Making An Amplifier From Raw Aluminum - The Back Panel and Installing The Amp Boards
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- Опубліковано 8 січ 2022
- Watch part 1: • Making An Amplifier Ca...
Now that the case is mostly finished, I can get the amplifier boards installed and tested. Not only that, but also to put the project on hold for a while and use it in the meantime. I'm waiting on parts that I haven't even ordered yet to complete the amp, but it's fully functional (as an amp) and figured the best place to store it while I wait is in my listening room hooked up to the subwoofers.
Another issue holding me up is the design for the front panel. I haven't come up with anything I'm completely happy with and the only cure for that is time away from the project.
Regarding heat: if you watched me install the first amp board, you will see that I put mica washers between the output transistors and the aluminum bottom plate of the amp. That washer is needed to electrically isolate the transistors from the case, since these transistors have a metal back that's tied to the transistor collector. Mica has about the same thermal conductivity of the glue I used to fasten the heatsinks (in the previous video), but it MUCH thicker than the layer of glue. As shown with the amp's bias turn up to 200mA+ per output, the heat has no problem finding its way from the bottom plate to the heatsinks. That bias, if you aren't familiar with this stuff, is way beyond anything used for normal class AB amps. Typical value is in the 10 to 100mA range.
The benefit of using aluminum to build the case is that the entire case becomes the heatsink. So even the cover is dissipating heat to cool the amps.
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Watch part 1: ua-cam.com/video/UKhRA_GcmPI/v-deo.html
Now that the case is mostly finished, I can get the amplifier boards installed and tested. Not only that, but also to put the project on hold for a while and use it in the meantime. I'm waiting on parts that I haven't even ordered yet to complete the amp, but it's fully functional (as an amp) and figured the best place to store it while I wait is in my listening room hooked up to the subwoofers.
Another issue holding me up is the design for the front panel. I haven't come up with anything I'm completely happy with and the only cure for that is time away from the project.
Regarding heat: if you watched me install the first amp board, you will see that I put mica washers between the output transistors and the aluminum bottom plate of the amp. That washer is needed to electrically isolate the transistors from the case, since these transistors have a metal back that's tied to the transistor collector. Mica has about the same thermal conductivity of the glue I used to fasten the heatsinks (in the previous video), but it MUCH thicker than the layer of glue. As shown with the amp's bias turn up to 200mA+ per output, the heat has no problem finding its way from the bottom plate to the heatsinks. That bias, if you aren't familiar with this stuff, is way beyond anything used for normal class AB amps. Typical value is in the 10 to 100mA range.
The benefit of using aluminum to build the case is that the entire case becomes the heatsink. So even the cover is dissipating heat to cool the amps.
So cool, John. I’m feeling sympathetic build satisfaction from this video, and I like it.
Aside, every Spring Annie and I put a fresh coat of glue on the roof and exterior walls of our house; Cut our summer climate expenses by 75%. The neighbors think we’re nuts.
Excellent build quality. My own DIY electronic builds look more like old rat’s nest of color coded wires 😂 they work but never pretty like yours 👍🏻
Although I am not into the audio, I certainly appreciate your passion and the attention to detail and craftsmanship. Enjoy your videos..
What a beautiful piece of equipment! Enjoyed watching you building it.
Really enjoying this new channel. In my younger days I installed very expensive car audio systems and though I’m really good at the installation and wiring I have always been interested in what makes audio equipment tick. Looking forward to more content.
This was such an awesome video, this whole amp series is. I can't wait for the follow up, hope those parts you're waiting for come soon!
Really loving the top cover frosted look and the grill and everything 😍
Even though you won't see the inside and the back, the quality of work done there is better than what I've seen on most factory produced electronic products. I think you've said before that years ago you wanted to do this full time. You would have done well.
I read a few comments here with a few knocking PL as a thermal paste and it just goes to show that some people do not think things through. Instead of enjoying the build and seeing the quality that most of us couldn't attain they focus on a non-existent problem.
What I'd like is to do something like this on one big "W" shaped circuit board and eliminate the wiring altogether. That would be neat!
the toner transfer also works as masking for etching to get recessed markings
Good stuff, John! Very neatly put together.
The first thing you do is not set idle current, it's measure for DC at the output.
That's also the first thing you do when you try out any new-to-you amplifier or receiver.
I am not into speakers and stuff but I am glad to see you back. Hope "the holidays" were good for you.
Great job, nice work John! I suggest next project - sheet bending machine/tool.
Nice job on the amp John! Looks great' Thanks for sharing the video with us💖👍😎JP
Nice project again.
You could made the box design by using 2 U shapes 90 deg. apart to form the base and lid. Front can then be wood glued into place or plastic or glass or whatever.
I'm really liking this series...well, all of your audio-related stuff to be honest. Are there going to be plans available for the amplifier? I've been wanting to try my hand at this and your work is an inspiration.
Brilliant
Although I've DIY'ed a Pass clone design, I don't believe I'd do it again.
Good lookin' out John, bravo 👏
Nice work
Looks great John!
Thanks Greg :)
So cool John!
Thanks :)
Perhaps try some Wago connectors in place of the choc block screw connectors
Masterpiece!
Awesome job! What is that drill bit you used after the stepper bit?
Nice looking stuff! A saw a lot of times some people split the capacitance at multiple pieces (4, 6 or 8 identical value). What would be the reason for that?
Hi John, do you still have a schematic for the soft start circuit? I've been trying to make a soft start circuit to add to a souncraftsman high power stereo amp ! Thanks for another great video!
Such a clean build. Even your component layout looks "designed". Is the chassis ground?
The chassis is earth ground, like all exposed metal that's connected to the mains needs to be. The star ground for the power supply is "lifted" above the earth ground using a 30 ohm 10watt resistor (see that in the overhead pic at the end of the video between the caps and the tansformer) that is bypassed with a pair of diodes. The input ground for each amp in further lifted with a 10 ohm resistor and another pair of diodes. This scheme kills any possibility of ground loops that cause hum.
@@IBuildIt Right on, thanks. It looked to be like the output ground was isolated from the chassis. I'm not an expert in the slightest and I'd never seen that.
The three grounds (earth, power and input) are still connected, so not isolated. The best way to look at this is to see them as pools of water that are connected with rivers. Current will gather in one pool, but will resist flowing into the next pool.
@@IBuildIt that's a fantastic analogy, thank you.
I use a laser printer on "decal paper" for labels. Just soak in water, position and apply clear coat.
This method (when it's done right) looks like silk screen printing. The decal method is ok, but not nearly as pro looking as this can be.
Hi John, quick question: between this video and the previous the interior was painted or coated black, was it just standard spray paint or something else?
did you use varnish to protect the toner? video show
SUPER!!!
Don't worry about the Glue for the heatsinks :)
I took my graphics card apart for cleaning and only then realized i didn't have any thermal paste. As I needed the PC to run i grabbed some oil resistant silicone sealant and put a dab of it on chip before mounting the heatsink. it was meant to be a quick "better-then-nothing"-fix, but i realized the difference to real thermal paste is maybe a few degrees and just left it like this. It's just my basement PC that does not get used very often, but it still works like this more then a year later!
The "thermal compound" I used to mount the amp board (in that white stick that I rubbed on) isn't thermal compound, it's a silicone based lubricant. Works just as well as the real stuff in my experience.
lol. there's no way it's within a few degrees unless it's thermal throttling under load.
This is great. I'm curious how you determine how much copper to give those giant caps? I'm almost ready to dive back into my Hafler rebuild and I've an assortment of sizes of chunky copper my scrapper genie gave me for a burlier bus bar. Any thoughts? I think my caps are around the same size, maybe 47,000
Caps can conduct huge current for a very shot time, but in audio they are mainly used for smoothing which isn't likely to draw much current in average. Look at the fasteners (or pins on "smaller" ones) on the cap to give you an idea.
hi where can i find the kit for this amp?
What kind of "paper / items" are you using with the Iron to get the text to stick ?
What’s the total cost of this amp?
John you really seem to know a amp design
Question for you
All amps I have built I used more caps in series to get capacitance up
Is it ok to do this or use 2 large value caps instead of the 6 smaller ones
Thank you
series caps increases ESR, paralleling caps decreases ESR(BETTER OPTION)
Hi, very neat trick of ironing a laser printed label on aluminium ! Where can I find the schematic of the amplifier ? Thanks for your videos
The iron on trick is not new for PCB design, but I had never considered using it for labeling, very neat solution, really looks effective.
@@rompdude Done that before using colour prints, laminated so they were more resistant, and then stuck down to the surface with glue.
Nice trick indeed! Would this work with photocopied paper as well?
What's the difference between raw aluminium and aluminium?
Greetings John! May I ask you what is the top cover aluminum sheet total width and after bending what is the width and height of your amplifier ? I need to make one box for my next project so maybe this could be awesome solution...
Could u give a dummies version of all this sound tech? The hardware and what one tries to accomplish? Sorry if this was already done.
I can't figure out what you've done wrong here but I'm sure it will come to me and I'll let you know about it. Great work as usual John.
OMG do you really work at a room temperature of 9° in your shop?
Do you screw the heatsinks down too?
If so maybe using CPU thermal paste would be better than the glue
The point is that when you say something is "better", it's better by how much? Is it 100% better or is it just 1% better? And when I say better, I mean at actually conducting the heat across the join, which is what I measured in this video.
If it's just marginally better, than it's not worth making a fuss over.
Obviously, the heat isn't having any problem reaching the heatsinks since they are the same temp as the back plate.
It is a sliding scale and depends on the temp range, if you look at most of the components used they are rated over 100ºc, so getting to 30-40ºc is nothing.
Getting to 30-40 C at nearly 10 times the normal bias current. The amp doesn't get above 25 with all 4 boards installed and running when they are set to the normal bias current.
Fussing over the efficiency of the glue for transferring heat is the kind of minutia that too many people get wrapped up in. They literally make mole hills into mountains.
@@IBuildIt
Can you run a test with the transistors driven with a resistive load? Because what you're checking here is essentially the resting state of the amp and doing the "will this burn down my house?" Check.
However if the transistors hit much higher Temps under load and the heat sinks can't keep up, you will toast the device. The fact that you had notable temperature deltas on Initial startup and moving into steady state tells me it's worth checking to make sure.
We're talking orders of magnitude between by the way. Not like 30% more like 0.8 W/mK vs 70 w/mK at the highend end of performance, So ~100x better (orders of magnitude)
May thermal adhesives are in thr 14 W/mK department so ~20x better.
Yeah good enough is absolutely a thing, and if it works then rock on, however from a general perspective, using an insulating adhesive is a bad idea.
You mean a test with a resistive load... like four 12" woofers? Been conducting that test at moderately high levels for several days now.
Guy, give it up. You know some stuff but what you lack is the real world perspective to rate the importance of it.
John, it dosen't matter how thin it is, any amount of a thermal insulator between the two surfaces will drasticallyreduce the effectiveness of your heat sinks. This is why thermal adhesives are a thing. Now if this bottleneck in your thermal management is still larger than your overall thermal loading, then who cares move on. However if your trying to get good thermal performance, and make actual use of that full heat sink, then a thermal interface is a must. Surprisingly there's a limit to how much a heat sink will do for you if the thermal interface point between the source and the sink sucks. Your not dumb, you know these things, I just wouldn't hand wave away this aspect of the build without making sure you don't have a critical thermal bottleneck.
I got as far as "it doesn't matter how thin it is".
Seriously? Think about that.
@@IBuildIt yes seriously think about, no wait don't, go actually read about it. The moment you add an interface like polyurethane adhesive with a conductivity of like 0.8 W/mK you absolutely obliterate the transfer effency. So even though it's only a thin coating, it's a massive bottleneck. Thermal compound is 70ish W/mK to give you some perspective. The metal itself is at 237 W/mK. This transfer effency is heavily effected by surface contact area as air is 0.025 W/mK.
thermal contact conductance coefficient is what comes into play here and surprisingly, even without a thermal interface, metal to metal and all its surface imperfections with sufficient (reasonable) clamping will still have better thermal transfer than if you just slapped a thick ass layer of what is essentially a thermal insulator
And yes, thick ass layer. We're talking about distances in the microns here when it comes to thermal interfaces. So your polyurethane adhesive is thick as hell in comparison.
This shit not straightforward and in some ways can be counterintuitive. Thermal interfaces and heat sinks are a rabbit hole of engineering. However ask yourself... Do they make insulation out of the material I'm about to use? (polyurethane) If the answers is yes then it's probably a bad idea to use it as a thermal interface. The mere fact that you have such noticeable temperature deltas along the heat sinks and such a delay is a great indicator of how not efficient polyurethane is.
Now again, if this isn't causing a bottle neck for your given application, then sure, keep on rolling.
However please don't tell people this is an generally acceptable heat sink mounting method, it's not.
It matters but it doesn't matter. It may make a measurable difference but that difference is so small as to not matter. And the thinner the TIM (thermal interface material), the less that thermal resistance matters. It makes a bigger difference where the thermal load is high (in the resistance analogy think high resistance with high current) and the source of the heat is very sensitive to not being cooled such as with overclocking CPUs. But even there people probably go overboard. Here, as long as John keeps the layer very thin and has literally checked and verified the performance, it doesn't matter if it is 2nd or 3rd or even the 10th best option, it is effective.
The PL has roughly the same thermal conductivity as the mica I used to isolate the transistors... but is probably 100 times thinner.
You saying the thickness doesn't matter blows out everything else you say. It's like starting a talk about the environment with "since the Earth is flat..."
In construction, glue is a thermal bridge, not a thermal insulator. Two very different things. An object's surface area and thickness definitely plays a role in heat transfer and dissipation, for sure. Even specifically designed thermal paste becomes all but useless if it's caked on in a thick layer. But the bot is a bit too anal retentive to accept that someone does something different. The reality is that it's not up to the bot to dictate what is or isn't acceptable. If it works, John, just tell him to fuck off and test it for himself.
4:30 You should really switch over to Speakon connectors for the output, they are far superior in every way to Banana Plugs, but you can't stack them and you can't reverse the output. But really, after things are set up and running, when would you ever need to do that anyway?
Someone else asked if it will have balanced inputs. It's not PA gear, it's for home audio - set it up and occasionally wipe the dust off it.
основательно сделано
TIM's are never as conductive as the metals they are adjoined to. The Mica sheets probably have pretty terrible conductivity, but it doesn't really matter as they are needed electrically and make little difference due to the thickness.
The glue would have likely been better than a dry connection as air is a terrible conductor.
There's thermal paste epoxies you can use
There are also ready made amplifier cases that I could use, or, skip that and go straight to the ready made amplifier that I could use.
It's not about what's available, it's about using what you have on hand if it does what you need to get done. Why is that such a difficult concept for so many people to understand?
@@IBuildIt it was more of a friendly suggestion, incase you weren't aware of the products existence, than anything else as always I admire your work, great job John
I see that a lot, though. And what most people don't realize is that these specialty products were developed for a market that requires a proven product with specs that can be looked at to fill the specific need. That usually means that they are hard to get and expensive in small quantities, and perform just marginally better than a similar product that's not speced for that use.
@@IBuildIt you're talking to a guy who repairs most of his stuff with a hammer, so I get it bro, keep up the great work
@@IBuildIt It's like 7-10 bucks for enough to do your whole amp. I just don't get why you're so firm on not using it. Why not just be like... "Oh cool, I didn't know that it. My I'll try it on my next build." instead of instantly rejecting the dozen people who are telling you otherwise. Obviously you didn't even look into even the pricing, let alone the science behind it.
Looks great. Please solder over any naked copper. It protects the naked wire fron oxidation.
🍌🔌 🤭 softstart wonder if that'll work on ac electric motors 🤔🤔🤔
why not making the front panel out of wood?
I've been watching this series and my nephew walks by and goes "Pfft, all this so he can listen to his crappy BOOMER music.." I responded "At least it's actual music, rhyming your words doesn't make it music, it makes it poetry."
Except poetry usually makes sense lol. Seems like your nephew is set up for a life of dependency on his future employer and the state. Sad that kids aren't learning any real skills anymore.
Thing about the BOOMERS (I'm not one, actually) is they BUILT nearly everything that young people today have the luxury of taking for granted.