Hi everybody,
I am a musician and I want to start building some pedal effects, pre-amplifier, filters and so on. Just for hobby
My target is to learn starting from descrete components (I think it is the most basic level, isn't it?), so my first project is to build a simple pre-amp using a transistor in a CE set-up.
I was experiecing some buzz/hum problems with my CE amp. Since I want to learn, I attach a detail report and two recordered audio instead of write here.
At the end of the report there are my questions
I hope this is the right way to explain to the comunity my troubles and I hope this will be helpful to somebody.
Thank you
Andrea
I am a musician and I want to start building some pedal effects, pre-amplifier, filters and so on. Just for hobby
My target is to learn starting from descrete components (I think it is the most basic level, isn't it?), so my first project is to build a simple pre-amp using a transistor in a CE set-up.
I was experiecing some buzz/hum problems with my CE amp. Since I want to learn, I attach a detail report and two recordered audio instead of write here.
At the end of the report there are my questions
I hope this is the right way to explain to the comunity my troubles and I hope this will be helpful to somebody.
Thank you
Andrea
Looks like radio frequency ( RF ) pickup . Try putting a 1K resistor in series with the input and directly after put a 470pF capacitor to ground to form an RF filter with an approximate turnover frequency of 338 KHz .
PS just read your info in more detail . I had missed the point where you say plugging the pickup directly into the Focusrite also gives hum/buzz . Maybe there is also an earthing issue .
PS just read your info in more detail . I had missed the point where you say plugging the pickup directly into the Focusrite also gives hum/buzz . Maybe there is also an earthing issue .
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Thank you epicyclic.
One important note: my pickup is a Shadow SH330 which is a SINGLE COIL pickup. Maybe, it picks 50Hz hum from electrical house circuit.
I suppose this because:
I think that I cannot do anything with a single coil
Howerer, I have two other questions if I do not bore you...
1. If I use a battery, I do not have a ground, right? I mean, the 0V battery is my reference, but I don't have any proper ground. Is it correct?
2. My test configuration was the following. I hear from both sides of the headphone. However, I did not plug the ground. Are there some corrections to do?
ps: it was quite surprising for me that just 1mW rms signal on my headphone is sufficent to hear a lot!
One important note: my pickup is a Shadow SH330 which is a SINGLE COIL pickup. Maybe, it picks 50Hz hum from electrical house circuit.
I suppose this because:
- if I move around there are some points where the hum lower a lot (never svanish anyway)
- I tried to build the second stage of my project using an emitter-follower amp...and it actually works! I can hear sound from my guitar using headphone. I powered-on the circuit (CE-CC cascade) with a 9V battery. The hum remains, and again if I move around the hum level change.
I think that I cannot do anything with a single coil
Howerer, I have two other questions if I do not bore you...
1. If I use a battery, I do not have a ground, right? I mean, the 0V battery is my reference, but I don't have any proper ground. Is it correct?
2. My test configuration was the following. I hear from both sides of the headphone. However, I did not plug the ground. Are there some corrections to do?
ps: it was quite surprising for me that just 1mW rms signal on my headphone is sufficent to hear a lot!
Attachments
Thak you very much for the replay.
So for point (2), if I understood correctly, I should do that...
For Balance/Unbalance: again, if I understood correctly, balance cables have a shield. However, a shield must be connected to a proper ground for working corretly. Does the following scheme make sense? The proper "ground" is the ground of my house connections I think (I am a little bit scared to do that ahah).
A note: I tried to input my mobile phone instead of guitar pick-up. No hum/buzz is present powering the circuit with a battery. I don't have humbacker pickups to confirm that noise is coming from the pickups
You speak about "grounding loop" problems...what do you mean?
Thanks
Andrea
So for point (2), if I understood correctly, I should do that...
For Balance/Unbalance: again, if I understood correctly, balance cables have a shield. However, a shield must be connected to a proper ground for working corretly. Does the following scheme make sense? The proper "ground" is the ground of my house connections I think (I am a little bit scared to do that ahah).
A note: I tried to input my mobile phone instead of guitar pick-up. No hum/buzz is present powering the circuit with a battery. I don't have humbacker pickups to confirm that noise is coming from the pickups
You speak about "grounding loop" problems...what do you mean?
Thanks
Andrea
An ordinary twisted pair of wires is balanced , each wire has the same resistance , capacitance and inductance . A balanced connection has to maintain that balance by terminating the each wire with the same impedance both at the transmitting and receiving ends . Having a grounded screen not necessarily an earthed screen round the pair helps to reduce interference . Balanced microphone cable has a twisted pair with an outer screen . Standard coaxial cable has a single inner wire with an outer screen and thus by design is unbalanced .
I would not advise making the house ground connection .
You did not say if you have input 2 of the Focusrite set to instrument or line .
You have not said if you tried the RF filter suggestion .
Another thing you can try or not try is to limit the low frequency response of your circuit as an ordinary acoustic guitars lower register doesn't go that low . Put a 2k2 resistor in series with the input and change the input capacitor C1 to 220nF . this will give an LF roll off starting at approximately 328Hz .
Suggestion ..... start another thread in " instruments and amps " and ask if others have had the same problem as you using the Removable Shadow Acoustic single coil pickup directly into a Focusrite Solo 2nd gen and laptop .
I would not advise making the house ground connection .
You did not say if you have input 2 of the Focusrite set to instrument or line .
You have not said if you tried the RF filter suggestion .
Another thing you can try or not try is to limit the low frequency response of your circuit as an ordinary acoustic guitars lower register doesn't go that low . Put a 2k2 resistor in series with the input and change the input capacitor C1 to 220nF . this will give an LF roll off starting at approximately 328Hz .
Suggestion ..... start another thread in " instruments and amps " and ask if others have had the same problem as you using the Removable Shadow Acoustic single coil pickup directly into a Focusrite Solo 2nd gen and laptop .
A cable shield/screen should be attached to a metal chassis at its connector. While a shield will probably have continuity to 'ground', the shield is not part of the 'ground' system or systems.
Note that the Safety Ground/Protective Earth is one 'ground' system and the ground rod/Planet Earth is another 'ground' system.
Note that the connection to Planet Earth is there for safety during unusual high voltage events. It has little to do with day-to-day AC power quality or audio system quality.
Note that the Safety Ground/Protective Earth is one 'ground' system and the ground rod/Planet Earth is another 'ground' system.
Note that the connection to Planet Earth is there for safety during unusual high voltage events. It has little to do with day-to-day AC power quality or audio system quality.