[CW] Headphones or Loudspeaker?

[D.J.J. Ring, Jr.]

Steve N4LQ has a wonderful video about resonant speakers.

He has a SKYTEC speaker and he took it apart and made a practical copy.
https://www.youtube.com/watch?v=MF8bk6958Hg


*Magical Audio Filter*
MAGICAL AUDIO FILTER USING MC1458 &
​ ​
MAX295 IC1s BY JIM PEPPER
​  BOARD FOR $6.50  available from faircircuits​.net


73 Nov 96
<https://archive.org/stream/fea_The_Magical_Audio_Filter/The%20Magical%20Audio%20Filter#page/n0/mode/2up>

https://archive.org/stream/fea_The_Magical_Audio_Filter/The%20Magical%20Audio%20Filter#page/n0/mode/2up

DESCRIPTION: This circuit uses two MC1458, one LM386, one MAX295, 78L05,
and 78L12.

Note: Maxim has obsoleted the Max295 IC's; Make sure you can get the IC's
before ordering the board!
(The MAX 295 is available on eBay for two for $13.00.)

​Milestone Technologies sells a CW filter, too.
https://www.mtechnologies.com/misc/filter.htm

73

DR​



On Fri, Jun 15, 2018 at 1:27 PM, Richard Knoppow <1oldlens1 at ix.netcom.com>
wrote:

>    You don't have to use resonant phones. In fact they are antiques now.
> Modern "hi-fi" phones are non resonant and can work at any frequency.
>    With some research you can probably find how to make a fairly sharp
> filter. An active filter with a small amplifier for the phones or a passive
> one that just goes in the line between receiver and phones. In the tube
> days there was a gadget called the _Selectoject_. It was first described in
> QST, then made as a commercial product by National. I don't know if there
> was a solid state version but I suspect there was. It could be used as a
> tuneable rejection filter or a tunable peaking filter.
>    A problem with any filter that is too sharp is that it rings on noise
> and can make CW harder to read rather than easier.
>    How did you tune the speakers?
>
> On 6/15/2018 8:18 AM, John Westerlage wrote:
>
>> I would like to use headphones to keep from bothering the rest of the
>> household.
>>
>> BUT - the frequency one prefers seems to have something to do with the
>> ear's
>> physical structure as well as other factors.
>>
>> For me, a tone of around 432 c.p.s seems to be MUCH louder than any other
>> freq
>> either higher or lower.
>>
>> So, I have built speakers tuned to that frequency, but I cannot find any
>> headphones
>> that do the same thing.  I suppose some sort of R/C network as pre-filter
>> in the
>> earphone line could do the job, but I haven't been able to come up with
>> the right
>> combination.
>>
>> Any suggestions on how I could do this ?
>> *vy 73, John, N5DWI*
>>
>
>
> --
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
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