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Class D Switching Power Amplifiers and Power D/A conversion

TPA3116D2 Amp
TPA3116D2 Amp
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Old 27th August 2020, 10:20 PM   #11581
Hofmann is offline Hofmann  Netherlands
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Join Date: Apr 2018
It is not a tube buffer I need. The amp delivers plenty of power for my application when I tested it with a phone as music source. If I would need a buffered preamp I'd opt for a NE5532 in this case.

Right now I am just looking for an explanation why this DC offset appears when the volume pot is adjusted. I will try remove the volume pot and wire it before the AUX input, see if that makes a difference. This way the bluetooth function will not be volume controlled by the pot, but this is not a big issue.
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Old 27th August 2020, 10:43 PM   #11582
Trileru is online now Trileru  Romania
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Quote:
Originally Posted by gasolin75 View Post
Did you just read a $31 wonder and thought something that cheap can't make a difference or did you actually read a few pages ?

I made my own 6n6p design and know what is involved. It can add some distortion to your sound and you might like that kind of thing. But for sure it isn't running in a linear region at 12V supply. You might use a dc/dc boost converter but that adds extra noise.

Here's the chart showing the working area of the tube:
Click the image to open in full size.


As you see, for let's say a -2V bias you need about 100V on the plate. I don't need to read what others are saying if the power supply is 12V. It might seem to sound "tubey" but it's a wrong implementation of the tube. As I said, I don't want to be a downer and I understand people defend their choices.
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Old 27th August 2020, 11:18 PM   #11583
Trileru is online now Trileru  Romania
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This is a nice implementation of tubes for buffer/pre. 290V on the plate, 22mA per triode. Running a bit hot but the 6n6p can handle it. CCS with DN2540.

You can play with the sim, has low distortion figures. It draws around 100mA at 290V DC.


Click the image to open in full size.
Attached Files
File Type: zip 6n6p.zip (14.5 KB, 1 views)
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Old 28th August 2020, 12:41 AM   #11584
silvervest is offline silvervest  Australia
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Join Date: Mar 2019
Location: Sydney
Quote:
Originally Posted by Kyrk View Post
This is a popular tpa3116d2 2.1 Amp. I ve out it in a anodized aluminum box with plastic pot caps and I get noise when changing the volume. I only get the noise when there is signal going through, if it doesn't its silent. At first I thought it was the common cracking noise pots make when they are dirty but its relative new and as I said it only does it when it's playing music. The psu is a generic laptop brick. I don't understand why it does this is it a ground problem? In the pictures you can see that the pots touch the frame which does not have isolation feet and it sits on a wooden table
While this is a popular module, the components are cheap and often broken/faulty. Those 50k pots are dirty from the factory and need to be replaced, and most of the filter caps on the output will be out of spec.

I've made a video covering the previous revision (without BT) but nearly the same design showing how poor quality they are, and I'm in the process of trying to figure out why the L/R channel have a high-pass filter removing all low frequency, regardless of the "ALL-FREQ/NORMAL" switch position that seems to do nothing.
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Old 28th August 2020, 01:16 AM   #11585
walpha is offline walpha
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Join Date: Jul 2020
from my board exists a dual TPA3116 version, that has 15mH coils and much bigger caps on output filter (at least the physical size is bigger)
are these just bigger because of 15mH coils?

red one the "big" output caps
green one some "smaller" input caps i replaced by 1f foil caps
blue one the output caps on my board.
zk1002T_a.jpg

how do i know (how does it sound) when the output caps are to "small"?

im using 6 ohm speakers (if that matters) and the board has 10mH coils

the TI datasheet says 0.68f for 10mH coils

and just in case they are to small, could i just add some 0.33f foil caps (which could fit there) in parallel to increase the capacity a bit?

Quote:
Originally Posted by Trileru View Post
Since you have two channels, you need to add two capacitors, one for each channel negative input to ground (for tpa3116 chip).
ok and it is impotant to not shortcut the l/r - before the capacitor(s)?

Quote:
But I would remove the heatsink (twist it sideways so you don't risk ripping the chip off the pcb). Then check if there's the two capacitors going to ground, from left/right negative inputs. They might be hidden under the heatsink.
this is the board without heatsink
board.jpg

i thinc C4/C5 (right) and C7/C8 (left) are the one.
Not measured yet, just from pic and looking at the traces.

Quote:
Originally Posted by Hofmann View Post
Yes, only I have the ZK-1002 version, which is dual chip 2x 100w.
The video shows exactly the issue I have. I wonder what could could be the cause and how it can be avoided.
My plan is to add a volume pot before the aux in, and completely forget about the bluetooth. But if there is a better solution I would like to know.
there are many zk versions (some have not even coils on output).
There is ZK1002L, ZK1002, ZK1002C and ZK1002T and same goes for single TP3116 ZK502(" "/L/C/T)
I think that is not related to bluetooth. I have the ZK-502T and i can turn the volume pot without any noise or speaker "movement" but i think that is related to the 2 opamps i have onboard which are missing on the ZK without bass/treble pots

Last edited by walpha; 28th August 2020 at 01:29 AM.
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Old 28th August 2020, 01:56 AM   #11586
Trileru is online now Trileru  Romania
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You need to measure both left/right channels traces to each cap, and be sure what cap is what channel, and if on positive or negative inputs. Space seems pretty tight there and you risk shorting stuff out to the heatsink. Hope you can pull it off if you want to replace them.

Input capacitors make a high pass filter with the input impedance. For 20db gain the tpa3116 chip has a 60Kohm input impedance. 1uF should be fine to not loose bass.

Output inductors + capacitors make a low pass filter, and if the values are not right, you can loose some of the highs.

Here's a simulation for a 6 ohm speaker with 10uH and 15uH inductors. Variable capacitance. Lower right you can see the best value for the most linear response. I put the cursor on the most linear trace (value for output capacitor).

10uH inductors is around 674nF so 680nF value is perfect.
Click the image to open in full size.


For 15uH inductors you need around 1uF output capacitance:


20Click the image to open in full size.


You can tie the negative input capacitors to ground in the same place, on the ground side. But on the input side left/right need to not be tied together.
You cannot tell the value of a smd capacitor with no markings on it. For this you either buy known value capacitors, either you get a measuring tool to test the installed ones. You need to desolder them and then measure each one individually.

Usually it's easier to just replace them with known value ones, especially if you want to upgrade their quality. But in your particular situation, if all 4 input caps are under that heatsink, it means you need to install wires so you're able to add in larger film ones. That might be tricky under that heatsink. Output caps must have a voltage rating of at least 25V. Do an ohm's law calculation for your 6 ohms speakers and max output power, add some 30% extra on the voltage and you have your rating. Input caps are not going to see much, but make them 16V rating just to be sure.

Also for reference the simulation has 8 steps with values from 470nF to 1.3uF or so, to get an idea on how it varies.



I also made a sim for 33uH output inductors since many of the cheaper boards (including the ones I got) come with 33uH inductors. They really eat into your highs. 1.3uF is the highest trace and 470nF is the lowest one. So 33uH + 680nF on a 8ohm speaker is not so great. On lower impedance speakers it's even worse.


Click the image to open in full size.

Last edited by Trileru; 28th August 2020 at 02:21 AM.
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Old 28th August 2020, 08:29 AM   #11587
gasolin75 is offline gasolin75  Denmark
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New Fosi audio BT10A recieved
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Old 28th August 2020, 10:00 AM   #11588
Yatsushiro is offline Yatsushiro  France
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Quote:
Originally Posted by gasolin75 View Post
New Fosi audio BT10A recieved
I seem to recall you saying that you didn't want an amp with tone controls and/or bluetooth?

Shall you pay for this one?
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Old 28th August 2020, 10:14 AM   #11589
zek is offline zek
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... and didn't want an amp with low power ...
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Old 28th August 2020, 10:33 AM   #11590
gasolin75 is offline gasolin75  Denmark
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Quote:
Originally Posted by Yatsushiro View Post
I seem to recall you saying that you didn't want an amp with tone controls and/or bluetooth?

Shall you pay for this one?
I normally don't use tonecontrols or altleast don't feel the need to have it, if the amp doesn't have tone controls.

There is always this freedom of not having tonecontrols and not beeing able to find the sweetspot for it, where it just sounds perfect, often 12 o'clock isn't always 0 db

Bluetooth often are known to add more noise and only nice to have if you have a big house (5-10 meter range no problem).

I din't find any fosi amp without bluetooth and tonecontrol for less money, also it should be 100% noise free,no noise from the volume,no pop noise when you turn the amp on and off and it seem to have good channel imbalance (volume start above 9 o'clock, might be therefor it's doesn't seem to suffer for channel imbalance as much as some class d mini amps have)

The amp is as good as you can expect for the money it cost

I didn't found this amp in any european store and don't know if it parks when connetcing the power and how noisy it is (pop noise,volume noise?)
V1 Fosi Audio 2 Channel Stereo Audio Hi-Fi Amplifier Receiver Small Mi
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