[SECC] Yamaha CM-500 Headphone Mod

Fri Aug 12 17:39:09 PDT 2011

To all

I'll take a chance and share my solution to making the CM-500 headset plug 
compatible with the Heil.  My CM-500 came from Sam Ash Music ($45) and had a 
battery box to contain two AA batteries to power the Electret mic element 
and as Hal noted, the Mic audio output with this power source in line is 
much higher than the Heil elements.  My solution was to open the box by 
removing the screws inside - between the batteries - and perform the 
surgical procedure per the attached MS Word file - if it comes through ok. 
You must change the 3-conductor plug on the battery box to a 2-conductor for 
it to work consistently with the Heil radio adapter "Y" cables.  The 
resistor values are of course not critical, as it's just a voltage divider, 
but I know of probably 8-10 headsets that have been thusly modified and it 
seems to work fine.  The transmit audio response if pretty flat, as is 
typical for Electret mics, so Mic EQ is recommended, especially for other 
than rag chewing.

My batteries have been going for about 8 months now with no issue noted.

cul

Bob Wilson - W4BW

----- Original Message ----- 
From: "Hal Kennedy" <halken at comcast.net>
To: "'Mike Greenway'" <K4PI at BELLSOUTH.NET>; "'Rich Arland'" <k7sz at live.com>; 
"'North Georgia QRP Group'" <nogaqrp at yahoogroups.com>; "'SECC'" 
<secc at contesting.com>; "'South East DX Club'" <sedxc at contesting.com>
Sent: Friday, August 12, 2011 2:25 PM
Subject: Re: [SECC] [SEDXC] Headphone Quest

> Just bought a set of CM500s.  Had them about three days.  The earphones
> are not noise canceling - there is no battery in the headphone part (I
> thought they were...but no luck).  They do cover the entire ear and
> reduce background noise pretty well.  They are comfortable.  The
> earphone response is very flat - I prefer something that peaks at the
> high end where my hearing goes bad.  I have an equalizer in line to get
> the response as I prefer it.  When running Bose phones I did not use the
> equalizer.  My high end hearing is shot - I tend not to notice hiss.
>
> The electret microphone puts out about twice the amplitude of a Heil,
> which I am not too happy about.  I was able to turn the mic gain down on
> the radio and take care of that, but the VOX gain needs to be reset and
> the computer DVD functions all need to be reset as well and I'd prefer
> not to do that.  I may instead, built a two resistor attenuator into the
> battery box or a plug/jack to get the microphone gain back to what I
> would call "typical."  The microphone has full freq. response.  It
> sounds great if you like Hi-Fi audio.  The Heil HC-5 element sounds
> pretty bad but is tailored to cut through pile-ups.  Take your pick.
> Since I don't ragchew on SSB, I think I like the bad sounding Heil
> better for a communications circuit.  Also, the CM500 microphone is omni
> directional - which is not too good for a multi-op station or when you
> have background noise in the shack.  The Heil only responds toward your
> mouth.
>
> Like Rich, I am still searching for a quality, noise canceling set of
> phones with a factory installed microphone that's not an electret and
> has that "cut through the pile-up" frequency response.  The best I have
> had so far was a pair of Bose QC2's with a Heil boom mic. bolted to the
> side.  Many folks have gone that route.  If you do, the Bose QC2 can be
> bought on eBay, used, for a fraction of the significant brand-new price.
>
> Any suggestions are most appreciated!  I will keep the CM500, but I hope
> to relegate it to backup when I find something better.
>
> 73,
> Hal N4GG
>
>
> -----Original Message-----
> From: secc-bounces at contesting.com [mailto:secc-bounces at contesting.com]
> On Behalf Of Mike Greenway
> Sent: Friday, August 12, 2011 1:58 PM
> To: Rich Arland; North Georgia QRP Group; SECC; South East DX Club
> Subject: Re: [SECC] [SEDXC] Headphone Quest
>
> You might look at the Yamaha CM500.  Around $54 through Amazon and it
> has a
> mic also.  If you use the K3 you don't have to use the batteries in the
> headset as it will pick up the voltage for the mic from the jack in the
> rear
> where they plug in directly.  The mic does require a bias so if your rig
>
> does not supply it you will need the batteries.  They are noise
> cancelling
> which tend to use more.  I don't have a set of these but thinking about
> ordering one.  The guys on the K3 Reflector rate them very good.
>
> -----Original Message----- 
> From: Rich Arland
> Sent: Friday, August 12, 2011 1:49 PM
> To: North Georgia QRP Group ; SECC ; South East DX Club
> Subject: [SEDXC] Headphone Quest
>
>
> Hi Gang:
>
> I am "shotgunning" this query to three of my favorite lists in hopes
> that I
> can receive some feedback that will help me determine a course of action
> to
> procure a new, comfortable and useable set of headphones for the shack.
>
> I don't know about y'all but I am about fed up trying to find a pair of
> headphones that cover the entire ear (not just sit on top of the ear),
> will
> work with the wide variety of gear in my shack, be comfortable for long
> periods of use, have the proper frequency response to reduce the
> listening
> fatigue encountered due to the amount of "hissssss" present in the audio
>
> passband, isolate me from the madhouse that normally surrounds my shack,
> and
> not cost several hundred dollars!
>
> The
> best ones I've tried so far and found to meet the majority of the
> criteria I have outlined are the Kenwood HS-5 Communications Headphones
> which run about $75 at Universal Radio (HRO has them for
> $87.95.....their "discount price"???). The reviews at e-ham seem to
> conclude
> that these headphones are very popular and they get consistently high
> review
> ratings.
>
>
>
> While the price is what I would consider a bit elevated, they certainly
> outperform the $10.99 padded full-ear muff earphones normally found on
> e-bay, at Wally-World, and at hamfest flea markets.
>
> So, with that criteria in mind, what seems to be the favorite among you
> DXers, contesters and QRPers??
>
> Opinions are welcome so enlighten me!!
>
> 73
> Rich Arland, K7SZ
> Bent Dipole Ranch, Dacula, GA
> "Cogito Ergo CQ" ("I think therefore I HAM")
> Author: "The ARRL's Low Power Communications, the Art and Science of
> QRP"
> (all 3 editions)
> Editor: "QRP POWER", QST Magazine (Jan 2000 to Dec 2003)
> Editor: "The Learning Curve", CQ Magazine
> Editor: "The Beginner's Column", CQ-VHF Magazine
>
>
>
>
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