[Elecraft] K3 Audio Low Pass Filter

[Brett Howard]

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Paul Christensen
Sent: Monday, July 06, 2009 12:13 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3 Audio Low Pass Filter

>And that jumps to ~ 200 Hz if you use 8-ohm cans.  If you stay cognizant of

>the headphone Z, you're in good shape.  If you want to pull a set of Koss 
>Pro4 AA phones off the shelf, you may want to revisit that.  It's all about

>the series C and knowing the headphone Z as a function of frequency.  It's 
>doubtful your 27 ohms headphones remain 27 ohms across their frequency 
>range.

Actually its 100Hz for 8 ohm cans because of the 8.2ohms inside the K3.

>Speaking of robust, when I started discussing the matter with Lyle many 
>months ago, I was concerned that increasing the C value above 10 uF at 
>C9/C13 would begin to introduce switching thumps that would become apparent

>especially in CW.  Stated another way, I was hopeful that the small C size 
>was not masking keying artifacts that were there all along, only to be 
>discovered by increasing the cap size!  But at 330 uF, I hear no artifacts 
>as a result of the change.

Good to know!!!

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