Hello,
I made a small guitar headphone amplifier powered by a ac to dc 9v psu.
It is noisy but it goes silent when I connect neutral to ground outlet pin.
I know it is not safe to do so, but at only 9v ?
Thanks
I made a small guitar headphone amplifier powered by a ac to dc 9v psu.
It is noisy but it goes silent when I connect neutral to ground outlet pin.
I know it is not safe to do so, but at only 9v ?
Thanks
Yes, post schematic. It sounds like perhaps you are incorrectly calling one of the transformer secondaries "neutral"?
Hi,
https://i.postimg.cc/y6XPRqx5/20230326-225319.jpg
I'm using a dc 9v power adapter.
The only way I found to get rid of psu noise is to add another wire connected between dc psu ground (neutral?) and electrical outlet ground pin.
https://i.postimg.cc/y6XPRqx5/20230326-225319.jpg
I'm using a dc 9v power adapter.
The only way I found to get rid of psu noise is to add another wire connected between dc psu ground (neutral?) and electrical outlet ground pin.
As given the circuit cannot work. Can the second stage be a simple NPN emitter follower?
Or do you need more gain than the first stage can give?
Are you sure the adapter actually puts out DC, instead of a pulsating rectified sine wave?
Try a 100uF 15V capacitor across the adapter output to see. Observe polarity.
Or do you need more gain than the first stage can give?
Are you sure the adapter actually puts out DC, instead of a pulsating rectified sine wave?
Try a 100uF 15V capacitor across the adapter output to see. Observe polarity.
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Hi Rayma, my schematic works, 2nd stage is PNP.
You must be right regarding psu. Adding a cap doesn't block DC.
Is it safe to wire live to earth at 9v ?
Thank you
You must be right regarding psu. Adding a cap doesn't block DC.
Is it safe to wire live to earth at 9v ?
Thank you
THat schematic would not work.
Better to use the schematic posted by rayma.
With a NPN transistor in output.
I believe it's a shielding issue. Guitar acts as an antenna. There' no hum when guitar is unplugged.
Believe it or not it actually works 🙂
I have more gain at 2nd stage.
I can post a photo if it helps.
But the collector of the PNP output transistor would have to go to a negative DC voltage
with respect to ground for it to work.
Can you post the complete schematic with all connections, audio, power supply, and
including the proposed "Is it safe to wire live to earth at 9v ?" connection.
I am not sure what you mean by this. A photo may also help.
Safety also depends on what you connect to the circuit, input and output.
with respect to ground for it to work.
Can you post the complete schematic with all connections, audio, power supply, and
including the proposed "Is it safe to wire live to earth at 9v ?" connection.
I am not sure what you mean by this. A photo may also help.
Safety also depends on what you connect to the circuit, input and output.
Hello, there you go :
https://i.ibb.co/D1fTWqq/20230327-231404.jpg
I roughly 99.99975% believe it's a shielding issue from the guitar.
Thanks for you help.
https://i.ibb.co/D1fTWqq/20230327-231404.jpg
I roughly 99.99975% believe it's a shielding issue from the guitar.
Thanks for you help.
Ok, but you still need an NPN transistor for the second stage.
Maybe the PNP that you have there is actually working at very low gain (unity or so).
If you just sub a NPN instead with the same EBC connections, you would get much more gain.
About the ground wire that you added to kill the hum.
Without knowing what's inside the 9V adapter, I can't recommend the connection as being safe.
It might be safe, but I can't in good conscience say that it is.
Are the two wires from the guitar twisted tightly together?
Or is there a grounded shield around just one wire?
If not, there's your problem.
Maybe the PNP that you have there is actually working at very low gain (unity or so).
If you just sub a NPN instead with the same EBC connections, you would get much more gain.
About the ground wire that you added to kill the hum.
Without knowing what's inside the 9V adapter, I can't recommend the connection as being safe.
It might be safe, but I can't in good conscience say that it is.
Are the two wires from the guitar twisted tightly together?
Or is there a grounded shield around just one wire?
If not, there's your problem.
Yes, there is enough gain for my needs.
Ok I will stop doing this then.
Yes it's a shielded cable. I will try adding aluminium tape inside the mic cavity.
Thanks Rayma !
Ok I will stop doing this then.
Yes it's a shielded cable. I will try adding aluminium tape inside the mic cavity.
Thanks Rayma !