[Elecraft] BHI HP-200 and other headphones

[Paul Christensen]

Need to correct myself:  I referred to the TS-950 when I meant the FT-950.

Paul, W9AC

----- Original Message ----- 
From: "Paul Christensen" <w9ac at arrl.net>
To: <elecraft at mailman.qth.net>
Sent: Wednesday, May 06, 2009 7:01 AM
Subject: Re: [Elecraft] BHI HP-200 and other headphones


>> I don't know about the big Icoms or their new 7600 and would be 
>> interested
>> to hear from anybody who has one.
>
> The Icom '7700 and '7800 are nearly hiss-free at the minimum AF setting. 
> My
> K3 is totally silent using Sony MDR-7506 and Bose Tri-Port headphones.
>
> There's generally only one time when I hear hiss from my K3 -- and that's
> right after a F/W flash.  I have now become accustomed to turning power 
> off
> after the flash is complete, then wait > 5 seconds and re-start.  If I do
> not wait ~ 5 seconds, I oftentimes hear slight latent hiss.  But it's 
> cured
> 100% by this off-on sequence.
>
> The rig tried here with the highest latent AF hiss was the TS-950.  In 
> fact,
> the hiss level was so high that VS designed a special relay "cut off"
> circuit to kill the hiss (and all audio) when the AF control is turned 
> full
> CCW.
>
> On the TS-950, the hiss comes into play when the AF control is just 
> slightly
> advanced.  IOW, at full CCW, a relay opens up the headphone line.  And 
> when
> the AF control is advanced, the relay closes and the hiss becomes 
> apparent.
> That's the first attempt I've seen by a manufacturer to mask a design
> problem by using a relay as an audio 'knife switch."
>
> Anyone owning a TS-950 can try this test without wearing headphones:  Turn
> the AF control CCW and repeatedly advance and retard the control slightly.
> Hear that relaying clicking inside the cabinet?  That relay's sole purpose
> is to mask hiss.
>
> Paul, W9AC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>