What were Trace thinking of?

[stevie]

I am enjoying my recently acquired AH300/7 but found the fan noise a little too loud. So I swapped it for a Papst of similar rating (same power consumption). Unfortunately, the Papst must be more efficient than the OEM fan because it's faster and therefore even louder. I now want to change it for a lower speed Papst, which I know will be quiet. However,....

Trace have designed the fan cooling on this amp in a most curious way. The fan sucks in from the outside (at the back) and blows air directly onto the heat sink inside. Not what I would do, but it obviously works. At either side of the fan are two large vents, which create an efficient open circuit for the cooling system: the warm air is blown out of the case right next to the fan, where it is sucked in again to be recirculated.

Is this normal? It strikes me as being absolutely bl**dy stupid.

I'm thinking of blocking the vents with tape and reversing the polarity of the fan so that it will vent to the outside of the case. As I'll be using a lower speed fan than standard, I'd be interested to know what you think.

Edited September 2, 2010 by stevie

[Mr. Foxen]

Would guess warm air will head up upon exit, so that would not be recirculated so easily. Probably best not to mess. Or maybe double up the fans contra rotating, so they can run at half speed or something.

[Ghost_Bass]

In my GP12X combo there is no exit grill for the air! It comes out of the EQ's slides tears. Here's some pics:
[url="http://picasaweb.google.com/106572846091439162015/TraceElliot1215GP12X#slideshow/5509231183298746082"]http://picasaweb.google.com/10657284609143...231183298746082[/url]
The air that does'n comes out from the grill on either side of the vent is pushed troug the front pannel. Some ether models have grills in both sides of the front pannel.

Either way the vent is very quiet and i never had overheating problems.

[stevie]

Ghost, mine is the same as or very similar to yours. Most of the exhaust air comes out right next to the fan, with a bit coming out through the graphic equalizer slots. I've no doubt it works, but it strikes me as extremely inefficient because the fan should really be pulling fresh, cold air through the case, across the heat sink and then out the opposite side.

I really do need to put a quieter fan in, and rearranging the cooling arrangement seems like an obvious thing to do at the same time. I'm just wondering if I'm missing something, as it seems unlikely that Trace would do this without some kind of reason, although I have to admit, it sure looks like a major design booboo from here.

Edited September 2, 2010 by stevie

[Stylon Pilson]

[quote name='stevie' post='942822' date='Sep 1 2010, 11:29 PM']I'm thinking of blocking the vents with tape and reversing the polarity of the fan so that it will vent to the outside of the case. As I'll be using a lower speed fan than standard, I'd be interested to know what you think.[/quote]

Reversing the fan sounds like a pretty good idea to me, but unless there's a vent on the front of the amp, you might find that blocking up the rear vents actually hinders rather than helps.

S.P.

[Colledge]

ive got a v-type head open next to me and its exactly the same as you describe. I'm making myself an aluminium headcase for it so i might have a go at making some slots for extra air flow.

[Ghost_Bass]

I once saw a guy playing with one of these strapped to the back of his 4x10" SMX:

It also had a on/off switch! I didn´t had the chance to question him about it though...

[Colledge]

it'd be pretty easy to solder in a small variable resistor so you can control the fan speed

[stevie]

Some excellent info - thanks, everyone. I'm going to go ahead and mod it. I don't need to buy the fan, as I have a few different ones in my workshop. The quiet Papst one works at 1600rpm, which should be OK - as long as there are enough holes in the front to allow it to work, as SP said.

Dave, I'd appreciate a set of those rubber mountings. There does seem to be quite a bit of noise being transmitted from the fan housing to the case.

Should anyone wish to follow my example, I'll post the results on here.

[Mottlefeeder]

One of the problems with fans is that they do not suck directionally, but they can blow directionally.

It is likely that the fan blows onto the heatsink to make sure that more of it gets cooled. If you change the direction of the fan, only the closest part of the heatsink will get cooled, unless the entire assembly is an airtight tube so the air can only flow through it and not sneak in through other gaps.

David

[bumnote]

I have an ashdown c100 combo which is basically an abm 300 head with a 1x10 speaker. I would imagine as the original trace designer still works for Mark Gooday they might be considered at least 'related'

The fan on this is also fairly noisy and sucks the air from the outside in. I did e mail ashdown about it as I was planning to use it in the studio, and they said that it was important that the fan was working, although they thought I might be possible to change it for a computer one.

If you compare that to the one fitted to my fairly old eden traveller, the traveller one is almose completely silent.

If you find a fix it would be interesting, im going to have a look when I get a minute.

[waynepunkdude]

Maybe you should just buy an SVT everyone knows that's the only good tone anyway.

[waynepunkdude]

Maybe you should just buy an SVT everyone knows that's the only good tone anyway.

[Stag]

Further to that my SVT has the fan and vents rather stupidly at the side. This is stupid, stupid I tell thee. However it is an SVT and therefore is better than anything that weighs under 6cWt. So nerrrrrrrrrrrrrrr.

[Ghost_Bass]

Oh my God! They're spawning and invading the surroundings... we better get a pest-controller to try to contain this menace!

To the OP: Listen to Mottlefeeder, my opinion is also to maintain the air flowing from the outside to inside unless you can come up with something close to what the fan in a PC does to it's processor. I had a Behringer BX1200 and it had 2 fans, one inside cooling the heatsink pulling air away from it and other on the chassis pulling out that same air.

[Colledge]

i think the cooling system must work well enough because my amp has never felt hot after running at almost full tilt.
ive even ran the head without a case and the heat sinks are just about warm to the touch after being run at a decent volume for about half an hour, they must have done something right.

[stevie]

I fitted another Papst into the Trace. This one runs at around 2500rpm (slower than the original Trace one), but it was still loud.

I then turned the fan round to blow air out of the back of the amp and taped over the vents. This caused the volume of air expelled by the fan to drop by around 75%. It's a fair assumption that air intake is being restricted by the lack of vent holes at the front, as some of you surmised. As it is, however, the fan is not moving enough air and is probably being placed under undue stress. Without any way of increasing the vent area at the front of the case, this configuration is a bit risky and I wouldn't recommend it. Worth a try though.

I've now installed a 1600 rpm Papst in the amp (blowing into the amp, as per the original Trace design). This is considered to be the quietest computer case fan in existence - inaudible from a distance 1 metre - yet installed in the Trace, it is still annoying loud. I'm hearing mechanical noises rather than wind noise and these are being transmitted through the wooden case. So, the next task is to install the rubber grommets Dave so kindly supplied (Thanks Dave!!).

I'll report back. If there are any fan experts here, I'd be happy to hear from them.

And before anyone mentions it, no I'm not being fussy. I work about 1 metre away from my PC which has two fans blowing out the back. My single fan in the Trace head sounds *much* louder.

Edited September 6, 2010 by stevie

[stevie]

[quote name='Colledge' post='944125' date='Sep 3 2010, 01:15 AM']i think the cooling system must work well enough because my amp has never felt hot after running at almost full tilt.
ive even ran the head without a case and the heat sinks are just about warm to the touch after being run at a decent volume for about half an hour, they must have done something right.[/quote]
It does sound like the amp only needs minimal airflow to keep the heatsink cool, which is good news.

[Ghost_Bass]

What is the model of your head? Can you post some pics of it so we can see what´s happening with it? I find it very strange to have so much fan noise... i had two TE amps and none had that issue. You can always buy a original spare fan from britishaudioservice (in USA):
[url="http://www.britishaudioservice.com/shop_trace_fans.shtml"]http://www.britishaudioservice.com/shop_trace_fans.shtml[/url]

Good luck with it

[stevie]

Ghost, it's the HA300/7 built around 1990. I could post some pictures but the cooling arrangement and the power amp section are exactly the same as on the pictures you posted earlier.

I don't really need a replacement OEM fan, as the ones I'm using are better quality than the original. I'll do some more experimenting tomorrow to try to get to the bottom of the noise problem.

[Spoombung]

Fans in amps are one of my pet hates. And they get noisier and noisier the older they get

[stevie]

This is the first amp I've had with a fan. I previously had a passively cooled power amp with a separate preamp, and before that, a Trace 200-watt head, which was passively cooled. I don't mind a quiet whoosh, but I can't stand this rattly buzzing.

[krispn]

What about those tiny wee laptop fans - make a a larger square out of 4 tiny ones - if they will fit and reverse two of them for air in air out action - smaller fans = less noise too right?

It sounds simplistic but it might just work right?

I'd be interested to hear the various way those who are more clever than me shoot this idea down

Commence

[stevie]

[quote name='krispn' post='948106' date='Sep 7 2010, 11:06 AM']- smaller fans = less noise too right?[/quote]

Exactly the opposite in fact. Fan speed is what causes noise. The slower the fan, the lower the noise. A large fan moving slowly will shift as much air as a small fan moving quickly but be quieter (less turbulence). That's why PC makers have moved from 80mm to 120mm fans.

[stevie]

I got to the root of the problem. There was a very slight gap between the fan and the case, which caused the fan to rattle against the case. It actually sounded like the fan was buzzing and rattling but it was in fact the casing creating the racket. The metal case is also screwed very firmly to the MDF outer sleeve, which makes the vibrating area even greater.

The only reason I discovered this was because Dave had supplied me with some silicon spacers for the fan. When I fitted them the racket subsided considerable, although I still had to use some thin foam to space the fan completely off the chassis - and that did the trick.

Clamping the fan firmly to the chassis helped a bit, but not much - and certainly nowhere near as much as spacing the fan away from the metal casing.

I ended up fitting a 2,600 rpm Papst that generates about the same amount of 'wind' as the original. All I can hear is the whoosh of air now. It's not quiet, but it's not an annoying noise like before. With a better design of case (i.e. a proper air inlet), I'm sure a 'silent' fan type would be fine.