With DHT hum can be a problem and by searching fro good, efficient solutions I found ttis site
PLL Hum Cancellation Circuit
th author claims the cancellation is obtained by injecting a AC to cancel hum out.
The project seems interesting. Is he a member here? can anyone provide some feedback on the schematic?
If more than one person is interested there may be an opportunity for PCB creation and a group buy.
alex
PLL Hum Cancellation Circuit
th author claims the cancellation is obtained by injecting a AC to cancel hum out.
The project seems interesting. Is he a member here? can anyone provide some feedback on the schematic?
If more than one person is interested there may be an opportunity for PCB creation and a group buy.
alex
Honestly, I think a PLL would inject more spurious content into the system than it'll cancel. The VCO in the circuit runs at 800~960 Hz (16x the mains frequency) so you'll have a spur there for sure. Smack in the middle of the audio band.
If you want to cancel the hum, why not just use regulated DC on the heaters?! Guaranteed quiet. You can see my website for some options on how to do that.
~Tom
If you want to cancel the hum, why not just use regulated DC on the heaters?! Guaranteed quiet. You can see my website for some options on how to do that.
~Tom
Thanks tomchr. Only problem with my project isthe total current which (tested) reaches 45A continuous @ 12.6
The cost, weight and overall requirements for such an output put me off from pursuing DC. The transformer I had made for this application was designed to achieve the best possibile symmetry between channels. The CT on the tubes will be grounded and a 1w pot will be in place between filament leads and with the wiper cap coupled with ground.
However I was researching the matter and active systems would appear to be something of an upgrade from passive devices.
I do have a 2 channel oscilloscope so testing can be done...
I do not have the experience to judge if this road is a wise one to walk.. I love experiemnting and learning. I'd rather not do anything DIY at all if it meant not trying new routes.
(I also arced my first MV rectifier just a couple of hours. Being nickel protected the cathode is perfect but I definetely learnt how to approach things there! )
In conclusion do you think the circuit is worth a try?
The cost, weight and overall requirements for such an output put me off from pursuing DC. The transformer I had made for this application was designed to achieve the best possibile symmetry between channels. The CT on the tubes will be grounded and a 1w pot will be in place between filament leads and with the wiper cap coupled with ground.
However I was researching the matter and active systems would appear to be something of an upgrade from passive devices.
I do have a 2 channel oscilloscope so testing can be done...
I do not have the experience to judge if this road is a wise one to walk.. I love experiemnting and learning. I'd rather not do anything DIY at all if it meant not trying new routes.
(I also arced my first MV rectifier just a couple of hours. Being nickel protected the cathode is perfect but I definetely learnt how to approach things there! )
In conclusion do you think the circuit is worth a try?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.