KJF Audio MA-01 Hypex NC252MP Amplifier Teardown

[Jim Matthews]

View attachment 126088

That's Captain Cabletie's side arm.

 

[DSJR]

I'd also echo the mains wiring on the track and exposed pins on spare? mains sockets. One day in the future, some ignorant numpty is going to open this thing up and start poking about. I know, way out of warranty and said numpty would have no need whatsoever to poke around apart from morbid curiosity, but I really would ask you to look again at the mains routing to the third board and somehow see if that lengthy circuit track carrying mains could be avoided altogether - comments were made about that one amp board being possibly rotated?

Sorry, I don't mean to butt in, but on the face of it, it *may* not take much at all to tweak the layout a little to satisfy even the fussiest engineers here. The old early 1970's US made amps I use and which came with certification, would horrify some of you lot now, things have moved on so.

 

[Phorize]

If this is the course of amplification going forward, it's depressing.

Hopefully this will cheer you up:

 

[mrmoizy]

I was impressed, as far as Hypex MP252-based amps are concerned, I think this one had the best SINAD if I'm not mistaken? I'm building a DIY amp based on the MP252 using a case from Ghent Audio. Still waiting for the case to arrive, but I'm taking notes and will come back to reference to see how I can route the connections best to optimize what the Hypex board offers. Overall, well done @KJF audio

 

[sarumbear]

I chose to use ribbon cable as the modules have a ribbon/IDC connection themselves so at some point there has to be a ribbon cable involved. I used the best quality copper ribbon I could find at 28 AWG (biggest that will fit) and IDC connectors with gold plated pins for what it is worth. While not quite as good as twisted pairs the signal lines all have GND wires between them which is how sensitive PC cabling works. In tests this was good.
Stefan

Maybe you should be made aware of this solution?

 

[mrmoizy]

Maybe you should be made aware of this solution?View attachment 126493View attachment 126494

Those look really nice, but for short-run signal cable, I'm not sure these would make a measurable difference. The ribbon cables, while unorthodox for the audio world, seem to perform fine and they kept the build pretty clean and organized

 

[KJF audio]

Maybe you should be made aware of this solution?

I do really like the look of those. I looked at similar when I was doing the design work, I also looked at shielded versions. I even tested some. It didn't make any difference to measured performance though. In fact unless I laid an AC cable directly on the ribbons I couldn't get the signal to deteriorate at all. I was still pretty set on using something similar though for completeness, however, I had to be able to make them myself otherwise the amps would have been much more expensive. Getting these made to all the multiple lengths I need would be prohibitive and off the shelf lengths would have meant untidy routing, so ribbons it is

 

[KJF audio]

Agree with the zip tie having nasty sharp ends. One of my pet hates too. Buy yourself one of the these:

Never seen one of those, I will get one, you can never have to many tools in my opinion. I've got a whole industrial unit and 3 sheds full of them

 

[KJF audio]

Thanks for some of the comments on mains wiring, I'll take some of it on board. I agree the 2 pins sticking up live in this example isn't ideal. Normally they are not populated and if they are they have a 'dummy' plug over them. My bad.

When I designed the PCB I wanted it to do some of the routing and as PCB layout isn't my area of expertise I did consult on this part, the Gerbers were looked at for obvious gotchas but were deemed OK. I also had a full visual inspection and full set of CE tests done on the first production sample which it passed no problem. I'm really glad I had those test all carried out, I don't think it is normal for small 'cottage' manufacturers like me to bother, seems essential in my eyes! It is eye wateringly expensive though!

The measured resistance between phase and GND @2500VDC was 17.2 GOhms which is about 20,000 times the minimum limit according to the test sheet, so it is pretty safe to say any wiring done in the PCB is not causing an issue with nearby GND points. The earth bonding was also tested on all panels which as I said before all have an independant cables, with serrated washers (except the front panel which has the anodising removed behind the brackets). The worst panel is the one recorded in the test sheet and it rated at 0.012 Ohms against the limit of 0.1 ohms so about 10 times the minimum requirement. These tests are carried out at 1.5 times the rated mains connector or 25A whichever is higher (25A in this case) The live 25A is connected to the earth terminal and each panel probed for voltage drop to determine the loss.

The most interesting test though I thought were the electoro-static tests, for these test an electro-static discharge gun is used to send discharges of 6kVa into the case and repeated 20 times at one second intervals. The equipment is powered up and in use during these tests to determine what effect this has on intended use. It had no effect whatsoever. I knew nothing about this test beforehand and I was very nervous when I found out it was being done. Firstly that is would not pass and secondly that they would fry my only demo amp! All good though!

 

[sfabio]

I agree the 2 pins sticking up live in this example isn't ideal. Normally they are not populated and if they are they have a 'dummy' plug over them. My bad.

Maybe you could use female connector on pcb and male connector on cable, so no "live pins" and no need of dummy plugs?

 

[KJF audio]

Maybe you could use female connector on pcb and male connector on cable, so no "live pins" and no need of dummy plugs?

Funnily enough I did ask JST the connector manufacturer about this but they have no plans. The connectors are the same as used on the hypex modules and it was important for ease of manufacturing the cables to be using the same connectors each end. In fact apart from screw and spring terminals there is very little out there that is female. I'll make sure to use the dummy plugs in the future or leave them out altogether.

 

[laidick]

Hi @KJF audio,
May I know if your latest production has improved according to the comments here?
For example the cable holder using screw instead of glue?

Thanks

 

[walt99]

I see the left and right side and the rear panel getting a chassis earth, and, by extension perhaps the base panel and the front panel via the right angle brackets and screws. The top panel has no connection to earth (unless there is a separate cable which @amirm removed (and flicked up the term block lever) to take off the top cover) as the 6 screw/nut arrangement sits in anodized slide channels in the extrusion. The earth connection from the IEC is also broken via the terminal block spring connection arrangement instead of going straight to chassis. And it is a spade terminal from the IEC.

I don't like a full width run of mains across the rear PCB at all. Or the runs of single insulated mains around the cabinet.

The front power switch/LED ring soldering looks poor and un-covered (heatshrink). Yes, I know it's LV, but it looks half finished.

Agree with the zip tie having nasty sharp ends. One of my pet hates too. Buy yourself one of the these:
View attachment 126088

Other than that, it appears just like any other guy screwing boring Hypex modules in a box with more holes in the base plate than Swiss cheese. If this is the course of amplification going forward, it's depressing.

Get the real thing! Panduit, one of my favorite tools. (or at least a pair of flush cutters for god sake)

 

[sarumbear]

... it appears just like any other guy screwing boring Hypex modules in a box with more holes in the base plate than Swiss cheese. If this is the course of amplification going forward, it's depressing.

This is the problem. They are DIY builds.

edit: I removed the Google maps images in response to the manufacturer’s request.

 

[KJF audio]

Thanks for posting a photo of my house

This is actually my registered business address, I have a small unit/warehouse close by where I keep all of my stock and do all of the amp and speaker builds.

 

[sarumbear]

Thanks for posting a photo of my house

I didn't post the photo of your house. I posted a Google image. You should ask Google to remove your house's view.

This is actually my registered business address, I have a small unit/warehouse close by where I keep all of my stock and do all of the amp and speaker builds.

That is why there are normally two addresses for businesses: Your registered office address and your business address, where you actually run your business from.