Posted by
Joe Subich, W4TV-4 on
Aug 26, 2010; 3:24pm
URL: http://elecraft.85.s1.nabble.com/K3-Modification-day-for-SN-01195-tp5463862p5466019.html
Bill,
> I use low pitch settings of 300-440 Hz and have considered both mods
> but haven't yet decided it's worthwhile. Without having two units
> (one with and one without) to compare, it's tough to know whether I'd
> notice any difference.
I added the LPF to my Rev.B DSP board and found that worthwhile. I
can certainly notice the decrease in high frequency "garbage" in both
speaker (Sony "bookshelf" speakers) and headphone (200/120 Ohm) audio.
The only receive effect of the DSP upgrade is to decrease the LF corner
frequency when using headphones. The corner (-3 dB point) frequency is
dependent on the headphone impedance. Here is a comparison of the
original 10 uF coupling capacitors and the new DSP board with 100 uF caps:
Z Original Modified Notes
---------------------------------------
600 26 Hz 3 Hz
400 39 Hz 4 Hz
200 80 Hz 8 Hz Heil ProSet
150 101 Hz 10 Hz Senheiser PC-350
120 124 Hz 12 Hz Yamaha CM-500
64 221 Hz 22 Hz Senheiser HD-280 Pro
32 398 Hz 40 Hz Direct Sound EX-29
24 497 Hz 50 Hz Sony MDR-V150
16 663 Hz 66 Hz Etymotic ER6i, HF5
8 995 Hz 99 Hz Yaesu YH-55
The obvious conclusion is that the new DSP board reduces the corner
frequency by a factor of 10 (as expected). Whether it matters to a
given user depends on his headphone preference and the importance of
LF response. With your EX-29, you might find the DSP replacement a
plus; with my CM-500, I decided to pass on the DSP board replacement.
73,
... Joe, W4TV
On 8/25/2010 10:17 PM, Bill W4ZV wrote:
>
>
> Nick-WA5BDU wrote:
>>
>> K3DSPLPF --- Active audio LPF to reduce artifacts in the audio chain,
>> add daughter board to DSP board
>>
>> <SNIP>
>>
>> I was most interested in the lowpass filter. I'm no golden ear, but
>> possibly the power of suggestion made me think I heard some of the
>> harshness others described. I found myself cranking the bandpass way
>> down toward the low end. At least preliminarily, I think I do notice
>> the improvement in the quality of the sound (I work CW) with the LPF
>> installed.
>>
>
>
http://www.elecraft.com/order_form_parts.htm>
> K3DSPUPGD Improves low freq RX/TX audio response below 300 Hz, and adds
> a Low Pass Filter (LPF) that rolls off RX audio above 4 kHz.
>
> K3DSPLPF Small LPF add on SMD board for earlier K3 DSP boards that adds
> a Low Pass Filter to roll off RX audio above 4 kHz. This is already included
> on the K3DSPUPGD (above)
>
> I believe it's the DSP mod which improves audio response at the low end.
> The DSPLPF rolls off audio artifacts above 4 kHz.
>
> I use low pitch settings of 300-440 Hz and have considered both mods but
> haven't yet decided it's worthwhile. Without having two units (one with and
> one without) to compare, it's tough to know whether I'd notice any
> difference.
>
> 73, Bill
>
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