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DIY Purifi Amp builds

starfly

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So, if I'm someone with very little electrical/electronics knowledge and never used a soldering iron, how hard and dangerous would it be to build my own amp with Purifi or Hypex modules, ideally one that would also have a 12v trigger and both XLR and RCA inputs with a switch to toggle between either input, and perhaps a buffer (I think that's what it's called?) or some other circuitry that would eliminate any plops being sent to the speaker when switching on/off the amp?
 
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JimB

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You don't need to be particularly skilled to apply thermal paste with CPUs:
...
As long as you don't use too little, it seems you can be pretty slap-dash without any detrimental effect.
I'm fully on board with CPU recommendations, but, in deference to the points made by @LarsS, you do want to achieve a VERY thin layer and you don't want air pockets. That is not trivial on a larger surface, such as the entire base of the 1ET400A. Too thick is actually worse than none, for us. So, you want to be able to work it down and out. It is very desirable to avoid starting with a large excess. You can't just put a big gob in the middle and screw down the corners to achieve the best result. However, a super good result is not needed (as has been noted by Hypex for their modules). Just bear in mind that too much, if not well squeezed out, can be worse than none. Unlike a CPU, you are likely to do better with "not enough" than too much. I can say more later (July?), when I can do a couple photos and a performance comparison test.
 
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I'm fully on board with CPU recommendations, but, in deference to the points made by @LarsS, you do want to achieve a VERY thin layer and you don't want air pockets. That is not trivial on a larger surface, such as the entire base of the 1ET400A. Too thick is actually worse than none, for us. So, you want to be able to work it down/out. It is very desirable to avoid starting with a large excess. You can't just put a big gob in the middle and screw down the corners to achieve the best result. However, a super good result is not needed (as has been noted by Hypex for their modules). Just bear in mind that too much, if not well squeezed out, can be worse than none. Unlike a CPU, you are likely to do better with "not enough" than too much. I can say more later (July?), when I can do a couple photos and a performance comparison test.

All good advices if you decide to go for thermal compound between chassi & amp modules.
Note that you should remove powder coating/paint from the chassi. Ideally the layers should be metal/thermal compound filling air gaps/metal.
Worst case you’ll end up with metal/powder coating/thermal compound/remaining air gaps/metal.

Just ordered my Purifi/Neurochrome/Hypex/HDPlex kit. Will be my next Corona-project after summer. In this application I’ll go for no thermal paste with chassi powder coating removed & polished ... ;-)

Edit: Nice table specifying thermal conductivity for various materials:

1589620026889.jpeg
 
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Count Arthur

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Given that Purifi and Hypex make no mention of it and don't require their amp modules to be mounted to a proper heatsink, I suspect that no thermal paste is necessary. :)

If you look at the Hypex UCD 700 modules, there's only a very small area available for mating with the case or a heatsink:

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Built these nCore monoblocks back in 2013 using chassi from 19zoll.com. They barely got lukewarm, note cooling fins & no powder coating. Sold after a few months so I’m hoping to like Purifi more then the nCores.

1589621228153.jpeg
 

boXem

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Given that Purifi and Hypex make no mention of it and don't require their amp modules to be mounted to a proper heatsink, I suspect that no thermal paste is necessary. :)

If you look at the Hypex UCD 700 modules, there's only a very small area available for mating with the case or a heatsink:

View attachment 63718
Maybe you should have a look at Hypex application note "thermal design".
It starts like this:
"Class D amplifiers’ known high efficiency often leads to a gross underestimation of the cooling required. This document outlines an approach to estimating the cooling necessary for a given choice of amplifier module and power rating."
 
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From Purifi’s document:

7.2 Thermal Requirements
While 1ET400A has very low idle losses and high overall efficiency, adequate cooling is essential for sustained power delivery. Careful considerations must be given to design of the thermal system in order to achieve desired output power specifications.
It is recommended to mount the module on a heatsink, e.g., an adequately design aluminum chassis.
 

starfly

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Is it better (from a performance point of view) to get two individual Purifi boards, or to get the EVAL board? I'm going for a dual channel setup.

I think I'm going to attempt my first amp build over the summer, and while I have 0 experience with doing such a thing, or anything with electronics really, I've built many PCs over the years and in general like tinkering. So I can probably figure this out, and it will be a great learning experience either way.

Are there any good online resources I can use to educate myself?

And reading through this thread it seems like most people are adding a Neurochrome buffer board. What is the purpose of a buffer board?

Either way, to build this amp I'll need:
- 2 Purifi boards (or 1 eval board)
- power supply (smps1200?). Is just one of these sufficient for two channels? Better to get one per channel?
- buffer board?
- chassis
- what else should I look into that will make this a good performing amp?
 

TimoJ

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Is it better (from a performance point of view) to get two individual Purifi boards, or to get the EVAL board?
Get the EVAL1 kit/board. I see no reason for other solutions if you are doing a dual channel system in one box. If you look Amir's review of the EVAL, there is very little point to search for more performance. And it's not actually guaranteed that you even get more performance.
 

March Audio

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Given that Purifi and Hypex make no mention of it and don't require their amp modules to be mounted to a proper heatsink, I suspect that no thermal paste is necessary. :)

If you look at the Hypex UCD 700 modules, there's only a very small area available for mating with the case or a heatsink:

View attachment 63718
The modules whilst efficient still dissipate power and heat. A thin layer of hs compound will assist the the thermal conductivity to whatever surface the module is bolted to.

Hypex do talk about thermal issues

Screenshot_20200516_234544_com.adobe.reader.jpg


Although it should be noted the Purifi is more efficient and therefore cooler running
 
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JimB

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Maybe you should have a look at Hypex application note "thermal design".
It starts like this:
"Class D amplifiers’ known high efficiency often leads to a gross underestimation of the cooling required. This document outlines an approach to estimating the cooling necessary for a given choice of amplifier module and power rating."
I'll just add that, for me, on my DIY projects, the point of good heat management is not only to allow the amp to run at the higher power (occasionally) without shutting down, but also to maintain lower device temperatures to have a longer operating life. With good heat-sinking, other components (caps?) might be the most common limitation on life. Other aspects of case integration can help there...
 
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Get the EVAL1 kit/board. I see no reason for other solutions if you are doing a dual channel system in one box. If you look Amir's review of the EVAL, there is very little point to search for more performance. And it's not actually guaranteed that you even get more performance.

You’re right. I decided for the Neurochrome buffer since the design layout I’m planning in one chassi requires separation of buffers. The other reason is I’d like to support a small, talented business.

Performance wise I don’t I’ll notice anything.
 

starfly

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You’re right. I decided for the Neurochrome buffer since the design layout I’m planning in one chassi requires separation of buffers. The other reason is I’d like to support a small, talented business.

Performance wise I don’t I’ll notice anything.

So what does a buffer board do exactly?
 

TimoJ

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So what to do with anodized brushed aluminium? It's not easy to sand it down to flat surface. But I think anodization is a thermal conductivity barrier, so it should be removed.
 

maxxevv

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In PC modding, there was a time when people did "lapping" of the CPU and CPU cooler's contact faces.
Basically grinding/polishing the surfaces until they were as smooth and flat as possible. It does improved heat transfer efficiency. But that's a pretty extreme application compared to what you get with amp modules here. You are talking about maybe 20~100 times the heat transfer density in terms of Watts per given area.

I don't think its necessary in this amp module application.

But do clean the surfaces of any dirt thoroughly before mating the surfaces. Contact cleaner sprays and a simple air blower would probably be suffice for the preparation work.
 

mocenigo

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So what does a buffer board do exactly?

1. Works as a breakout board making the connections on the 36 pin board connector easily useable
2. It provide impedance adaptation, making it easier for sources to drive the Purifi 1ET400A module - you get more linear response, including better bass, for instance
3. It can be configured to provide additional gain- the Purifi module only has 12.8db of gain.
 
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