Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
Search
Ubitx V4 opinions?
Hi all.
I¡¯m about to buy another ubitx, but I¡¯m a little concerned about one or 2 of the posts concerning the audio of this latest board. Has anyone with the V4 experienced any distorted audio or any other related issues? I¡¯m hoping this was an isolated case and not an issue with the audio circuit on these new boards....? Regards Carl M0CLS |
Gordon Gibby
¿ªÔÆÌåÓýWell there actually is some feedback, it is in the form of those emitter resistors in the final audio amplifier. R75 R77The crossover distortion may be that in order to properly bias those transistors ¡°on¡±, just a bit of emitter current has to flow, creating a voltage drop across those two emitter ?resistors (e.g. choose 10mA * 4.4 ohms=44mV), which is not accounted for
by the Voltage drops across the?diode¡¯s on their base side.
Current through R75 should be about 0.6 mA.
Suggests added series R = 44mV/0.6mA= 75 ohms
Gordon (back of the envelope calculation¡¯s)
|
to navigate to use esc to dismiss