[Elecraft] K3 headphones

[Joe Subich, W4TV]

> This is not always the case.  The headphones that I'm 
> planning on using are Etymotic ER-4P's which are designed 
> with a low impedance to remain efficient with portable music 
> players but have very flat responses.

Unfortunately, the 10 uF coupling capacitors in the output of 
the K3 headphone amplifier form a voltage divider with the 
impedance of the headphones (plus the 8.2 Ohm resistors Lyle
references).   For 8 Ohm headphones the -6dB point in the 
response is 1 KHz (Xc=16 Ohms).  With 200 Ohm phones the -6dB 
drops to about 75 Hz (Xc=208 Ohms) and with 600 Ohm phones 
the -6dB point drops to about 25 Hz (Xc=608 Ohms).  

This is purely a function of the series RC output of the 
headphone amplifier and does not effect the speaker 
response.  K9AC has recommended replacing the 10 uF caps 
with 220 uF caps which would reduce the corner frequency 
for low impedance headsets to about 50 Hz but since my 
primary headset is the Proset I have not tried it as yet. 

73, 

   ... Joe, W4TV 
 


> -----Original Message-----
> From: Brett Howard [mailto:brett at livecomputers.com] 
> Sent: Monday, June 22, 2009 1:52 PM
> To: lists at subich.com; 'Roy Morris'
> Cc: elecraft at mailman.qth.net
> Subject: RE: [Elecraft] K3 headphones
> 
> 
> This is not always the case.  The headphones that I'm 
> planning on using are Etymotic ER-4P's which are designed 
> with a low impedance to remain efficient with portable music 
> players but have very flat responses.
> 
> The dip in the top end is intentional as they are sealed into 
> your ear and they need to put that in so that you don't feel 
> like there is way too much in the high end.  There is much 
> less rolloff when something is sealed into your ear canal vs outside.
> 
> I've made some plots of the ER4s along side the Grado SR60.  
> The Grado is an often known standard for relatively 
> inexpensive cans with good sound.  The Grado's run around 60 
> to 80 bucks where as the ER4's are around 300 MSRP. But you 
> can get them for at least half that.
> 
> Response curve: 
> http://graphs.headphone.com/graphCompare.php?graphType=0&graph
> ID[]=733&graphID[]=393
> Impedance curve: 
> http://graphs.headphone.com/graphCompare.php?graphType=7&graph
> ID[]=733&graphID[]=393
> 
> ~Brett
> 
> 
> -----Original Message-----
> From: Joe Subich, W4TV [mailto:lists at subich.com] 
> Sent: Monday, June 22, 2009 9:36 AM
> To: 'Brett Howard'; 'Roy Morris'
> Cc: elecraft at mailman.qth.net
> Subject: RE: [Elecraft] K3 headphones
> 
> 
> Low impedance headsets are the ones with decreased low end 
> response - or apparent excessive high frequency response and 
> the resulting "tiring" sound.
> 
> I strongly recommend 200 Ohm (Heil ProSet) or 600 Ohm 
> (professional) headsets. 
> 
> 73, 
> 
>    ... Joe, W4TV 
>  
> 
> 
> 
> > -----Original Message-----
> > From: elecraft-bounces at mailman.qth.net
> > [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Brett Howard
> > Sent: Monday, June 22, 2009 11:47 AM
> > To: Roy Morris
> > Cc: elecraft at mailman.qth.net
> > Subject: Re: [Elecraft] K3 headphones
> > 
> > 
> > Was it high or low impedance that was causing issues?  I'm
> > contemplating plugging in two pairs of headphones which is 
> > probably going to put me somewhere around 11 to 15 ohms 
> > nominal.  I'm sure it'll do fine but hadn't been able to find 
> > much in the way of specs for the K3 in this regard.
> > 
> > 
> > On Mon, 2009-06-22 at 11:30 -0400, Roy Morris wrote:
> > > Gary,
> > > I use a 33 ohm headset  with my K3.  I have not noticed any
> > reduction of audio and the impedence match seems to be good.
> > I use an AKG K240 Studio headset and get excellent 
> > reproduction.  Roy Morris  W4WFB
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