PPi A600 upgrade to Class A

[carlinux]

talking with a friend and I said 'can upgrade the amp (ppi a 600) and let it work to the class A ,someone they' know 'more' to do about this change (component & scheme)
Tnx

[Perry Babin]

How do they define 'class A'?

[carlinux]

Yes not pure class A (new amp) but a working to go into Class A

[Perry Babin]

This amp does not have enough heatsink to operate at class A above a few watts (high bias class AB). The sound quality is likely to degrade or remain the same if pushed into class A beyond normal biasing. The only likely outcome is that you will have an amplifier that will be less reliable.

[carlinux]

Ok all clear
now i move to other amp for my 2 tweeter
tnx Perry have a nice week end

[ppia600]

The art amps have a hollow tube running down each side of the sink, you can see them if the ends are removed. If you were hardcore serious about doing it and your friend had the know how, you could just run coolant through the tubes to keep the amp cool. I ran a first series art 600 bridged mono at 4ohms for several years with coolant, a small fuel pump, small radiator and fan, and it never failed. Of course it was only running normal A/B. The first art series seemed to slightly drop power output when ran hard, which is why I decided to run coolant. (ppi also sold the art amp specific coolant system back when the art amps were made if I remember correctly)

[Perry Babin]

The cooling was mainly a gimmick. Look at the attached image. You can see that there is a lot of thin aluminum between the transistors and the tube. Unless you're using chilled water (well below room temperature), the water cooling won't do much more than fan cooling would.

[carlinux]

too much work to go to class A, and if the result is not 'justified I think it useless to make a water cooling system and create hardships in the car at the limit and only for car tuning

[1moreamp]

Perry is calling that one right! It was kind of a gimmick back then. And to prove my statement lets look at the amps of equal power back then. They all had FINS on the sink to add surface area to aid heat emission, except for Hifonics and Proton which were a different class amp with their special multi-stage power supplies. If you compare the heatsink surface area of any Art Series amp to any other Class AB amp except Hifonics and Proton and do the simple math of surface area you will see the Art series had less surface area then most amps back then. This is why they offered liquid cooling to this very artfully designed amp. PPI Art series was one of the only smooth bodied Art deco amp designs available, and while sleek and sexy it had less heat sink emission surface area then just about any other amp on the market at that time. So in comes the liquid cooling option for 2 ohm operation and below to extend operation before thermal rollback and shutdown. Oh and the later PC and PCX series had internal fins on the inside of the sink so as to appear smooth on the outside, and the cooling fan blasted cooling air over those fins inside the amp.

I had a A1200 in for repair that had been liquid cooled and in competition a while back and the power devices were just fine, but the rest of the amp cooked off like it had been in a oven. It needed a internal cooling fan, and PPI added them on the later PC and PCX class amps instead of liquid cooling, like DUH!

The SIP driver boards leaked DC all over the place, all the SMD solder joints on the SIP were cooked grey and cracked from heat and all the electrolytic caps were cooked to a different color and all the shrink wrap sleeves were split and popping off. DC offsets were all over the place, and uncontrollable and the amp needed to be completely gutted to bring it back to life correctly.
Such a waste, and a huge disappointment for me and my client as he paid top dollar huge money for a nice looking door stop. < there is a lesson here about used competition car amps I think >.

So the water cooling while possibly good for the power devices still leaves the rest of the amp to melt down under the excessive heat build up of driving a amp into extremes like that one had seen. And the only time I would consider liquid cooling is if you were to place your Class AB amps under plexiglass on show with no air flow to them or if you wanted extended service at 2 ohms or less operation. Then liquid cooling makes sense for these amps. At least to me anyway....

Oh and Class A is so inefficient you will most likely see 80% of your 12 volt power draw came back to you as pure heat load on the amp and its internals. It is also a great way to turn a 300 watt amp into a 30 watt amp. I don't know anyone that has beat that law of physics yet. And if anyone has please send me their link so I can learn the new laws of science and keep up with that Nobel prize winner that invented that amp.

[ppia600]

So basically you're reiterating what I said yet still agreeing with Perry that the liquid cooling was a gimmick and not effective? Its not a gimmick when it does what I claimed, which is drop the temperature low enough to keep power output stable when running 2 ohms stereo / 4 ohms mono. I never claimed it magically made the amp capable of running full power in class A mode, I simply suggested it to the OP to aid in his efforts. I know for a fact the liquid cooling worked as demonstrated in my setup for several years. I actually had the amp several years previous to using the liquid cooling and could notice power output change when running fully loaded on fairly hot days. Houston summers are not amp friendly when running with no a/c and the windows down. I purchased the (a600, not .2) amp at an EZpawn in houston for $60 and it had the driver board issue. I immedially sent it to PPI and they performed all necessary repairs for only $150 if I remember correctly and it never had a problem after. I didn't run liquid cooling until a few years later, Louisiana summer weather is also not amp friendly when running windows down and no a/c.

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 but I'm sure there would be someone crazy enough to try

Originally Posted by 1moreamp

Perry is calling that one right! It was kind of a gimmick back then. And to prove my statement lets look at the amps of equal power back then. They all had FINS on the sink to add surface area to aid heat emission, except for Hifonics and Proton which were a different class amp with their special multi-stage power supplies. If you compare the heatsink surface area of any Art Series amp to any other Class AB amp except Hifonics and Proton and do the simple math of surface area you will see the Art series had less surface area then most amps back then. This is why they offered liquid cooling to this very artfully designed amp. PPI Art series was one of the only smooth bodied Art deco amp designs available, and while sleek and sexy it had less heat sink emission surface area then just about any other amp on the market at that time. So in comes the liquid cooling option for 2 ohm operation and below to extend operation before thermal rollback and shutdown. Oh and the later PC and PCX series had internal fins on the inside of the sink so as to appear smooth on the outside, and the cooling fan blasted cooling air over those fins inside the amp.

So the water cooling while possibly good for the power devices still leaves the rest of the amp to melt down under the excessive heat build up of driving a amp into extremes like that one had seen. And the only time I would consider liquid cooling is if you were to place your Class AB amps under plexiglass on show with no air flow to them or if you wanted extended service at 2 ohms or less operation. Then liquid cooling makes sense for these amps. At least to me anyway....Oh and Class A is so inefficient you will most likely see 80% of your 12 volt power draw came back to you as pure heat load on the amp and its internals. It is also a great way to turn a 300 watt amp into a 30 watt amp. I don't know anyone that has beat that law of physics yet. And if anyone has please send me their link so I can learn the new laws of science and keep up with that Nobel prize winner that invented that amp.