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The photo you posted is not all that different from the QSC/Behr design. Remember that QSC/Behr are using consumer production techniques (auto-insert, through- hole higher-power components, etc.) because they are selling into an extremely competitive market where every fraction of a cent counts against the bottom line.

Your photo is beautiful, admirable, even, but I'd rather work on the QSC, if I had my choice.

OTOH, the thermal design of the board in your photo appears to leave a bit to be desired. Placing the power devices out on the edges certainly makes it easier to repair, but consider the thermal profile of having the heat source out at the edges rather than more centrally positioned.

Indeed, much like plywood which comes in a wide variety of types and grades. Except for the most expensive "marine" types, the inner layers are typically cheaper, less dense material (wood slices, oriented fibres, particles) as the outer layers and the bonded combination are primarily responsible for the strength and physical appearance.

It was carefully, quantitatively designed. We also tested dozens of fets to destruction. If all the fets were in the center, all the heat would be in the center. At these power levels, lateral (spreading) thermal resistance of the heatsink is a big deal, hence the copper spreaders and the fet distribution. Note that the P and N fets are interleaved, which wasn't popular with my PC layout guy. Two smaller temperature peaks are better than one big one.

The thermal design of the Europower unit gives me the willies. That dinky fan, blowing down the length of those restricted heatsinks, can't be very effective. And one end will be a lot hotter than the other. In my amp, 360 cfm of air hits the heatsink broadside.

John

Yes I see those details now that I viewed the image in a larger size. The board is beautiful and elegant, no issue with that.

But consider not only the economic marketplace the QSC was designed for (I don't consider the Europower to be "designed" but rather cloned from the QSC) but also the technical/physical conditions of the equipment in that niche market. If your board is made for any kind of rack-mount equipment, it must be rather large. OTOH, the QSC (and its ilk) are designed for maximum power density in 19-inch racks with no space between units. I suspect that QSC expended a proportional amount of physical/ thermal design activity, but their objectives and limitations were significantly different than yours. I suspect that both QSC and even Behringer would be out of business if they designed power amp boards as elegant as yours. But they would leave a nice- looking corpse.

Yup.

Very similar in concept ( and performance ) AIUI to these pcb materials wrt how it works regaring the core and the outer layers..

Any more ideas about whether phenolic is always brown in colour ? That is my own experience but I have no idea if it's an inherent limitation of the material.

Graham

Right Right, or Left to Right.

Now when you say.... hmmm, I also cannot remember any.

Right.

Why have the American bombed at all? England I can understand...

Kind regards,

Daniel Mandic

Not necessarily.

Depends on the board material, and whether the color is inherent or the result of the addition of a colored filler and/or pigment.

This link shows the QSC substrate pretty clearly:

The tip-off that this isn't paper/phenolic is the cloth pattern.

I did a little research and found a commercial non-phenolic material that had an essentially identical appearance.

This is all in the AAPLS google archives from a month or two ago.

Phenolic isn't always brown, I've seen a ton of black phenolic.

However, black phenolic is black because it is filled with carbon black (for strength). Not a good choice for a circuit card!

The substrate material is made by the same vendors, and using much the same process as the kinds of laminates people put on the kitchen countertops, etc. Micarta, for example appeas to be a major OEM in both the countertop and PC substrate (and other industrial insulator) markets.

The cloth pattern doesn't look like a "normal" glass-epoxy PC board to me. The "weave" is much too open. And it is so remarkably regular that at first I thought the pattern was printed on.

And the appearance of the shear/break line looks more like paper in the middle than layers of fiberglass mat or cloth. I have laid-up much more of each in my lifetime than I care to remember. Granted it is difficult to tell from a photo.

From some Googling I did yesterday, I learned that a thin layer of fibreglass on either side of a paper core is one of the kinds of substrate material available for cost-sensitive products (such as those amplifiers).

I have seen blue in NAD gear that certainly wasn't fibreglass. And a red PC mobo that was fibreglass (i think).

geoff

It was your "education" that is as faulty. Catechism would be a better description. I got the US version. In what i was taught, there was essentially no European contribution to defeating WWII Germany. It was clearly false then, when i was i kid.

Stymied is a better description. If they had defeated the RAF, your so called navy would not have mattered, they would have rolled you up like a rug.

A truly hideous misconception, you did not have any heavy bombers. You do not understand the difference of being able to carry 50,000 lbs of bombs instead of 3000 lbs.

I am not sure what "power parts" you saw; all that i could deduce were covered by a large heatsink, very visible in the right third of the third photograph (the second in the block of photos).

Is the amplifier rated in excess of 1 kW? That is a lot of air.

The spacing of the fiber bundles is made to accommodate the lead location of the power semiconductors. This increases the life of the punches quite a bit (They are not punching through the glass fibers). Tools / tooling are still expensive in China. (not that they are all that cheap in the US)