Wall-Wort for DAC

Postposted on Wed Feb 26, 2014 3:38 pm

If you don't mind a tiny bit of DIY work and want to test whether improving the PSU will make any perceptible difference, try batteries. Batteries should offer the cleanest power possible. The simplest route would be to use a single 12V lead acid battery (you may have one in your UPS). A fully charged 12V lead acid battery should be about 13.5V (or slightly more) if in good shape, which should be close enough to the target 15V not to make much if any difference.

Connect the positive terminal to the wire feeding the inside contact of your barrel connector that plugs into the DAC, and the negative terminal to wire feeding the outside contact of the barrel connector and you're done. Edited thanks to correction from JBI

If you like the results, you could try building your own Lithium battery PSU, by using 4 cells in series. Eg, with one of these and 2 packs of these. This has the benefit of a nice portable PSU for around $25. But then you need a charger if you don't already have one...
Last edited by cynan on Wed Feb 26, 2014 3:59 pm, edited 4 times in total.
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Re: Replacement Wall-Wort for DAC

Postposted on Wed Feb 26, 2014 3:46 pm

cynan wrote:Connect the negative terminal to the wire feeding the inside contact of your barrel connector that plugs into the DAC, and the positive terminal to wire feeding the outside contact of the barrel connector and you're done.

Are you sure about that? On most "wall wart" power supplies the outside contact is negative (though there are exceptions).
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Re: Replacement Wall-Wort for DAC

Postposted on Wed Feb 26, 2014 3:57 pm

just brew it! wrote:
cynan wrote:Connect the negative terminal to the wire feeding the inside contact of your barrel connector that plugs into the DAC, and the positive terminal to wire feeding the outside contact of the barrel connector and you're done.

Are you sure about that? On most "wall wart" power supplies the outside contact is negative (though there are exceptions).


Woops. I wrote it backwards. Yes, this is how the polarity is on the few switching PSUs I've checked. Thanks for the correction.

With a volt/multimeter, it's easy enough to verify the polarity on the existing PSU and just make sure you have that batteries connected to the connector in the same way.
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Re: Replacement Wall-Wort for DAC

Postposted on Wed Feb 26, 2014 4:33 pm

Some high end equipment does almost exactly what you're proposing -- there is a maintenance charger when in standby, and when power is connected, the maintenance charger is disconnected from the battery and the equipment is connected via a throwover relay.
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Re: Replacement Wall-Wort for DAC

Postposted on Wed Feb 26, 2014 5:31 pm

I'm pretty sure this is a differential design with a virtual ground (as noted earlier). I can't think of any other logical reason for the BB op-amp to use a pair of 100V caps unless they were floating it. Above that there's a pair of larger 35V caps (presumably) for the positive and negative supplies. Interesting parts selection in this thing. I like it.

I wouldn't worry about using a switching supply with this design. It's common mode noise rejection will be very, very good.

btw - the silkscreen on the back of the unit shows positive center pin.
Last edited by sluggo on Wed Feb 26, 2014 9:41 pm, edited 1 time in total.
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Re: Replacement Wall-Wort for DAC

Postposted on Thu Feb 27, 2014 12:16 am

ludi wrote:Big inductors are characteristic of high-current supplies, and even then, modern SMT packages may not show an inductor in the form you're accustomed to seeing. FWIW the device on the heatsink is TO-220 but with a five-pin interface -- slightly better view angles here. Could be something like this, with L1 from the "typical application" schematic replaced with more aggressive RC output filtering to save money.


I came up with the SI-8050S as a candidate too, however there would be no reason for a heatsink on a +/-5V converter at this power level. The more I think about it, the more I suspect that this is the primary linear regulator for the whole circuit with the smaller surface mount jobs providing the lower voltages from the ouput of this one.

[quote=sluggo]I'm pretty sure this is a differential design with a virtual ground (as noted earlier). I can't think of any other logical reason for the BB op-amp to use a pair of 100V caps unless they were floating it. Above that there's a pair of larger 35V caps (presumably) for the positive and negative supplies. Interesting parts selection in this thing. I like it.[/quote]

I thought it was pretty well designed too. If the analog layouts are done with care, I would expect the limiting factor to actually be the DACs - assuming that isn't a knock off Burr Brown op-amp.

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Re: Replacement Wall-Wort for DAC

Postposted on Thu Feb 27, 2014 3:38 pm

SecretSquirrel wrote:I thought it was pretty well designed too. If the analog layouts are done with care, I would expect the limiting factor to actually be the DACs - assuming that isn't a knock off Burr Brown op-amp.


Unlikely I would think. Everything I've seen from Topping seems to be nice, well made stuff. The brand definitely appears to be a cut or two above most if not all of its fellow budget brands for generally only slightly more money.
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