Fixing Objective2’s Power Jack

** We’re moving to a new office on Friday, May 31st. Orders placed after 10am CST tomorrow (5/31) will ship Monday! **

If you’ve assembled NwAvGuy’s Objective2 in the past year, you must have noticed that its power jack is discontinued. Alternatives to Kobiconn 163-7620-E do not fit.

One of many alternative 2.1x5.5mm DC jacks -- Does not fit!Substitute power jack for O2. Does not fit.

NwAvGuy last reached out to us on July 1, 2012 before mysteriously disappearing. Two months earlier, he’d discussed revising the O2 PCB. The discussion is archived for those interested: [expand title=”NwAvGuy Emails”]

From:Northwest AvGuy
Sent: Tuesday, May 01, 2012 12:30 PM
To: John Seaber
Subject: John: O2 Power Jack

Have you found an alternate power jack for the O2, are you modifying jacks to fit, or do have enough of the old ones for now? I’m getting more questions about the discontinued jack and trying to decide what the best solution is.

If I revise the PCB artwork I would fix the jack footprint and move the via under the corner of the gain switch. Are you aware of any other necessary board revisions?

On Tue, May 1, 2012 at 11:57 AM, JDS Labs Inc. wrote:

We source unique parts in large quantities, so we have enough power jacks to last all year.

Kobiconn 163-179PH-EX is close. Dimensions aren’t a perfect match to 163-7620-E, but it should fit existing O2 boards and front plates [Edit: 163-179PH does not fit]. Breaking mechanical compatibility with the original board/plates would be a mess.

No other revisions should be necessary!

On Tue, May 1, 2012 at 2:08 PM, Northwest AvGuy wrote:

Thanks for the reply. Yeah, I have a sample of the 179PH already and, as I posted on the O2 Summary comments, two of the tabs are a bit too big. A revised board shouldn’t change form, fit, or function of the assembled board.

Just beware before ordering a large number of PCBs the artwork may be revised so you might want to check in with me first.[/expand]

We believed NwAvGuy would eventually update O2. Now that almost a year has elapsed, we can only hope he’s doing okay.

We’ve spent the past few months seeking substitute power jacks. No success. Jack manufacturer Kycon quoted a custom part, with tooling and minimum order quantity totaling $25k-$100k. Not worth it! The last thing we want to do is violate NwAvGuy’s work by disregarding the O2’s no-derivatives license. We’ll gladly respect any wishes he may have if he’s able to return in the future. Until that time comes, we’ve decided it’s time to proceed with NwAvGuy’s intention of sustaining O2 as a viable DIY project. That means the O2 PCB must accept common power jacks.

NwAvGuy only supplied Gerbers for the O2, which makes the design nearly impossible to modify without re-drawing the schematic and PCB from scratch (definitely unacceptable).

O2 v1.1a PCB Gerbers
Original O2 v1.1a PCB Gerbers

Zooming in on the power jack (J1), you can see that plenty of copper surrounds its 2.3mm holes:

Original O2 v1.1a PCB Close-up

Most power jacks have pin widths of 3.0mm, instead of the small 2.3mm pins used by 163-7620-E. So, we only need to increase hole diameter at J1 by 0.7mm.

NwAvGuy left us with wonderful documentation. You can find this table in the O2 readme, and tool “T8” looks like the drill bit relevant to jack J1:

Tool Hole Size Hole Type Hole Count Plated
T1 28mil (0.7112mm) Round 104
T2 32mil (0.8128mm) Round 44
T3 42mil (1.0668mm) Round 23
T4 53mil (1.3462mm) Round 24
T5 55mil (1.397mm) Round 8
T6 62mil (1.5748mm) Round 12
T7 68mil (1.7272mm) Round 12
T8 91mil (2.3114mm) Round 3
T9 125mil (3.175mm) Round 3
Totals 233

To test this idea, I searched the drill file for “T8”. The first instance occurs at line 13, where this table is defined explicitly in Gcode:


Tool names gain a prefix of ‘0’ throughout the rest of the drill file, and T08 appears with three coordinates on lines 250-253:


To confirm that T8 is the appropriate drill bit for the DC jack, I set T8 to an arbitrarily large size on line 13 and checked the visible result:

Changed drill size in NC Drill file to use arbitrarily large holes
Arbitrarily large T8 drill size confirms T8 is only related to O2’s DC jack

This test proved that T8 only affects holes at the DC jack. Thus, I changed T8 in the drill file to our desired hole diameter of 120mils (3.05mm). Here’s the visible result, showing successful 3mm, plated holes at the power jack:

O2 v1.1b PCB: Equal to NwAvGuy's v1.1a, with J1 holes enlarged from 2.31mm to 3.05mm
New O2 v1.1b PCB: Equal to NwAvGuy’s v1.1a, with J1 hole sizes increased from 2.31mm to 3.05mm

O2 v1.1b PCB fabricated and confirmed perfect!

CUI PJ-002A power jack (3.0mm pins): Fits new v1.1b PCB
O2 v1.1a in Green, O2 v1.1b in Purple.
Original O2 v1.1a in Green, Modified O2 v1.1b in Purple.


Modified O2 PCBs are Now in Stock. You may also download the v1.1b Gerbers for your own use.


O2 v1.1b is a straightforward manufacturing alteration to the O2 v1.1a circuit board. Specifically, holes of the power jack, J1, have been enlarged to accommodate standard power jacks. All aspects of the Objective2 remain unchanged from NwAvGuy’s work. The PCB layout is identical. Performance is identical. Even the silkscreen still shows “v1.1a” (admittedly confusing). The O2 v1.1b PCB merely allows builders to assemble O2 without encountering frustration from the DC jack.


How to Finish Aluminum

Disclaimer: This article has no audio related content. We hope the following manufacturing information will be useful to others.

A couple years ago, we naively expected that aluminum manufactures would perfectly interpret our engineering drawings and produce beautiful, black parts. After rejecting 4500+ aluminum cases in these past two years, I can tell you with certainty that this guy gives a false impression. There’s much more to fabricating a nice aluminum product than simple anodizing. Photos below are a chronicle of our progress.

Raw Aluminum

Our raw cases arrive from the aluminum manufacturer looking something like this:

Raw Aluminum
Raw aluminum extrusion for C5, “mil” finish (i.e., no finishing)
Scratch on right -- oops!
Right-most part was scratched prior to anodizing

Rough, huh? Sometimes we see deeper scratches and dents, and parts can even arrive covered in grease and oil.

Anodizing fixes none of this! Any scratches or defects visible before anodizing will remain visible after anodizing.

Brushed + Anodized Aluminum

We added brushed finishing to c421 after realizing that we couldn’t expect aluminum manufacturers to deliver parts in perfect condition:

Similar case w/brushed texture and black anodizing

Brushing solved the immediately visible problem in our first manufacturing attempts, but created new issues. The texture of production parts was rougher than samples. And here’s what happens with a heavy brush intensity:

Brushing can remove too much material, altering the case profile
Heavily Brushed piece at Left, Original piece at Right.


  • Relatively fast to perform
  • Generally low cost
  • Brushed appearance is popular


  • Since brushing a part is essentially like rubbing sandpaper against its surface, brushing can alter part tolerances (see above image).
  • An aggressive brushed finish can create a rough, undesirable texture.

Bead Blasting

When we began designing C5, we knew that enclosure quality needed to match the awesome new circuit board. Brushed cases had to go. Our local anodizer suggested a very fine bead blast (aka, “peening”).

Bead blasting is essentially like a pressure washer that uses “abrasive media” instead of water. Any media can be used: walnut shells, sand, and glass beads are common. Pick a media, a pressure, a distance from the part, and then blast the surface. Most shops say it’s an art.

Ultra fine glass beads produce a soft appearance similar to Apple’s Macbook:

Same part with bead blasting
Bead blasted extrusion (C5 case)

Bead blasting dulls the part finish. While appearance is excellent before and after anodizing, surface texture oddly changes after anodizing, we used a stud welding equipment, Stud welding can be used within a number of industries, including companies working with electrical goods and electronics, machinery and machine parts, heating and ventilation equipment, and also decorative and consumer items, we highly recommend to use it.

We also noticed that black parts turned out especially dull, unlike other colors.

Same bead blasted parts in Red and Black anodizing
Same bead blasted parts in Red and Black anodizing


  • With the right bead blasting media and pressure, a bead blasted part looks excellent
  • Part tolerances are not altered


  • Requires significant sampling/experimentation from your metal finishing shop
  • Cost is 50-100% higher than brushing
  • Most shops manually blast parts, which can lead to surface inconsistencies
  • Especially rough parts must be tumbled prior to blasting (even higher cost)
  • Anodizing yields a matte appearance, especially unsuitable for black

Bead Blasting + Bright Dipping + Anodizing

Aluminum parts are normally caustic etched immediately prior to anodizing. If you substitute etching for a process called Bright Dipping, dullness is magically replaced by a brilliant appearance and pleasant texture.

Bead blasted parts at top; bead blasted + bright dipped parts at bottom
Bead blasted parts at top; bead blasted + bright dipped parts at bottom

The bright dipped parts shown above are not actually brighter. At another angle, you can see instead that light reflects more brilliantly at all angles. Notice the bright dipped pieces appear darker in this photo:

Bead blasted pieces at Top; bead blasted and bright dipped pieces at Bottom
Bead blasted pieces at Top; bead blasted and bright dipped pieces at Bottom


  • Excellent surface appearance
  • Excellent surface texture
  • Cost is comparable to standard anodizing


  • Bright dipping is extremely corrosive, so it’s rarely offered in the United States
  • Carries all other downsides of regular bead blasting (see above)

Hopefully this helps someone in their manufacturing adventures. Special thanks to Tom at Archway Anodize for making our experiments possible!