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Amp+ Power Supply

John Hagensieker

January 12, 2016 23:48

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Got my new AMP+ today in the mail.  Bought a 120v to 15v linear power supply and temporarily wired it up and booted.  Works great.  Sounds pretty great.  I'm cranking it with 11 ohm speakers (which I know is outside recommendations) however that's just another temporary thing. 

 

I'll take what I learned from my LCD project and then I need to find some kind of enclosure to put it all together in.   Running LogitechMediaServer with Spotify Pandora and TuneIn Radio.  I can probably slap a 1TB drive on here as well however if I do that I'll probably move to a Pi B+ or Pi 2.  Might do that anyway. 

 

Enclosure is either going to be antique radio or brand new shiny stereo modern enclosure.  Whatever catches my imagination and eyes I guess. 

Anyway, proof of concept is over.  It works and is going to be perfect for what I have planned for it.  Is this overkill?  Yes.  Do I care?  No.

Enjoy.

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8 comments

• 0
  
  Peter January 13, 2016 02:18

  Wow, great job!  Now all it needs is a nice 2~3 inch volume control knob... :D

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  HiFiBerry team January 13, 2016 05:44

  Hi John,
  
  while this will work fine on lower volume, you might run into trouble at higher volumes. I would guess that this power supply can provide 1A max (or even less). With 11 Ohm speakers it is less likely to be a problem than with lower-impendance speakers.
  We recommend 3-4A at this voltage.

  Best regards
  Daniel

• 0
  
  John Hagensieker January 13, 2016 11:12

  I was a bit conflicted when I ordered it because of the lower amperage and the recommendation of 3.   I went ahead and bought it as I have another project I could use it for if it failed.  I also have a 3A computer type brick I ordered from Digikey.  I hooked it to the +16v outputs and some 8 ohm single drivers and it sounds great and gets way too loud.  I have about an hour playing and no overheating problems or drops.  

  Mathematically you are definitely correct but it is working just great.  I could squeeze some more current out of it if I need to by changing some things but for now it's performing beyond what I'll ever drive it to.

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  John Hagensieker January 13, 2016 13:59

  Just to follow up a bit more I brought it to work and hooked it to some 8 ohm bookshelf speakers and have it at what I'd call extremely high volume for about 2 hours now.  So far it hasn't cut out once, clipped nor are the transistor heat sinks warm at all. 

  All I can say (as an electronics tech rep for DOD) is that the math says it "might" not work so great but the deployment of it suggests that it is indeed working great.  I agree 100% with the math as you stated though.

  The Pi is headless with a single Edimax wifi dongle only and this will only be a streaming box.  No external hard drive will ever be hooked up.

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  Peter January 13, 2016 16:57

  You do not actually need a lot of power for good sound, at least not with a pair of decent (modern) speakers, and not for one person in one room.  Note Nelson Pass, who is a legend among older audiophiles, and his "First Watt" project (firstwatt.com).

• 1
  
  John Hagensieker January 13, 2016 17:07

  We're mostly talking about electrical current draw.   The power supply is roughly 16v output (+ and -) and maybe 1.5 amps at best. 

  A raspberry pi with a bunch of gear hooked to it should theoretically pull more current than that and that was Daniels point.

  The Pi with amp and a dongle and a USB hard drive and a monitor and keyboard and mouse and an LCD would need more than 1.5 amps of current.  Heck I have a Pi B with a USB DAC that won't work with anything less than a 1 Amp power supply.

  As somewhat of an electrical/electronics guy I'm a believer in the "theory" that if I say something will perform at 16 volts and 1.5 amps that means forever and maxed out when in reality those published numbers are probably 85% of reality (in regards to current).  You're operating at the high end of its intended capacity. 3 or 4 amps is a nice comfortable area of overhead.  

  Daniel is 1000% correct about the power supply, it's rating and that it "shouldn't" be enough.   Yet it is.  Now will it fail in 8-10 years instead of 15?  Maybe.  Clearly it works and works well though.

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  Peter January 20, 2016 03:09

  Having a decent toroidal transformer and a true linear power supply is really the best possible start to good sound.  It may not guarantee a good result, but its a step in the right direction.  Are you basically using one output of a bipolar supply, or am I not seeing this right?

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  John Hagensieker January 20, 2016 09:45

  Good eyes.  I literally hooked it up like that just to test it  It is now wired with both sides hooked up.  Hot and neutral at both ends and jumpers from each skipping a block