First has anyone ever taken a household box fan and made a shroud and piping to pipe it into an amp? They tend to be rather quite and they move a large volume of air at a lower velocity. Velocity though can be steeped up in the same way you steep up hdralic pressure in a free fall hydraulic circuit where you use gravity and ever shrinking tubing size to increase pressure. In this case shringing the tubing would increase the velocity of the air. If you kept the fan speed at low to medium you would have a very quite solution for cooling high powered amps.
When I younger I do a lot of import tuning and some racing as well both sanctioned racing and street racing. Using Electric cooling fans, electric water pumps and such often gained a lot of horse power. Seems like these same types of all in one fan and shroud might work well on an amp too. On a car you only need a fan for speeds bellow 35mph's once above that speed you have more air flow then you need. Again they turn slower and move more volume. I have no idea how loud or quite they would be though. Just an idea.
I am not buying the Muffin fan thing for most tubes especially in the 800+ watt range. Sure a muffin fan or two might help but not going to be up tot he task of really keeping the tubes bellow 220°C where most of them start to have seal issues.
I do think that a muffin fan makes sense for the bottom of a tube to keep the socket pins cool on most of the Triode Russian tubes with home made sockets so long as you have a way for the air to get at them!
If you do not have a pressurized socket like some of the Eimac ones then I think it makes more sense to move more volume of air then it does to try and reach a pressure @ X volume because most encloser's are anything but air tight and donot channel the air in the best way for the given amount of air pressuer and volume.
On top of that how many people have a calibrated anemometer(sp) basically glass tube filled with dyed water to measure the airflow at give pressure. You can make one easy enough but it is still kind of silly to expect anyone to go to that length.
So if you can not easily pressurize the system in a way that is very specific and you can not give each area it's own cooling design high volume of air makes a lot of sense and use a prope to make sure that under your hardest usage cycle you have the tubes bellow their operating limit. The probe though needs to be on the tube not in the air flow coming out of the tube. In home and commercial heating and air-conditioning no one goes for high pressure they go for high volume. Like wise in aircraft and automobiles again no one goes for high pressure air they go by volume needed to cool the parts.
Air at high pressures is always noisy as can be because you would need a huge huge fan to build up enough pressure at low speeds so what do they do they take a squirel cage and spin it at 3000 rpms or faster! That is the worst possible way to make something quite. Now in a commercial applications it makes sense because the amp and it's cooling system is not even close to the guys in the booth with the mic's and people talking.....In a ham shack in someones house though often the amp is rather close tot he mic and we hear the sound of a leaf blower going because the amps cooling system in loud and in too close proximity to the mic. Ideally your amp would be in another room or the cooling system would be in another room so no noise on the air. Since most of us can not do that practically and spinning the squirrel cage slower kind of defeats the purpose of a pressurized system maybe we need to rethink the solution based on common sense and the fact that few of us have ham shacks set up like commercial broadcast stations!
So chime in with pro's and con's and past experience etc....
When I younger I do a lot of import tuning and some racing as well both sanctioned racing and street racing. Using Electric cooling fans, electric water pumps and such often gained a lot of horse power. Seems like these same types of all in one fan and shroud might work well on an amp too. On a car you only need a fan for speeds bellow 35mph's once above that speed you have more air flow then you need. Again they turn slower and move more volume. I have no idea how loud or quite they would be though. Just an idea.
I am not buying the Muffin fan thing for most tubes especially in the 800+ watt range. Sure a muffin fan or two might help but not going to be up tot he task of really keeping the tubes bellow 220°C where most of them start to have seal issues.
I do think that a muffin fan makes sense for the bottom of a tube to keep the socket pins cool on most of the Triode Russian tubes with home made sockets so long as you have a way for the air to get at them!
If you do not have a pressurized socket like some of the Eimac ones then I think it makes more sense to move more volume of air then it does to try and reach a pressure @ X volume because most encloser's are anything but air tight and donot channel the air in the best way for the given amount of air pressuer and volume.
On top of that how many people have a calibrated anemometer(sp) basically glass tube filled with dyed water to measure the airflow at give pressure. You can make one easy enough but it is still kind of silly to expect anyone to go to that length.
So if you can not easily pressurize the system in a way that is very specific and you can not give each area it's own cooling design high volume of air makes a lot of sense and use a prope to make sure that under your hardest usage cycle you have the tubes bellow their operating limit. The probe though needs to be on the tube not in the air flow coming out of the tube. In home and commercial heating and air-conditioning no one goes for high pressure they go for high volume. Like wise in aircraft and automobiles again no one goes for high pressure air they go by volume needed to cool the parts.
Air at high pressures is always noisy as can be because you would need a huge huge fan to build up enough pressure at low speeds so what do they do they take a squirel cage and spin it at 3000 rpms or faster! That is the worst possible way to make something quite. Now in a commercial applications it makes sense because the amp and it's cooling system is not even close to the guys in the booth with the mic's and people talking.....In a ham shack in someones house though often the amp is rather close tot he mic and we hear the sound of a leaf blower going because the amps cooling system in loud and in too close proximity to the mic. Ideally your amp would be in another room or the cooling system would be in another room so no noise on the air. Since most of us can not do that practically and spinning the squirrel cage slower kind of defeats the purpose of a pressurized system maybe we need to rethink the solution based on common sense and the fact that few of us have ham shacks set up like commercial broadcast stations!
So chime in with pro's and con's and past experience etc....
