[Elecraft] KPA-1500 Fan Noise

Fri Jun 1 23:07:20 EDT 2018

Just thought I would add a few thoughts as far as the fan noise.

I'm not certain a YouTube piece would help, but perhaps personal observations might.

First, via the menu, you can select the minimum fan speed, 0-5.  Of course, the fan speed will go up with the Amp temperature.

These are my personal observations:

0-Nothing
1-Barely perceptible
2-Acceptable fan noise, even for SSB operating.  Low pitched whine
3-The noise and the pitch of the whine is past the acceptable point.  Even a very directional mic will probably pick up the noise.  This is where Noise Cancelling headphones would start to help.
4-Louder and higher pitched whine
5-Very loud and higher pitched whine

So, the fan noise becomes particularly bothersome on level 3 and above.  If you are doing CW and/or Digital, the noise will only be a factor with the operator.  On SSB, the noise will probably be noticeable on the air.  However, the SSB duty cycle may not require higher fan speeds.  Those who have been active in contests will probably know that answer.

Rich, if fan noise is going to be that strong a factor, perhaps you should be looking at tube amps instead.  Personally, if I found the KPA-1500 fan noise excessive in the future, I would plan on moving it off my desk or remoting it rather than replacing it.  It's integration with the K3 would be very hard to give up.

’73 de JIM N2ZZ
#106

-----Original Message-----
From: elecraft-bounces at mailman.qth.net [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Dr. William J. Schmidt
Sent: Friday, June 01, 2018 8:59 PM
To: 'Elecraft Reflector'
Subject: Re: [Elecraft] KPA-1500 Fan Noise - YouTube ?

So just a bit of thermodynamics... if the input to any amplifier is 1500 watts and it is 50% efficient, since energy is conserved, 750 watts will come out in another form.. and in this case it's heat.  Doesn't matter what the converter is (transistor, tube, resistor, etc.).  It all behaves the same.  Need to get rid of 750 watts of heat.  The only difference may be the way the heat is taken away of the converter... convection (heat sink), forced convection (heat skin plus fan), liquid convection (water cooled heat sink).  The poison is the heat removal device not the converter.

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ 

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email:  bill at wjschmidt.com

-----Original Message-----
From: elecraft-bounces at mailman.qth.net [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bill Stravinsky via Elecraft
Sent: Friday, June 1, 2018 7:33 PM
To: Elecraft Reflector <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] KPA-1500 Fan Noise - YouTube ?

 Rich

You pretty much hit the nail on the head about solid state amps.  As they say there's no free lunch.  Solid state has made great strides in high power ampsbut its still solid state and a p/n junction or some form thereof.  1500 watts of heat in those junctions has to be cooled down or it won't be long before it needsnew parts.
Depending on your operating habits (contesting, casual, or whatever) there will be varying degrees of fan noise.  The higher the duty cycle the higher thefan requirements.  Pick your poison, a small light weight amp easy to move around or one you need a fork lift to pick up.  I prefer tube amps for a few reasonsand have the Acom 2000a (and an Alpha 89 that now sits in the living room temporarily) but I'm still glad I got the kpa1500 at least so far.
The kpa sits nicely on top of the Acom without causing the table they sit on to crash to the floor in pieces, hi.  I'm surprised nobody has made a you tube ofthe amp in operation actually.  But there are only just over 200 of the new amps out there.  Good luck with your investigation, Rich.
BillK3WJV

    On Friday, June 1, 2018, 8:00:29 PM EDT, Richard Thorne <rthorne at rthorne.net> wrote:  

 This fan noise issue has me concerned to the point that I’m considering cancelling my order.

While the amp won’t be on my operating desk, it will be on a rack next to my operating desk.  Remoting the amp is not an option. Quite frankly I have no interest in remoting the amp.

Is there anyone out there that has a KPA-1500 willing to post a YouTube video so we can hear the fan in action and judge the noise for ourselves?

>From the research I’ve done it appears that if you want a solid state amp, regardless of make, you need to be prepared for fan noise.

Thanks

Rich - N5ZC

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