Is there any update on this subject? I bought an Amplifier Board from a big supplier in China. The board has a mode switch to select the RCA input or bluetooth streaming.
With the Bluetooth streaming, no problem at all but with the RCA input a noise appears after a while. I had a look to the PCB and I found the 4053 and also 5532 op-amps to create a bass and treble adjustment. Unfortunately I don't have a detailed diagram but I was wondering if the above explained problem, which looks the same with the same components, was ever solved and how.
With the Bluetooth streaming, no problem at all but with the RCA input a noise appears after a while. I had a look to the PCB and I found the 4053 and also 5532 op-amps to create a bass and treble adjustment. Unfortunately I don't have a detailed diagram but I was wondering if the above explained problem, which looks the same with the same components, was ever solved and how.
To clarify: it concerns this board:
AIYIMA 2.1 Amplificador Subwoofer TDA7498E Hifi Power Amplifier Audio Board 160Wx2+220W DIY BTL Class D Sound Speaker Amplifier on AliExpress
The described noise is 'pink noise' and independent on the volume level.
I tried different audio sources (mobile phone, laptop, DAB+ receiver, and so on) on the RCA input but all give the same problem.
When I restart (power off, power on) the board, the noise disappears but comes back after a while (sometimes some seconds, sometimes after minutes).
AIYIMA 2.1 Amplificador Subwoofer TDA7498E Hifi Power Amplifier Audio Board 160Wx2+220W DIY BTL Class D Sound Speaker Amplifier on AliExpress
The described noise is 'pink noise' and independent on the volume level.
I tried different audio sources (mobile phone, laptop, DAB+ receiver, and so on) on the RCA input but all give the same problem.
When I restart (power off, power on) the board, the noise disappears but comes back after a while (sometimes some seconds, sometimes after minutes).
Well the original post is lacking the mandatory decoupling capacitor for the analog switch chip, and for the opamp come to that...
No idea if that extends to that board, but lack of decoupling is a classic newbie error with logic chips which require decoupling whether the datasheet bothers to mention it or not.
No idea if that extends to that board, but lack of decoupling is a classic newbie error with logic chips which require decoupling whether the datasheet bothers to mention it or not.
I am a newbie so please can you clarify what you mean with 'decoupling capacitor for the analog switch chip'.
In previous posts they speak about a resistance between the switch chip and opamp.
Pretty much every chip needs decoupling, logic chips especially need high speed decoupling, ie a 100nF ceramic capacitor from supply to ground very close to the chip.
Without decoupling chips can misbehave in strange and mysterious ways(*). The capacitor needs to be ceramic to be fast enough - the timescales involved are nanoseconds as that's how fast logic gates switch current from the supply pin.
(*) This can be intermittent too, so people build a circuit, think it works and one day it stops working and then a lot of head-scratching goes on. Typical symptoms are multiple switching, oscillation, bizarre changes of state (even to forbidden states). Never use a logic chip without decoupling the supply right close up to the chip's pins - much grief is saved.
Without decoupling chips can misbehave in strange and mysterious ways(*). The capacitor needs to be ceramic to be fast enough - the timescales involved are nanoseconds as that's how fast logic gates switch current from the supply pin.
(*) This can be intermittent too, so people build a circuit, think it works and one day it stops working and then a lot of head-scratching goes on. Typical symptoms are multiple switching, oscillation, bizarre changes of state (even to forbidden states). Never use a logic chip without decoupling the supply right close up to the chip's pins - much grief is saved.
4053's are good enough until video frequencies. Pay attention to decoupling the power lines, and erase the 2KΩ resistors. Attach them with low impedance, say, from a follower. Load it with high impedance, like the follower you have. They work pretty fine until ±7.5VDCrespect to ground. In any case, there are several other switches of the DG series, that will perform better as they are ±15V lines compatibles.
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