turning off the fan in my class D head
 

Dear TBers,
I'm the happy owner of a class D head whose brand I won't mention here.
I like its sound BUT it has an annoying feature.
The fan is constantly on and the noise is definately a pain after a while.
When pause from practicing I MUST turn the head off because of the noise.

The head has a single tube preamp.

Two question :

1) what could happen if I unplugged the fan from the power soak on the board ?

I would like to reproduce the maximum heat possible conditions and see if the heat gets to a dangerous level.

2) in which conditions the head will (in theory) produce its maximum heat ?

(I mean Gain at 10, Volume at 10, jack plugged in, no bass on the other side, Gain at 10, Volume at 10, playing or what ??)

Sorry for the very non-technical question.

DO NOT DO IT! You can't react quick enough to prevent heat damage. Most designs should have a heat activated fan and usually variable speed. Class D runs cooler than most other output typologies so your amp may have a fault in the fan circuit or you are running too much load (like a 2 ohm speaker load with a 4 ohm minimum unit).

I noticed that many of the earliest generation of switchmode bass heads had no fan. Now they all have fans. There must be a reason.

In a lot of power electronics, a surprisingly small amount of air circulation is better than no air circulation at all.

Like B-string says, you can't detect over-heating until it's too late. Especially on switchmode gear, where the internal heat sinks might not be at ground potential, making it potentially dangerous to find out.

It's always possible that the bearings in the fan have worn out, making the fan particularly noisy.

Yes GET the fan checked just could be bad bearings... DO NOT DISCONNECT IT!

These fans should be and are silent unless they're pooched. Get a new fan put in.

Next years models will not have fans, and everybody will need to upgrade

If the fan failed for some mechanical reason, I doubt the amp would destroy itself. It's bound to have temp sensor to shutdown. I'd still talk to the manufacturer, they might have a low noise fan replacement.
Like a thermal fan that only turns on when it gets hot. A lot of electronics have smarter fans now.

Scotty would say "ya canna change the laws of physics cap'n" ;)

There is heat to be dissipated, so either the enclosure size increases or there is a fan. Now, good engineering will have speed control over the fan, or you could have two fans at half speed for less noise, but regardless, next years models will still have fans... especially and particularly those with tube preamps..

Anyone who just disconnects the fan and assumes it will be ok can blame Darwin when their amp cuts out or worse.

Even if an amp is 90% efficient, that still means that some heat is generated. How to get rid of the heat is just an engineering problem. Bigger heat sink? That costs money. A small fan may very well be the cheapest and most practical way to ensure that the amp won't come back for warranty repair.

I think "...howmuch heat can the head stand before the thermal protection (if any, BTW) kicks in..." is the wrong question.
Ah, I wish all the heads were engineered like my GK MB500, you can play it for hours and the fan will never kick in. It has no valve pre though.
I wonder if the GK Fusion has the same fan problem.

The engineers who put the fan in you amp did it for a reason. And it wasn't to annoy you.......

DONT DO IT

I think that is exactly the question you need to ask before you kill your mystery amp head in pursuit of dead silence. Obviously it's engineered the way it is for a reason. The fan is probably an integral part of the amp's design and function. I don't see what the problem is. That's like me being annoyed with my laptop's fan for always being on and doing it's job.

Then why don't you use the MB500?

Hey - the fan in your car makes a lot of noise, too, so why don't you just disconnect that, too? For the same reason -it will damage your engine! They wouldn't put it there if it weren't necessary - they would like to have that $6-10 extra profit.

Just to back up the good advice above -

The fan may be faulty and need replacing (which means it could die and your electronics will fry),
The fan controller may be bad and running it at high speed all the time,
Something in your amp may be overheating and causing the fan to run at max.

Get it checked out now, before something really expensive happens.

Don't disconnect the fan ! Do have the fan/amp checked !

Try a Crown, my PA has 2 XLS 2000s & 2 XLS 2500s. None of them make any noticable sound.

I have a class-d amp with no fan.
Heat sinks, form factor - it's designed with no fan. There are many home theater class-d with no fan. And they have FTC certification on power output (Watts FTC).

90% efficient means it has to dissipate 100w for 1000w output. And it's not always running at 1000w out. It doesn't always need to dissipate 100w. Alas, the heatsink adds weight and costs.

Class-ab with no fan, now that is impractical.

If your car is in your practice space, and it's running, you have other problems, fan or no fan. :D

And many cars - electric fans that turn on when needed.

I bet you could find a silent computer fan to match up with the specs of your fan.

Of course - just like amp fans - but you don't disconnect it!

To the OP:
Do other amps like yours have a quiet fan?
If so, yours is a pig and needs a new fan just like 75% of the walkabouts.
Mentioning the make and model would get you instant response from guys that own them.

I'm going to do this for my WXT500 sometime. The fan is really loud! Eden told me I could disconnect it when playing quietly into 8 ohms, but I'd rather just find a much quieter fan. They are out there and not too expensive.

FTC has undergone a number of revisions, causing it to morph into a pretty lame rating method, based on the assumption that home audio applications involve a very low crest factor / duty cycle. The days of credible ratings for home audio gear are over.

I've got two micro heads. One is convection cooled, but the later model of the same amp (more power) has a fan.

The other has a two speed fan that has never been audible in my use. It's a GK MB200, which is in such a cost sensitive market that if the fan were unnecessary, there would be no fan. Given how amps are marketed, I'm betting that the prudent gear maker designs them with the expectation that they will be ridden pretty hard. The design will based on extensive knowledge about operating conditions and failure modes.

Want a fanless switchmode amp? They are certainly available.