Pin One Problem on DL1608

[RoadRanger]

No different than the hundreds of million Laptops and LCD panels currently using these supplies.

Those don't have FUBAR grounding systems like the DL1608 .

[WK154]

In defense of Mackie the mixer works fine if you keep all your systems balanced and use shielded cable. It just has more noise than it can have.

Those don't have FUBAR grounding systems like the DL1608 .

And you know this how???

[RoadRanger]

Those don't have FUBAR grounding systems like the DL1608 .

And you know this how???

Because that's how you get them to pass CE with a two wire AC adapter .

[WK154]

Because that's how you get them to pass CE with a two wire AC adapter .
They don't have a Safety ground pass thru!!
You really need to read and understand Bill Whitlock's 2005 Seminar paper about Grounding Audio and Video systems.

[RoadRanger]

I give up - carry on  .

[Topsøe]

@WK154
Of your setup , with special attention to audio-ground  and safety ground

[WK154]

No need it's quite simple. I attached chassis ground lead to both screws (only one is necessary) in the power supply/network connector area. This is the one used to provide direct connection to AC safety ground (typically a green wire). There are 6 other screws  on the base of the DL that are also chassis ground connected but inconvenient to attach AC safety to.

[WK154]

The results from 4 power supplies for the DL. I am measuring power supply and DL electronics chassis leakage. Not using IEC60601-1 Human impedance load.

 I have a lab supply with very low ripple and noise ( <= 2mA and <= 1 mV) . Hooking up + and - produced < .1mV @ 1.2 uA without any chassis ground connected and needless to say no audible noise from the unbalanced C50 speaker. All test except for the speaker required one was performed without
any devices attached to the DL not even the iPad. With the chassis ground all readings were below the measuring equipments range (0.1 mV and 0.1 uA). Very quiet but remember the noise will always be there just not relevant. This indicates that the noise is not from internal electronics RFI as one theory goes. The pin one problem was eliminated. Unfortunately the size and weight make it an impractical solution. It did give current draw of the DL at 12V to be between 1.35 - 2.2 amps depending on load and iPad charging. I did not fully load all 16 channels and 6 aux-es and 2 outputs. Actually it was fairly light 3 mics, the speaker and the iPad charging. One condenser requiring phantom power. Anyone for testing with a 12V battery? 10hrs like the iPad would require about 25-35 Ah sealed lead acid battery.

Next lets tackle the original issue PS the APX with safety ground tied to the DC return output. In its original configuration  it measures 0.3 - 0.5mV @ 16 - 18uA. The safety return shunts an additional 51 uA for the PS total of 79 uA total leakage. The manufacturer rates this at 120mV ripple/noise @ 3.5mA leakage max. It certainly beats max specs by a goodly margin. Unfortunately it's not good enough for low noise or the pin one effect by injecting this as the input to the DC to DC converters. Adding the chassis ground drops the values to 0.1 - 0.2mV @ 4.2 - 4.5uA but the noise injected into the DC to DC converters even at this level is the real reason for the poor performance. No change in the pin 1 problem it just hums a little less.

Now for one of the solutions. The first is a three prong AC connector but no pass thru safety ground. The  Model #1206 LCD AC supply no manufacturer given by Amazon. The measurement without the chassis ground are 5.1mV @ 187uA which drops to <= 0.1mV @ 1.4 - 1.5uA with the chassis ground connection. No safety ground noise dumped onto the DC return line and yes no hummer noise. Pin one problem gone.

Solution two a two prong plug model ST-C-075-12000600CT from e-bay adaptermonsters again no manufacturer name. The non chassis ground values are 7.1mV @ 195uA that gets reduced to <0.1mV @ 1.9 - 2.0uA with the chassis ground. Again no hum and no noise with and without the hummer. Reversing the AC plug has no effect. Great for mis-wired AC outlets.

Most Pro Audio folks would simply state that if a unit has pin one problems "Don't Buy It". I believe the Dl has the fortune of being corrected with a minimal cost change. Of course Mackie should do this instead of it's customers.

[Greg C.]

I believe the Dl has the fortune of being corrected with a minimal cost change. Of course Mackie should do this instead of it's customers.

Nice work. Big kudos to you for isolating the cause. That last statement is the crux of the issue. Mackie is poor about acknowledging issues let alone fixing them sadly. And this is why I can't recommend their gear.

[WK154]

This was my first Mackie product and will be my last. I did work of and on for 15 yrs. with a C1604VLZ an average but reliable workhorse that now needs to be replaced. Greg Mackie's name was on the company and he cared for his customers far more than the current Bean Counters. I always believe in voting with your money. No Apple, no Mackie and the list goes on. Going on the chopping block soon. My XDM works fine as a replacement for my applications.

[robbocurry]

I haven't had a problem with the noise on the aux channels as all my monitors are balanced. The solution, if the problem arises, isn't going to sink my ship technically or financially or so it would seem. Perhaps Mackie will replace the PSU on current production models?
I can only think that it was an oversight that Mackie didn't test unbalanced sources and their shortcomings.
Perhaps their aim was at a more professional market (or more 21st century) in their unbalanced oversight.
How many "beans" difference between the supplied and the optimal PSU? Enough to make it worthwhile financially and potentially cause all this ill will towards a great little desk?
Regardless, my experience with the DL is getting better with use. It's not perfect, but it's pretty good for the price. Think back a few years and what we would have paid (and how we would have drooled) for a desk like the DL!

[WK154]

I finally received Mackie's reply to their pin 1 problem. Please note that I never mentioned balanced or unbalanced in my request. Their answer tells me that they were clearly aware of the unbalanced problem. Professional market with that advertising??? You've got to be kidding!!!!  They list all the usual documents on the subject, unfortunately they don't understand them. Well here is their reply in it's entirety.

Subject:    RE: Pin one problem with DL1608
   Priority:    Normal    Date:    Tuesday, June 11, 2013 6:57 PM    Size:    7 KB

Sorry for the delay. From our findings when using the unit as it comes out of
the box, the noise experienced only happens with unbalanced connections and not
due to a failure with the DL1608.  We (the manufacture of this product) strongly
recommend all DL1608’s to be operated with balanced cables and balanced devices
for Aux Sends and Main Outputs.  Doing so will result in No Hum and No Whine at
all. Mackie always recommends using balanced cables and connectors whenever
possible. The DL1608 is a professional product and it is designed to be used
with professional balanced connections.
 
Balanced connections give you the best possible performance with the least
possible noise. With unbalanced connections, many things can contribute to
increased noise including the following: the length and type of cables, the
devices in use and how they are powered, other devices in the environment, and
the power supplied at the location.
 
Balanced connections ensure that the signal and its reference are completely
separate from the shield, and that they both have any noise induced equally; the
receiver then looks at the difference between the signal and reference lines for
the desired audio signal, cancelling out any induced noise. This cancelling out
of equal noise on each line is called “Common Mode Rejection”.
 
When using an unbalanced cable for outputs from the DL1608, like with other
products designed for balanced connection, the noise is not canceled at the
receiver and can work its way into your audio. When the shield of an unbalanced
connection forms part of a loop (e.g. by connecting to other chassis, with other
shielded cables and/or grounds), various types of hum/buzz/noise currents can
circulate. These can easily create noise in the audio signal when it flows
through any part of the loop shared by the audio signal/return loop and has
resistance (“Common Impedance”). For unbalanced connections, at minimum there is
usually a loop in the cable shield itself; larger loops have more chance of
interference causing noise currents.
 
Here’s a link to a video that gives a simplified visual of how this works:
 
http://youtu.be/jo5HhfIUSP0
 
 
 
For even more detail, these two PDFs from our friends over at Jenson
Transformers are full of useful information:
 
http://www.jensen-transformers.com/an/an003.pdf
 
 
http://www.jensen-transformers.com/an/an004.pdf
 
 
 
Unfortunately, the combination of gear in your particular environment(s) is
noisier than desired when using unbalanced cables. As described above, this is
never the cause of one particular device, but a symptom of the combination of
all the devices in your system and power and environment being used.
 
The ideal, safest, and most reliable way to ensure a noise free cable run when
both devices have balanced connections, is with a balanced cable run.  There are
solutions for those situations that don’t contain balanced inputs, and for that,
we recommend an isolation transformer or DI box, or using specially created
unbalanced interconnects. The fine folks at Rane have a great document to help
including instructions for building your own custom interconnect cables:
 
http://rane.com/note110.html
 
 
 
I hope this helps, let us know if you have further questions.
 
Technical Support
Mackie/TAPCO/Ampeg/Crate
LOUD Technologies Inc.
800-258-6883 ext. 1633
  Please feel free to contact us if you have further questions.
 
-----Original Message-----
Sent: Monday, June 03, 2013 6:24 PM
To: Technical Support
Subject: Pin one problem with DL1608
 
I have tested your DL1608 for pin one issues and it has failed. Do you have a
solution for this problem? The test was from a chassis ground on the DL to any
pin 1 or sleeve contact with a hummer.

[Greg C.]

Yup, they totally ignored the fact that by failure of the hummer test that they have a faulty grounding scheme. And they're still blaming end users and everyone else's gear but their own. Also, they claim in the manual that those jacks are dual mode which means balanced cables are not required like all their other mixers. But then they renege on that function in public. Lame.

[WK154]

Aside from the word "professional", the ones that stick their heads in a urinal and flush, I really like this one.
 For unbalanced connections, at minimum there is usually a loop in the cable shield itself; larger loops have more chance of interference causing noise currents.
Mackie now has traffic cops to route the electrons in the shield to make sure that there is a loop formed! I must be interpreting this wrong or did they just develop a new electronic miracle.

[WK154]

One of the things in my testing I forgot to mention was the spectral content of the noise. The old Doo-Wop  group that's been around for ages "Sixty Cycles and the Harmonics" are a no-show. The ugly chopper PWS created 60 cycles has other frequencies generated thru out the audio spectrum.