[Elecraft] KPA1500 fan noise concern

[Wayne Burdick]

Thanks for the offer, Clay. But we actually did extensive thermal analysis of both the heat sink and fans, tested many different fan types and configurations, and did comparative noise testing of the KPA1500 vs. a number of other amps. 

As you allude to, there’s no magic bullet. Heat must be removed, with various physical and electrical constraints to be satisfied. 

We have some pretty amazing thermal imaging devices that we use to examine heat signatures of electrical components. These were used during R&D, which is how we determined that two LDMOS devices were far better than one for heat distribution. We also used it to evaluate the design of our very large/very thick copper heat spreader. On the production line, we review all modules for hot spots during burn-in and make sure the cooling is working perfectly (onset temperature, air distribution around modules, etc.).

Of course supplemental cooling of various types has been used with amplifiers in the past. I believe we have a couple of customers and staff experimenting with this idea, and anything that emerges will be posted here.

73,
Wayne
N6KR



> On May 28, 2018, at 4:34 PM, Clay Autery <KY5G at montac.com> wrote:
> 
> I don't have a fancy schmancy degree in acoustic design, but in my 20+ years of thermal control design for computing and other electronic products, I necessarily dealt with acoustic design as it pertains to device chassis.  They are often competing demands.
> One of my main selling points to many of my clients was that while meeting their requirements for thermal control, I could generally improve (reduce) the acoustic stress on their staff.  I had several long-term relationships where they kept adding adjunct projects to the original contract that were primarily acoustic and only secondarily thermal control as a result.
> 
> I'd be happy to trade some "free thermal/acoustic" analysis time on the KPA-1500 in return for the simple pleasure of having one on the bench during the process.  <big grin>
> Assuming I can produce a viable/economically feasible solution for both the company and customer base, perhaps a deal could be reached on a price to avoid returning the "test bed". <bigger grin>
> 
> Wayne?  Eric?
> 
> 73,
> 
> ______________________
> Clay Autery, KY5G
> (318) 518-1389
> 
> On 05/28/18 15:33, Jim Brown wrote:
>> On 5/28/2018 11:24 AM, Ralph Parker wrote:
>>> I ordered the '1500 In the quest to be a couple of instant db louder, but if I don't hear some resolution of the noise 'problem', I'm going to put the order on hold until it is solved. I do have many headsets which I usually wear, including the Bose QC15 noise cancelling model, but I'd hate to be FORCED into using them.
>> 
>> This is exactly one of the many issues that Acoustic Consultants address in the design of buildings that house recording studios, concert halls, and student practice halls in music colleges. I regularly worked with world-class guys in my own consulting practice, which only did sound system design, and I learned just enough to know that I shouldn't try to do their work. :)  There are many elements to the design problem, and the fan itself is only one of them. Other elements I'm aware of is turbulence of air flow, mechanical vibration coupled from the fan to the structure to which it is mounted, where the fan(s) are located, and so on.
>> 
>> I don't know if one of them was involved with Elecraft, but if not, I'd suggest that Elecraft buy some time from one of them. And I'd be happy to provide names of some good people/firms. In the early K3 days, I referred a good acoustics guy to Wayne to solve the problem of acoustic coupling between the speaker and the synthesizer that added a sideband to RTTY, and suggested adding the stiffener to that board solved the problem and became a running mod.
>> 
>> 73, Jim K9YC
> 
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