Strange thing happened yesterday.
I stopped bothering with TPA32XX about year ago due to constant issues with amplifier noise floor. It was not acceptable, I heard it 2m from speakers. I started working on my class ab amp, which finished with great success (no noise). My friend asked me if I can make him an amplifier as he got older Dynaudio speakers, so I just grabbed my TPA3251 amp, went to his place (60km away), hooked everything up and I was shocked, there was no noise. It was hard to evaluate sound quality as the source was only a TV, but there was no noise.
What do you guys think about it?
I stopped bothering with TPA32XX about year ago due to constant issues with amplifier noise floor. It was not acceptable, I heard it 2m from speakers. I started working on my class ab amp, which finished with great success (no noise). My friend asked me if I can make him an amplifier as he got older Dynaudio speakers, so I just grabbed my TPA3251 amp, went to his place (60km away), hooked everything up and I was shocked, there was no noise. It was hard to evaluate sound quality as the source was only a TV, but there was no noise.
What do you guys think about it?
There is very little as difficult as telling what went wrong at an earlier moment in time where most details are probably forgotten. Unless it was an evident mistake of course.
Noise is a trivial phenomena with a vast number of reasons. Type of noise? Which elements were involved? How where the elements connected? Could there have been a source of radiation that disturbed the system? etc.
Most likely you overlooked a small "failure" (inconvenience) in the system at that time.
Now, make sure it really works well and be happy that you need not bother with noise problems anymore.
Well, if I tell you the details, it would be even harder.
Amplifier is in case from Modushop galaxy series, power supply is meanwell hrp-150-36. Inputs shorted.
At my home, connected to old Canton LE-103 loudspeaker I heard noise from distance of 2m. Its pure white noise (maybe pink, hard to tell by ear). In the past I also tried different power supplies like meanwell LRS-150-36 and regulated bench power supply. All with the same result = noise
At my friends home, connected to Dynaudio Excite floorstanders, there was no noise.
I tested the amp at home, then next day took it to my friends house.
There is difference in sensitivity at some frequencies between these loudspeakers. The Canton have huge peak from 8kHz up to 15kHz, its about 10dB. That might make noise more evident.
You are right, knowing the details makes it even more difficult:
Just to summarize:
With shorted inputs, Canton speakers, Meanwell SMPS or regulated bench supply - > NOISE.
The day after;
TV as source, Dynaudio (good stuff!) speakers, Meanwell SMPS (I assume?) -> NO NOISE.
Strange that you do not hear at least some noise in the Dynaudio speakers.
Would you have some other simple speakers to test the amplifier at home (inputs shorted)?
Last edited:
I mentioned the TV just for the lack sound quality evaluation. In both cases inputs were shorted. The TV itself was quite noisy.
Last edited:
OK, I see two theoretically possible reasons for the noise:
1) As you probably already know, a class D amplifier output filter does not fully remove the carrier frequency but leaves typically more volts at the output. The cables, speaker cross-over and the inertia of the driver should remove any sign of the carrier frequency. A theoretical possibility is that the carrier frequency makes the Canton cross-over or driver generate audible sub-harmonics of the carrier frequency. This is why I suggest test with two other, eventually very simple, speakers.
2) When you test for noise, the amplifier is running idle with minimum loading of the power supply. An SMPS with very low loading may generate audible frequencies due to its idle control method. If so, the Meanwell should be a problem in both cases but not the bench supply.
Gonna check that, but now I have to solder new amplifier, since the only one I had is now at the friends place.
Thanks for suggestion
Spec sheet says just few dBs. I know that Canton has huge 10dB peak at high frequencies, but I don't expect it to make a huge difference
Hi amigo,
I started my new DIY project. I just received the "non public" TPA3255 Zero Zone board that I am going to use for my test.
At first view, the board is really well made. It's using Nover Audio Grade and some Nichicon capacitors. I am going to use a Toroidal PSU 28V / 300W made in Poland for this DIY project and also got a great idea for the case (you will see later)
So that you can get an idea about the board itself, I found it smells quality :
PCB Size： 141*188mm
Height about 40mm
I started my new DIY project. I just received the "non public" TPA3255 Zero Zone board that I am going to use for my test.
At first view, the board is really well made. It's using Nover Audio Grade and some Nichicon capacitors. I am going to use a Toroidal PSU 28V / 300W made in Poland for this DIY project and also got a great idea for the case (you will see later)
So that you can get an idea about the board itself, I found it smells quality :
PCB Size： 141*188mm
Height about 40mm
Last edited:
