I realize we're straying rather far afield from amplifier topics, so pse
overlook my wading into the discussion. The proliferation of outboard audio
devices for transceivers, and the desire to mix and match vintage mics and
rigs with modern ones, has caused hum pickup problems to plague many hams. I
discovered this fact to my dismay with my StationPro station controllers.
Most StationPro builders had no problems, but probably five percent reported
audible hum when routing their microphones through the StationPro.
Fortunately, these problems were nearly always easily cured, but the "fix"
usually required the builder to understand the possible origins of hum in
their microphone audio circuits. Hum is not ordinarily, as many suppose,
induced "pickup" from nearby fluorescent lights, transformers or whatever.
I ended up writing a brief tutorial on the subject, which can be found here.
http://www.w8zr.net/stationpro/images/download%20files/Microphone%20Hum.pdf
This will be old hat to most of you, but might be useful those who don't
know what the "pin 1" problem refers to.
73,
Jim W8ZR
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Jim Brown
> Sent: Thursday, June 06, 2013 11:29 AM
> To: amps@contesting.com
> Subject: [Amps] The Pin One Problem
>
> On 6/6/2013 10:05 AM, Peter Voelpel wrote:
>
> > The pin 1 problem generally is not a problem with the gear but with the
external wiring
>
> Actually, it is a problem built into equipment by a
> designer/manufacturer who fails to terminate a cable shield for external
> wiring to the shielding enclosure, but instead to interior wiring
> (usually a circuit trace). The most common way this happens is that
> connectors are mounted to the circuit board, not to the shielding
> enclosure. This manufacturing defect is nearly universal in consumer
> electronics of all sorts, in nearly all ham gear (except antenna
> connectors), in most semi-pro audio and video gear. I still see Pin One
> Problems on the exhibit floor of audio and video trade shows.
>
> The Pin One Problem is addressed by AES48, which can be downloaded from
> www.aes.org. There is a fee for the download for non-members. There is
> also considerable detail at k9yc.com/publish.htm
>
> Fundamentally, The Pin One Problem couples common mode current into
> equipment, where it is then detected and added to the signal.
> Corresponding suppression for unshielded wiring should typically include
> chokes on the conductors and bypass or feedthrough capacitors to the
> chassis.
>
> 73, Jim K9YC
>
>
>
>
>
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