RFI Shielding??

[megabigeye]

I recently finished my Quickie and am proud to say that I got it (mostly) right on the first try!  This is my first go at point-to-point assembly, though I've built the Quicksand and a CMoyBB, so I can't say it's really my first DIY.  But I'm proud of myself anyway!

Here's the problem, though: first time I turned it on there was a lot of noise, both a constant static-like sound as well as a constant rhythmic clicking.  Long story short, it turned out it was the Raspberry Pi and HiFiBerry DAC+ Pro I was using that caused all the noise, not the Quickie (somewhat to my surprise and pleasure).  The RPi was causing the static and the DAC was causing the clicking.  I plugged in another source and everything sounded mostly good, so I'm apt to think there isn't anything wrong with the Quickie.
To be clear and fair, the the oscillator crystals in the HiFiBerry DAC cause lots of problems with WiFi interference, and I've already bought a replacement because it's been such a PITA.  So I'm not terribly concerned (yet.  I always reserve the right to become concerned later!) with the clicking.
BUT!  I was hoping to use the Raspberry Pi as the primary source in this system.  As it is, I'm not able to do that.

So I'm wondering if there's some way to shield the Quickie from RFI?  I recently read that WiFi has difficulty going through metal...  so would I benefit from putting it in a metal chassis?  I think the tubes are acting like antennas (the noise gets worse if I put my hands near the tubes while the RPi is on); so do I just need to somehow shield them?  Does shielding need to be grounded?  If so, can it just be connected to the Quickie's ground, or does it need to be actually grounded, like, to my apartment building?  Would I need to replace all wire with shielded wire?  That doesn't sound fun!  (well, okay, kind of it does, but I just got this thing finished)  I even had the (semi-serious) idea of wrapping different parts in aluminum foil to see what happens.

Any input would be greatly appreciated!

Ken

PS-- Of course, this all goes without saying that when I used a different source the Quickie really improves the sound of the Quicksand-- even compared to the $450 DAC/pre I was using before!  I'm really looking forward getting to listen to it more.

PPS-- I was greatly amused that the packing list that came with my Quicksand (a year or so ago) had a handwritten note on it saying that whoever wrote it used to live right across the street from me outside Boston, MA.  I'm kind of assuming it was Josh, since he's the one that packs the kits.  ??  Anyway, whoever it was might be interested to know that the building you used to live in recently sold for $40,000,000 (!!!  Yeesh!) to the "worst landlord in Boston."  Anyway, I really appreciated the personal touch of the note on the slip.  It really made my day!

[fullheadofnothing]

Yes, that was me. That was the last Somerville apartment I lived in. The management company at the time was really great (way better than the one we lived under on College Ave), so it's a bummer to hear about the sale. That building is huge and really nice, so that price actually sounds pretty close to market value.

For RFI, distance from the source is usually more useful than shielding. So try some longer cables, then grab a beer at Highland Kitchen (do they still have that banana bread pudding...?). All will be fine!

[megabigeye]

Hey,
Thanks for getting back to me.  Yeah, I already tried moving the Pi as far as my interconnects would allow, which is to say some three feet.  It did get quieter as it got further away, but it was already beyond the edge of the desk I have it on and it was still distracting during quiet passages.  I guess a new set of longer interconnects may be in my future, huh?

How long ago did you live in Somerville, if you don't mind my asking?  I've been here about seven years and it feels like it's changed in that time.  They're going to start developing Union Square and I'm still unclear on whether the Green Line is going to extend out here.  We actually looked at an apartment in that building before we moved into this place, but it seemed like they must've divided some of the apartments in weird ways.

[caffeinator]

Hi there,

A lot of things like RPi's can cause RF noise...my old Blackberry phone would cause this Morse Code-sounding noise on speakerphones and other similar devices.  Count yourself lucky that you've been able to ID the source.

I just took a class about this topic, and one rule of thumb (or it was more like a rule, actually) was to, whenever possible, shield the noise source as opposed to the device(s) receiving the noise.  Not sure what that would look like for an RPi, but having seen metal box enclosures on various other noise-makers, I'd guess that's the ballpark in which you may find quiet.  Distance also helps, but that's not always convenient or attractive.  The ubiquitous Hammond 1590 series diecast enclosures come to mind, as does a metal junction box to use as to test the theory.

Hope this helps,

david

[Doc B.]

whenever possible, shield the noise source as opposed to the device(s) receiving the noise.

David, that makes too much sense. Stop that. 

[fullheadofnothing]

I lived in MA from 1998 to 2011, first Newton, then Jamaica Plain, and Somerville from 2004-2011. It changed a lot while I still lived there, and continues to. I have family in Newton and Cambridge, plus my wife and I still have a lot of good friends in the area, so we try to visit about once a year.

You're well situated for getting longer cables, being a nice walk from either Q Audio or The Audio Lab. Or if you're looking to roll your own, You Do It Electronics in Needham is pretty great (pain to get to via transit though); they would also have metal project boxes. It's right off 128, near those tall radio antennas. That's where I bought the solder station I still use!
I lived in the area for a long time before anyone ever told me about the MIT flea, which runs one Sunday a month from April to October. Always worth popping in for parts, tools, and just to gawk at cool stuff.

[megabigeye]

David, thanks!  Doc is right: that makes too much sense.  I feel like a dolt for not thinking of it! Might that interfere with the RPi's WiFi reception?
You're right, I was pretty lucky to figure out the source of the problem so fast.  It was coincidence that the first thread I clicked on here happened to be about RFI from a phone or something.  I had a laptop, my phone and the RPi in the same room, so it was pretty quick process of elimination.

You're well situated for getting longer cables, being a nice walk from either Q Audio or The Audio Lab. Or if you're looking to roll your own, You Do It Electronics in Needham is pretty great (pain to get to via transit though); they would also have metal project boxes. It's right off 128, near those tall radio antennas.

Ohh!  I forgot about You Do It.  I've never been, but I remember looking it up and thinking what a pain it would be to get to.  Then, of course, I promptly forgot about it.  Maybe I'll check it out.
I wouldn't mind never going back to The Audio Lab.  Every time I've been I get the feeling that the guy has no interest in helping me and doesn't seem to take me very seriously.  Anyway, this is supposed to be my "DIY and cheap 'n' cheerful" system, so I should probably make my own, anyway.

Also, sorry if I'm prying about your life.  I just had this idea that you probably hadn't been here in a long time and that the place has probably changed a lot (as exemplified by Johnnie's Food Master now being a Whole Foods.  Good bye, sweet carpeted grocery store!)

[caffeinator]

Yeah, there was a kind of corollary to that rule..."things that interfere with transmission tend to interfere with reception also."  So, yeah, most likely the metal box / enclosure would reduce if not eliminate wi-fi reception.

If you gotta have the wi-fi, you probably next turn to shielding the noise victim as opposed to the source.  Might be interesting to try putting the Quickie into a toolbox or other metal container to see if there's any benefit, and if so, maybe some kind of metal enclosure...hey...weren't most quickies built into metal chassis to begin with?  Maybe that plastic top panel needs a layer of foil on the underside with good contact to the metal lower box...

[caffeinator]

Okay...did some quick research on the products page; looks like there's a metal top plate, but a wood base underneath (I think my quickie was a special run with a metal base and plastic top plate...I'd have looked, but made the mistake of lending it to a buddy to try as a way of warming up the input to his solid state effects pedals and amp...never saw it after that).

Sooo, experiment putting the whole thing in some kind of metal box, and if it works, find a metal project box you can put under that top plate.  If that's not sufficient, maybe switch out the tube sockets for the kind with shields.  Or switch the Pi to an ethernet connection and put it in a box...those are so small they might fit in an altoids tin...

[megabigeye]

Wait!  What?  There's a metal top plate for the Quickie??  I can't find it on the parts page.  You had a Quickie with a metal base?  How is it I've never seen these things?

No, using Ethernet is not an option, unfortunately.  So this is kind of going back to what I was originally thinking, wrapping the whole dang thing in aluminum foil.  I can't say trying to line the bottom of the top plate would be fun.  Some of those wires are pretty snug against it.

...Or maybe I'll just do the longer interconnects.

[caffeinator]

Oops...apologies.  I quickly glanced at the Quickie product page and though the pictured top plate appeared metallic.  Reading the description, though, I see it's described as acrylic, like mine.

My Quickie is, though, one of a run that was pre-assembled by Bottlehead, and included a metal box as a base onto which the acrylic top plate had been fastened with screws.  I had no noise problems, but never had a noisemaker like an RPi near it.  I'd guess the metal box is a Hammond, Budd, or one of the many other project box product lines.  It measures the same size LxW as the Quickie top plate and about 2 inches deep. 

It may be that it's not necessary to metalize the top plate - perhaps just using the bottom box would provide enough improvement.  If it is necessary to do more, though, the metal layer could be applied to the top of the chassis plate instead of the bottom.  It would likely be most effective to ensure continuity between the top plate cover and the bottom box (though experimenting with both would be a good idea).  If using a flexible (foil-like) covering, wrapping it around the edge and under to a bare contact patch on the box might be a workable solution.  It seems to me it'd be easier to put the layer on top of the box, since even though it has a lot of protrusions, there at least aren't wires laying all over to try to get underneath.

[Paul Birkeland]

My Quickie is, though, one of a run that was pre-assembled by Bottlehead, and included a metal box as a base onto which the acrylic top plate had been fastened with screws.  I had no noise problems, but never had a noisemaker like an RPi near it.  I'd guess the metal box is a Hammond, Budd, or one of the many other project box product lines.  It measures the same size LxW as the Quickie top plate and about 2 inches deep. 

I'm stoked that you still have one of those hanging around.  We (well, I guess I should say I) built up a run of these to take down to a Can Jam in the Bay Area a long time ago as show specials. 

[caffeinator]

Hey PB,

Yeah - pretty sure it is one of those - this one all in white.  It is definitely still alive and kicking, though I've not seen it in a bit.  I loaned it to a friend to use somewhere in the chain between his guitar, some effects and his amp, to warm up the sound. He liked it so much I've never seen it since.

Your legacy is beginning to loom larger, PB...that Gourmet Spud amp we built in your VSAC class has been used by a couple of guitarist friends as a practice amp or likewise to make a SS amp sound more tubey...fairly often it's had one channel out fed back to the input of the other channel.  I'm told it distorts quite nicely, though I've not heard it myself...like the Quickie, I'm more likely to see it on the side of a milk carton than anywhere else.

Which is why I don't loan things out much anymore...and I've already told 'em to keep their 'strat-skinners' offa my Tode!

[Paul Birkeland]

Your legacy is beginning to loom larger, PB...that Gourmet Spud amp we built in your VSAC class has been used by a couple of guitarist friends as a practice amp or likewise to make a SS amp sound more tubey...fairly often it's had one channel out fed back to the input of the other channel.  I'm told it distorts quite nicely, though I've not heard it myself...like the Quickie, I'm more likely to see it on the side of a milk carton than anywhere else.

It's funny, I still have one that I use as the amp in my workshop.  It has run 24/7/365 for the last 5 or 6 years, still on the same pair of tubes!