[Elecraft] [K3] K3 Rev C +AF filter

[Joe Subich, W4TV]

> I don't see what purpose an audio filter board would serve, 
> given that we have a crystal filter followed by DSP filtering 
> and then RX equalization already. Any high frequencies that 
> can get past that lot must be at a pretty low level already.

The add on audio filter board reduces (eliminates) clock 
and audio image leakage from the DAC output.  These are not 
related to the DSP process but hardware artifacts.  

I see several responses between 5 and 15 KHz although they 
may be down 50 dB or more from the peak audio levels.  Still, 
they are as much as 15 or 20 dB above the noise floor above 
4 KHz and this can make the K3's audio somewhat tiring when 
listening to weak signals since these leakage signals do not 
respond to the RX EQ or DSP. 

73, 

   ... Joe, W4TV 
       



> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Julian, G4ILO
> Sent: Thursday, December 17, 2009 9:22 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] [K3] K3 Rev C +AF filter
> 
> 
> 
> 
> 
> Ian Maude wrote:
> > 
> > Just to make it clear, I am not unhappy with the way Elecraft do 
> > business.  Neither am I bothered about buying a small 
> add-on board to 
> > improve my reception.  I am quite willing to pay for the 
> small board 
> > but do not see why I should have to pay £60-£70 (which it 
> will be here 
> > after shipping and VAT
> > etc) for a replacement DSP board that I do not need.
> > So, is the add on audio filter board available to buy as a separate 
> > unit?
> > 
> > 
> I can't find any mention (other than rumour) of an add-on 
> board. But if such an add-on was designed to fit the new DSP 
> board presumably it would not fit on to the old board.
> 
> The only benefit of the new DSP board as far as I can find 
> out is extended bass response through the headphone socket. 
> While that would be nice to have, like you I can't justify 
> the cost (which I would expect to be more like £80-£90 once 
> you add in the tax collection charge and sending back the old board.)
> 
> I don't see what purpose an audio filter board would serve, 
> given that we have a crystal filter followed by DSP filtering 
> and then RX equalization already. Any high frequencies that 
> can get past that lot must be at a pretty low level already.
> 
> -----
> Julian, G4ILO. K2 #392  K3 #222.
> * G4ILO's Shack - http://www.g4ilo.com
> * KComm - http://www.g4ilo.com/kcomm.html
> * KTune - http://www.g4ilo.com/ktune.html
>