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

Is there no description in the 3e manual? It is quite simple and only needs some bridge/ jumper changed and a two wire connection between the boards.

How exactly it is done for 3 modules is on page 2 and 3 of the linked manual. With pictures and all!
I posted the description and the manual.
Unsure of why it’s needed because who uses an AM receiver?
 
I posted the description and the manual.
Unsure of why it’s needed because who uses an AM receiver?
@3eaudio often claims that the master/slave mode is related to some sort of AM radio interference, and he even writes it in his manuals. I don't know where he got this idea, but it is wrong and has nothing to do with that.
Note that I am not saying that wiring the modules in master/slave mode will solve your problem, I have no clue what the issue is, just don't get confused by the AM radio BS.
 
@3eaudio often claims that the master/slave mode is related to some sort of AM radio interference, and he even writes it in his manuals. I don't know where he got this idea, but it is wrong and has nothing to do with that.
Note that I am not saying that wiring the modules in master/slave mode will solve your problem, I have no clue what the issue is, just don't get confused by the AM radio BS.
Yeah I’ve been running them without master/slave mode for over a year in another system with less sensitive speakers with zero issues. This new system I built has very sensitive drivers. It’s a non issue there too. Unless my head in stuck in the horn, I don’t hear anything. Amps are never off and is in my living room. I’ve chalked up the slight hiss I do hear to gain and have started looking for lower gain amps (1et6525SA) for the horns.

 
OK, you don't hear it, so the possible reduction in sound quality doesn't matter to you. On the other hand, maybe you miss some of the great sound quality this D-amp chip has to offer, done right.
I try to explain what this is all about, so you may understand why this makes sense.
When you can read and understand some basic developer sheets from the manufacturer, you can check yourself.
If you come from a culture where braking rules and taking any shortcut is the way to success, this may not matter for you.

The tpa3255 runs on a frequency of usually 450.000 Hz, 450 kHz or 0.45 Mega Hertz. This is AM territory.
The section inside the chip that generates the frequency is not perfect. It may oscillate at 430 kHz or even 470 kHz. Completely inaudble in a speaker.
Now imagine they are quite close, one 450kHz and one 450.9 kHz. These two meet at the power supply. The mix of these two gives you 900 Hz.
You will hear that quite well in your speaker, but it may also be a difference that gives you an inaudible load of 22 kHz at the tweeter. Most will not like that, even as they don't hear it.
So if you want to feed two or even more TPA3255 on one power supply, you should maybe take the TI data sheet more serious than 3eAudio does.

The next advantage, for example 3 amps connected correctly, do not only run on the same frequency, but also load the power supply more even, as it installs a delay. The first amp is running at 0°, the second at 180° the third 60° etc.
This is not the phase of the output! Only the working frequency is delayed, to make better use of a SMPS.

I hope that helps.

PS this is not only for the TPA3255, it is the same with any TPA32xx and others, like the TPA3116D2
 
OK, you don't hear it, so the possible reduction in sound quality doesn't matter to you. On the other hand, maybe you miss some of the great sound quality this D-amp chip has to offer, done right.
I try to explain what this is all about, so you may understand why this makes sense.
When you can read and understand some basic developer sheets from the manufacturer, you can check yourself.
If you come from a culture where braking rules and taking any shortcut is the way to success, this may not matter for you.

The tpa3255 runs on a frequency of usually 450.000 Hz, 450 kHz or 0.45 Mega Hertz. This is AM territory.
The section inside the chip that generates the frequency is not perfect. It may oscillate at 430 kHz or even 470 kHz. Completely inaudble in a speaker.
Now imagine they are quite close, one 450kHz and one 450.9 kHz. These two meet at the power supply. The mix of these two gives you 900 Hz.
You will hear that quite well in your speaker, but it may also be a difference that gives you an inaudible load of 22 kHz at the tweeter. Most will not like that, even as they don't hear it.
So if you want to feed two or even more TPA3255 on one power supply, you should maybe take the TI data sheet more serious than 3eAudio does.

The next advantage, for example 3 amps connected correctly, do not only run on the same frequency, but also load the power supply more even, as it installs a delay. The first amp is running at 0°, the second at 180° the third 60° etc.
This is not the phase of the output! Only the working frequency is delayed, to make better use of a SMPS.

I hope that helps.

PS this is not only for the TPA3255, it is the same with any TPA32xx and others, like the TPA3116D2
And this would still apply when both amps are feed from a very large capacitor bank?
Couldn’t be 20dB gain amps on a 112db@1m compression driver?
 
It is a known issue in the industry that OCCASIONALLY a power supply does not get along with a particular class D module. For example I know of a top end Meanwell supply that hummed when connected to a Starkrimson amp module. It happens...Try a different psu

This morning I tried using another PSU (Drok 48V 10A) with only one amp module connected and the behavior is the same

So it is not output related. It seems not to come from the PSU.
After you checked connecting only one module as @antcollinet proposed.
Does it change with frequency? Does it change with input level? Singing in idle?

It changes with frequency and input level (it acts like there is a tiny speaker in the amp module itself). Here's a video:


NOTE: in the video, there is only one module connected to the PSU, the output is connected to a dummy load (but it doesn't matter what it's connected to), the input is being fed a sine wave at a high level (not enough to light up the clip LED, though).

@DaN0
i would suggest try this
  1. unplug input 2 signal cable to verify one amp board
  2. if the noise gone,then it is noise coupling from SMPS in experience
  3. if the noise still there, just power one board in your enclosure means un-power other 2 boards
  4. if the noise still there, take off SMPS and one amp board, place to some insulated material like a desktop, repeat test
btw,what is this? resister?

View attachment 415400

1) Using only one module hooked up to the PSU, if I unplug the CH2 header, there is no change in behavior of CH1
3) I'm only using one module currently
4) I tried a different PSU that was physically outside of the amp chassis and there is no change in behavior

Those are wires connecting the TRS sleeve with the XLR pin 1 and then also to the jack's chassis ground. I've tried with and without the connected to jack ground and there's no change.
 
This morning I tried using another PSU (Drok 48V 10A) with only one amp module connected and the behavior is the same



It changes with frequency and input level (it acts like there is a tiny speaker in the amp module itself). Here's a video:


NOTE: in the video, there is only one module connected to the PSU, the output is connected to a dummy load (but it doesn't matter what it's connected to), the input is being fed a sine wave at a high level (not enough to light up the clip LED, though).



1) Using only one module hooked up to the PSU, if I unplug the CH2 header, there is no change in behavior of CH1
3) I'm only using one module currently
4) I tried a different PSU that was physically outside of the amp chassis and there is no change in behavior

Those are wires connecting the TRS sleeve with the XLR pin 1 and then also to the jack's chassis ground. I've tried with and without the connected to jack ground and there's no change.
Oh wow never heard that before. Not what I’m talking about at all
 
NOTE: in the video, there is only one module connected to the PSU, the output is connected to a dummy load (but it doesn't matter what it's connected to), the input is being fed a sine wave at a high level (not enough to light up the clip LED, though).
Well, that is cool! You do not even need speakers any more. ;-)
So it is not the the PSU, but the sound comes from the module and it is input driven. But what part can even make a sound?
My guess is that the output filters produce this, as there is still switching going on even without load, but why is it not dependent on output current? Strange.
Did you try to put your finger on it (literally)?
Maybe sound is from the capacitors as it might be voltage driven (though I do not know how)?
 
Capacitors and coils can "sing". You should be able to modulate the sound when you touch the oscillating component. In this case, if you only feed a signal in one channel, there are three pairs of similar caps and coils I would see as suspect.
 
Has anyone successfully implemented a VU meter with this board without deleterious effects?
I'm at the point of machining the cover and would like to install one on this particular unit.
Thanks all...

Screenshot_20241223-091715.png
 
It changes with frequency and input level (it acts like there is a tiny speaker in the amp module itself). Here's a video:
I have heard this type of noise coming from a smd capacitor.

The culprit was an smd ceramic capacitor in a DC-DC upconverter (installed in a laptop as part of a power supply "repair").

Touching/pressing the capacitor muted the noise.

Unsoldering the capacitor and soldering it with a little more space between it and the board solved the problem.

The high frequency noise was quite audible and annoying.
 
Did you ask 3eAudio for a solution? Any response? If not them, who should know? They say their customer service is first class...
 
I've been chatting with 3e Audio but haven't made any progress as of yet. At this point, the noise is loud enough that it's not going to be usable for me.
 
So what did they say? Please understand, the product working just fine is what you deserve, but if it has problems, that is where customer service is important.
Is 3eAudio helpfull, even after money received? How your case works out is sure interesting to many potential customers...
Since they are selling finished amps now, not any problem can be blamed on the DIYS guys installation, as it was with unfinished modules.
 
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Hi @DaN0

Suggest let's start from here and share me(other very good diyer too) the result for below step:
so far we knew: the amp without input signal cable connect ->OK(no any noise),the noise is only happen during playing some signal,next step is to figure out whether the noise if from source or from the amp board itself.
  1. please verify above(without cable) for all 3 boards
  2. please verify all 3 boards with you initial connection which will generate noise
1/2 step is to confirm the 3 amp boards are consistence with or without issue in different condition.

3. if you have scope or other tools can measure the signal for both input and output,we can easier to see what happen on the amplifier whether the noise is from source or the amp boards itself.
4,if step 3 is not flexible then can you please try to get an audio isolator or cable to see whether the noise still exist.
5.if you can get a phone with 3.5mm output to RCA to the amp then will also work as the phone not connect to any ground(isolated),a pc also work without charge cable connected.

please share some picture or video capture that can fully see your setup clearly,it take some time to figure out but this is some idea make sense to try. thanks!
 
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.

 
@DaN0

looks like i miss understand your previous description, after check with my engineer, now your case is that the noise is only happen with sine-wave(especially 1-3KHz range) input with Dummy load and also need reach a decent power output.
our engineer confirm the noise is from the inductor during high power output and there is a resonant frequency from the inductor itself which due to not full body glued.
any other amp use not full glued inductor has the same behavior, but nothing impact on performance.
so what is your intention to test with 8ohm load instead of a speaker?
 
A solution would be to fill the inductors with low viscosity epoxy glue. This will stop them from singing. Anyway, even as this may be irritating to the customer, it is no serious problem and should not have any influence on the modules performance. The inductor windings are just wrapped a bit too loose around ferrite and additional glueing would have been too expensive. About half a Cent saved in production.
A much more annoying and quite common problem with substandard coils are flat screen TV's. Sometimes they emit a high pitch from the internal SMPS, independend of output volume. That is really annoying, because of the high cost of a service call the TV manufacturer usualy doesn't want to change out the singing power supply.
 
Ah ok, so this level of singing is expected? It's definitely louder than any other amps I've dealt with in the past. Maybe I'll try to glue it myself and see how that goes.

My use case is probably not typical. The amp will be with me in my office in the basement, but it will feed inefficient speakers on the other end of the house. If the glue doesn't quiet it down, I may need to move the amp to another location.
 
About half a Cent saved in production.
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.
 
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