The headphone outputs from my radios are switched with some relays. The
switching system has a common ground, which creates a ground loop,
resulting in 60 Hz hum in the headphones. (Call it common impedance
coupling, if you prefer.) I should have isolated the headphone grounds,
but a path of less resistance was to insert the isolation transformers.
They are just common 600 Ohm transformers, like the ones in the K3 line
outputs, but they're a bit lossy driving headphones.
73,
Scott K9MA
On 1/16/2019 09:02, Bob McGraw K4TAX wrote:
I see no need for isolation transformers with headphones. Likely the
transformers is the reason the HP output won't drive a pair of
headphones. Isolation transformers? Are they 3 winding hybrid
transformers? I've used them in professional audio installations
but they are rare and expensive.
73
Bob, K4TAX
On 1/15/2019 11:23 PM, K9MA wrote:
I found that the level at headphone output, at least the rear panel
one, was too low to drive two pairs of headphones in parallel in my
setup, which includes some isolation transformers. The speaker
output works fine with the headphones. (Don't try this with super
sensitive low impedance headphones.) I just wired a switch to an
external speaker.
73,
Scott K9MA
On 1/15/2019 20:51, Nr4c wrote:
Why use Line Out for speakers. There is a perfectly good jack
marked Speakers right next to the Phones jack. Be sure and use a
Stereo plug but it is for ........wait for it. Speakers!
--
Scott K9MA
[email protected]
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