Improving amp performence

[kgveteran]

I'm planning an amplifier project for the winter.I'll be using ashly fet-200's.They bridge mono to about 360 watts/8ohm.The manufacurer says it will do 4 ohms as I discribed to him with no problem.I'll be driving the RS WTMW center with it.I'll be eliminating the fan and mounting the heat sinks outside of the chassis to cool them.There are a couple other mods like bridge rectifier upgrades and some other hardware changes too, just to make it easier to use.

Is there anything I can mod on this amp to help it deal with the 4ohm load in the bridged mode ? My thought is to just run it for a while and see if it gets real hot or just shuts down.I like the idea of mono's for the mains, which are three RS centers.
KG

[whoaru99]

It would seem easier just to get quieter cooling fans. There are some Panasonic fans (and probably others too) that run very quietly.

Perhaps you should take a look at the fans in DigiKey to see what options may suit your needs rather than turn the whole amp inside out.

Often, pro amp heat sinks are based on a forced air tunnel system that is not very conducive to convection cooling.

[Karma]

HI,
Here's a source for some very quiet fans.

http://www.endpcnoise.com/cgi-bin/e/std/category=Quiet_Case_Fans.html?id=V7qcAQWF

Sparky

[kgveteran]

What I have noticed is if I hold my noisy fan in my hand, it too is quiet.Once it gets mounted, thats where the noise starts.


Getting back to OP What can be done to increase an amps ability to deal with a 4 ohm load in the bridged mode. Lets forget the fans for now .

KG

[whoaru99]

Heat dissipation would be one, I'd think. That would mean more cooling air, not less. So in that regard, I'd have to assume any conversion to convection cooling would be counter productive unless you are going to increase the size/thermal efficiency of the heatsinks.

Another would be power supply capacity. Running bridged at 4 is equivalent to 2 ohms non-bridged so it will require more current from the power supply to deliver the commensurate power output.

This is purely opinion, but at this point one would have to consider whether or not all these changes are worth it, or whether it's just better to get the correct amp up front.

It may not ever be a problem unless you are going to have some pretty high continuous volume levels. If most of the power will remain in reserve for peaks, again, it's probably not that much of a concern to run bridged at 4 ohms.

I certainly would not be getting rid of the fans in that situation and would consider looking for one with more cfm and less noise.

[kgveteran]

Heat dissipation would be one, I'd think. That would mean more cooling air, not less. So in that regard, I'd have to assume any conversion to convection cooling would be counter productive unless you are going to increase the size/thermal efficiency of the heatsinks.

Another would be power supply capacity. Running bridged at 4 is equivalent to 2 ohms non-bridged so it will require more current from the power supply to deliver the commensurate power output.

This is purely opinion, but at this point one would have to consider whether or not all these changes are worth it, or whether it's just better to get the correct amp up front.

It may not ever be a problem unless you are going to have some pretty high continuous volume levels. If most of the power will remain in reserve for peaks, again, it's probably not that much of a concern to run bridged at 4 ohms.

I certainly would not be getting rid of the fans in that situation and would consider looking for one with more cfm and less noise.

Nice post Thanx for all the help.Most movies are up and down.I'm looking for headroom not max output.I looked at the fans in the link and I'm thinking that would be worth it for me to do a 15.00 upgrade instead of,"turning it inside out". My current amp is about 105wpc, increasing the power to 350wpc gives me the headroom I think i'll need for most movies and music listening. thanks for the advice.

I did a fan mod on my four QSC's that I use for my subs.I find that the fans sound very quiet outside the amp and increase quite a bit in the amp its self.Next step is they all go down stairs in the basement :B .

[ThomasW]

When you bridge amps you sum the distortion of the 2 channels. So yes you get more power, and you also get double the distortion.

Since you don't really need the power bridging provides, just biwire the speaker. Run one channel of the amp to the woofers and the other to the TM section.

[kgveteran]

When you bridge amps you sum the distortion of the 2 channels. So yes you get more power, and you also get double the distortion.

Since you don't really need the power bridging provides, just biwire the speaker. Run one channel of the amp to the woofers and the other to the TM section.

They are 100watts per.But there are four devices per channel also.I'll play around once they begin to roll in.

[sokoban]

When you bridge amps you sum the distortion of the 2 channels. So yes you get more power, and you also get double the distortion.

Would it be possible then to invert the signal of one of the amps before and after amplification so that the distortion would then sum to zero?

[kgveteran]

When you bridge amps you sum the distortion of the 2 channels. So yes you get more power, and you also get double the distortion.

Since you don't really need the power bridging provides, just biwire the speaker. Run one channel of the amp to the woofers and the other to the TM section.

Would the distortion only be there if I push beyond it's limit ? How do I do a bench test to see where the amp starts to breakup ?