Stereo mixer amplifier

[Phil Allison]

bitrex wrote:

-------------

If he's worried about RF ingression there should probably be something
in the circuit that would help with that.



** Those cheap and nasty audio transformers on each inputlikely
make dandy RF filters ...


I'm 40 and I can only hear out to 12kHz.

** You have some hearing damage ?

Or is that what some dopey "audioligst" told you.

Perhaps at 65-70 one's auditory
bandwidth is such that one can start saving a few bucks on transformers.

** The transformers are nasty cos they have no low end.

IIRC, the spec reads " 250Hz to 15kHa +/- 2db. "

Typically the low end ( ie all the bass ) will be riddled with core saturation distortion too - so massive IM of the whole audio band.

A radio ham built it...


...... Phil

 

[bitrex]

On 10/7/19 5:04 PM, Phil Allison wrote:

bitrex wrote:

-------------



If he's worried about RF ingression there should probably be something
in the circuit that would help with that.



** Those cheap and nasty audio transformers on each inputlikely
make dandy RF filters ...


I'm 40 and I can only hear out to 12kHz.

** You have some hearing damage ?

Or is that what some dopey "audioligst" told you.

Just a non-audiologist self-test with a headphone amp, sine generator,
and AKG K240s. It's hard to say exactly where I can hear nothing at all.
Definitely, nothing after about 14k. I can hear a little at 13k, maybe.

I thought that was fairly normal for presbycusis for around 40.
Girlfriend is 33 she can hear to 15k.

I've been an electric guitarist off-and-on since I was 15 but rarely
played at high volumes.

Perhaps at 65-70 one's auditory
bandwidth is such that one can start saving a few bucks on transformers.


** The transformers are nasty cos they have no low end.

IIRC, the spec reads " 250Hz to 15kHa +/- 2db. "

Typically the low end ( ie all the bass ) will be riddled with core saturation distortion too - so massive IM of the whole audio band.

A radio ham built it...


..... Phil

THIS is a (step up) input transformer:

<https://www.dropbox.com/s/hz2gd566j7wkl6b/IMG_20191007_184742374.jpg?dl=0>

rated at 500Hz-14kHz, at 1 watt. It can do much better than that at
lower power. It weighs about 3-4 lbs so I've tried not to drop it on my
feet by mistake

 

[Phil Allison]

bitrex wrote:

----------------

If he's worried about RF ingression there should probably be something
in the circuit that would help with that.



** Those cheap and nasty audio transformers on each inputlikely
make dandy RF filters ...


I'm 40 and I can only hear out to 12kHz.

** You have some hearing damage ?

Or is that what some dopey "audioligst" told you.

Just a non-audiologist self-test with a headphone amp, sine generator,
and AKG K240s. It's hard to say exactly where I can hear nothing at all.
Definitely, nothing after about 14k. I can hear a little at 13k, maybe.

** Think that is a bit below average for 40.

Had your ears de-waxed by a doc lately?

I thought that was fairly normal for presbycusis for around 40.
Girlfriend is 33 she can hear to 15k.

** Women have better HF hearing - many teenage girls can hear up to 22kHz .

Hence the "audio band is defined as " 22 to 22kHz "

A number of such were employed in testing done by the BBC, Philips and Sony to establish limits for LPFs ( anti ailiasing ) for digital audio.

I've been an electric guitarist off-and-on since I was 15 but rarely
played at high volumes.

** Explains a lot ...

THIS is a (step up) input transformer:

https://www.dropbox.com/s/hz2gd566j7wkl6b/IMG_20191007_184742374.jpg?dl=0

rated at 500Hz-14kHz, at 1 watt. It can do much better than that at
lower power. It weighs about 3-4 lbs so I've tried not to drop it on my
feet by mistake

** You can get perfectly nice input transformers, low cost an fully mag shielded well under the size of a golf bal. But no radio have would have the faintest about that.


...... Phil