power busbars for my eurorack case

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BWBKc6VyUr
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power busbars for my eurorack case

Post by BWBKc6VyUr » Wed Mar 18, 2020 6:14 am

I'm building a eurorack case for myself, fitting racking rails and a power distribution system into a suitcase. I'm a bit obsessive with keeping my equipement's noise floor as low as I can. So after reading a few MW discusions on the topic, as well as Graham Hinton's web pages, I've decided there's valid grounds to install power busbars in this system.

Everybody seems to go for aluminium bars. I understand that aluminium is very lightweight but many people use it in cases that are clearly not designed for mobile usage. So my first question is, why not use copper, which is about 1.7 times more conductive than aluminium?

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Re: power busbars for my eurorack case

Post by StillNotWorking » Wed Mar 18, 2020 6:35 am

Cost. Aluminium are MUCH cheaper
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EATyourGUITAR
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Re: power busbars for my eurorack case

Post by EATyourGUITAR » Wed Mar 18, 2020 9:17 am

for a small case there really isn't a problem with copper. the biggest problem is keeping it free of oxide before you do the install. this all comes down to impedance. if you have the inputs of the two bus boards less than 12mm apart and they are connected with 12 AWG then it is almost ridiculous to think that the bus bar is significantly better.
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Re: power busbars for my eurorack case

Post by sduck » Wed Mar 18, 2020 10:53 am

I used these guys - https://www.digikey.com/product-detail/ ... -ND/348251 - copper, but aluminum (I think?) covered. They're kind of expensive, but they're also long, so you may be able to cut them in half. Scroll down on that page for some other useful stuff.
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BWBKc6VyUr
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Re: power busbars for my eurorack case

Post by BWBKc6VyUr » Wed Mar 18, 2020 11:03 am

StillNotWorking wrote:
Wed Mar 18, 2020 6:35 am
Cost. Aluminium are MUCH cheaper
Granted, there's a price difference. But I can pick up 16cm-sided, square, C101 copper bars from eBay for under £10 so that's acceptable to me.
Besides cost considerations, any reason to stay clear of copper bars?
EATyourGUITAR wrote:
Wed Mar 18, 2020 9:17 am
... bus boards ...
To clarify, I'm not planning on using boards: you are right it nulls the benefits of the bars. Plan is PSU sense outs straight to the bars with shortest, thickest wires as practically possible; crimp-on eyelets plus adequately thick wires to connect the bars to each module.
EATyourGUITAR wrote:
Wed Mar 18, 2020 9:17 am
the biggest problem is keeping it free of oxide before you do the install.
can you elaborate? (I understand the impedance implication of oxide layer around the bar.)
Last edited by BWBKc6VyUr on Thu Mar 19, 2020 8:54 am, edited 1 time in total.

BWBKc6VyUr
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Re: power busbars for my eurorack case

Post by BWBKc6VyUr » Wed Mar 18, 2020 11:11 am

sduck wrote:
Wed Mar 18, 2020 10:53 am
copper, but aluminum (I think?) covered.
Thanks for the recomendation! Tin-plated (not aluminium), because tin doesn't oxydise -- would solve the issue raised by EATyourGUITAR, and not really more expensive than plain copper bars of similar dimensions I've come across so far...

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Re: power busbars for my eurorack case

Post by KSS » Wed Mar 18, 2020 12:27 pm

BWBKc6VyUr wrote:
Wed Mar 18, 2020 11:03 am
Besides cost considerations, any reason to stay clear of copper bars?
Weight.
Corrosion.
Difficulty machining. Copper is work-hardening, and dulls tools quickly.

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Re: power busbars for my eurorack case

Post by astrosound » Wed Mar 18, 2020 12:39 pm

From what I've gathered, the superior conductivity of copper is not a meaningful difference in a bus bar distribution system for a modular. If there was, I suspect Hinton for example would be using copper. When you start splitting hairs over fractions of ohms, other parts of the power distribution start showing weaknesses that are more significant than copper vs aluminum.

And yeah, copper can be a bitch to machine. Has a nice color though!

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Re: power busbars for my eurorack case

Post by Graham Hinton » Wed Mar 18, 2020 1:08 pm

BWBKc6VyUr wrote:
Wed Mar 18, 2020 6:14 am
So my first question is, why not use copper, which is about 1.7 times more conductive than aluminium?
All your questions and more were discussed in the thread when I originally introduced the concept: Ground loops / star ground / shielding theory

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Re: power busbars for my eurorack case

Post by EATyourGUITAR » Wed Mar 18, 2020 1:29 pm

BWBKc6VyUr wrote:
Wed Mar 18, 2020 11:03 am
can you elaborate? I understand the impedance implication of an *oxide (edit: spelling) layer around the bar.
there are a few. it depends on the condition you get it and the storage and handling conditions after you receive it.

the green is CuCO3. greenish blue is a mix of CuCO3 and CuOH2. CuO is black and Cu2O is copper color. I live near salt water air. but anyway, in general, aluminum or copper reacts with O2 very quickly. the good news is that the oxide created a barrier to air and an electrical insulator that stops or retard further oxidation. some metals always have an oxide on the surface like aluminum. it happens very fast but it is very thin and the thin layer stops any further reaction. all aluminum is wearing this skin suit. very easy to clean because it is super thin. it matters with semiconductors though. sometimes this leads to new semiconductors. when you attach the wires to the aluminum bus bar you are actually cleaning it just from metal on metal contact. that oxide is so thin and weak it can't persist with mechanical wear. the copper is a bit different. I prefer copper for obvious reasons. but I treat it is dirty unless it is clean. I only clean it when it is time for bonding (time of installation and wiring). there are definitely chemicals available for this reason. they have been posted here on muffwiggler in the past. you etch a PCB then spray it and put it into storage.
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BWBKc6VyUr
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Re: power busbars for my eurorack case

Post by BWBKc6VyUr » Thu Mar 19, 2020 9:03 am

Now that's what I call elaboration, fantastic explanation thanks EATyourGUITAR. That's me off plain copper now, although I still like those Phoenix Contact busbars, with a tin-plated copper core.

Now I'm going to read the specific thread pointed by Graham Hinton.
Last edited by BWBKc6VyUr on Fri Mar 20, 2020 5:36 am, edited 1 time in total.

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Re: power busbars for my eurorack case

Post by KSS » Thu Mar 19, 2020 12:02 pm

BWBKc6VyUr wrote:
Thu Mar 19, 2020 9:03 am
That's me off plain copper now, although I still like those Phoenix Contact busbars, with a tin-plated copper core.
You don't need to be put off by the Phoenix bars. Bus bar is what they're designed to do and the plating solves any issues EYG brought up and also the machining issue I brought up. If you can use them and they make sense for you do not be put off by them. I do believe personally that plain aluminum *is* a better choice than plain copper.
Now I'm going to read the specific thread pointed by Graham Hinton.
A very good idea indeed! :tu:

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