[mikeaj]

The thing that plugs into the wall is just a simple AC/AC transformer, as opposed to some kind of AC/DC regulated power supply.  There are parts in the board for a dual half-wave rectification:  it uses the positive side of the AC cycle to create the positive DC rail, and the negative side of the AC cycle to create the negative DC rail.  Voltage regulators (7912 and 7812), filter caps, etc. all are on the board.
 
With the parts as specified (unless with low line voltage from wall, using the recommended cheapest option wall wart with the relatively low output, and maxing out the output power into low impedance loads), the ripple into the regulators will be small enough that they can take care of most everything.

 

[cheapskateaudio]

C13 and C14 are coupling capacitors right? I replaced those with Panasonic 2.2uf polypropylene capacitors and I swear it sounds a little better. Midrange details come through more clearly, and bass notes seem a bit more musical and punchy. For instance, on Jimi Hendrix's live performance of "Purple Haze" it's very easy to hear the electrical hum in the background when he stops playing to sing "that girl put a spell on me"..
 
After all the mods song beats seem less driven by the *&@^#% snare drums, thank god. I can't stand loud snare drums, it's like being stabbed in the eardrum 120 times a minute.
 

 

[fubar3]

 
Quote:

Why are unregulated wall warts being recommended for the build? Wouldn't a regulated power supply be better? 

It is possible to use an external DC supply. However, the wires, jacks, and plugs impose a resistance between the regulator and the load which degrades performance. Computers are often designed like that to use an external DC power-pak but they are noisy beasts with additional switching supplies and digital circuits.
 

 

[deadlylover]

Quote:

It is possible to use an external DC supply. However, the wires, jacks, and plugs impose a resistance between the regulator and the load which degrades performance. Computers are often designed like that to use an external DC power-pak but they are noisy beasts with additional switching supplies and digital circuits.

 
If by possible you mean 'having to tweak the entire power supply rectifier section and use two DC wallwarts for the dual rails' then yes, it's possible.

 

[estreeter]

Man, I'm glad Oliver is taking care of all this minutiae for me. All power to the DiYers, but it would really do my head in if I was halfway through a build and stumbled into this thread. 

 

[limpidglitch]

Quote:

Man, I'm glad Oliver is taking care of all this minutiae for me. All power to the DiYers, but it would really do my head in if I was halfway through a build and stumbled into this thread. 

The build is as straight forward as a build can be, but even the simplest of tasks can be made complicated if you just try hard enough.

 

[Willakan]

The irony of subjectively modifying an O2 is almost unendurable 

 

[mikeaj]

Quote:

The irony of subjectively modifying an O2 is almost unendurable 

Modded Objective2 -> Objective1.  It has lost some of its objectivity.  Also it is now an O1...which we recall from basic chemistry principles, is unstable and does not exist in nature (O2 being normal diatomic oxygen form and O3 being ozone). 

 

[francisdemarte]

Quote:

 

It is possible to use an external DC supply. However, the wires, jacks, and plugs impose a resistance between the regulator and the load which degrades performance. Computers are often designed like that to use an external DC power-pak but they are noisy beasts with additional switching supplies and digital circuits.
 

Thanks for clearing that up. I'm going to start my build this weekend but I haven't looked at any of the parts in detail. I just cut and pasted the BOM into Mouser's project manager and checked out I have a ton of power supply parts in my parts bin to experiment with.
 

 

[estreeter]

Quote:

The build is as straight forward as a build can be, but even the simplest of tasks can be made complicated if you just try hard enough.

And I would argue that several in this thread are trying very hard indeed. I know thats the DiY way - start with the basics and 'improve on it' - but I wonder how many are now looking at their wallwart and thinking 'man, I really need something better than this !' ..................
 

 

[kiteki]

 
Quote:

Modded Objective2 -> Objective1.  It has lost some of its objectivity.  Also it is now an O1...which we recall from basic chemistry principles, is unstable and does not exist in nature (O2 being normal diatomic oxygen form and O3 being ozone). 

 

Clever!
 
If I make a DAC, remind me to call it the liquid helium-4.
 

 

[Pars]

One look at the schematic would show that it is using a half-wave rectified DC power section with 7812/7912 regulators. Input is max. 20Vac, min. of 200mA, so the Mouser AC-AC wallwart listed above would be a good fit at 16Vac, 400mA. This looks approximately equivalent to what you would find inside an Elpac regulated DC wallwart, such as the one used on a Gilmore Lite, etc. Sure, you could use a DC regulated wallwart, but you would lose ~0.7V across the rectifier diodes, etc. By not populating the DC power components other than the last set of diodes, you could wire any dual +/-12V DC power supply you wanted to (Amb Sigma 22 :devil.

 

[Willakan]

True, but the power supply is not the limiting factor in the amplifier's performance (I doubt it is a limiting factor for the majority of well-designed amplifiers TBH), so it would be a total waste of time.

 

[svyr]

True, but the power supply is not the limiting factor in the amplifier's performance (I doubt it is a limiting factor for the majority of well-designed amplifiers TBH), so it would be a total waste of time.

yea,i really don't understand the purpose of people discussing it, when as you said the designer states black on white (uugh well, the blog is white on black ), that the psu noise is not a limiting factor at all, and that's reflected in the measurements.

 

[Pars]

IME, PSU quality is paramount, even in well designed amps. A well designed PSU like the sigma can probably outdo batteries in terms of the noise performance. I would think there is someone around here who has a sigma22 or equivalent PSU that could reconfigure it for 12V output and try it out with an O2. Maybe even let someone measure it?