I'm looking for help with the playback volume on my Meazzi project, it does repeat and echo, but when I turn up the echo pot there's quite a hum and the echo isn't very loud , I've changed all the valves and put a 100 ohm resistor on the centre tap of the heater circuit but the more I turn up the echo the more it hums

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Sounds like you have too much ripple on the Power lines which is getting worse as you draw more power. Have you tried more capacitance after the bridge rectifier.

 

Thankyou I will try that, do you think it might need a choke?

 

Thankyou I will try that, do you think it might need a choke?

You specify this issue is only with the Echo function so based on that if the rails are good the next step would be to try and identify the propagation of the noise going through the echo function, is the 'low volume' a symptom of an unlying issue?.

If you turn the volume up and echo up with no signal you should see your 'noise' with an oscilloscope. You may need to start at the potentiometer and try and follow the noise. You know its getting to the output so you'll need to trace it forward/back as appropriate.

It could be something as simple pickup from low freqency wires or the transformer is in proximity to the echo function.

 

When I turn it off it makes all sorts of weird noises for quite a while unless I immediately pull out the mains cable as I switch it off then it's quite