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Class D Switching Power Amplifiers and Power D/A conversion

TPA3116 D2 mono amplifier as a stereo system?
TPA3116 D2 mono amplifier as a stereo system?
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Old 13th September 2019, 04:46 PM   #211
grahamgraham is offline grahamgraham  United Kingdom
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Quote:
Originally Posted by chermann View Post
Hi Graham

The problem with big cap banks with a smps (brick) is that it could be that your PSU run into the over current protection mode because of the high current flow for the cap bank -during switch on. additionally i measure that a big cap bank can have a overvoltage = overswing because of its regulation.

regulation:
the smps try to have the recommenden voltage up to its max power - so the current is regulated by the smps. the cap bank is a big storage of energy. if the amp (music) request a big current then the caps at the amp board must deliver this. the cap bank load the caps at the amp board + the smps load the cap bank. this current demand force the smps to regulate as fast as designed the voltag/current/ and this you can see at the scope. eg. about 3-6V overshoot.

i learnt that the design of the smps is mandatory for your needed power and for the used impedance of your speakers. e.g. 8R more voltage - but for TPA3116 its max is 24V. tpa3118 26V , TDA7492 26V
so your 20V 6,7A psu is fits to your amps.

my proposal is to solder good caps at the amp board = low ESR/ESL as big as possible = 2200 -3300F 35V and try during loud music if the bass is stable enough. then you can try as "cap bank" additionally a 2200 - 4700F /35V.

chris
Cheers man, that is what I will do then!

As far as running any 2 of this type of amp board from 1 PSU goes, its osc. sync essential? I can't find the thread where I guy used a diode.

Can a TPA and a TDA be synced?
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Old 14th September 2019, 11:11 AM   #212
FauxFrench is online now FauxFrench  France
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Hi Graham,

Good advice from Chris.

To your question, can a TPA and a TDA be synchronized to one another?, the reply is that it is not foreseen but perhaps possible.
The heterodyne effect typically relates to frequencies that close to one another. A TPA3118 operates at 400KHz and upwards. A TDA7492 running on internal oscillator operates at 310KHz. The difference in operational frequency is so large that the heterodyne frequency should be no bother. Therefore, the possibility of synchronization of the two is more theoretical.
A TDA7492 can operate up to 400KHz with an external clock. The TPA can generate a clock for 400KHz operation. So, in theory you can let the TPA be master and the TDA be slave at 400KHz. But, it requires that the synchronization signal, often a clock signal at double the frequency of the operational frequency, is suitable for the TDA7492 and the clock signal level is right. You can try but you will hardly notice an improvement even if you succeed.
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Old 21st September 2019, 02:03 PM   #213
erikthegreek is offline erikthegreek
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Quote:
Originally Posted by FauxFrench View Post
You can connect the 4K7 directly on the volume potentiometer:
With the volume potentiometer axis (the one that is turned) pointing towards you and the three potentiometer terminals pointing downwards, you connect the 4K7 between the left-most terminal and the middle terminal. The middle terminal is actually the potentiometer output.
I'd need to dismantle pretty much the whole setup to get the boards out in order to connect resistors to the volume potentiometers. Instead, will the same effect be achieved if I connect the resistors at the signal inputs, since I can access these without any fuss. If this solves the issue I have, I can then remove the boards and solder the resistors in at the potentiometers.
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Old 21st September 2019, 04:06 PM   #214
FauxFrench is online now FauxFrench  France
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Hi Erik,
I understand that the volume potentiometer(s) are mounted on the amplifier board(s). If you connect the resistors before the potentiometer, you lower the impedance for the source but for the TPA3116 input it changes very little.
Could you please make me a couple of photos showing access to the potentiometers?
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Old 21st September 2019, 04:51 PM   #215
erikthegreek is offline erikthegreek
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Quote:
Originally Posted by FauxFrench View Post
Hi Erik,
I understand that the volume potentiometer(s) are mounted on the amplifier board(s). If you connect the resistors before the potentiometer, you lower the impedance for the source but for the TPA3116 input it changes very little.
Could you please make me a couple of photos showing access to the potentiometers?
Sure, I'll take the boards out and post some photos.
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Old 21st September 2019, 05:23 PM   #216
erikthegreek is offline erikthegreek
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The mono board - from rear of the board, the solder points for the potentiometer are the 3 points that form a triangle:

https://www.diyaudio.com/forums/atta...1&d=1569082704

https://www.diyaudio.com/forums/atta...1&d=1569082704

and the stereo board:

https://www.diyaudio.com/forums/atta...1&d=1569082882

https://www.diyaudio.com/forums/atta...1&d=1569082882
Attached Images
File Type: jpg IMG_1662.jpg (595.8 KB, 107 views)
File Type: jpg IMG_1667.jpg (524.4 KB, 108 views)
File Type: jpg IMG_1663.jpg (606.6 KB, 103 views)
File Type: jpg IMG_1664.jpg (731.5 KB, 101 views)
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Old 21st September 2019, 10:00 PM   #217
FauxFrench is online now FauxFrench  France
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Quote:
Originally Posted by erikthegreek View Post
The mono board - from rear of the board, the solder points for the potentiometer are the 3 points that form a triangle:

https://www.diyaudio.com/forums/atta...m-img_1662-jpg

https://www.diyaudio.com/forums/atta...m-img_1667-jpg

and the stereo board:

https://www.diyaudio.com/forums/atta...m-img_1663-jpg

https://www.diyaudio.com/forums/atta...m-img_1664-jpg

Many thanks Erik,

As I see the rear of the boards, it leaves the possibility to mount the 4K7 resistors on the rear side. Am I right?

You said it was quite a job to get access to the boards, are they normally inside active speaker cabinets (the white background)? I went a bit back in the thread history but could not find evidence of your construction.
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Old 22nd September 2019, 06:31 AM   #218
erikthegreek is offline erikthegreek
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I think I gave you the wrong impression - it's not a big problem to access the boards, they are mounted in a simple enclosure, on stand-offs. To add resistors to the potentiometers will entail me removing the boards entirely from the enclosure, so my alternative suggestion was to connect resistors at the easily accessible signal inputs, as a test to check whether this would cure the noise, and if so, I would then proceed to remove the boards and solder the resistors in place on the potentiometers. This was my attempt at a 'quick fix' to test what may work.

You have since explained to me that connecting resistors at the signal inputs will not have the same effect as connecting at the potentiometer outputs, so I am happy to remove the boards and solder the resistors to the potentiometer outputs on the back of the boards, having been guided by yourself as to connection points.
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Old 22nd September 2019, 01:49 PM   #219
FauxFrench is online now FauxFrench  France
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Quote:
Originally Posted by erikthegreek View Post
I think I gave you the wrong impression - it's not a big problem to access the boards, they are mounted in a simple enclosure, on stand-offs. To add resistors to the potentiometers will entail me removing the boards entirely from the enclosure, so my alternative suggestion was to connect resistors at the easily accessible signal inputs, as a test to check whether this would cure the noise, and if so, I would then proceed to remove the boards and solder the resistors in place on the potentiometers. This was my attempt at a 'quick fix' to test what may work.

You have since explained to me that connecting resistors at the signal inputs will not have the same effect as connecting at the potentiometer outputs, so I am happy to remove the boards and solder the resistors to the potentiometer outputs on the back of the boards, having been guided by yourself as to connection points.
Hi Erik,

I checked on my own TPA3116 mono-board. The small trim-potentiometer used as volume control on that board also increase the volume when you turn clock-wise. For that board and looking at the rear side, the 4K7 resistor has to connect the lower pad/pot.terminal (furthest away from the edge) to the pad/pot.terminal to the right (direction of the power supply terminals).

For the stereo board and as you show the rear side, the pad/pot.terminals to the left have to be connected with two 4K7 resistors to the pad/pot.terminals in the middle. One resistor pointing upwards and one downwards.

Good luck!
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Old 22nd September 2019, 03:25 PM   #220
erikthegreek is offline erikthegreek
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Thank you FF, I should get time in the next couple of days to do this mod, then I will post the result.
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