PlasticDoc
Active Member
No it is not.Ah ok, so this level of singing is expected?
No it is not.Ah ok, so this level of singing is expected?
Is the humming/singing of the coils also present in real music at this volume?1) Input: none, Output: none -> no sound is generated (by any of the 3 boards)
2) Input: 1kHz sine, 1.97Vac rms, Output: none or dummy load -> audible 1kHz sine emitted (by any of the 3 boards if the input is present)
3) I don't have an analog scope, but if I connect a speaker to any output and play regular audio, the only noise issue is that the physical boards themselves are behaving like tiny speakers and emitting audio from anything that is above 1kHz
5) My only bus powered DAC is an old Behringer UMC204HD that is only capable of +3dBu output. Using it with my laptop or my phone will cause the issue, but it's quieter (as it's maxing out at about 1Vac rms)
My setup for these tests is very simple. MacBook Pro -> USB Audio Interface -> 1/4 TRS to XLR cable -> 3eaudio modules
(Note: I've tried with a MOTU 1248, MOTU Ultralite mk5, Behringer UMC204HD, and Behringer UMC1820 and all behave exactly the same)
Taking a suggestion from earlier in the thread, I tried poking around the boards to find which component was generating the audio. Pressing on the Coilcraft inductors lead to reduction in the noise (not fully, though). Next, I tried pressing on the bottom of the chassis right under where the boards are screwed down and that also led to a reduction. Out of curiosity, I unscrewed the amp module from the chassis and picked it up while it was connected and that reduced the noise even further. It appears that whatever is ringing on the board is made worse when it's physically attached to a larger chassis (which I chose to do for heat dissipation reasons).
Here's a video of this behavior. At first, I'm plugged into the middle amp module (that's firmly screwed down to the chassis). Then, I switch the input jack into the first amp module that's just resting on the chassis but isn't screwed down. Finally, I pick up the amp module as well as press on the inductors and the noise is reduced even further.
Are you testing with an 8 ohm dummy load?It's present with real music as well. It basically acts like a tiny speaker with a low cutoff of around 700Hz. I can post a clip of it playing music if that's helpful to anyone
this is not a quality control issue, these coilcraft(all inductors) without fully glued will ringing at higher power/current situation,that is cause by the magnetic reflection between the coil wire and the core,you can test other similar switching (class D)amplifier to see what happen with same condition.Expensive...
Again, a problem in 3e Audio's quality control process:
* if a board sings, they should put it aside and send the customer a new (silent) one;
* latter pick the defective board(s) and do some more testing;
* do whatever it takes to make it stop singing.
Do not be quick to point the finger at the test procedure the customer is using to illustrate a problem.
The board should not have a problem in the first place, period.
That doesn't surprise me, the board is specified for 36-51 V DC. The 12 V voltage conversion is probably designed for at least 36 V, or a little less.Doing some testing and it is Interesting that the Aiyima A04 32V 5A SMPS will NOT power this board up.
I tested the el-cheapo 36V 5A SMPS and it powers right up.
I've thoroughly tested and put the 3E PFFB board through it's paces with the el-cheapo 36V supply and the new Meanwell 48V (LOP 600-48) supply. Already excited about the XRK-3255 PFFB build using this 48V-10A SMPS as it is dead quiet, has ample bass punch at any listening level and most importantly fits my case designFound a 48V 10A smps that will fit the case.
The Meanwell LOP 600-48 is small and powerful. Its DC output of 48V/8.3A makes it a good match for TPA3255 based amplifiers.the new Meanwell 48V (LOP 600-48) supply.