tpa3116 coils change

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baszek

Member
2018-08-26 12:52 pm
Hi,
I was watching some cheap class D reviews on youtube and it was said that chinese coils are always bottlenecks in terms of quality.
Wchich coils can you recommend for my tpa3116:
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What coils value should be used ? I was reading that it depends on speakers impedance (I have 8 ohm speakers).
I am not sure if it will be easy to unsolder that old coils :)
I saw that allo tpa3116 is using some WURTH ELEKTRONIK coils (Volt AMP). I heard also that Sagami & Coilcraft are good coils.

What do you think about coils change ? is it worth it ?
 
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Yes, the coil values are in the datasheet (10µH). Make sure you have types that don't saturate early, the large-ish coils in your images should be OK. I have seen Chinese implementations for this chip that either have too small inductors or even no inductors at all (cheap cheap!).


Tjerk
 
You definitely do NOT want to do that - the -26 (yellow/white) and -52 (yellow/blue) materials used in those are NOT suited for the ~400kHz switching frequencies of these class-D amp chips, and they'll just get hot as hell (huge core losses).

I couldn't see the 3 images, but in any instance can't you get some unused PC SMPS, for example, and rewind the toroids? It is an easy task.
 
If you play music with some average speakers, you will only use a few watt´s, even when it get´s quite loud. For normal use these coils are just fine. There is not much sense in transplanting 25$ of coils into a 7$ amp. Better get an amp that can give you more power, like an TDA7498e for about 20$. It will have much bigger coils and these get saturated later. Sound is just as good as the 3116, just stronger (bass).

Another option is a high pass for the 3116 and a low pass and sub with a powerful amp for the rest.
This way the 3116 will go as loud as you want, without ever touching the coils limits.
There is not much "sound quality" to be gained only by coils, as long as the existing ones are not driven too far.
Better look at the power supply and, maybe, add some good, fast caps to the board.
 

baszek

Member
2018-08-26 12:52 pm
If you play music with some average speakers, you will only use a few watt´s, even when it get´s quite loud. For normal use these coils are just fine. There is not much sense in transplanting 25$ of coils into a 7$ amp. Better get an amp that can give you more power, like an TDA7498e for about 20$. It will have much bigger coils and these get saturated later. Sound is just as good as the 3116, just stronger (bass).

Another option is a high pass for the 3116 and a low pass and sub with a powerful amp for the rest.
This way the 3116 will go as loud as you want, without ever touching the coils limits.
There is not much "sound quality" to be gained only by coils, as long as the existing ones are not driven too far.
Better look at the power supply and, maybe, add some good, fast caps to the board.
Maybe you are right :) I have also somewhere not tested tda7942 amp with 24V power supply. I am searching also from time to time for a good deal for ICEpower 50asx2.
 
Hi Baszek,

For me there are two very important qualities of good filter chokes:

1) They must have a current rating such that they at no moment saturate with the current flowing through the chokes (substantially the speaker current).

2) They must have low losses at the carrier frequency and a permeability at the carrier frequency such that the inductance of the chokes is as you assume.

Ad 1). This is the typical problem because good chokes are expensive and physically big. Many boards use chokes that may saturate at full volume and with low impedance speakers. If they saturate, the inductance very rapidly decreases and the loading of the class D chip is heavily increased (in particular for the carrier), the current limiter may be invoked, the filter effect is heavily reduced etc. In short, the performance is seriously affected.

Ad 2). Some ferrite materials are not suited to operate as high as 600KHz and if you try, the inductance (at 400-600KHz) you obtain is much lower than what you expect from calculations and measurements at lower frequencies. The filter effect is reduced, the core losses become high and the chokes heat up, the class D chip heats up as well in order to supply the increased energy to the chokes etc. Again an important reduction of performance. It is more rare that the chokes initially used are not able to work at the carrier frequency. It is more an issue if you buy unspecified chokes yourself to replace the original chokes. I had some bad experiences myself.

If the chokes comply with both 1) and 2) above, the class D amplifier should work well (with respect to the chokes at least). Then the difficult question: among the many good looking but expensive chokes, can you hear a clear difference and which are best. Honestly, some of the forum members like Chris, The Doctor, voltvide, Think and Turbowatch2 have far more experience than I. You really have to try the different chokes to know if you can hear a difference.

My last comment; I would only invest in really good chokes if it was for one of the best class D chips. For me, the TPA325x may be worth really good chokes, perhaps also the TDA8932 on a good board.
TPA3116/18 is really value for money and Allo.com has made a version with TPA3118 and high quality chokes that should sound really good. Personally I would not put too much money in a TPA3116/18 amplifier.
 
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