Musings on Switching Power Supplies (LPS for Oppo / DirecTV/ Radiance)

First step was obvious.  I had been looking at that Oppo linear power supply on the OPPOMOD website for a while now, but always thought that it was lower down on the priority list.  Well, obviously, it just rose up to priority #1, lol.  So, I pulled the trigger and ordered it.

The OPPOMOD LPS came.  I ordered the “SE” version (though it looks like that the non-SE version is no longer being offered for the older players, no big deal, the SE is better).  I am quite impressed with this power supply.  Nichicon KW capacitors throughout!  A whopping 60,000uf just for the 5V regulated output!!! (for digital).  Upgraded schottkey diodes.  It looks like the post-regulator caps are WIMA MKP and the tantalum to really stabilize the voltage.  I don’t think this needs post-regulator electrolytic caps because the digital board already has these as power supply filters.  This thing is HEAVY!  The build quality is absolutely excellent. 

First thing to go is the stock AMR fuse he puts in.  I placed in a 2A Hi-Fi Tuning Supreme fuse I had sitting around.  I figured, it’s a digital transport and silver digital cables are best, so let’s use silver for power supply fuse as well.  In addition to the LPS, I also upgraded the internal 15-pin power connector between the LPS and digital board – using the 22awg upgraded cable found on ebay listed as “Tweak OPPO BDP 93EU 103EU 103D 103US 103AU nappe d'alimentation optimisée”.  I applied dynamat to the top of the disc drive, the top of the case/cover (where it didn’t impede the LPS transformer) and to sections of the bottom of the Oppo chassis.  These things were just tweaks and wouldn’t hurt, but the main upgrade was the LPS.

So, initial findings.  The LPS does get hot!  The LPS has a thick metal L-bracket that thermally connects the voltage regulators to the bottom of the Oppo chassis (for heat).  I found that the bottom of the case gets really hot after a few hours.  I did notice that after a few days of burn-in, it did not get quite as hot.  I think the regulators became more efficient during burn-in.  I don’t think this heat is a big concern for the 103, as my Krell processor also warms up.  The rest of the Oppo case is only mildly warm, so I think the case does a good job as a heatsink.  The digital board definitely uses a lot of current!  It’s almost like a Class A analog circuit!

So, I did notice a good improvement of video quality from the Oppo.  It is apparent that the stock switching power supply was introducing noise into the picture.  Images were much sharper and cleaner than before.  Surprisingly, the audio had a distinct jump in sound quality as well.  Everything was more solid and, man, the bass was so strong and hit hard!  So, even though it’s “just a digital transport”, the linear power supply matters a great deal!

Okay, so what’s next.  There’s still those switching power supplies in my DirecTV receiver and Radiance video processor.  Upon investigating, I can see that the switching power supply adapters clearly show voltage specifications:

Radiance:  12V DC, 2.5A

DirecTV: 12V DC, 4A

The Radiance uses an industry standard DC plug (5.5mm outer diameter / 2.1mm inner diameter).  However, the DirecTV uses a very proprietary 2-pin DIN connector.  The 2-pins are off center at a weird angle with the DIN notch at top.  I could not find an industry standard connector for this, so I knew I was going to have to chop the DirecTV adapter.  I just ordered another DirecTV adapter from ebay ($10 for a spare EPS44R0-16, you can buy these all day long on ebay).

So I started looking for external linear power supplies and came down to Teradak as a solution.  Now, I could have gotten two separate linear power supplies for the DirecTV/Radiance.  There were a 12V 3A supply and another 12V 5A supply.  I also saw Teradak had a dual 12V / 6.5A power supply.  It would have been more money to buy the individual power supplies.  I am also a fan of oversizing power supplies to ensure completely smooth DC.  Additionally, I would only have to worry about one extra power cord instead of two extra power cords.  So I decided on this unit from ebay:

TeraDak dual 12V / 6.5A chord hugo Hifi DC-200W Linear Power Supply

It had two individual 12V / 6.5A DC outputs, which was perfect for me.  The TerDak power supplies on ebay are often marketed for a specific piece of equipment (“chord hugo”, “auralic aries”, “Logitech squeezebox”, etc.).  This makes it easy for those consumers because the power supply is “plug-n-play” with those devices because it uses the proper DC voltage and DC connector.  However, these are just linear power supplies and can be used in other types of equipment, as long as the DC voltage is correct and you attach/wire-in the proper DC connector.  In any event, this item came with the same 5.5/2.1 connector used in my Radiance, so it was plug-n-play for that.

On the extra DirecTV adapter I bought from ebay, I cracked open the adapter case using a chisel/hammer.  I could see that there was a center white conductor that was +12V.  The shield wire (or black conductor) was ground.  Easy-peasy.  I could not find out the type of connector used on the Teradak unit itself, so I just un-soldered the existing connector and soldered that onto the DirecTV wires.  Make sure that you connect the right wires to the right points – verifying with a multimeter several times!!  It would be really bad to cross-wire your DirecTV power and damage the unit.

Okay, looking at the TeraDak unit itself.  It is very well built for a Chinese product.  Nothing cheap here.  All the solder connections looked really nice!  Very well made!  The electrolytic capacitors could be better.  They did use 105 degree caps (which are not as good for audio in my opinion).  The description in ebay indicates they use Panasonic capacitors, which is a good thing.  I did not spend the time trying to validate this.  This dual 12V external linear power supply is still $100 cheaper than the OPPOMOD LPS, so who am I to argue.  I will say that testing this showed that it was light years better than the stock switching power supplies, so I win in the end in any event.  I did not think it was worth it to try to get some of the higher end $500+ linear power supplies (such as Teddy Pardo, Paul Hynes, etc.)

I threw in a 4A Synergistic SR20 fuse (another fast silver-like fuse I had lying around) because the stock fuse was so obviously junk.  Hooking this up and testing it showed good results after a few hours burn in.  Video quality just shot through the roof as the picture detail was amazingly clean and clear.  I could see motion details in the actors facial skin that was just so realistic I thought I was looking at real surfaces!  The video noise was completely gone!  Also, audio from the DirecTV satellite channels now sounded more like bluray sound because all that harshness/brightness was gone.  DirecTV satellite always had a bright “bite” to the sound which prevented my enjoyment as much as bluray movies.

This next step in the process came about a day after the Teradak was in the mix, during burn-in period.  I found that the audio had suddenly become a little bright/harsh again.  After extensive testing, what I found was that the fuses and power cords for the Oppo as well as the Teradak/DirectTV “digital transports” were influencing the audio coming from the Krell HT Processor.  In additional, a fuse in one source transport was influencing the sound from another source transport, even though it wasn’t selected as an “active input”, or was put in standby mode.  The DirecTV Genie receiver is always powered up and running even when it’s in “standby” mode (internal computer and DVR are 24/7).

This discovery came when I decided to remove the Hi-Fi Tuning silver fuse from the Oppo and put in a 2A PADIS fuse instead.  The result was, even though the Oppo was powered off and in “standby-mode”, the sound from DirecTV was not as bright, but just did not sound right in the end.

At that time, the Oppo had the PADIS fuse, but had a power cord that uses cheap braided 20awg solid-core Radio Shack copper with Furutech rhodium connectors.  In other testing, I found this Radio Shack copper sounded good, but it was too warm with rolled-off highs.  Interestingly enough, this power cord on a digital HDMI source was affecting the sound from a separate DirectTV digital HDMI source through the Krell HT processor.  I switched the power cord on the Oppo to a much better braided 20awg solid-core OCC copper teflen Neotech cable wit Furutech rhodium connectors.  The sound quality improved immediately.  Weird!  In research, I think there are two wires in the HDMI cable that could contribute to this result:

Pin 18 - +5V DC

Pin 17 – Ground

Pin 18 is +5V that is supplied by the source device to power external items that do not have an external power source (this would be something like active cables or external headphone DACs or something else).

Pin 17 is ground, which is the ground plane shared across all devices in the equipment chain).

Since the +5V DC voltage is generated by the Oppo or Teradak, I believe it is making its way into the Krell processor (through the HDMI input) to the normal 5V power rail.  This will definitely influence the character as the DAC href uses this +5V voltage for generating it’s DC output voltages (among other things in the circuits).  The ground plan can influence sound as well between devices.  It could also be that the power supply on the transport is affecting how good the digital signals are (voltage levels, jitter, etc.).

So, under testing, putting a warmer fuse into the Teradak (such as an Isoclean) definitely contributed to making the audio sound warmer in the whole system.  In the end, I ended up with Furutech fuses in both Oppo and Teradak and Audioquest NRG-4 power cables with Furutech Rhodium plugs.  In the end, that was the best combination as the Furutech fuse / OCC solid-core cables are my reference in all applications.  Both the video quality and audio quality are absolutely amazing for me now.

To sum it up, the argument that “switching power supplies are not bad for digital circuits” is completely wrong for me.  I can hear the difference!  It’s amazing to me that many high end audio equipment pieces still use switching power supplies for digital sections (even though they may use linear power for analog sections).  Emotiva started on a crusade a few years ago when they started touting “switching power supplies as the future”.  I believe they were paving the way for consumer belief so that they could put in switching power supplies and make the item lighter/cheaper for shipping.  I have also read many electrical engineer statements that switching power supplies are perfectly fine as long as you have a good filter in them.  I strongly disagree!!  In fact, one of the reasons I love my Krell S1200 is that it does not use switching power supplies at all!  It uses linear power for everything.  In fact, it actually uses a fully discrete shunt regulator circuit for the +5V DAC vref, and a normal LM7812 regulator for 12V required for some digital circuits.

So, new project on my list for next year is to upgrade my computer power supply (upstairs computer audio system) to a Teredak Computer Linear Power supply and upgrade the DAC to something that uses non-switching power supply (maybe LKS MH-DA004).

Hi auxinput,

I bought on of these to replace the wallwart switching power supply for my router modem: http://www.ebay.com/itm/Accubasston-Steady-Linear-Power-Supply-12V-15V-24V-DAC-Phono-Head-Amp-Steamer-/172908731517?hash=item284229dc7d:g:WGoAAOSwhxBZtshm

Very well built and the finish is superb. Very pleased. $100!

Dave