A strange problem with Rod Elliott's P3A

[pmkap]

and for those not current on modern materials developments, a laymans article discussing this new carbon form was in the
New York Times

SCIENCE | April 6, 2004
A Flaky New Carbon: It’s Feather Light and Magnetic
By KENNETH CHANG (NYT) News

access requires registration, but at no cost.

http://query.nytimes.com/search/que...ast30days&submit.x=0&submit.y=0&submit=Search

 

[moving_electron]

One last quibble: at these low voltages, I don't see the need for the high voltage parts he specifies. MJ15030/31 and even mj15001/2 devices would serve equally well. There are plenty of other lower voltage parts that would work well and save a few bucks. I don't understand why he thinks the latest goodies from ON are needed here (no doubt they are great parts, just not needed here).

Hmm.. On his project page he links to a site that lists various parts that can be used successfully. What he does say in his project page is that with the the linearity and high gain of the newer devices the amp will be at it's best. Seems reasonable.

Given that he has designs that are straight forward to construct, the extra margin of a larger SOA certainly does not hurt in helping increase the chances that a new constructor will end up with a working amp to enjoy good sound through.

I like mine with MJ15003/MJ15004. No noticeable bump at turn on.

 

[moving_electron]

I also don't like mounting devices under boards, because you lose heat dissipation ability from the board side. The outputs are almost insulated thermally, never good. I would prefer it if the board is spaced away, and the outputs are mounted outside the board area for better cooling. So I don't think I will be building any of his boards soon.

The amount of heat a device would release to air from the plastic side of the package would seem to be pretty minimal compared to the amount that is being removed via the heatsink. This is evident from the short time a part will live if not attached to a heatsink. Given that the PC board absorbs some heat, the overall effect of mounting separately seems pretty negligible.

In any event, the under PC board mounting seems to be working for reasonably high throughput from these devices without trouble.

 

[gmphadte]

heat sink paste

If it was not due to a bad solder, I suspect the culprit could be the heat sink paste, if you had used.
The heat sink paste can conduct to the heat sink.

Phadte