SVT Cooling Fan: Push air in, or pulls air out?

[Toptube]

PCs have fans at the back (exhausting) and usually not the front for 3 reasons:

1. Noise. In uh, most situations, the rear of the case is away from the user. Wherever the fans are at is where most of the noise is going to be. So we keep it away from the user.

2. In a computer, anything that needs direct cooling has its own fan on it. Anything that doesn't have a fan on it is ok with passive cooling. Ambient temps WOULD be better if the fans were blowing in, but if they were blowing in from the front, the noise for the user would be greater. If they were blosing in from the rear, the hot air would be exhausting from the front and heating the user. So we have the fans exhausting at the rear because its the only thing acceptable.

3. Think about the power supply. Power supplies usually aren't included when counting the number of fans in a computer. But, power supplies almost always are exhausting and therefore are helping to pull air out of the case. The main reason a power supply exhausts though is not to directly exhaust the main case's air, its to directly exhaust the power supplie's air. because it creates a lot of heat, and if you were blowing that into the main case, you'd be raising the ambient temps. So a power supply MUST exhaust unless isolated from the main case. Power supplies are pretty efficient, so they are ok with usually only having an exhaust and using already hot air from the main case. So we can get a secondary benefit of pulling air from the main case.

 

[JustDavid]

Without assessing the airflow paths & heat source locations I'd go for an intake fan. It'll create the most internal turbulence & hence the most total cooling. & without airflow design, I think the shotgun approach is the best.

With a well-designed airflow path I'd go for an exhaust fan.

I don't see either one resulting in less dust, as both intake from the same unfiltered environment.

 

[bobyoung53]

i'm glad you piped in, jerrold. this might have started a run on blown transformers with everyone reversing their fans.

my tech told me that the fan keeps the whole amp cool, not just the transformers. he said never run it without a grill in front because the air bounces off of it and into the rest of the amp. don't know how true that is but it seems to make sense.

btw, i'm afraid my fan has about had it. i have to crank it with my finger to get it going. any of you fan experts know what's the best modern fan to replace the fan in a 69?

Very old thread and I'm sure you probably fixed it already but my 70 head had a Rotron fan that needed to be oiled, it had a little thing in the middle which you unscrewed with a screwdriver (1/2 turn) then you squirted 3 in 1 oil in and it would turn fine for months afterward. A lot of owners used to ruin these fans by not oiling them, they would eventually freeze up but I mean who would think of that?.

 

[agedhorse]

There are some pretty funny responses in this thread!

In general, when designing cooling systems for amps, a real designer will install thermocouples to measure the areas identified for cooling needs and adjust the fan(s) and air paths to achieve the necessary cooling effect.

One issue with running with intake suction drop is cavitation of the intake air which reduces flow and efficiency.

 

[BassmanPaul]

On the SVT-VR the fan is drawing air into the cabinet from the back. Cooling would be more efficient if they were to draw the air from the inside and blow it out the back, as others have said.

Sorry but I have to disagree. If the fan pulls hot air through it it's going to get hot leading to premature failure. That's how I see it anyway!

 

[beans-on-toast]

Sorry but I have to disagree. If the fan pulls hot air through it it's going to get hot leading to premature failure. That's how I see it anyway!

I've tried the fan both sucking and blowing. Concluded that blowing out the back worked best with the VR.

Interestingly, I use a small very quiet fan that I set up to blow into the back of amps. To give them a bit of help. It works very well. On some amps the tubes are barley warm to the touch. Perfect for the bench and when playing.

The fan that I use is a Caframo two speed. I think that it is made in Ontario.

 

[BassmanPaul]

My Province thanks you for the support!

 

[monsterthompson]

How is the answer not "both"?

 

[agedhorse]

How is the answer not "both"?

It COULD be...

 

[gumtown]

Install a glycol liquid circulating cooling system and a miniature water cooling tower on top of your amp.

The last DIY practice combo I built
(500watt class D + SMPS + tube preamp + quad 6.5" drivers + jolly rodger grill cloth with amp driven led eyes),
I installed 2 fans in the back of the amp, left side blowing in, right side blowing out.

Gumtown's DIY 500 watt quad 6.5" bass combo

 

[beans-on-toast]

Install a glycol liquid circulating cooling system and a miniature water cooling tower on top of your amp.

The last DIY practice combo I built
(500watt class D + SMPS + tube preamp + quad 6.5" drivers + jolly rodger grill cloth with amp driven led eyes),
I installed 2 fans, left side blowing in, right side blowing out.

I had an Apple computer with a cooling system like that, it had a radiator, pipes, and a lot of fans.

 

[byacey]

Kinda funny that no-one thinks about the effect of air cooling from a purely physical angle: The law of thermodynamics.

Another funny thing is that many amp designers opted to put the heat generating tubes on the bottom side of the chassis in a semi-enclosed box where they can slow cook the entire chassis over time, rather than putting the tubes topside and allowing the heat to rise away. Seems pretty stupid from my perspective.

 

[BadExample]

PCs have fans at the back (exhausting) and usually not the front for 3 reasons:

1. Noise. In uh, most situations, the rear of the case is away from the user. Wherever the fans are at is where most of the noise is going to be. So we keep it away from the user.

2. In a computer, anything that needs direct cooling has its own fan on it. Anything that doesn't have a fan on it is ok with passive cooling. Ambient temps WOULD be better if the fans were blowing in, but if they were blowing in from the front, the noise for the user would be greater. If they were blosing in from the rear, the hot air would be exhausting from the front and heating the user. So we have the fans exhausting at the rear because its the only thing acceptable.

3. Think about the power supply. Power supplies usually aren't included when counting the number of fans in a computer. But, power supplies almost always are exhausting and therefore are helping to pull air out of the case. The main reason a power supply exhausts though is not to directly exhaust the main case's air, its to directly exhaust the power supplie's air. because it creates a lot of heat, and if you were blowing that into the main case, you'd be raising the ambient temps. So a power supply MUST exhaust unless isolated from the main case. Power supplies are pretty efficient, so they are ok with usually only having an exhaust and using already hot air from the main case. So we can get a secondary benefit of pulling air from the main case.

I have yet to meet a PC I can't thermally shutdown with a Pi calculator. Every modern workstation or server I have worked with has front mounted cooling fans sucking in. Some with rear blowing out as well, usually workstations. Those can run the CPU's long and hard. I recently had a complaint of a year old workstation being slow, and I calculated Pi to 1 million digits in less than 6 seconds. If you try that on an enterprise level PC with 1 rear fan + PS fan, it will shut down. Home PC would probably shut down for good. My point is not meant to be disrespectful, but that PC's are kind of like Behringer watts, only good in very short spurts. If you don't believe me, I will be happy to link the Pi calculator I use. I highly recommend installing speccy to watch CPU temperature if running such tests: [Invalid or Expired Link Removed]

I do indeed torture my test subjects before buying for the masses I have never worked on gaming type PC's.

 

[BadExample]

My Province thanks you for the support!

Dear Paul, Province? I thought you were in the US. My favorite State, Canada, such a lovely place to hunt bear.

 

[Mr123Clark]

reviving this thread with the idea of 3D printing a new rear plate for my Fender Super Bassman that could have 3 120mm fans exhausting the air that comes in via the front grill cloth. In my practice space the head is pretty close to my head and i'd love to avoid blowing lots of hot air into my face which can get hot in the summer for sure. Anyone attempt something like this before?

 

[beans-on-toast]

reviving this thread with the idea of 3D printing a new rear plate for my Fender Super Bassman that could have 3 120mm fans exhausting the air that comes in via the front grill cloth. In my practice space the head is pretty close to my head and i'd love to avoid blowing lots of hot air into my face which can get hot in the summer for sure. Anyone attempt something like this before?

I've printed a number of ducts that are used for heat removal with PETG. There are more heat resistant filaments but may not be necessary. Commercial products also used 3D printed ducts, fan holders, … It won't hurt to try it.

 

[Wasnex]

reviving this thread with the idea of 3D printing a new rear plate for my Fender Super Bassman that could have 3 120mm fans exhausting the air that comes in via the front grill cloth. In my practice space the head is pretty close to my head and i'd love to avoid blowing lots of hot air into my face which can get hot in the summer for sure. Anyone attempt something like this before?

?

AFAIK the Super Bassman has one fan that blows air directly on the output tubes.

I would expect a small amount of air to pass through the front grill, but most of it should circulate out the back grill.

If you have three big powerful fans on the back panel all pushing air into the amp, more will exit the front. This air will definitely be hotter than the nominal air temp. How much hotter will depend on the air flow.

AFAIK the Super Bassman fan is temp-controlled, variable-speed. As long as the fan and control circuit are functioning properly, you probably don't need extra fans unless the amp is buried in a deep rolling rack. If this is the case, it could be useful to add some fans to the case to help clear the hot air.