Everything arrived safely in Norway. Chassis last week, electronics yesterday. I'm deep inside the building process now. It is funAnd the build guide is awesome.
Great, then I hope DHL decide to ship mine done too.
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For peace of mind, I’ll first switch the two power filter grounds highlighted. Then make the two OPS grounding schemes symmetrical.
Then I’ll do the meticulous measuring if there’s still a problem.
Lesson learned (again): Don’t keep working into the wee hours.
Then I’ll do the meticulous measuring if there’s still a problem.
Lesson learned (again): Don’t keep working into the wee hours.
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I would isolate which board the problem is even on, one of the first steps in troubleshooting. I've even had failed / intermittent RCA connections give me problems in the past. Filter board is fine, don't need to mess with that.
There is a known good FE board and a known good OS board in the amp. For example, I would free up the filter board then pop the bottom cover off. Then with a quick temporary rewire, try driving the right OS with the (known good) left FE board. What is the result? It's a way to home in on where the problem is. Then further steps can be taken to try and solve the issue.
There is a known good FE board and a known good OS board in the amp. For example, I would free up the filter board then pop the bottom cover off. Then with a quick temporary rewire, try driving the right OS with the (known good) left FE board. What is the result? It's a way to home in on where the problem is. Then further steps can be taken to try and solve the issue.
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The Mean Well SMPS switches at 220 kHz (citation).
What number do you get when you estimate the self resonant frequency of that motor run capacitor with those leads? I get approx 50 kHz.
That looks awfully dangerous to me and I recommend NOT doing it.
What number do you get when you estimate the self resonant frequency of that motor run capacitor with those leads? I get approx 50 kHz.
That looks awfully dangerous to me and I recommend NOT doing it.
Besides the very serious warnings of two very heavy hitters in this arena, what are you expecting to achieve with those? I have no idea what they are. What will they bring to your system that is lacking or different in the current design?
Just to learn! For what is worth, I would avoid something that has Jim and Mark warnings all over the place.
Rafa.
Yes, this is the great thing about having a large and very experienced community to help out.
With the warnings from 6L6 and Mark Johnson, I removed the motor run cap before proceeding any further.
I have had previous experience with adding motor run caps to my M2x, which proved beneficial. Big difference is the switching frequency of the SMPS, which I did not take into account.
With the warnings from 6L6 and Mark Johnson, I removed the motor run cap before proceeding any further.
I have had previous experience with adding motor run caps to my M2x, which proved beneficial. Big difference is the switching frequency of the SMPS, which I did not take into account.
Perhaps I failed to mention that voltages can be measure referenced
to ground, and in some cases, like the power resistors, from one lead
of the part to the other.
You have the advantage of a working channel. You might start by just
randomly comparing voltage points and document the ones that are
significantly different.
I blame Zen Mod for this one.
Wow... OK, I need to hear the theory on this one. From you or ZM. I totally get motor run caps in the context of a high voltage tube amp supply, but here? Low voltage, constant-current load... what am I missing?
SRF of that cap is unlikely to perturb the power supply - it's on the far side of the filter board, which has two poles at what... 1/2π√(LC) = 460Hz? So the impedance seen through the filter on the supply side is waaay down in the weeds.
But if it's RF noise suppression on the rail you're after, I think you'd be better served with a small array of surface mount ceramic caps on a low-inductance PCB layout, sitting load-side behind that series filter inductor. Perhaps just as important might be some common-mode filtering on the power lines coming in to the chassis... the cord already has a ferrite, so that's good. A common-mode choke wouldn't do any harm. Lots of good ways to tackle noise.
That said, in stock form the rail looks well filtered to me. Will measure when I get mine built, but I doubt there's going to be much if any observable residual 220kHz ripple to be seen.
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The motor run caps are oil-filled polypropylene. In the correct application, they provide a lower impedance bypass for higher audio frequencies than the typical 15,000+ uF bulk bypass electrolytic caps in the more common linear PSU. The benefit to my M2x was improved placement and timbre representation of acoustic instruments.
In this application, using a high frequency SMPS, their use was misguided. I stand corrected.
In this application, using a high frequency SMPS, their use was misguided. I stand corrected.
Thanks, Nelson. I went through and measured everything I could get to.
Results attached.
Next I’ll compare to the left channel.
Then disassembly to get at the TO3 pins... I think I can take the bottom pate off after unscrewing the filter board. Then I could stand the amp in the faceplate (with scratch protection)...
Results attached.
Next I’ll compare to the left channel.
Then disassembly to get at the TO3 pins... I think I can take the bottom pate off after unscrewing the filter board. Then I could stand the amp in the faceplate (with scratch protection)...
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