TDA8954TH - XH-M252 board - anyone?

But it is not shipped yet...


How much time it takes usually, if you buy something and if they shipped then how many days it takes to arrive?

I bought this powerful, XH-M252 module from 28. october and today I got it (Estonia), seems pretty nice quality except for some solder joints but yes, output inductors probably is not good and need to replace for better ones.
 
How much time it takes usually, if you buy something and if they shipped then how many days it takes to arrive?

I bought this powerful, XH-M252 module from 28. october and today I got it (Estonia), seems pretty nice quality except for some solder joints but yes, output inductors probably is not good and need to replace for better ones.


What is wrong with the output inductors?
 
What is wrong with the output inductors?

They are very small and I am sure that they may be sendust core or something similar but given that this low prices, definitely this inductors is not good enough. Core outer diameter is somewhere 18mm - 0.7in, this is small.
I think that I bough those: T106-2 MICROMETALS - Ferrite: torique | Long: 11,1mm; Oint: 14,5mm; Oext: 26,9mm; 13,5nH | TME - Composants electroniques
and make new inductors but before I need to do some test without this inductor changes.

Very sure I am that even if this amplifier put out 250W or even more, then this inductor is too small.
 
They are very small and I am sure that they may be sendust core or something similar but given that this low prices, definitely this inductors is not good enough. Core outer diameter is somewhere 18mm - 0.7in, this is small.
I think that I bough those: T106-2 MICROMETALS - Ferrite: torique | Long: 11,1mm; Oint: 14,5mm; Oext: 26,9mm; 13,5nH | TME - Composants electroniques
and make new inductors but before I need to do some test without this inductor changes.

Very sure I am that even if this amplifier put out 250W or even more, then this inductor is too small.

Many thanks for the reply. The chokes look like the small SAGAMI chokes that should be able to handle some 16A. I forgot the spec-promise of many hundred Watts. My amplifier will do 100W max. (SE coupling) so I will try "as is".
Thanks for the link to better chokes.
 
SAGAMI chokes

Ok, you mean this module which located in post #39, yes, they really seems like Sagami 7G inductors, Sagami is good and I am almost lost them.
But I mean this inductors like post #38 - there is toroidal inductors and I have this XH-M252 board where is the same look toroidal inductors. I was bought maybe bad module because I did not do proper preliminary work and virtually I bought the first one what I saw, but loss is marginal ~20€ , coming days show was it worth :)
 
The shipping from China to Bulgaria is 3 to 5 weeks...
And my amp was shipped on 2019-11-17, so we will see when it will arrive...

I got my board today. I tested it with +/-18Vdc not to stress it for a start. It worked right away and the immediate sound impression is good.
As already announced on the sellers site, the rail capacitors are 8x1800uF/35V. While the 4x1800uF for each rail is in the low end for higher power levels, 35V voltage rating is clearly too low for 6-8 Ohm use and a chip that allows up to +/-42.5V supply. I can probably replace them with 50V rated capacitors. Do not use transformers above 2x22Vac before the capacitors are changed. The "valid" transformer range up to 2x28Vac is wrong and will harm your board from 2x24Vac and upwards.
The speaker protection relay is quite small and I would not try 2x210W with such a relay. It would be nice if specs were not uncritically taken from datasheets without giving further consideration to the actual board implementation.
My first impression is a rather well build board, that still needs a few modifications but is much better implemented than the TDA8954 board I previously bought very cheap.
 
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I got my board today. I tested it with +/-18Vdc not to stress it for a start. It worked right away and the immediate sound impression is good.
As already announced on the sellers site, the rail capacitors are 8x1800uF/35V. While the 4x1800uF for each rail is in the low end for higher power levels, 35V voltage rating is clearly too low for 6-8 Ohm use and a chip that allows up to +/-42.5V supply. I can probably replace them with 50V rated capacitors. Do not use transformers above 2x22Vac before the capacitors are changed. The "valid" transformer range up to 2x28Vac is wrong and will harm your board from 2x24Vac and upwards.
The speaker protection relay is quite small and I would not try 2x210W with such a relay. It would be nice if specs were not uncritically taken from datasheets without giving further consideration to the actual board implementation.
My first impression is a rather well build board, that still needs a few modifications but is much better implemented than the TDA8954 board I previously bought very cheap.


A small correction: I increased the voltage to 2x24Vdc. The speaker protection circuit (based on C1237) no longer switched the speakers ON! Back to 2x18Vdc - still no reaction from the speaker protection circuit:mad:.
I have both rail voltages, outputs near 0V (before relay), no heating or other visible reaction. I will have to analyze the board circuit. A bit early a malfunction shows up. I will let you know.
 
The speaker protection circuit is designed with a simple relay that only connects or disconnects the speakers from the amplifier. No amplifier load when the relay disconnects the amplifier. That, I do not find good when a class D amplifier is started up without a load.
I short-circuited the relay contacts such that the speakers are also connected to the amplifier at start-up and shut-down. Then, the amplifier functioned well and all I hear in the speakers during start-up is a small "click". This type of protection circuits with a relay, I find mainly belongs to Class AB amplifiers without integrated diagnostic and protection functions. For this class D amplifier, I will probably disable the protection circuit.
Now the amplifier plays well with +/-24Vdc supply but even when the amplifier funtions well, the relay coil is not activated. I have a slightly high DC offset at one output (around 85mV) so I will try to make a compensation circuit later. 85mV should not influence the protection circuit.
 
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You are right that as an engineer I should investigate and repair the problem. However as a pragmatic, I should realize it is a useless feature anyway and just bypass it. I chose half-way with a quick investigation.

The design values shown in the NEC datasheet are used without further thinking. That means for pin 8, 15K to Vcc and 56K from pin 8 to pin 7. 15K to pin 8 is for 45V positive rail supply. However, as the rail capacitors are rated to only 35V and Fig.6 of the datasheet is disregarded, 15K is a poor choice. With +/-18Vdc supply, I measure 2.8V on pin 8 of the C1237HA and it has to be minimum 3.0V. The Vcc-ON detection is invalid for lower range supply voltages which the TDA8954 can else operate with.
I stopped my investigation here but now you know where to look if also you have problems. I for a start continue with my relay by-pass and the amplifier part itself seems to work well (luckily). Later on, the C1237HA will be removed and perhaps also the relay, if not too much of a hassle.

If anyone is looking for an amplifier board that needs no modification, this board is not it. With some modification, I believe it can be turned into a very well sounding amplifier. If you aim for high power as promised for this board (more hundreds of Watt), I would rather go for an IRS2092 based board as the cooling abilities are better with external power FETs.
 
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Help! X-M252 noise

Hi All,

Taco5000, im very sorry for my poor name choise... :rolleyes:


Nevertheless, i have bought an X-M252 Amplifier, and im getting some horrible noise from it...

I have tried alot, to no avail..

The noise im getting from the amplifier is a 200Hz hum. (This is measured with my phone close to the speaker)

The setup im using is a toroidal transformer (24-0-24), and a pre-amplifier (See below)

NE5532 OP-AMP HIFI Preamp Preamplifier Volume Tone EQ Control Board Module HighQ | eBay

The hum is originating from the amplifier, but it is quite low when only the amp is connected to a speaker.
As soon as i connect an input to the amplifier, the noise/hum gets louder. When the pre-amplifier is connected, to the amp, the noise is at its worst (compared to just RCA connectors directly into the amp). The noise hits its highest, when the volume pot on the pre-amplifier is turned all the way down. When i turn the pre-amp up to half volume, the noise is at it's lowest.

All wires to and from the amplifier & pre-amplifier are twisted to keep out noise (as much as possible).

I have created a DC-Filter to the mains, just before the transformer. This helped a bit on the hum.

It is also worth mentioning that i can hear my transformer hum when i place my ear next to it. It is not that loud though.

Can anyone point me in a direction? I'm all out of ideas of what to test next..

Best regards
 
Hi Dzwer,

Thank you for your swift answer!

I have tried multiple sizes of resistors on the input of the amp. Nothing changes the hum of the amplifier.

Regarding the volume pot, i will give that a go as soon as I get hold of a logarithmic pot. :nod:

I'm i to expect hum from this chip/board combo? or am i just unlucky? (I will maybe guess that it is the layout of components that might influence this??)
 
Yes, please see below:
 

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First, disconnect the preamp and the fan. The little PCB is some kind of dual rail switch mode DC/DC converter? For the fan use entirely separate PSU... If you load a symmetrical PSU with not symmetrical load - there is one reason for hum and noise...
Second, the transformer is with 2 separate secondaries? Are the two voltages the same? Did you connect in the correct order the secondaries?
They have to be connected like this: (+)_(-)-(+)_(-), where + and - are the current phases of the two voltages.
Then connect the two inputs to GND and see what is at the outputs.
The outputs have to be connected to loads! Resistors or loudspekers!
I see also, that you have a DC blocking module before the transformer - it's OK, but see with the oscilloscope what is the shape of the secondary voltages. If needed, use resistor deviders.
And isolate the DC blocking and mains cables, to not touch them by accident!
 
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Thank you for your help with this!

Yes, the preamp is powered by a +-15V switchmode PSU, this is fed from its own 5V psu (5V phone charger). This setup works just fine on other amplifiers! - The fan is also powered directly from the 5V phone charger aswell. (The fan was added yesterday, just to see if it could cool adequate with 5V input - I did not add or remove any noise from the system)

The transformer have two secondary windings, both 24VAC. I see your point in loading with a symmitrical load. But even with two speakers hooked up, (symmetrical load) the hum is still there!

Oh, that is a very good point, with the current phases of the two secondaries.. I must admit that I did not think of this! I would guess i can see the current phases with my o-scope(?).

I presume you mean that I measure the AC/DC voltage on the output terminals with the speaker plugged in?

If there is a voltage difference on the secondaries, do you suggest that I equal them out by using power resistive divider?? I just need to understand you correct!

The DC blocking PCB is taped on the button to avoid accidental short circuits!! - But this is only for testing purposes! I absolutely hate working with exposed mains wires. This DC filter was one of my attempts to remove the hum.