PPi A600 upgrade to Class A

[ppia600]

Originally Posted by ppia600

That being said, not everyone runs their amplifiers in competition mode every day. I really only did the coolant mod to help it run a that much lower of a temperature for extended life and allow longer bursts at full power if desired. The amp was actually in perfect shape on the inside when I sold it, nothing was cooked / baked. Of course trying to run in full class A would create a lot more heat but you could also use fan cooling through and over the amp and coolant. Not saying it would be worth it to spend so much effort for relatively low class A output capability but I'm sure there is someone crazy enough to try

Quoting myself for my late edit attempt

[1moreamp]

It was a gimmick because no one else offered it and the heatsink was too small for the amps to run low ohms like they were rated at. Sorry to not clearly make my point but I really want you to focus on the heatsink surface area issue. I still feel the liquid cooling was a bandaid/gimmick to solve a real engineering issue with the amps heatsink design. Sometimes things can go hand in hand on a issue like this. And I am sure it is also depending on every-bodies point of view of the engineering issue. This was mine, even though I may seem to be on both sides of the fence...

[ppia600]

There are a couple of definitions of "gimmick", and if you have to use one for ppi's coolant system I would choose the latter.

gim·mick (g m k) n. 1. a. A device employed to cheat, deceive, or trick, especially a mechanism for the secret and dishonest control of gambling apparatus.


-or- my choice:

an ingenious or novel device, scheme, or stratagem, especially one designed to attract attention or increase appeal




I totally understand their reasoning behind the heatsink design. And while insufficient for continuous low impedance setups (2 ohms stereo) on the normal art (not talking about the pro art) models, it is plenty of area for continuous normal load operation. There is also more to look at than the amps' external surface area. You have to look at transistor location in relation to the area with greatest contact to air as well.

There are a few issues when people debate this subject:

-transistors mounted vertically, using primarily the outer edges of the amp will be slower to conduct heat to the top of the amp with largest area. This is similar in one way to the arts' conduction from the inner area (top surface) out to the side areas, but their transistors are already closer to the top surface.
-fins may have more surface area but can also act as insulators when there is low air flow (trunk mounting for example) or when airflow is not running directly through the fins (across them instead of through). In those cases, the heat is actually radiating from one fin to the next and the air is acting almost as an insulator so the overall actual radiating area of the amp can actually be pretty limited.

This subject has been debated since differing amp sink designs have been around. The reasoning behind the smooth art sinks is to allow air to smoothly pass over the surface with no rough obstructions (fins) hindering air movement. The smooth surface promotes convection of surrounding air which allows contact with other air. Its even explained in their literature. I'm not saying its better than fins, especially with a directed fan, but its not an ill thought out design. They didn't use internal fans which would have helped internal components immensly in competition setups, but for the average high end listener who just wanted great sounding music and great looking equipment they are excellent.

[Perry Babin]

I know you like these amps but these heatsinks are close to the worst as far as heatinsking goes. Look at the area under the transistor. They have a deep groove that makes the aluminum thinner. This increases thermal resistance and hinders cooling.

Fins are better in every respect as far as cooling goes. They increase surface area which helps cooling.

For a good heatink, you need low thermal resistance between the semiconductor and the area that will dissipate the heat. On this amp there is a thin area directly behind the semiconductors that limits the heat transfer. There is very little surface area due to the smooth surface.

On the more efficient heatsinks, the fins also have ridges. These increase surface area even more.

If a smooth surface was better, the manufacturers of heatsinks would produce smooth profiles (no fins).

[ppia600]

Oh for crying out loud, I never said smooth surface sinks were better. Only that they are not bad. They obviously have the lowest surface area because they are smooth (is anyone surprised?) but they are not horrible. And yes, of course I like the arts (and most of the early finned ppi amps as well) but I'm not blindly defending the design. Btw, I'm currently running an adcom four channel (internal fan cooled) and earthquake phd3 (er... I meant ph5000) so no ppi bias (no pun intended) as far as I'm concerned. I'm a fan of many amps, mainly american made but several japanese as well. Don't let my username fool you.