Question about transformers/grounding with single all wood chassis
Sep 18, 2009 at 9:52 AM Thread Starter Post #1 of 13

rshuck

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To go along with the other thousand questions I've already asked, I have another.

My plan for the Beta 22 is now going ahead. I am slowly gathering the materials I'll need for the project, and I've come across a great looking all wood chassis. It's essentially the same thing that amplifiers came housed in during the 60s and 70s. I know that Dynaco had one just like this. It's basically a four-sided box with a removable front and back panel, which I plan to make from thin MDF and plexiglass.

This will have no metal in the chassis aside from the screws holding the panels in.

I want to integrate the Beta 22, Sigma 22, and Buffalo 32 into the chassis with all three transformers inside. It'll be a bit of a tight fit, but all should work out ok.

My idea for shielding the components from the transformers is to build a faraday cage inside the chassis, surrounding (but not touching) only the transformers. Will this be sufficient sheilding to minimize interference? I'd have to connect the cage to earth ground of course.

And then, how would I connect pin 1 of the XLR (hypothetically, there will be no actual XLR, just internal wiring). I read in another thread that a metal chassis should be connected to earth ground and signal ground. In this case, presumably not to the cage as it would introduce badness into the ground reference.

Any tips for how I can pull this off? Also, will high frequency (4kHz) switching from an ElectroLuminescent inverter cause problems in either the cage or the unshielded part of the enclosure?
 
Sep 18, 2009 at 7:13 PM Post #3 of 13

MoodySteve

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To save space (and possibly cost, if you haven't gotten parts yet) why not get a single shielded/potted transformer with all of the required voltages for your ß22 and Buffalo? Around 150VA should be more than enough.
 
Sep 18, 2009 at 9:10 PM Post #5 of 13

Emooze

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I agree with everyone else, shoot for shielded transformers. 1 toroid causes very little noticeable noise in my all-word M3 + S11 case but I can't imagine 3 is going to do very well at all.

I am assuming you will need to connect the XLR ground to the signal ground and those to ground with a group loop breaker but get a second opinion on that.

And yes, that inverter is going to make noise. Shield that too if possible.
 
Sep 19, 2009 at 7:30 AM Post #6 of 13

rshuck

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Thanks for the replies guys. Any tips on how I could pull this off? What would I need to get rid of the noise?

That plexiglass build is ok, but I'd have the three transformers.

Want to avoid buying a single shielded transformer because it'd be dual primaries (for 110/220), and SIX secondaries (+/-30, +/-15, +/-9). Getting a shielded one would cost a fortune I'm sure.

*** after further reading, it appears that I'd need three separate transformers anyway.
 
Sep 19, 2009 at 12:52 PM Post #8 of 13

rshuck

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Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif
Not necessarily, you can even use it to power speakers, just grab one of these.
DIYCable.com : Intro » Home » Exodus/Hypex Amps » Amp Parts »

0-16V 1A
13V-0-13V 1A
x2 30V 10.5A

It's massive overkill, but it's potted, shielded and CHEAP



That actually looks really good, but I thought I read something about the Buffalo32 needing separate transformers for the analog and digital sections so they wouldn't have a ground short.
 
Sep 19, 2009 at 7:05 PM Post #10 of 13

DoYouRight

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I wanted to put my b22 and b32 in one case as well but the shear size is unreal it would have to be mega tall or something to fit all the boards and stuff. even if there is a b22/b32 chassis and than a psu chassis still insane space needed.
 
Sep 20, 2009 at 1:18 PM Post #11 of 13

vixr

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I know you guys will think this is BS, but I left the toroid (not shielded) in my B22 loose enough to rotate when I built mine. I was able to get all the hum out by rotating the toroid until the noise stopped, then tightned the thru bolt on the toroid. It also worked on my CKII3
 
Sep 20, 2009 at 2:48 PM Post #12 of 13

qusp

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no I could understand how ^^ that might work, but that was just a beta22, not only does he have more thaings he must avoid influencing with the toroid, but we are dealing with elements that are much more sensitive to noise in the first place,such as the digital section of the B32. its possible, but as mentioned I feel it would have to be huge unless a shielded trannie is used. i'm no expert in this area thats for sure, so take my opinion with a grain of salt, but I wonder if it could be more trouble than its worth. why not a 2 box build?? one with trannies for both builds and the other with the B22 and B32
 
Sep 20, 2009 at 4:46 PM Post #13 of 13

rshuck

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Quote:

Originally Posted by qusp /img/forum/go_quote.gif
why not a 2 box build??


Well, I could, but I have this thing about using two boxes when I could use just one.

The more I look at this and the dimensions of the target enclosure, the more I think I'll have to use two boxes anyway.

Here's the enclosure I'm looking at - Metal Project Boxes - it's called "Wood Audio Amplifier Cabinet" and is down on the right hand side. I was worried about him selling out, but it says he has several HUNDRED of them.
 

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