Low power audio circuit design

Thread Starter

Newtopprojects

Joined Mar 19, 2021
8
We have designed a low power audio circuit with TS472 and PAM8304D. We took the reference from their datasheets, connected all components, powered it on, and verified all components had voltage. It did not work :-(

Can some senior members please take a look and shed some light? Thank you,

audio circuit - TS472 - 20210302.jpg
 

ericgibbs

Joined Jan 29, 2010
18,766
hi Ntp,
Welcome to AAC.
Using a scope did you verify exactly where on the circuit the test signal was interrupted.?
Try injecting a low level test signal into the C12/13 and or C14/16. [ you may have to lift off one end of C12/16]
That will check the amp stage, lets know your results.

I have used the PAM8303 Audio amp without any problem

E
 

Thread Starter

Newtopprojects

Joined Mar 19, 2021
8
hi Ntp,
Welcome to AAC.
Using a scope did you verify exactly where on the circuit the test signal was interrupted.?
Try injecting a low level test signal into the C12/13 and or C14/16. [ you may have to lift off one end of C12/16]
That will check the amp stage, lets know your results.

I have used the PAM8303 Audio amp without any problem

E
We need a mono audio circuit. We checked the PAM8303 first but their website said it's not recommended for new design. That's why we switched to PAM8304, which is stereo. We don't have many needed equipment yet. So we only checked the voltage at each pin. But not sound was produced at all. We will try to test the voltage changes at each pin along the way while supply an audio input.
Thank you for your advice.
 

Audioguru again

Joined Oct 21, 2019
6,673
On the other website forum it was asked if the mono PAM8304 has one of its bridged outputs connected to the speaker and wrongly had the other speaker wire connected to ground (thinking wrongly it is a stereo amplifier).
 

Thread Starter

Newtopprojects

Joined Mar 19, 2021
8
On the other website forum it was asked if the mono PAM8304 has one of its bridged outputs connected to the speaker and wrongly had the other speaker wire connected to ground (thinking wrongly it is a stereo amplifier).
A PAM8403 was an old mono amplifier. It is obsolete and not available.
A PAM8304 is a stereo amplifier that is also obsolete but is still available.
Your circuit has many parts that are not needed:
Thank you so much for your advice again. Diodes website does not say PAM8304 is discontinued. That's why we use it. If its product life is ending, can you please recommend another mono alternative? Thank you,
 

Audioguru again

Joined Oct 21, 2019
6,673
I also got my numbers mixed up.
The PAM8304A is a mono amplifier. Digikey has 1530 of them in an 8msop package.
The PAM8403 is a stereo amplifier. Digikey has 25,000 of them in a 16msop package. 3 other packages are obsolete.

Do you understand that the PAM8304A mono output is bridged with the speaker directly connected to its two bridged output pins?
 

Thread Starter

Newtopprojects

Joined Mar 19, 2021
8
I also got my numbers mixed up.
The PAM8304A is a mono amplifier. Digikey has 1530 of them in an 8msop package.
The PAM8403 is a stereo amplifier. Digikey has 25,000 of them in a 16msop package. 3 other packages are obsolete.

Do you understand that the PAM8304A mono output is bridged with the speaker directly connected to its two bridged output pins?
I also got my numbers mixed up.
The PAM8304A is a mono amplifier. Digikey has 1530 of them in an 8msop package.
The PAM8403 is a stereo amplifier. Digikey has 25,000 of them in a 16msop package. 3 other packages are obsolete.

Do you understand that the PAM8304A mono output is bridged with the speaker directly connected to its two bridged output pins?
Not really. What we have is PAM8304. Does PAM8304A mean different packaging like ASR? Can you please advise if the attached PAM8304 circuit might work? Thank you!
 

Attachments

Audioguru again

Joined Oct 21, 2019
6,673
Your PAM8304 has no speaker connected so it will not work.
We want to see if you wrongly connected one speaker wire to ground like you would with a normal stereo amplifier.
 

Thread Starter

Newtopprojects

Joined Mar 19, 2021
8
Your PAM8304 has no speaker connected so it will not work.
We want to see if you wrongly connected one speaker wire to ground like you would with a normal stereo amplifier.
I thought the circuit in the attached screenshot included PAM8304 connection to speaker? Can you please double check?
Thank you,
 

Audioguru again

Joined Oct 21, 2019
6,673
How will you prevent acoustical feedback howling?
The preamp connection instructions are a nightmare. Poorly translated?
Why is the preamp connected with differential inputs and outputs when an ordinary electret mic is unbalanced.
I see extra parts.
 

Attachments

Qmavam

Joined Nov 6, 2016
16
Just a note, I just posted the schematic, not vouching for the PCB.

How will you prevent acoustical feedback howling?
I'm not sure what you mean? How do you prevent acoustical feedback howling with any mic and speaker.
In my case, it is for a parabolic mic, so I have headphones and the mic is somewhat directional.

The preamp connection instructions are a nightmare. Poorly translated?
Where did I post any preamp connection instructions? The mic is connected to In+ and In-.
Which makes sense to me, I cannot make any sense out of how to use external bias.

Why is the preamp connected with differential inputs and outputs when an ordinary electret mic is unbalanced.
I see extra parts.
I don't know, but I do see that you can change component values to provide roll off of the high and low end.
It looks like it would work better in the balanced configuration.
However I'm looking for information as none is provided with the Aliexpress PCB.
https://www.aliexpress.com/item/4001234143286.html?spm=a2g0o.order_list.0.0.21ef1802T0HYon

btw, I do have it working using the (balanced?) connection, driving a headphone amp.
https://www.aliexpress.com/item/4000924681693.html?spm=a2g0o.order_list.0.0.21ef1802T0HYon


View attachment 263478View attachment 263478

Attached are two mic connection scenarios provided by STMicroelctronics the TS472 manufacturer.

Qmavam


TS472 Manufacturer Suggested Mic connections.jpg
 

Audioguru again

Joined Oct 21, 2019
6,673
Since most electret mics have a grounded case and only 2 wires then the single-ended input schematic has fewer parts and should be used. The output can also be single-ended because the inputs to the new headphones amplifier are single-ended stereo, not differential.

Before you had a PAM speaker amplifier driving a speaker and producing feedback. Now you have a headphone amplifier driving headphones with no feedback.
 

Qmavam

Joined Nov 6, 2016
16
The schematic was my first post in this thread. I just wanted to get the info out because the Aliexpress PCBs come without any information and I have seen others asking. This was not the best thread as I se the OP is using the TS472 chip not the pcb.
But it may help the next guy searching as it may come up in a search.
 
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