Here is my latest project.
Pair of 2 channel stereo, one mono line + one mono mic pre-amplifier.
The mixer is made fro m2 pcb's , one for the input sockets and volume controls and the other for the valves and output sockets.
In the picture the 2 valves face downwards but will go out through the top of the enclosure when mounted.
I have used 2 mains transformers, one to drop to 12vac for the heaters then another mains transformer backwards to get 160VAC.
Pair of 2 channel stereo, one mono line + one mono mic pre-amplifier.
The mixer is made fro m2 pcb's , one for the input sockets and volume controls and the other for the valves and output sockets.
In the picture the 2 valves face downwards but will go out through the top of the enclosure when mounted.
I have used 2 mains transformers, one to drop to 12vac for the heaters then another mains transformer backwards to get 160VAC.
An externally hosted image should be here but it was not working when we last tested it.
I have had the mixer working with music while I worked on my pc.
I started getting howl and noise through the speaker after a while.
I thought Oh no layout problems.
Any way I disconnected the mixer from the amp and the noise was still there.
Turns out my amplifier doesn't like my mp3 player playing right next to it.
Could be the backlight supply oscillator interfering.
I started getting howl and noise through the speaker after a while.
I thought Oh no layout problems.
Any way I disconnected the mixer from the amp and the noise was still there.
Turns out my amplifier doesn't like my mp3 player playing right next to it.
Could be the backlight supply oscillator interfering.
I learned quite a bit from previous projects to reduce hum and noise in the layout.
I kept input pcb tracks as short as possible.
I used HF diodes on the supply to stop glitches.
I used grid stopper to prevent RF interference.
I kept input pcb tracks as short as possible.
I used HF diodes on the supply to stop glitches.
I used grid stopper to prevent RF interference.
I raised the heaters to 45 volts DC.
I balanced the connection to 45 volts with two 220r resistors.
Its now dead silent.
Here is the mixer boxed up.
An externally hosted image should be here but it was not working when we last tested it.
if you have hum ...should see the power supply.but buzz noise like vizzzzzzzzzz
can remove by filament grand .
in amp with high gain power supply hum com to output.
filter transformer in +b line kill hum .
- Status
- Not open for further replies.