3E Audio 260-2-29A : TPA3255 / HA3588 CoilCraft / PFFB Fully differential.

[PlasticDoc]

Ah ok, so this level of singing is expected?

No it is not.

 

[Roland68]

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.

https://flic.kr/p/2qDiZtD

Is the humming/singing of the coils also present in real music at this volume?
Or only in the sine wave test signals?

 

[DaN0]

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

 

[Roland68]

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

Are you testing with an 8 ohm dummy load?
How high is the power you are testing with?
Does the humming/singing of the coils change when you play real music on a loudspeaker? Instead of the dummy load.

Please do not use silicone, bitum, other casting compounds or hot glue under any circumstances.
It is only sensible to use suitable epoxy resin in this case, not 5-minute epoxy or hobby glue.

 

[3eaudio]

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.

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.
@MicroAudio should has more experience on the SMPS transformer dipping paint(similar to glued) to avoid the audio-able noise,but most of supplier won't specify this parameter unless customer defined.

 

[xschop]

XS-3E Billet case design finalized....

 

[xschop]

 

[xschop]

For now I glued the XLR connectors in and will get plated alloy XLR housings.
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. What I can say is that the alloy case housing is definitely ridding the EMF/RFI from the unit just a foot away (Main design goal). The amp is DEAD silent unless I remove the billet cover, then I heard some errant noise with ear right to speaker (Testing on B&O C30's). I'll move this 3E amp back to the main rig when I add a bigger power supply to the new connector. For now, just gorgeous sounds on the bedroom rig...

 

[Roland68]

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.

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.

Very nice build by the way.

 

[xschop]

So should I get another 36V-6A or go a little bigger 42V-?A..

 

[xschop]

Found a 48V 10A smps that will fit the case.

 

[xschop]

Found a 48V 10A smps that will fit the case.

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 design

 

[PlasticDoc]

the new Meanwell 48V (LOP 600-48) supply.

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.
Being "Medical EN/UL 60601" usually means quieter and safer than other power supplies.

 

[xschop]

I can report back that the SMPS doesn't get hot either. I will not need to add an internal fan for my listening levels. After 3 hrs playing loud, I paused the track and put ear to tweeter. Was still dead silent.

 

[Treborha]

Hello. I have a question, can I use two 3E Audio 260-2-29A modules to build a dual mono amplifier. I will use one input from each module, the second input will be inactive. Mono versions are no longer available on Ali Express, and the two-channel REV C has an improved input for SE operation (additional decoupling capacitors can be soldered)

 

[Roland68]

Hello. I have a question, can I use two 3E Audio 260-2-29A modules to build a dual mono amplifier. I will use one input from each module, the second input will be inactive. Mono versions are no longer available on Ali Express, and the two-channel REV C has an improved input for SE operation (additional decoupling capacitors can be soldered)

The 3E AUDIO 480-1-29A PFFB Mono are available from Audiophonics, but they're a bit more expensive, but they come with a warranty in the EU.
I wouldn't wait long, though; there are currently seven left, and since Aliexpress is out of stock, they'll probably go quickly.

Alternatively, you could also use the 3E Audio 260-2-29A for bi-amping per speaker; then you'd have full power for the bass and a channel for the mid/high frequencies.

 

[Wolf11Man]

In fact with these modules, using two in parallel (wrongly called bridge) makes only sense with loads lower than 4 Ohm. So if you have the option, better use two channels to bi-amp a speaker. You will get the same maximum power.

 

[KL....]

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.
Being "Medical EN/UL 60601" usually means quieter and safer than other power supplies.

Thank you, the Meanwell LOP 600-48 is small and powerful, isn't it?

• Height (33.5mm) Width (76.2mm) Depth (127mm)
• Do you know what the Ripple Noise measurement?

Have a look at Daitron SMPS, and let me know your thoughts, and are they worth the price....
Using an Ultra Low Noise SMPS - How it achieves Low Noise Performance

• PFS300A Series Low Noise
• RFS50a - Ripple Noise: 1mVp-p
• RFS Series Ultra Low Noise AC/DC Power Supply

 

[antcollinet]

You will get the same maximum power.

No, you won't. Because the high frequncy amp wil only be outputting about 10% of the power of the low frequency amp due to the lower power content of music a the higher end of the spectrum. Most of the power is needed for bass.

 

[jlx]

Thank you, the Meanwell LOP 600-48 is small and powerful, isn't it?

• Height (33.5mm) Width (76.2mm) Depth (127mm)
• Do you know what the Ripple Noise measurement?

Have a look at Daitron SMPS, and let me know your thoughts, and are they worth the price....
Using an Ultra Low Noise SMPS - How it achieves Low Noise Performance

• PFS300A Series Low Noise
• RFS50a - Ripple Noise: 1mVp-p
• RFS Series Ultra Low Noise AC/DC Power Supply

View attachment 436497

View attachment 436500

something is odd with the RFS550a "ultra low ripple" unit. They measure ripple & noise to their own standard (why do this?) NOT to the usual standards AND the efficiency of 80% is lousy, They do have a paper detailing their ripple spec methodology but I don't have the inclination to dig into it further. Any PS that is top end/medical grade should easily be at or over 90% peak efficiency. Their white paper lacks the depth of data I would expect from any top grade product as well. No efficiency or thermal derating graphs etc.
"Superior Ultra Low Noise"? I doubt it, but it may still be a good/decent supply none the less
Any YouTube video sponsored by the reviewed product's company is a YouTube video I won't watch.