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PCB mounting for Beta22

post #1 of 22
12/22/09 at 1:40pm
Thread Starter 
After a long hesitation, I decided to take the plounge and start building a B22, 3 boards.
I'm still gathering pieces right now but already started thinking about the layout. I'll probably go with a single-box chassis (ordered a nice shielded and encapsulated toroid from primrose) and would like to make it very compact. So, logically, mounting the pcb perpendicularly to the bottom would be the most space saving layout... using some kind of rail or slot.

I haven't seen any example of B22 done this way... is there any reason ?
What kind of accessory should I use to mount a board this way ? I've done some research but didn't come up with anything...

Thanks !

The most compact layout I came up with was : 3 boards @90, the psu and above, the sigma 22 board. The feasability will depend a lot on the heat realeased by the transformer... will see.
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post #2 of 22
12/22/09 at 1:47pm
Quote:
Originally Posted by LeMat View Post
So, logically, mounting the pcb perpendicularly to the bottom would be the most space saving layout... using some kind of rail or slot.

I haven't seen any example of B22 done this way... is there any reason ?
What kind of accessory should I use to mount a board this way ? I've done some research but didn't come up with anything...
Heat dissipation will suffer if you use the normal heat sinks because they are designed to be mounted upright. If you want to try it, I would suggest making/finding some sort of angle bracket that would let you mount the boards using all four screw holes. With the heat sinks on top mounting the boards using the bottom pair of holes probably isn't going to be enough to keep them in place.

/U.

EDIT: The transformer shouldn't produce any significant amount of heat if you stick to the recommended sizes.
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post #3 of 22
12/22/09 at 1:53pm
I know the one-box build is very attractive but time and time again, its been shown that the 2 box method for the b22 ends up the best. even with magic trafos.

a word to the wise. reconsider putting the trafo (at least) in its own box. the psu board and b22 boards can go in the same box (actually quite optimal that way).

then you also have more room for heatsink radiation.

b22 tends to want to pick up trafo hum. again, word to the wise..
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post #4 of 22
12/22/09 at 2:02pm
Thread Starter 
Quote:
Originally Posted by Nisbeth View Post
.... I would suggest making/finding some sort of angle bracket that would let you mount the boards using all four screw holes. ....
That's a good idea but all side have the same length... I'm not sure I can manage to have 3 boards parallell though.

I appreciate the consideration of hum due to transfo proximity... I won't go single box if I hear hum on my workbench before boxing everything up ! I definitely want something dead silent !

Regarding the heat, I feel I can manage that. I learned my lesson when I made my own pc Usually you just need an opening below and one one the top... air flow will form and cool the system. Well...it works as long as components don't go crazy hot !
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post #5 of 22
12/22/09 at 2:09pm
definitely play around BEFORE you commit to a box.

I used wooden mdf boards to glue (temp hot melt) some standoffs to and mount the boards and psu boards to. try some layouts and pick the least noisy one. config DOES matter here!

I tend to favor the connection from the psu board to the b22 boards as being short and 'internal' (not umbilical). the box-to-box cable would then be ac voltage (after the trafo) and this is much less critical as the energy is stored in the PSU and that DC link seems much more critical to me than the AC link before the PSU.

also, I like putting the trafo on the floor as it keeps it away from the b22 boards but ALSO any other nearby stereo gear, as well! don't forget, mag fields affect all nearby systems, not just the one connected to it

by putting the trafo in its own 'floor box' that box can be plain, unfancy, cheap and small. all good things
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post #6 of 22
12/22/09 at 4:02pm
Thread Starter 
Quote:
Originally Posted by linuxworks View Post
definitely play around BEFORE you commit to a box.

I used wooden mdf boards to glue (temp hot melt) some standoffs to and mount the boards and psu boards to. try some layouts and pick the least noisy one. config DOES matter here!

I tend to favor the connection from the psu board to the b22 boards as being short and 'internal' (not umbilical). the box-to-box cable would then be ac voltage (after the trafo) and this is much less critical as the energy is stored in the PSU and that DC link seems much more critical to me than the AC link before the PSU.

also, I like putting the trafo on the floor as it keeps it away from the b22 boards but ALSO any other nearby stereo gear, as well! don't forget, mag fields affect all nearby systems, not just the one connected to it

by putting the trafo in its own 'floor box' that box can be plain, unfancy, cheap and small. all good things
That's an interesting approach ! Basically, you suggest to replicate what's done in most of electronic devices, ie. a transfo attached to the power cable and filtering stage, regulation, ..., being part of the device. Laptop, squeezebox, my dacmagic, to name a few are plugged this way. That will be more bulky than usual but definitely cheaper than a fancy dedicated enclosure !
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post #7 of 22
12/22/09 at 4:08pm
What linuxworks described is "option 2" found in the "Wiring & ground" section of the β22 website, under "Power supply configurations & wiring".
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post #8 of 22
12/22/09 at 4:48pm
Thread Starter 
Quote:
Originally Posted by amb View Post
What linuxworks described is "option 2" found in the "Wiring & ground" section of the β22 website, under "Power supply configurations & wiring".
I noticed that but never really considered it... I should have ! Sounds like a good approach.

Ti, from your experience, have you ever encounter these kind of rail, slot or whatever they could be, that enable the perpendicular mounting of a pcb ?
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post #9 of 22
12/22/09 at 5:17pm
You could use a L bracket cut to length, with an attached aluminum plate. That's what I have contemplated before.
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post #10 of 22
12/22/09 at 5:30pm
Quote:
Originally Posted by LeMat View Post
That's an interesting approach ! Basically, you suggest to replicate what's done in most of electronic devices, ie. a transfo attached to the power cable and filtering stage, regulation, ..., being part of the device. Laptop, squeezebox, my dacmagic, to name a few are plugged this way. That will be more bulky than usual but definitely cheaper than a fancy dedicated enclosure !
you can pick the ugliest plastic box you want, even; and since it sits stowed away on the floor behind things, who cares!

spend money on what you look at.

its a huge huge wallwart that sits on the floor. floor-wart, if you will

regulation likes shorter wires. the wires *up to* the wall wart don't matter and the wires after it don't matter; but the wires between the regulation stage and the load, THAT matters. so I like keeping the psu near the amp modules and keeping that wiring short and also internal to the box.

my trafo box is on a long cord, at least 15' if not more. I intended to trim it back but I never got to it and probably never will. it can almost sit in the next room (lol). maybe I exaggerate a tiny bit but its a long cord and that means it sits where ever there is room, tucked away behind other gear.

oh, and keeping the floor-wart on the floor saves shelving from heavy audio gear. no reason the trafo *has* to sit on the shelf and bow the poor wood like it tends to, over the years

I've seen a lot of pro audio gear that sends a/c to the gear via a wallart and then the local rackmount thingie converts the ac to dc and regulates. and the hummy trafo is on the floor somewhere. that model makes sense to me, even though its ugly as hell with the extra 'lumps' on the cords.
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post #11 of 22
12/22/09 at 5:52pm
Thread Starter 
Quote:
Originally Posted by linuxworks View Post
you can pick the ugliest plastic box you want, even; and since it sits stowed away on the floor behind things, who cares!

spend money on what you look at.

its a huge huge wallwart that sits on the floor. floor-wart, if you will

regulation likes shorter wires. the wires *up to* the wall wart don't matter and the wires after it don't matter; but the wires between the regulation stage and the load, THAT matters. so I like keeping the psu near the amp modules and keeping that wiring short and also internal to the box.

my trafo box is on a long cord, at least 15' if not more. I intended to trim it back but I never got to it and probably never will. it can almost sit in the next room (lol). maybe I exaggerate a tiny bit but its a long cord and that means it sits where ever there is room, tucked away behind other gear.

oh, and keeping the floor-wart on the floor saves shelving from heavy audio gear. no reason the trafo *has* to sit on the shelf and bow the poor wood like it tends to, over the years

I've seen a lot of pro audio gear that sends a/c to the gear via a wallart and then the local rackmount thingie converts the ac to dc and regulates. and the hummy trafo is on the floor somewhere. that model makes sense to me, even though its ugly as hell with the extra 'lumps' on the cords.
OK I'm sold to this design... but will still try to make a nice black cube with rubber feet for the transfo

Regarding the L bracket... I'll give it a try.
Well...seems I have to do some soldering before tackling these issues
You'll probably hear from me during the process.... I would be surprise not encountering some kind of problem !
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post #12 of 22
12/22/09 at 6:27pm
as to the connector, I used very cheap (but pretty solid) microphone (ham/cb) connectors. they have 4 or 5 or even more connectors, they are keyed, they screw in and don't fall out, they don't take up a lot of space, they have plastic ribs to make soldering wires to them easy and they are sort of easy to find (rat shack and others have them). they are not really *power jacks* but they work well enough for it and they are mechanically simple enough to last years trouble free

on the umbilical cord, you need 2x the # of jacks and plugs. the mic connectors are in the $5 each range and so even at 5*4=$20 its not a huge investment.

some like the fancy huge connectors (like what AMB uses, amphenol I think?) but I find them rather expensive and overkill for the job. even powering speakers, I find the mic connectors good enough to send ac power to the s22 PSU board.
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post #13 of 22
12/22/09 at 7:12pm
Yeah, those 4 pin CB microphone connectors are perfectly adequate. Like XLRs, they're rated for carrying far greater currents than their typical applications require. 4 pin XLRs are typically rated for 8 amps per pin. The 4 pin CB microphone connectors can easily handle the same.

se
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post #14 of 22
12/22/09 at 8:08pm
Thread Starter 
Yeahhh another way for saving up some $ ... wouldn't have think about a CB connector.. clever. I'm not very into voodoo power cable so this will perfectly make it.
Speaking of voodoo and boutique stuff, I haven't found anything special regarding a 1/4" female headphone jack. I would have thought wbt, furutech,... have something in their catalogue. So, I'll go with the neutrik. Shouldn't make any difference anyway.
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post #15 of 22
12/22/09 at 9:10pm
with the b22 (or amps where you can blow the finals just by removing the phones cord) I like to go with locking TRS jacks. or I use an a/b switch right after the b22 and one position goes to speakers and one to phones. always before changing phones, switch to spkrs (it switches 'away' from phones, which is all we wanted), pull out the cord, put new one in and switch back. problem solved IF you remember to always do this. you never have to change volume level, either, this way.

but the locking TRS is a good reminder of 'oh yeah, this equipment needs to be treated differently' and you think twice before yanking out the plug.

final thought: even if not intended, cords can still come out if you forget and pull on it too hard or walk while listening. in that case, its better to have the locking jack save the plug from coming out and causing the short. in that case, I'd have some other strain relief (inline cord connector?) that would break cleanly (no shorts) if pulled too hard. would be neat to have an apple magnetic lock kind of thing for phones! (maybe my next idea...)
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