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DIY Purifi Amp builds

starfly

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So I need some advice regarding correctly and properly wiring up the electrical parts of the system, specifically correctly and safely grounding both electrical and signal.

From my reading so far, I should connect the ground wire from the IEC socket to bare metal on the chassis. And on the XLR socket, the ground (Pin 1 I believe) should also make direct contact with bare metal on the chassis and I shouldn't bother connecting Pin 1 to the input buffer. But I see that for example the SMPS power supply also has a screw next to the socket for the A/C wires to which I could connect a ground wire (I saw at least one build on here that did so).

I have so far also been shaving off the anodization where I've drilled holes for attaching components to the base plate, so that the screws make direct contact with bare metal (and thus probably also provide some form of grounding for every component).

Are all my assumptions correct so far? Am I missing anything?
 

barrows

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Jan 24, 2020
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So I need some advice regarding correctly and properly wiring up the electrical parts of the system, specifically correctly and safely grounding both electrical and signal.

From my reading so far, I should connect the ground wire from the IEC socket to bare metal on the chassis. And on the XLR socket, the ground (Pin 1 I believe) should also make direct contact with bare metal on the chassis and I shouldn't bother connecting Pin 1 to the input buffer. But I see that for example the SMPS power supply also has a screw next to the socket for the A/C wires to which I could connect a ground wire (I saw at least one build on here that did so).

I have so far also been shaving off the anodization where I've drilled holes for attaching components to the base plate, so that the screws make direct contact with bare metal (and thus probably also provide some form of grounding for every component).

Are all my assumptions correct so far? Am I missing anything?

I have built a Purifi amp, and did it this way in order to achieve both safety and the lowest noise:

1. Always connect a short, large gauge wire directly from the IEC input connector to the chassis, remove anodization at the mounting point.
2. If using the SMPS 1200, its bottom plate is grounded, so I recommend removing some anodization from the chassis at one corner hole where the SMPS 1200 screws in-this only needs to be done at a single corner (in fact, it is probably better to do it at just one corner). I would test for ground continuity from the SMPS heatsink to chassis and IEC ground pin after the SMPS and IEC remounted and the ground connection is made.
3. Best practice, is to connect the XLR jack pin 1 directly to chassis, with as a short a wire as possible. I use 18 AWG here, with ring terminal on one end, and secure it to one of the screws holding the XLR jack in place, again, remove anodization around the XLR mounting hole (and on the XLR jack if using ones that are painted, like Neutrik black ones).
4. The eval board ground (output) needs to be connected to ground as well, it can go to chassis, I connected each one to the other XLR mounting screw (not the same one which has the pin one connection).

BTW, the above connection scheme was what Bruno Putzeys recommended back in the days of the introduction of the NC-400s.
 

starfly

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I have built a Purifi amp, and did it this way in order to achieve both safety and the lowest noise:

1. Always connect a short, large gauge wire directly from the IEC input connector to the chassis, remove anodization at the mounting point.
2. If using the SMPS 1200, its bottom plate is grounded, so I recommend removing some anodization from the chassis at one corner hole where the SMPS 1200 screws in-this only needs to be done at a single corner (in fact, it is probably better to do it at just one corner). I would test for ground continuity from the SMPS heatsink to chassis and IEC ground pin after the SMPS and IEC remounted and the ground connection is made.
3. Best practice, is to connect the XLR jack pin 1 directly to chassis, with as a short a wire as possible. I use 18 AWG here, with ring terminal on one end, and secure it to one of the screws holding the XLR jack in place, again, remove anodization around the XLR mounting hole (and on the XLR jack if using ones that are painted, like Neutrik black ones).
4. The eval board ground (output) needs to be connected to ground as well, it can go to chassis, I connected each one to the other XLR mounting screw (not the same one which has the pin one connection).

BTW, the above connection scheme was what Bruno Putzeys recommended back in the days of the introduction of the NC-400s.

So, wire the IEC like this?

20200706_211221.jpg

As for the SMPS1200, I had already filed off the anodizing at all 6 screw holes. What's the risk of that vs just having one hole with bare metal?

And what's the best way to test for ground continuity? Use an ohm meter?
 

kukocz

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Hi all, I just finished the 7 channel power amplifier. Thanks for all of them in thread because I acquire a lot of very useful information :)
Nice project.
This module with two orange relays is standby or soft-start module?
 

barrows

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So, wire the IEC like this?

View attachment 72229

As for the SMPS1200, I had already filed off the anodizing at all 6 screw holes. What's the risk of that vs just having one hole with bare metal?

And what's the best way to test for ground continuity? Use an ohm meter?

Yes, that looks fine. The sMPS 600 used in the NC-400 amps had a single metal standoff in order to ground the power supply at only one point, apparently this was to reduce RF emissions. As the entire bottom plate of the SMPS 1200 is at ground, perhaps this is not as important with this supply. In nay case, yours will be well grounded to the chassis with your approach and you should be fine.
Yes, check continuity with an ohm meter/DMM.
 

Luc

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Jul 7, 2020
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Hi All,
For the very first time in the known universe :cool:, Purifi amp powered by Micro-Audio SMPS with PFC function!
So many thanks to Sami for the help and for allowing me that world first :D I'm so glad with that build.
Now checking everything and finalizing layout, details. And then soon to play music!
 

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Luc

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specifically designed with the Purifi in mind, pfc, many optional outputs, keeps very cool... and i did not want hypex :facepalm: :D
 
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