I have tried disconnecting the tone control board and problem disappears but when I connect it again then problem comes back . Please help me to solve this issue
Do you happen to have any schematics or detailed photos of how you did your inputs and grounding?
I think the fan is kicking up static electricity and charging up your amp, and you are discharging it with a spark via the metal tool. Your hand would do that too, but your hand alone is too resistive to cause the spark. It must be dry there. This is exposing a grounding issue with the amp.
I'm betting you have your inputs grounded to the chassis box. When you spark to the chassis, it is causing a voltage discharge across the chassis box and becoming an input voltage signal.
This type of enclosure should have a star ground- Pick a single point, such as the negative side of the electrolytic bypass caps- that is the center of the star. The ground lead from the transformer, the ground return from the speakers, the ground going to the input connectors, pre-amp, and tone control, and amplifier module are all "arms" of the starfish, and each should not tie to the chassis or to each other, but only to the center of the star via their own paths. Then tie the chassis via a separate wire to the center of the star. The inputs should not be grounded to the chassis- they should be insulated from the chassis, so the spark appearing across the chassis does not get coupled into the input ground.
I think the fan is kicking up static electricity and charging up your amp, and you are discharging it with a spark via the metal tool. Your hand would do that too, but your hand alone is too resistive to cause the spark. It must be dry there. This is exposing a grounding issue with the amp.
I'm betting you have your inputs grounded to the chassis box. When you spark to the chassis, it is causing a voltage discharge across the chassis box and becoming an input voltage signal.
This type of enclosure should have a star ground- Pick a single point, such as the negative side of the electrolytic bypass caps- that is the center of the star. The ground lead from the transformer, the ground return from the speakers, the ground going to the input connectors, pre-amp, and tone control, and amplifier module are all "arms" of the starfish, and each should not tie to the chassis or to each other, but only to the center of the star via their own paths. Then tie the chassis via a separate wire to the center of the star. The inputs should not be grounded to the chassis- they should be insulated from the chassis, so the spark appearing across the chassis does not get coupled into the input ground.
If the problem disappears with the tone control disconnected.
Would expect the problem from the tone control.
Unless the amplifier is not AC coupled or have DC blocking input capacitors?
Any DC going in will come out amplified if their is no AC coupling.
Otherwise the tone control has some sort of issue.
Same thing either grounding issue or tone control might pass DC.
Schematic would help.
Nice endeavor by the way. Impressive array of transistors and cooling.
Would definitely call it a high power amp. Nice build and case
Would expect the problem from the tone control.
Unless the amplifier is not AC coupled or have DC blocking input capacitors?
Any DC going in will come out amplified if their is no AC coupling.
Otherwise the tone control has some sort of issue.
Same thing either grounding issue or tone control might pass DC.
Schematic would help.
Nice endeavor by the way. Impressive array of transistors and cooling.
Would definitely call it a high power amp. Nice build and case
I didn't tried star grounding . I will do that now but in few amps I have seen that the single point for star grounding is enclosure itself . And today I tried earthing my amp and problem solved . But I still want to solve this problem without earthing as my other amps are performing well without earthing.
Will update u after star grounding
Thanks
This is the ground connection of my amplifier. Sorry for my bad drawing. Can you check it and let me know if there are any mistakes?
There is no noticeable humming in the amplifier, but if I place my ear close to the speaker, I can hear a very minor hum.
Attachments
a] attach the Safety Ground/Protective Earth to the chassis near where the power cord enters the chassis.
b] attach each audio circuit common to the chassis at it's input connector. (only one chassis connector)
c] attach the DC supply common to the same single point as the audio circuit common.
b] attach each audio circuit common to the chassis at it's input connector. (only one chassis connector)
c] attach the DC supply common to the same single point as the audio circuit common.