[Elecraft] KPA Fan Noise

[Eric Swartz - WA6HHQ, Elecraft]

Hi Toby, I believe the 6th fan speed setting is OFF. :-)  Your temps 
look about right to me.

The KPA500 is about as quiet as we can make it for a compact solid state 
600W amp. We took special care to select the quietest fans we could get 
for this application. In general our user feedback has been extremely 
positive with respect to this. I'm a user too and have not had a problem 
with it, but my operating habits may be different than yours.

Solid state amps must move more air over their cooling fins at a much 
higher rate than tube amps due to the lower operating temperature 
difference between transistors vs tubes and the ambient air. The higher 
operating temperature of tube amps does provide a more efficient flow of 
energy away from the tube to the much cooler surroundings.

Also, since the KPA500 is pretty much automatic in its operation, it 
certainly can be located away from the operating position. Providing 
more clearance for cool air flow above and behind the amp will also 
help. But in general, contest usage of any compact solid state amp is 
going to generate a higher level of fan noise.

Regards,


Eric
---
www.elecraft.com

On 11/8/2012 5:51 AM, Toby Pennington wrote:
> Eric,   yesterday Don emailed a number of us off list with the things he did to quieten the fan noise of the KPA500..
>
> I will leave it up to him if he wants to post his modifications or not,  but one of the things he suggested was to entirely isolate the fan itself from all metal sheeting or chassis or the amp.
>
> He does not utilize metal screws to hold the fan in place now,  but uses other means to hold the fan in place,  thereby eliminating vibrations from the fan from transferring to any other part of the amp.
>
> He also actually balanced the blades of the fan so there was no noise that occured from imbalance of the fan blades.
>
> He did other things but now says his fan speed never gets over a setting of 1 or 2.
>
> AS an aside,   I tried to determine at what temperatures each fan speed came on at and am missing one speed.  When I first noticed the fan speed came on it was at 50C;,  then 55C,  60C,  65C, and then 70 C.   That is only 5 speeds so I am missing one speed.  Can you tell me what temperature setting I am missing?  My thinking is I may be skipping one fan speed somehow and that could be making the amp overheat faster.
>
> Thanks for your help.    Toby  W4CAK
>
>
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