[Waxletter]

Background

Hi guys! New user of the forum here. I've been looking into chifi DACs and tube preamps for awhile and I keep seeing the same consistent comments in the reviews.
They always go something like this:

The power supply that comes with this DAC, amp, etc. needs to be replaced for the device to sound right.

The products usually have this same power supply in all of their images.

Question:

With that being said, can anyone verify this? If this is true, what replacements are recommended? This is an especially difficult thing to shop for since power supply outputs and inputs can be of varying sizes.

 

[tomb]

Most likely they're referring to the fact that most (all?) Chinese-supplied power supplies are of the switching type. Switching power supplies are known for high-frequency hash and noise that can easily bleed over into the audio spectrum. Even if your amplifier design is excellent at rejecting power supply noise, a noisy switching power supply can defeat it. PSRR (Power Supply Rejection Ratio) is a recognized amplifier circuit value and it can be calculated based on the theoretical values of the components in a circuit. Any power supply noise will negatively affect an amplifier's audio quality to one degree or another. It just depends on the resolving power of the equipment you're using and whether it's audible and/or measureable.

The best and quietest power supplies for audiophile components are those that are linear-regulated. Similar to Class A amplifier operation, linear-regulated power supplies "burn" off excess voltage from a transformer to control the noise produced in rectifying from AC to DC. That "burned" off voltage results in heat. So most linear-regulated power supplies generate heat and come with heat sinks or ventilating slots in the case, even if it's a walwart. (One reason switching power supplies are popular - they're cheap and don't generate a lot of heat, but they stink for audio.)

Jameco sells some of the best linear-regulated walwarts in the business. Most are just as quiet as the best audiophile power supplies that are custom-made. Here's one at 12VDC, rated for 500ma, which will probably handle most cheap smaller Chinese amplifiers:
https://www.jameco.com/z/DDU120050F...Adapter-12-Volt-0-5-Amp_162996.html?CID=MERCH

If you need more, a 1 amp (1000ma) version is here:
https://www.jameco.com/z/DDU120100H...t-12-Volt-1-Amp-12-Watt_170245.html?CID=MERCH

I didn't check the actual plug on either of those. Center-positive is a common standard worldwide, but some are 2.1mm diameter and others are 2.5mm diameter, in equal prevalence in my experience. So check carefully for which plug size you need. Just make certain whatever you select from Jameco says "linear-regulated."

 

[Waxletter]

Most likely they're referring to the fact that most (all?) Chinese-supplied power supplies are of the switching type. Switching power supplies are known for high-frequency hash and noise that can easily bleed over into the audio spectrum. Even if your amplifier design is excellent at rejecting power supply noise, a noisy switching power supply can defeat it. PSRR (Power Supply Rejection Ratio) is a recognized amplifier circuit value and it can be calculated based on the theoretical values of the components in a circuit. Any power supply noise will negatively affect an amplifier's audio quality to one degree or another. It just depends on the resolving power of the equipment you're using and whether it's audible and/or measureable.

The best and quietest power supplies for audiophile components are those that are linear-regulated. Similar to Class A amplifier operation, linear-regulated power supplies "burn" off excess voltage from a transformer to control the noise produced in rectifying from AC to DC. That "burned" off voltage results in heat. So most linear-regulated power supplies generate heat and come with heat sinks or ventilating slots in the case, even if it's a walwart. (One reason switching power supplies are popular - they're cheap and don't generate a lot of heat, but they stink for audio.)

Jameco sells some of the best linear-regulated walwarts in the business. Most are just as quiet as the best audiophile power supplies that are custom-made. Here's one at 12VDC, rated for 500ma, which will probably handle most cheap smaller Chinese amplifiers:
https://www.jameco.com/z/DDU120050F...Adapter-12-Volt-0-5-Amp_162996.html?CID=MERCH

If you need more, a 1 amp (1000ma) version is here:
https://www.jameco.com/z/DDU120100H...t-12-Volt-1-Amp-12-Watt_170245.html?CID=MERCH

I didn't check the actual plug on either of those. Center-positive is a common standard worldwide, but some are 2.1mm diameter and others are 2.5mm diameter, in equal prevalence in my experience. So check carefully for which plug size you need. Just make certain whatever you select from Jameco says "linear-regulated."

Well that explains the comments! I guess I'll have to measure the diameter myself if I pick one up. Thanks for the enlightening reply!

 

[tomb]

Guess I should've added that the reason linear-regulated power supplies are so quiet is because they are so simple. They burn volts to regulate, meaning they're very inefficient, but exceedingly simple. Simple circuits can be made very, very quiet compared to complicated switching circuits, intended to bypass laws of physics by generating more power in tiny, noisy bursts that don't generate constant, searing heat.