I have created my own Class D amplifier based 2.1 Karaoke Music System using ready to connect modules according to the following diagram to create the music system.



I have used probably three very common modules which many of you may already be familiar with. I am still linking sample Amazon links for these 3 modules, so that it becomes clear.

• Module 1 - FM/BT/Module with display and remote: https://www.amazon.com/BOOMBOOST-Bluetooth-Player-Decoder-Receiver/dp/B08H15KMFM
• Module 2 - IOTAudios PT2399 Microphone Amplifier and Reverberation Module: https://www.amazon.com/XH-M173-Microphone-Amplifier-Karaoke-Reverberation/dp/B09GC9MRLJ
• Module 3 - 2.1 Channel TPA3116 Class D Amplifier Module with BT Audio 50W+50W+100W: https://www.amazon.com/Amplifier-TPA3116D2-Subwoofer-Voltage-Equipment/dp/B08XKJVJGY

TPA3116 Class D Amplifier has a push button cum VC to adjust volume and switch between the built-in BT Audio or AUX IN.

Problem:
When I play music using the TPA3116 Class D Amplifier module's built-in BT Audio, the audio quality is fantastic with very satisfying bass from the subwoofer. But when I switch to AUX IN, it effectively plays the audio from the FM/BT/AUX player via the PT2399 Module mixed with the Microphone inputs and the audio quality drops. I seem to hear an audio with very low bass and high treble.

Question:
I know how to use a high pass filter/ subwoofer amplifier standalonely to drive a Subwoofer for high bass. I can also build a simplified high pass filter with a Capacitor and a Resistor. But I don't know where it fits in the circuit to make sure the audio from the PT2399 board only gets the boost and not the built-in BT Audio of the Class D Amplifier module. I am not sure low pass filter is applicable at the output of which one among the first two modules. So, can someone please help me figure out if I can put a cap + resistor based high pass filter in each of the left and right audio inputs between Module 1 and Module 2 OR between Module 2 and Module 3 to get the bass boost I'm looking for? Is there any simple hack I can do within the PT2399 module to boost the bass of the output without sacrificing the gain?

 

Hello,

How does it sound when you connect the mp3 module to the amplifier module?
If the basses are ok, then the karaoke module messes up the basses.

Bertus

 

You already have adequate Bass,
so You do not need any type of EQ Circuit.

A Filter will not fix the problem.

You have an incompatibility problem between Modules, and/or, an Impedance mismatch.
.
.
.

 

Hello,

How does it sound when you connect the mp3 module to the amplifier module?
If the basses are ok, then the karaoke module messes up the basses.

Bertus

I tried this, this doesn't sound correct either. The bass is very low if I directly connect the MP3 Player directly to the amplifier as well. So, seems the problem is with the origin of the music tracks from the MP3/BT module only. Any solution for this?

 

You already have adequate Bass,
so You do not need any type of EQ Circuit.

A Filter will not fix the problem.

You have an incompatibility problem between Modules, and/or, an Impedance mismatch.
.
.
.

Agreed, the amplifier is already capable of generating adequate bass when playing from it's onboard BT Module. I really wanted to give these 3 modules in combination a try. So seems, that's what making things odd. Is there anything sir I can try to fix the Impedance mismatch?

 

Any Chip or completed-Module that does not come with a
comprehensive Spec-Sheet and Operators-Manual is most likely Chinese-Junk,
and You "might" get what You pay for, but there's no guarantees at all.

No one can tell You what the solution to your problems are
with these Modules unless they are very well versed in the particular Chips used
in these various Modules and have worked-out any bugs found in the Circuitry of these particular Boards.

Don't give-up,
there's a huge amount of collective experience in these Forums,
and somebody may be able to give You some guidance as to what to check, and what to look for.

Karaoke Circuits are infamous for taking a Stereo-Signal and removing
any Mono Content from the recording,
this is how they "remove" the Vocals, which are mostly, or completely, in Mono,
this, of course, also removes all of the Bass-Content, which is also always in Mono.

So your entire problem may be due to the fact that
You are using a product that has the word "Karaoke" on it.

Do not use any product that says "Karaoke" on it, unless that's what You intend to use it for.
.
.
.

 

I believe that there is currently another thread that includes a lot of discussion on that exact topic of removing the voice portion of a recording. That may provide more insight, although it is very difficult to amplify what is not present.

 

I think something like this, wired between your PT2399 and TPA3116, would give tonal control meeting your needs.
The seller gives very little in terms of signal levels or dB gain/attenuation at high/mid/bass – but it’s fairly cheap.

https://www.ebay.co.uk/itm/13465015...rand=Unbranded&_trksid=p3650466.c101465.m3507

 

If the bass is removed by the "Karaoke" circuit as it apparently is, then the bass could be extracted by using a low-pass filter from the original stereo signal going into the PT2399 module.

This LP subwoofer control board could extract the bass signal with adjustments for frequency rolloff and gain, which then is summed it into the amp input, bypassing the Karaoke unit.
Likely could be summed with a few 10kΩ resistors (two per channel) at the input to the amp board.

Sound feasible?

 

Any Chip or completed-Module that does not come with a
comprehensive Spec-Sheet and Operators-Manual is most likely Chinese-Junk,
and You "might" get what You pay for, but there's no guarantees at all.

No one can tell You what the solution to your problems are
with these Modules unless they are very well versed in the particular Chips used
in these various Modules and have worked-out any bugs found in the Circuitry of these particular Boards.

Don't give-up,
there's a huge amount of collective experience in these Forums,
and somebody may be able to give You some guidance as to what to check, and what to look for.

Karaoke Circuits are infamous for taking a Stereo-Signal and removing
any Mono Content from the recording,
this is how they "remove" the Vocals, which are mostly, or completely, in Mono,
this, of course, also removes all of the Bass-Content, which is also always in Mono.

So your entire problem may be due to the fact that
You are using a product that has the word "Karaoke" on it.

Do not use any product that says "Karaoke" on it, unless that's what You intend to use it for.
.
.
.

Yes, unfortunately these are Chinese modules with very less specs but have huge popularity here in India. I am sorry if I misled using the term "Karaoke", these modules are called Karaoke mixer, because it expects that the AUX IN will likely be a music track (Karaoke) played from an MP3 player and then the board mixes the Mic inputs to the track to produce music+vocal output. So, they call it "Karaoke Mixer" here. There is nothing on these board to "remove" vocals from AUX IN audio track. You can simply not plug any MIC to it and use it just as a normal music player (with vocals). So, it basically outputs AUX IN Audio + Mic Audio, nothing suppressed (except the bass )

 

I believe that there is currently another thread that includes a lot of discussion on that exact topic of removing the voice portion of a recording. That may provide more insight, although it is very difficult to amplify what is not present.

Sorry for misleading with the term "karaoke", it doesn't remove vocals from input audio. It just adds vocal audio from the 2 Mic inputs to the audio input, to produce a mixed audio output.

 

If the bass is removed by the "Karaoke" circuit as it apparently is, then the bass could be extracted by using a low-pass filter from the original stereo signal going into the PT2399 module.

This LP subwoofer control board could extract the bass signal with adjustments for frequency rolloff and gain, which then is summed it into the amp input, bypassing the Karaoke unit.
Likely could be summed with a few 10kΩ resistors (two per channel) at the input to the amp board.

Sound feasible?

That's an interesting solution. I didn't know if it can be used this way. Let me give it a try! If the PT2399 board is the culprit, then this should work very well. One problem which I noticed in the board you have referred it - it converts the Stereo input to mono output. That will be a drawback. The stereo to stereo ones are usually equipped with onboard amplifiers as well, which will be a problem. But let me find.

 

Have you tried bypassing the karaoke module and connecting the MP3 module output directly to the amp?

 

One problem which I noticed in the board you have referred it - it converts the Stereo input to mono output. That will be a drawback.

Don't see why.
The mono bass output is just equally summed into the stereo signal from the karaoke unit.
It won't affect the stereo signal.

 

Don't see why.
The mono bass output is just equally summed into the stereo signal from the karaoke unit.
It won't affect the stereo signal.

Got it. Let me give it a try!

 

Have you tried bypassing the karaoke module and connecting the MP3 module output directly to the amp?

Yes. See this

 

Yes. See this

Yes, sorry I missed that.

 

Yes, sorry I missed that.

You wanted me to try something like this, right?

 

You wanted me to try something like this, right?

View attachment 332220

Close.
You need to add a resistor in series with each of the PT2399 outputs before it connects to the amp to get proper summing of the signals.
(This will reduce the signal level by 1/2 or -3dB, but that should be easily compensated by just increasing the volume control).

 

Close.
You need to add a resistor in series with each of the PT2399 outputs before it connects to the amp to get proper summing of the signals.
(This will reduce the signal level by 1/2 or -3dB, but that should be easily compensated by just increasing the volume control).

Yes, got it!
One quick question though. The modules takes couple of days to arrive. Can I try a passive low pass filter just to try out in place of the NE5532 module?