Scratchy audio

[bozz66]

Hi, I’ve had this issue since finishing the build, but I get really scratchy audio when I turn the volume below 9 or so. Above this number it sounds fine. Does this on all modes and filter settings. Any ideas? Thanks!
Mark W7MMG

[bozz66]

https://youtube.com/shorts/I4ThPQA505E?feature=share

Here is a clip of the problem…

[bozz66]

Here are some results of my troubleshooting. Used 2 instruments to measure; an oscilloscope and a Circuit Specialist multimeter. Cannot figure out why pin 8 on U9 is only 4.9V Schematic shows it’s powered by 12V and labeled Vcc. Does anyone see anything else that’s weird with these measurements? Thanks!

[on4ccu]

I just received my “pre-built” radio, which seems to have the same issue: audio goes scratchy at lower volumes. Turning off the agc helps somewhat.
Did you get any results from your troubleshooting?

[DL2MAN]

Hi,

unfortunately that´s completely normal. Your speaker gain seems high and amplifies even the internal noise of (tr)uSDX.
Simply try a headphone or another active speaker with less gain.

73 Manuel; DL2MAN

[on4ccu]

Hi Manuel,
Indeed, the sound improves when I’m using less sensitive headphones so that I can keep the volume at a higher level (>9 or so).
Thanks!

[bozz66]

Hi,

unfortunately that´s completely normal. Your speaker gain seems high and amplifies even the internal noise of (tr)uSDX.
Simply try a headphone or another active speaker with less gain.

73 Manuel; DL2MAN

Thanks for the reply! It helps a little with some ear bud type headphones. It’s very useable either way. I just wanted to make sure there wasn’t something I did wrong during the build. Thanks for a fun kit and a fun radio Manuel! 73!

[bozz66]

I just received my “pre-built” radio, which seems to have the same issue: audio goes scratchy at lower volumes. Turning off the agc helps somewhat.
Did you get any results from your troubleshooting?

Hi, no other results. Apparently it’s a normal thing to be happening. The measurements I took were at the advice of someone WAY smarter than me with this stuff, lol. We did get the voltage on one the pins wrong though. We thought it was supposed to be 12v when in reality, it’s supposed to be 5v. That’s mentioned in my original post. And thanks for the AGC tip. That helps a little too…