One note, though: You'll get better performance (lower THD) if you connect the feedback return path to the power ground instead of the signal ground.
As others have pointed out already, you need to connect the power ground and the signal ground at some point. I prefer the speaker ground point for this.
You want to make sure that at least 1 mA flows in the mute pin when the chip is un-muted. So your minimum supply voltage is ±26 V. It's not disastrous if less current flows, but the performance does start to degrade below 1 mA even though the chip un-mutes at 500 uA.
Tom
As others have pointed out already, you need to connect the power ground and the signal ground at some point. I prefer the speaker ground point for this.
You want to make sure that at least 1 mA flows in the mute pin when the chip is un-muted. So your minimum supply voltage is ±26 V. It's not disastrous if less current flows, but the performance does start to degrade below 1 mA even though the chip un-mutes at 500 uA.
Tom
If you are going to buy, you can send an e-mail to Tom from the site in the link.
@tomchr
I turned the amp on and it works great. However, I am experiencing a parasite problem that I cannot find a solution to. When I remove the C4 capacitor, the problem goes away. I connected the C4 capacitor to power ground and the problem was not resolved. It is affected by phones, why do you think this is happening? Things I tried: I disconnected the audio cables. I checked the GND cables. I checked the entire circuit. I installed an EMI filter on the feed and got no results. Then I noticed that it was picking up noise from the computer. I disconnected the audio connection of the amplifier to the sound card and the problem continued. Then I removed the sound card from the computer and the problem was solved, but the sound card was picking up noise from the air while it was working. When no amplifier is connected to the sound card, the amplifier picks up this interference from the sound card through the air, but I don't understand why.
I turned the amp on and it works great. However, I am experiencing a parasite problem that I cannot find a solution to. When I remove the C4 capacitor, the problem goes away. I connected the C4 capacitor to power ground and the problem was not resolved. It is affected by phones, why do you think this is happening? Things I tried: I disconnected the audio cables. I checked the GND cables. I checked the entire circuit. I installed an EMI filter on the feed and got no results. Then I noticed that it was picking up noise from the computer. I disconnected the audio connection of the amplifier to the sound card and the problem continued. Then I removed the sound card from the computer and the problem was solved, but the sound card was picking up noise from the air while it was working. When no amplifier is connected to the sound card, the amplifier picks up this interference from the sound card through the air, but I don't understand why.
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This is the operation of the amplifier. The sound quality and soundstage are amazing and the sound is incredibly clear.
C4 should connect to the power ground.
Does the amp have the issue when you short its input?
Tom
Does the amp have the issue when you short its input?
Tom
There is no problem. I solved the problem a little bit, I have no problems when I connect the sound card to my phone, but when I connect the sound card to the computer, there is interference. I haven't had this problem with other amplifiers. I think this is GND related, maybe the computer's PSU is faulty? There is no problem when I make sound from the phone.
Tom, this problem is caused by the audio source. There is no interference on the phone, but there is interference on the computer. Thanks Tom. I'm thinking of making a 1206 SMD version of this amplifier. Do you think I can use 47pf and 680pf capacitors 1206 SMD?
I'd change R6 to 2.7 Ω and C6 to 100 nF as per the LM3886 data sheet.
I bet the power supply of the PC is injecting noise through the USB. I'd try a USB isolator or an optical link from the PC to the sound card.
1206? Why not go smaller? I use 0603 now. It's not too difficult if you use a solder paste stencil and toaster oven reflow. For hand-soldering I prefer 0805 or larger. I used to be able to hand-solder 0603 but these days I'd have to use a microscope (or at least different reading glasses) to solder them reliably.
Do watch the power dissipation on the small components. You'll probably find that R4 wants to be a 1206. R6 and R7 will likely be 2512 size. The rest can be smaller.
The small capacitors should be C0G/NP0 ceramic. The rest can be X5R or X7R. Note that you only get about 20% of the marked capacitance from X5R/X7R when they're charged to the full rated voltage, so select 50-100 V types.
Tom
I bet the power supply of the PC is injecting noise through the USB. I'd try a USB isolator or an optical link from the PC to the sound card.
1206? Why not go smaller? I use 0603 now. It's not too difficult if you use a solder paste stencil and toaster oven reflow. For hand-soldering I prefer 0805 or larger. I used to be able to hand-solder 0603 but these days I'd have to use a microscope (or at least different reading glasses) to solder them reliably.
Do watch the power dissipation on the small components. You'll probably find that R4 wants to be a 1206. R6 and R7 will likely be 2512 size. The rest can be smaller.
The small capacitors should be C0G/NP0 ceramic. The rest can be X5R or X7R. Note that you only get about 20% of the marked capacitance from X5R/X7R when they're charged to the full rated voltage, so select 50-100 V types.
Tom
Hi, I wanted to make this amplifier, to combine with Dynaudio 4 ohm speaker. I have a 120VA 2x15v transformer available. I'm wondering if they're okay, given that I listen to music at low volume. Thank you in advance.
Yes, it should work fine for 4ohm load & will be loud enough. I think 6800uf per rail is ok for stereo setup.
It will work, but your speakers must be fine. It would be better if you keep the transformer in a different box. You should use symmetrical capacitors per channel. It would be better to use 2.5mm copper wire cables.
Ciao, scusa se ti disturbo, ho appena finito di costruire l'amplificatore, la qualità del suono mi sembra decente, tranne per il fatto che sento un leggero ronzio a 50 Hz credo, ho provato di tutto per risolvere il problema (ground loop breacher, ecc.) ma non cambia nulla. Lo schema che ho seguito è allegato. Grazie in anticipo per il chiarimento.
Attachments
Re above: " Hi, sorry to bother you, I just finished building the amplifier, the sound quality seems decent to me, except that I hear a slight hum at 50Hz I think, I've tried everything to fix the problem (ground loop breacher , etc.) but nothing changes. The diagram I followed is attached. Thanks in advance for the clarification."
Hi, sorry to bother you, I just finished building the amplifier, the sound quality seems decent to me, except that I hear a slight hum at 50Hz I think, I've tried everything to fix the problem (ground loop breacher , etc.) but nothing changes. The diagram I followed is attached. Thanks in advance for the clarification."
