Thanks Faux French. I'm first trying to understand this - I get that the BT module may be going into low power state, but why is this only audibly evident through the amp and not through the earpods? Is it because the amp cannot deal with high impedance input but the earpods can?
My point is that if the Bluetooth module goes into low power state and leaves the outputs high-impedance, the amplifier inputs are more-or-less open. The level of buzz you then hear depends on how the amplifier inputs are "tied". Perhaps the earpods amplifier input has already got 10K-47K to ground.
The 10K (or 4K7) I propose serve to tie the inputs to ground if they are left floating.
You are already aware of the "hiss"-issue for TPA3116 amplifiers?
Just to be clear, there is no earpod amplifier involved - the comparison is purely as follows:
Laptop BT to BT receiver module, earpods plugged in directly to module, no buzz/hum when audio is not playing.
Laptop BT to BT receiver module, cable connected to inputs on TPA3116 amplifier, plenty buzz/hum when audio is not playing.
It's very difficult to accesss the output on the BT module - it's solidly enclosed and I would have to resort to cutting the case open.
1. Can I achieve the same effect by placing the resistors on the end of the cable that connects to the amplifier inputs?
2. I don't have 10K resistors on hand and nowhere close to get some. I do have 4K7 resistors - can I use 2 of these in series?
I've read a lot about the hiss issue for these boards but this is not a problem for me.
1. Yes, that was what I actually meant. The Bluetooth output is for me where it connects to the amplifier input.
2. Try with a single 4K7 on each channel. The 10K was just a guess on how much the Bluetooth module can pull without too much lowering of the signal amplitude. Most likely the output is some kind of OP-AMP output and such can easily be loaded with 4K7.
Now I understand that the Bluetooth module has an earpod output of its own. It is very likely that the module cuts off the line output if earpods are connected.
The most frequent reason for buzz is a sensitive (high impedance) input.
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Thanks for your time with this.
The Bluetooth module has only one output - stereo mini jack.
So I've just tried single 4K7 on the amplifier inputs, it takes the buzz down quite a bit, maybe by 20%. I'll put 2 in series and check what happens.
Edit: Don't know whether this helps, but when the amplifier inputs are completely open, the buzz is significantly lower than when the Bluetooth module is connected.
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I have 2 output devices - the earpods, which are competely silent when plugged into the Bluetooth module, and the TPA3116 amplifier, which has a lowish buzz through the speakers when the inputs are open, and this buzz gets considerably louder when I connect the Bluetooth module.
Is it possible/practical to measure the input impedance of both devices using just a DMM, so I can establish what the difference may be?
More resistors will not improve the situation. If 4K7 can't remove the buzz, something else is needed.
You have a TPA3116 amplifier powered by a power supply. When you connect the Bluetooth module you get considerable buzz. Which power supply do you use for the Bluetooth module? The same as for the amplifier?
The difference between the earpods and the amplifier as loads for the Bluetooth module is probably that the earpods are pretty low impedance and the buzz signal is too high impedance to drive the earpods. An amplifier input is sensitive even to high impedance signals. What is the impedance of your earpods? Can the Bluetooth module drive the earpods with music?
I run the Bluetooth module off the integrated lithium battery to avoid power supply noises. I also made sure that the module comes nowhere near the power supply for the amp. It is this module:
RIVERSONG Bluetooth Receiver Bluetooth Transmitter Portable Wireless Music Audio Adapter Aptx Low Latency Home Stereo System TV-in Wireless Adapter from Consumer Electronics on Aliexpress.com | Alibaba Group
I'm using Apple Earpods, official specs are difficult to find but it seems they have an input impedance of 42-45 ohms. The Bluetooth module does a good job of driving the earpods with music, and no buzz at all.
The amplifier I use is this one:
TPA3116 2.1 channel digital power amplifier board
I've looked about quite a bit but cannot find specs for the input impedance.
RIVERSONG Bluetooth Receiver Bluetooth Transmitter Portable Wireless Music Audio Adapter Aptx Low Latency Home Stereo System TV-in Wireless Adapter from Consumer Electronics on Aliexpress.com | Alibaba Group
I'm using Apple Earpods, official specs are difficult to find but it seems they have an input impedance of 42-45 ohms. The Bluetooth module does a good job of driving the earpods with music, and no buzz at all.
The amplifier I use is this one:
TPA3116 2.1 channel digital power amplifier board
I've looked about quite a bit but cannot find specs for the input impedance.
Sadly, my electronics knowledge is very limited, which is why I'm seeking assistance here. I'm beginning to suspect that the amplifier requires a signal of much lower resistance.
It could be the BT receiver turns off the output to save power, which may be the reason why no buzz when playing music.
I'm sure this is the problem, but the buzz is only evident when connected to the amplifier and not when connected to the earpods. Maybe the impedance of the earpods is such that the receiver does not go into power saving mode?
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Have you tried grounding the unit to earth? Or add addition ground to the receiver and amp.
The amp is not earthed. Can I take a ground lead from the amplifier input signal ground?
Try with the casing first, then signal ground. If you hear weird sound then immediately off the power.
This is a TPA3116 module, in a box, so no casing earth available.
The good news is that you are spot on with it being a ground issue - I tried a quick fix and took a lead from signal ground to earth: the buzz/hum is reduced very significantly, to the extent that the amp is very usable now. The hum only becomes apparent if I take the amp volume up over 50%, which almost never happens. I will put a proper earth lead in shortly.
TPA3116 for subowoofer
Hello,
Wanna do a small amp with TPA3116 for my passive DIY subwoofer.
Power source will be 24V / 6A laptop power brick.Subwoofer have 70W / 4ohm woofer.
Audio signal will come from subwoofer pre-out of 5.1 AV Receiver.
I bought this one:
Aiyima TPA3116 2.0 Digital Amplifier Board Amplificador 50W*2 Support PBTL Parallel Mono Model 100W DC12 24V-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
I get it mainly for its simple configurability. When you short pads on PCB in particular combinations, you can adjust gain or switch it into PBTL mode
As I am planning to use it for subwoofer and it is a stereo amp, as far as I know it would be easiest to configure it to PBTL. Then I dont need to mess with grounding inputs and dummy load on one channel.
I am also planning to lower gain to 26dB, thats may reduce possible hiss. As I read somewhere, it is shipped with gain set to 32dB, which can be too much.
Altough I am messing with similar DIY stuff, I am pretty new to those class D amps. If anyone tested this particular board, or just generally, can you please tell me few things?
1. If there is something that can be somewhat tweaked what it would be? Maybe those electrolytic caps? As it will reproduce mainly bass, I think there would be good to have bigger caps. Or are those okay?
2. does anyone know, what those unused terminals on PCB are for? Labels like VSW, DS, Vout. And how to use them? Seller on aliexpress does not seem to know.
3. Generally for any class D TPA3116 amp, what will happen, if I change switching frequency, for example from 400kHz to 800kHz or even higher? It will have any effect on amplifier's sound, or effectivity? Can be the switching frequency taken as something similar like 44.1kHz sampling freq. used in digital playback? So, the higher freq., the better audio quality?
4. When there is a need to connect some pin of TPA3116 to "low" or "high", what it means exactly? I know that there are TTL levels of 0, 3.3 or 5V, which are used for this low/high logical states.
So here, "low" means 0V or GND? And from where is required voltage for "high" taken?
For example, if I want to mute the amp, I need to connect MUTE pin to ground?
Thank you all for replies
Hello,
Wanna do a small amp with TPA3116 for my passive DIY subwoofer.
Power source will be 24V / 6A laptop power brick.Subwoofer have 70W / 4ohm woofer.
Audio signal will come from subwoofer pre-out of 5.1 AV Receiver.
I bought this one:
Aiyima TPA3116 2.0 Digital Amplifier Board Amplificador 50W*2 Support PBTL Parallel Mono Model 100W DC12 24V-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
I get it mainly for its simple configurability. When you short pads on PCB in particular combinations, you can adjust gain or switch it into PBTL mode
As I am planning to use it for subwoofer and it is a stereo amp, as far as I know it would be easiest to configure it to PBTL. Then I dont need to mess with grounding inputs and dummy load on one channel.
I am also planning to lower gain to 26dB, thats may reduce possible hiss. As I read somewhere, it is shipped with gain set to 32dB, which can be too much.
Altough I am messing with similar DIY stuff, I am pretty new to those class D amps. If anyone tested this particular board, or just generally, can you please tell me few things?
1. If there is something that can be somewhat tweaked what it would be? Maybe those electrolytic caps? As it will reproduce mainly bass, I think there would be good to have bigger caps. Or are those okay?
2. does anyone know, what those unused terminals on PCB are for? Labels like VSW, DS, Vout. And how to use them? Seller on aliexpress does not seem to know.
3. Generally for any class D TPA3116 amp, what will happen, if I change switching frequency, for example from 400kHz to 800kHz or even higher? It will have any effect on amplifier's sound, or effectivity? Can be the switching frequency taken as something similar like 44.1kHz sampling freq. used in digital playback? So, the higher freq., the better audio quality?
4. When there is a need to connect some pin of TPA3116 to "low" or "high", what it means exactly? I know that there are TTL levels of 0, 3.3 or 5V, which are used for this low/high logical states.
So here, "low" means 0V or GND? And from where is required voltage for "high" taken?
For example, if I want to mute the amp, I need to connect MUTE pin to ground?
Thank you all for replies
Attachments
Leave as is, "bigger" caps won't improve anything here. Have a good supply with short thick leads and you're set.
This is for an auxiliary voltage output realised by an LDO. Input voltage is derived from amp voltage input.
Leave as is, increasing the fSW only increases swtiching losses on here.
Low is <= 0.8V , High >= 2V up to PVCC+0.3V.
Hi I tried everything to get rid of buzz and hiss on my 2 x 100w tpa3116 amp and found the problem to be laptop type 19v power supplies.
In the end I made my own power supply using 15v 30VA transformer 4 amp rectifier with some capacitors it gives me 22v DC.
Amp is now silent.
You could try it on a battery first to see if its power supply problem I tried it on a car battery first.