Well, after some more testing, it is still humming. I'd say less than before but still unpleasant as it is very tiring to listen to.
Compared to the Schiit Audio Magni 3 I now have this is just a pain to listen to. I guess I am giving up. Having the ability to roll opamps was nice to have but having nice and clean sound sure is better.
I guess I have a nice list of quality components on the board, that is sad.
Thanks anyway to all members of DIY audio for your help. I'll keep watching this thread in case someone comes out with a different fix.
Compared to the Schiit Audio Magni 3 I now have this is just a pain to listen to. I guess I am giving up. Having the ability to roll opamps was nice to have but having nice and clean sound sure is better.
I guess I have a nice list of quality components on the board, that is sad.
Thanks anyway to all members of DIY audio for your help. I'll keep watching this thread in case someone comes out with a different fix.
Darksky, please don't feel like the lone ranger here when it comes to a humming Lehmann clone.
I wacked and cut on my board several times trying to eliminate the ground loop(s). In the end I was never able to do so.
Unfortunately I lost my temper one evening and took a 4lb. hammer to it and put it out of its misery.
Even when the hum wasn't "that objectionable", the Magni 3 sounded much better to my ears despite "rolling" several FET and bipolar op-amps in the Lehmann clone.
Plus, there was absolutely ZERO hum with the Magni 3.
If sound quality is what you're seeking, I would personally stay away from the Lehmann clones.
Just my 2 cents.
I wacked and cut on my board several times trying to eliminate the ground loop(s). In the end I was never able to do so.
Unfortunately I lost my temper one evening and took a 4lb. hammer to it and put it out of its misery.
Even when the hum wasn't "that objectionable", the Magni 3 sounded much better to my ears despite "rolling" several FET and bipolar op-amps in the Lehmann clone.
Plus, there was absolutely ZERO hum with the Magni 3.
If sound quality is what you're seeking, I would personally stay away from the Lehmann clones.
Just my 2 cents.
I convinced myself to cut the ground plane and connect the wires as shown on the picture that flyingfish posted.
Result: no more hum. It doesn't look very good, but the hum is gone and that's the most important thing. Thanks again!
I am now running some endurance tests before I hook up my expensive Ultrasones. It seems like the output transistors are running really hot. That's not surprising, since it is biased very hot. But still, I'm a bit worried. How hot is 'too hot'?
Thanks again,
Olivier
Hi, i have almost same hum noise wit my lehmann clone the only difference is that the hum is intermittent, some time it is there, sometime not.
İ think it is a transformer hum at 50Hz. İ wonder whether it can be solved with the same grounding operation or not
You should check all connectors at first. And don't use different crappy chinese kits, it's not difficult to make own pcb.And, yep, don't use switches in NFB of OPamp.
Here is the my L clone, generally the hum is gone at night hours, the amp working well and powerfull all the time, the hum is independent from the volme pot
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Hum 50 Hz or 100 Hz?
I guess your transformer too close to PCB...
100Hz i think.. i compared it with the 100Hz sound from tone generator
İ applied the three step star grounding mentioned at one of the previous posts but no difference at hum noise and i found a lot of people suffer from this hum noise with this lehmann clone. İ start to think it is a crap design since i saw a guy who has an original lehmann mentioned hum problem same with me in a different forum
It's not schematic problem, it's a problem of PCB from Junk.., sorry, Jim's Audio PCB.
A few time ago I made own PCB, here is resault.
https://www.diyaudio.com/forums/hea...grading-lehmann-bcl-clone-29.html#post4716292
Hello,
Don’t own such an amp, but I do have a Matrix HPA-3B instead. I used to have a tiny mains hum, especially on high gain, like others stated here.
Issue was from the toroid, so shielding it did helped me. So try moving away the transformer from the PCB an also try to angle it 30-45 degrees and check if hum lowers or not.
If this doesn’t helps at all, then maybe someone can upload here a scope screenshot with how the DC rails look like (AC ripple and noise), but also a FFT should help.
However, I am confident that moving the transformer few inches away from the PCB it will notch down the hum.
Don’t own such an amp, but I do have a Matrix HPA-3B instead. I used to have a tiny mains hum, especially on high gain, like others stated here.
Issue was from the toroid, so shielding it did helped me. So try moving away the transformer from the PCB an also try to angle it 30-45 degrees and check if hum lowers or not.
If this doesn’t helps at all, then maybe someone can upload here a scope screenshot with how the DC rails look like (AC ripple and noise), but also a FFT should help.
However, I am confident that moving the transformer few inches away from the PCB it will notch down the hum.
Very old thread, But I'm gonna chip in:
All the ground optimizations in this thread are good to do, but the most important, and smallest i believe is cutting off the ground loop on output jacks. They form a huge ground loop from the output right to the power supply part.
See attachments:
First of all, gotta remove the jacks. Then cut off traces along red lines. Check with multimeter if none of the points conduct to ground anymore. Then, checking the other screenshot, connect the ground points along yellow line to the trace between potentiometer's legs - it goes straight to opamp decoupling caps.
This changed got rid of the ground loop completely.
You are free to do other changes too though - looks like this pcb is a crap fest of ground loops so every fix here has a potential to improve sound.
All the ground optimizations in this thread are good to do, but the most important, and smallest i believe is cutting off the ground loop on output jacks. They form a huge ground loop from the output right to the power supply part.
See attachments:
First of all, gotta remove the jacks. Then cut off traces along red lines. Check with multimeter if none of the points conduct to ground anymore. Then, checking the other screenshot, connect the ground points along yellow line to the trace between potentiometer's legs - it goes straight to opamp decoupling caps.
This changed got rid of the ground loop completely.
You are free to do other changes too though - looks like this pcb is a crap fest of ground loops so every fix here has a potential to improve sound.
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