Hello to all,
I read this thread, it contains interesting insights on this circuit and several mods.
I bought a kit of this amp from aliexpress. PCB is of good quality so are the parts provided with the kit.
It works well, but a fact that I noticed is that channels are inverted. I respected the printed labels for R and L channels connections, they are the same I see in many photos of this 3D, but they result on inverted channels.
Could you please check your amps for this issue? Many thanks.
I read this thread, it contains interesting insights on this circuit and several mods.
I bought a kit of this amp from aliexpress. PCB is of good quality so are the parts provided with the kit.
It works well, but a fact that I noticed is that channels are inverted. I respected the printed labels for R and L channels connections, they are the same I see in many photos of this 3D, but they result on inverted channels.
Could you please check your amps for this issue? Many thanks.
Misprints like that is common on boards nicpom. The silkscreen labelling is done later after circuits are laid out so its easy to overlook these things. Don't worry too much about it and flip it around on the board, they probably noticed it but decided to leave it like that since it doesn't affect performance.
I must disgree, a channel inversion does affect performance a lot, especially if it remains undetected. As these clone PCBs seem very similar, even the silkprint, I wonder how many users have the same problem, and did not noticed it. I would suggest a check of this to all owners of these clones.
This modification solved the intermittent power supply noise issue, i think Lehmann Audio should use this simple mod, my clone is dead silent now
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Hello!
I have a couple of yellow PCBs kits.
One populated with the parts included as complete kit and another one that I bought bare and have populated myself with upgraded parts from Mouser.
Both sound good but I am inclined to believe that the upgraded 'Mouser board' sounds better.
I have also another PCB (either blue or green-can't remember) coming, so when it comes I will look for any differences.
The yellow PCB is a 'ZeroZone LEM-Copy' and I think it is pretty well made since it has tolerated well with all the soldering/desoldering that took place...
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And something for the gurus:
I get a DC offset of around -15mV on the right channel and around -5mV on the left.
This has been pretty constant with several opamps used (OPA2134, LM4562, OPA2227, NE5534, MUSES 8820). The only opamp that resulted in a lower DC offset was the NJM2068. It achieved -11mV right, -1 mV left. Actually, this opamp has been a pleasant surprise regarding its overall performace/price ratio.
Anyway, I 've ordered a couple of 200Ohm trimmer pots for each channel that will go in place of the two 1.1kOhm resistors next to the 100Ohms ones on the board. I'll use them in series with a 1kOhm resistors to adjust the Voltage regulators, in hope of lowering the DC offset.
Is this a valid approach?
I have a couple of yellow PCBs kits.
One populated with the parts included as complete kit and another one that I bought bare and have populated myself with upgraded parts from Mouser.
Both sound good but I am inclined to believe that the upgraded 'Mouser board' sounds better.
I have also another PCB (either blue or green-can't remember) coming, so when it comes I will look for any differences.
The yellow PCB is a 'ZeroZone LEM-Copy' and I think it is pretty well made since it has tolerated well with all the soldering/desoldering that took place...
------------
And something for the gurus:
I get a DC offset of around -15mV on the right channel and around -5mV on the left.
This has been pretty constant with several opamps used (OPA2134, LM4562, OPA2227, NE5534, MUSES 8820). The only opamp that resulted in a lower DC offset was the NJM2068. It achieved -11mV right, -1 mV left. Actually, this opamp has been a pleasant surprise regarding its overall performace/price ratio.
Anyway, I 've ordered a couple of 200Ohm trimmer pots for each channel that will go in place of the two 1.1kOhm resistors next to the 100Ohms ones on the board. I'll use them in series with a 1kOhm resistors to adjust the Voltage regulators, in hope of lowering the DC offset.
Is this a valid approach?
No, I haven't tried it actually.
Would you think they would lower DC offset?
Are the zeners supposed to be used in place of the 1.1kOhm resistors?
I see a few guys doing it, but could never figure out their purpose.
Forgive my ignorance.
Do not worry. Ask what you want.
Yes, this mod. will help you reduce the offset. It is not the only way but it is one of the simplest and most effective.
Very interesting!
So the original idea with those Zeners was to lower DC offset?
I completely missed that.
Can you recommend particular Zeners for this application?
I'm ready to fill a Mouser order as we speak.
Also, would it be mandatory to use two of them in parallel as it's shown on your photo?
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