Self Etch Phantom pcb layouts ?

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PeteC

Well-known member
Joined
Jul 1, 2011
Messages
240
Hi

I want to find some self etch phantom pcb layouts to try - but there is a real shortage of info on the web about this - surprisingly !!

does anyone have one I can use - its to add to my REDD47 P2P 2 channel build.

cheers
PeteC
 
Sorry, I don't.  I just want to add that lately, there are so many inexpensive off-the-shelf low current 48VDC switcher modules, it hardly makes sense to build a 48V PSU anymore.  There are dozens available from Mouser in the $15-30 range these days. 
 
OK, fully understand your POV,  but I like the feeling of building as much of the finished unit as I can myself.  Including etching my own boards whenever possible.
For me its part of the pleasure of DIY audio.

Rgds
PeteC
 
Sure, I get that.  Just thought it worth mentioning, not long ago there were no good off the shelf options. 
 
emrr said:
I just want to add that lately, there are so many inexpensive off-the-shelf low current 48VDC switcher modules, it hardly makes sense to build a 48V PSU anymore.  There are dozens available from Mouser in the $15-30 range these days.

Are they really good enough? What models exactly, and what is their intended use? Can't put an effective RC filter on a phatom line due to the load that is a bit random (0.5-10mA) if there is switcher noise at the outputs.
 
JLM is selling one Mean Well for this purpose, that can be had for $30 from Mouser.  Full load noise is generally 200mV for most models in the 500mA max range, and reports indicate noise is more on the order of 3mV with light load, no additional filtering.  Add any filter at all and it gets better, then there's the individual filter typical at each phantom switch as well.  This appears competitive with off the shelf linear supplies. 
 
closest i have found so far is this ..
http://mnats.net/adjustable+phantom_power_supply.html

might just try etching the 48v half of the board

Mouser kits not really a cost effective option as I'm in the UK.

any other options ?
cheers
PeteC
 
+1 for a stripboard.

If you have some 12-15V AC available already, you could copy&paste the G9 phantom power part (based on a voltage tripler).

Jakob E.
 
letterbeacon said:
Ian sells a PCB, or you could just stripboard his circuit: http://www.groupdiy.com/index.php?topic=42745.0

I am happy to send you the Gerber files for use in a self etch project.

Cheers

Ian
 
gyraf said:
+1 for a stripboard.

If you have some 12-15V AC available already, you could copy&paste the G9 phantom power part (based on a voltage tripler).

No PCB's needed, I agree. And G9 phantom is a solid design.

There was this one time I didn't have veroboard at hand and still needed phantom circuit that exact second. I implemented the G9 circuit as a ball-of-parts-and-wire and later sunk it in epoxy for extra safety. :D
 
I have done all manner of zener drop circuits, voltage doubler/tripler circuits, etc, all hand rigged.  Lots of options for sure.  Since I seem to do more for-hire custom work than anything, I like PSU's with certifications more and more. 
 
10x less than the entire G9 at the XLR, or before the individual channel filters?    And after the effects of common mode rejection on those perfectly balanced 6K8's?  Let's be sure we are not apples to oranges here.    I see absolutely none of the 500 rack manufacturers list PSU noise #s. 
 
emrr said:
10x less than the entire G9 at the XLR, or before the individual channel filters?    And after the effects of common mode rejection on those perfectly balanced 6K8's?  Let's be sure we are not apples to oranges here.    I see absolutely none of the 500 rack manufacturers list PSU noise #s.

I meant just the isolated 48V line. these zener-with-CRC-referenced pass-transistor regulators tend to be good and work similar performance as HV supplies. This 0.3mVAC is actually the threshold of my measurement rig, they might be better. Yes indeed common mode rejection should eradicate the effects of phantom 3mVAC ripple. My point was somewhat academic. But again, this is less than $5 in parts, maybe an hour for an advanced tinker. It presents serious competition to a 15-30 dollar on-the-shelf PSU. Also the certifications are not a stability guarantee, just something not to burn down the house and a no-cancer policy.

Exploring the options here, $15 off-the-shelf phantom with only I/O wiring left to do sounds great. I don't care about 500 type rack manufacturers and have a hard time trusting any commercial design nowadays. I also think a mic front-end is not the place to skimp out on performance.
 
I have now used the Mean Well 48V supply I mentioned above, with a 200 ohm resistor feeding a 47mfd phantom bus cap (random selection), before hitting the individual channel switches with their local filtering and iso networks.  In practice, from 1-4 channels, I measure 0.2-0.4mV AC noise at the XLR.  Likely down in the noise floor of my meter.  If I have no load, and turn on one mic channels phantom, my meter captures a turn on surge noise figure around 40mV, which is gone within 2 seconds.  The PSU has a voltage adjust trimmer as well. I find with 4 random condensers powered, and voltage trimmed to 48V, when I turn all 4 off the bus rises to 49.2V. 
 
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