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zigzagflux 28th January 2008 07:48 PM

Front Panel Express finishes
Had two different panels made up with this vendor, to see what kind of craftsmanship and finish I could get. To say the least, I am extremely satisfied. The holes are perfect, and everything smooth and perfectly aligned (as much as my drawing dictates, of course). The time and effort in using punches, drills, and cutting fluid has come to an abrupt end !

Now, my issue comes down to finish. One panel I had constructed with raw aluminum, the other anodized. Both have their merits, I suppose. Here are my dilemmas:

1) Anodized finish: Long lasting, durable finish. No oxidation or need to clearcoat. However, the bottom side of the panel is nonconductive, which I like using for a ground plane. For instance, ceramic caps from heater pins to chassis, or shields of dual triodes. Only solution I can come up with here is to sand/buff the surface down to bare metal for conductivity.

2) Raw finish: Good conductivity on the bottom surface, nice finish on the top. However, with light polishing (say, with Mother's) will the finish remain oxidation-free for an extended period of time? Even though the amp will be indoors, raw aluminum is very reactive with oxygen.

3) Raw finish with alodine coating. Is this conductive? If not, I'm somewhat at point 1.

4) With any of these above methods, I can copper and silver plate the aluminum, so can end up with a permanent conductive surface. Silver oxidizes quite easily also, but it's easy to polish and restore to a very conductive surface. My thought was to have a silver surface on the bottom for conductivity purposes, and whatever permanent and oxidation-free surface is practical on the top surface.

What finishes have you chosen, and how has it held up long term ?

kstagger 28th January 2008 07:55 PM

I use the anodized finish for the top-plate (black, gold and 'gunmetal grey' on different units). I've also used the raw aluminum for (cheaper) bottom plates.

For grounding, it hasn't been an issue since the holes themselves were non-anodized. I use a bus-bar or star with a single grounding point with a washer that can bite into the aluminum.

Boris_The_Blade 28th January 2008 10:07 PM

I was thinking about using FPX for a preamp panel. Can you post pics of yours to show the craftsmanship?


dave_gerecke 28th January 2008 10:25 PM

You could pick locations where you would like to attach your grounds and use a mill bit to spot face the region. This cuts through the anodizing to reveal the base aluminum. Thus you have a region that allows conductivity, while still having most of the plate protected. From my experience, you would be better off with alodine, not anodizing. It is a stronger surface finish. I work with a lot of aluminum like this, the anodizing scratches easily, especially black. Then you really can't get the scratches out. You would have to check with the metal shop or plater to confirm, but I think that alodine is conductive also.



zigzagflux 29th January 2008 02:54 AM

You know, sometimes it just helps to read a little further. From the Front Panel Express website:

Anodized aluminum/chromated (reverse side pictured)
Available thicknesses: 2.0 mm / 2.5 mm / 3.0 mm / 4.0 mm.
The front is natural anodized. The reverse side is chromated and thereby conductive, making it suitable for EMC applications.

Fantastic. That's EXACTLY what I need. Front is clear anodized, for a nice finish and durable life. Rear is alodine (which is basically a chromating process, thereby conductive). So, I just spent $135 on a piece of aluminum that really has little value. Serves me right.

zigzagflux 29th January 2008 02:59 AM

2 Attachment(s)
Picture of the panel attached. Not a very good picture with the flash, but you get a good idea of the cutting precision. From their website, they do not guarantee the finish of raw aluminum, so the very light scratches are there, but are exaggerated in the picture. From what I have seen with their colored anodizing, the finish is superb.

All in all, the price is low given the labor and chemicals it would take me to build something similar.

Boris_The_Blade 29th January 2008 03:27 AM

very nice! thanks

G 29th January 2008 09:58 AM

Is that a 4 channel PP amp plate I see?

kstagger 29th January 2008 11:41 AM

2 Attachment(s)
a finished project of mine using a FPE aluminum top-plate - anodized black. And yes, it can scratch easily, so you have to take care assembling the hardware.

zigzagflux 29th January 2008 11:43 AM

That would be a power supply only, my friend. For a Karna amp,

Two 500V supplies for output stages, and two 400V supplies for driver and input stages. Electraprint power trannies. Hammond chokes. ASC motor runs. 6DE4 dampers. I wanted to avoid a 4 chassis design, and managed to squeeze both power supplies in one. The supply will sit in the rack, the monoblocks will sit underneath each speaker.

I know in general where I'm going with the amp proper, but haven't concluded the final design yet. I'll have more questions for the forum gurus when I get the power supply completed, and start testing the individual stages.

Wenge wood will be the chassis for the power supply, and curly bubinga for the monoblocks. Can't wait to see the final product.

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