Hi,
I'm working on a replacement preamp and amp for an old B&O. See this post https://www.diyaudio.com/forums/class-d/342430-beomaster-refit-controversial-6.html
I have a TPA3116 based board from Aliexpress, XH-M569, this board had some bad noise issues from an unnecessary opamp on the input, I removed this as suggested elsewhere and now it has acceptably low noise.
I am trying to hook it up to an NE5532 based preamp, aliexpress XH-A901, but it has a terrible whine noise, which is not dependent on volume. I have tried several power supplies an configurations, running both amps on same power and separate power.
Both the preamp and the amp have single line inputs, would it be possible to convert the preamp output to balanced? Would this help with the noise?
Can anyone help with how to eliminate this constant whine noise?
Thanks,
Theo
I'm working on a replacement preamp and amp for an old B&O. See this post https://www.diyaudio.com/forums/class-d/342430-beomaster-refit-controversial-6.html
I have a TPA3116 based board from Aliexpress, XH-M569, this board had some bad noise issues from an unnecessary opamp on the input, I removed this as suggested elsewhere and now it has acceptably low noise.
I am trying to hook it up to an NE5532 based preamp, aliexpress XH-A901, but it has a terrible whine noise, which is not dependent on volume. I have tried several power supplies an configurations, running both amps on same power and separate power.
Both the preamp and the amp have single line inputs, would it be possible to convert the preamp output to balanced? Would this help with the noise?
Can anyone help with how to eliminate this constant whine noise?
Thanks,
Theo
I don't have schematics for either board. It's a high pitched tone noise, not a hiss.
As an audio source I'm using my phone, but the whine is there whether it is connected or not.
I have tried lots of ways to connect power, common 24V from the same supply and with different supplies.
As an audio source I'm using my phone, but the whine is there whether it is connected or not.
I have tried lots of ways to connect power, common 24V from the same supply and with different supplies.
Check the feedback on the item on AliExpress... I think the board must be of bad design.
XH A901 NE5532 Tone Board preamp Pre amp With treble bass volume adjustment pre amplifier Tone Controller For amplifier Board-in Amplifier from Consumer Electronics on AliExpress - 11.11_Double 11_Singles' Day
XH A901 NE5532 Tone Board preamp Pre amp With treble bass volume adjustment pre amplifier Tone Controller For amplifier Board-in Amplifier from Consumer Electronics on AliExpress - 11.11_Double 11_Singles' Day
If the tone goes away when the preamp is disconnected from the amplifier, then the preamp is likely to be the problem. However, it's possible that there is a feedback mechanism through the common power supply, could you describe that?
That was with no volume on the preamp. Different power supplies still give the noise but it sounds a slightly different tone with each. If I use a 9V battery on the preamp the whine goes away, but I need to power it from a supply, preferably the same one as the amp.
Using a step down isn't a separate power supply as such.
Try a totally seperate supply like a seperate power brick or even a 9v battery for the preamp and see what happens
Try a totally seperate supply like a seperate power brick or even a 9v battery for the preamp and see what happens
Ok great, probably it is a ground loop of some kind. Either use a completely isolated supply or use a supply isolator between amp and preamp something like
1pcs new dc dc converter 12V to 5V 12V 3.3V 9V 15V 24V regulated isolated dc-dc power module quality goods
AliExpress
Thanks ubergeeknz. don't really want to wait another 5 weeks for a component from Aliexpress! Is there no other way to eliminate this kind of noise? A filter of some kind?
Also, this all needs to go in the same box, so can't have isolated supplies. I could try that isolator, but I have doubts it will fix it.
Also, this all needs to go in the same box, so can't have isolated supplies. I could try that isolator, but I have doubts it will fix it.
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Try an RC filter in each supply line to the preamp. Run the power lines to the amp.
Then connect a 1k series resistor in each power line to the preamp. Then add a 10uF or more
capacitor (observe polarity) from each preamp power terminal to the preamp ground terminal.
Then connect a 1k series resistor in each power line to the preamp. Then add a 10uF or more
capacitor (observe polarity) from each preamp power terminal to the preamp ground terminal.
OK, so I tried a 1k resistor in series with the +ve to the preamp with different capacitors (0.1uF to 470 uF) accross the +/- power on the preamp side. It made no difference to the whine (which is about 1000Hz), Other than the reduced voltage to the preamp lowering the volume of it a bit.
Mucking around randomly, this is what worked! Connected the amp directly to 24V. Ground of the amp connected to ground of the preamp (same as it was before), then a 330ohm resistor from +24V to the preamp.. no cap, and the whine has disappeared completely. I have no idea why.
I apologies for resurrecting an old thread , Ive done something similar with the same pre amp running from an smps. The above method/tricks did not work for me. What worked reducing to hum/buzz to almost nothing was to hook earth/ground from the smps (earth/ground from the mains) to the ground of the amps "signal-in ground" (the signal after the pre amp - signal out - and thus before into the amp).
It seems to be working fine, my question is that is this safe? Perhaps ive overlooked something in haste of getting it to work. Its 100% something with these preamps. Ive etched custom pcbs for the pots.. anyway the whole things looks like a mess and im not too keen it catching on fire. Thanks heaps for any feedback.
It seems to be working fine, my question is that is this safe? Perhaps ive overlooked something in haste of getting it to work. Its 100% something with these preamps. Ive etched custom pcbs for the pots.. anyway the whole things looks like a mess and im not too keen it catching on fire. Thanks heaps for any feedback.
I've just completed a project with the XH-A901 preamp/EQ, and I wanted to share my experience. This thread was a top hit when searching "XH-A901 whine", so I figured it was good to add some info here in case anyone else is running into this issue. Also, I'm very grateful for the suggestions in this thread.
I found the XH-A901 preamp to be extremely sensitive to noise from the power adapter. I use a computer power supply as a bench power supply for testing. It's relatively clean power. The XH-A901 didn't whine when attached to this supply... but I could hear the noise from the fan clearly coming from the speaker! It will transmit every bit of noise in the power line.
The power supply I wanted to use with this is a 12V 2A switching power adapter providing power to the preamp and the amp (HW-404). The amp itself sounds fine with this adapter, but the XH-A901 gets a terrible whine. I think it is high frequency switching noise.
rayma's suggestion of an RC filter ultimately worked, but I had to play with the values a bit. Putting a filter on the XH-A901 power line reduced the whine, but did not eliminate it. I also needed a filter on the amp too.
rc filter for XH-A901: 100Ohm resistor, 10uF capacitor
cutoff frequency: 159.15Hz
rc filter for HW-404: 10Ohm resistor, 100uF capacitor
cutoff frequency: 159.15Hz
I used this calculator to find the cutoff frequency:
https://www.omnicalculator.com/physics/low-pass-filter
If you use rayma's suggestion of 1K resistor and 10uF capacitor you get a cutoff frequency of 15Hz. Seems like that should have worked, but it didn't for me. And I found the 1K resistor dropped the voltage too much.
Just like tallnutt, only adding a resistor and not a capacitor did help quite a bit. It seemed important that the XH-A901 was running at a slightly lower voltage than the amp-- it whined more if they were at the same voltage. I tried just a 330Ohm resistor and that helped, but didn't eliminate the whine. I expect results vary depending on the particular noise from your switching power adapter.
I tried Rolz solution of connecting the amp's signal-in ground to the power adapter's ground. This was not effective for me. I suspect Rolz was experiencing a ground loop and not noise from the power adapter. Rolz described a hum not a whine, so that seems to check out. I think his solution is safe, and it makes sense for a ground loop. You provide a more direct path to ground so the power does not flow to the amp. Not a solution for power supply noise though.
After a lot of trial and error I settled on the values listed above. Using the rc filter (with the capacitor) was an improvement over just the resistor. The 10Ohm resistor on the HW-404 didn't drop the voltage as much. The whine was completely eliminated, but there is still some soft white noise when the system is powered on.
I found the XH-A901 preamp to be extremely sensitive to noise from the power adapter. I use a computer power supply as a bench power supply for testing. It's relatively clean power. The XH-A901 didn't whine when attached to this supply... but I could hear the noise from the fan clearly coming from the speaker! It will transmit every bit of noise in the power line.
The power supply I wanted to use with this is a 12V 2A switching power adapter providing power to the preamp and the amp (HW-404). The amp itself sounds fine with this adapter, but the XH-A901 gets a terrible whine. I think it is high frequency switching noise.
rayma's suggestion of an RC filter ultimately worked, but I had to play with the values a bit. Putting a filter on the XH-A901 power line reduced the whine, but did not eliminate it. I also needed a filter on the amp too.
rc filter for XH-A901: 100Ohm resistor, 10uF capacitor
cutoff frequency: 159.15Hz
rc filter for HW-404: 10Ohm resistor, 100uF capacitor
cutoff frequency: 159.15Hz
I used this calculator to find the cutoff frequency:
https://www.omnicalculator.com/physics/low-pass-filter
If you use rayma's suggestion of 1K resistor and 10uF capacitor you get a cutoff frequency of 15Hz. Seems like that should have worked, but it didn't for me. And I found the 1K resistor dropped the voltage too much.
Just like tallnutt, only adding a resistor and not a capacitor did help quite a bit. It seemed important that the XH-A901 was running at a slightly lower voltage than the amp-- it whined more if they were at the same voltage. I tried just a 330Ohm resistor and that helped, but didn't eliminate the whine. I expect results vary depending on the particular noise from your switching power adapter.
I tried Rolz solution of connecting the amp's signal-in ground to the power adapter's ground. This was not effective for me. I suspect Rolz was experiencing a ground loop and not noise from the power adapter. Rolz described a hum not a whine, so that seems to check out. I think his solution is safe, and it makes sense for a ground loop. You provide a more direct path to ground so the power does not flow to the amp. Not a solution for power supply noise though.
After a lot of trial and error I settled on the values listed above. Using the rc filter (with the capacitor) was an improvement over just the resistor. The 10Ohm resistor on the HW-404 didn't drop the voltage as much. The whine was completely eliminated, but there is still some soft white noise when the system is powered on.
