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3D Printed amplifier chassis - with or without aluminum
I was looking at some Class D modules today and started thinking about chassis. It can easily be the case that the chassis is the most expensive part of a DIY amplifier. I have done enough searching to know that a chassis does not HAVE to be metal, but it is still the case that most are. This got me thinking about 3D printing a chassis, where I can pretty much do whatever I want - whatever dimensions and cool face plate I come up with.
If I wanted to put some aluminum in the chassis for shielding, I could 3D print the panels with some groves to hold a piece of aluminum (Diagram A below) or I could completely sandwich the aluminum within the walls (Diagram B ). I could put aluminum in all of the walls, or just the top, or the top and back, etc. since the choice is completely up to me. Another alternative would be to buy a cheap aluminum "project box" and just build the 3D printed chassis to enclose it.
From my quick Googling, I think Diagram A is a bad idea from a grounding perspective if I put aluminum on multiple walls as the metal sides would not be tied together for grounding. If the aluminum was completely within the walls, then I don't think that would be a problem So, is there a "best" way I could do this?
I can get cheap aluminum sheets in 1/32", 1/16" or 1/8" - is 1/32" fine for shielding?
Comments
I work with a HAM guy. He said if you want to shield a device for a given frequency, there can be no opening larger than 1/4 wavelength. For 2.4Ghz (wifi, microwave ovens, etc), that's 3.125cm or 1.23".
I guess do with that information what you will.
They also make conductive shielding paint for use in guitars. That's another option, though spendy to coat the entire interior.
It also depends on the amp, and how sensitive the speaker is. Have you tried the amp bare yet?
Spray adhesive and aluminum foil... I'm only half joking
I do have aluminum-foil tape and copper-foil tape.
I don't have specific speakers in mind, but likely the typical DIY speakers of around 83-86db.
I didn't have an amp yet when I posted, but just bought a two refurbished Hypex UCD180 amps and a Hypex SMPS400A180 power supply for less than I could get a refurbished Dayton APA150, so I guess that is what I'll be working with, LOL.
What are you trying to shield? The PSU from the amp modules?
_My advice would be to use aluminium for some heat sinking, and how it much depends on your ambient temperature. _
Here's why:
In the case of UcD, if you're thinking of Electro Magnetic Interference, you don't really need to do it with aluminium shielding. The SMPS and amp modules are well designed, taking into account considerations like component placing, careful layout and design of PCB, shieldign of critical parts, filters etc to address EMI/RFI issues.
I've been using Hypex since 2012, particularly UCD400 and nCore400.
My Designed in Sweden dual mono block 100WPC class A/B Primare got cooked in tropical northern Australia.
Had to replace the entire circuit board thanks to Primare modern design and complete reliance on SMTs, and of course Far Eastern Manufacture. So it meant it was cheaper/faster for me to get an entire replacement board than request my local authorised repairer to troubleshoot/repair it.
After the replacement and the ~US$700 repair bill, to prevent in happening again he advised me to "use amplifier an air-conditioned room". Hmm right
. So I sent that amplifier 1,600 miles away, to a cooler more temperate place (my parent's place)
OTOH, my Hypex UCD400MP (UCD400 + integrated PSU) didn't get cooked, but was infiltrated by a small insect that had crawled along a line PCB trace and blew it. Talk about "bugs" in the system. My tech guy said "the case needs to be protected against insects". So I did, but decided against sealing it completely, in case of over-heating...
At no time did I use an internal aluminium shielding for EMR/RFI for my Hypex amp modules or power supply, and I don't have any noise/hiss issues (and my midrange is 100dB/2.83V sensitive)
So that was my main thinking. And I had read similar things on other forums, but they were short and not very convincing. Thanks for the additional background, as I feel comfortable not worrying about the EMR/RFI in these modules.
I guess my other concern was whether there were some reasons to use, or not to use, aluminum shielding that I wasn't aware of. Obviously, if I can 3D print a simple box without extra complications, I'm all for it.
Obviously, if I can 3D print a simple box without extra complications, I'm all for it.
^^^
That's my recommendation.
I used the long-winded story (context, background and comparison point) in hope that it would explain why heatsinking is more important than EMR shielding for these Hypex designed modules.
If I had just said "she'll be right" perhaps @GeoffMillar may have understood me.
But it would have been too short and may have sounded dismissive of your concerns, which are completely legitimate for traditional class A/B amps using through hole components.
I once had a DIY class A/B amp where I could JUST NOT get rid of that slight hum and buzz...
BR,
Thanh
I haven't heard 'she'll be right' for a few years, nowadays it seems to be 'no worries' or 'no probs'?
Geoff
All good 👍