The isolated RCA input grounds must individually go to the amplifier (-) input terminals, and not be connected together.
The amplifier power grounds can each go to the chassis, either directly, or each through a safety network
of parallel R, C, and high current diodes. The latter connection may yield less hum in the complete system.
Regardless, each audio channel can only be connected to the chassis at one point.
The amplifier power grounds can each go to the chassis, either directly, or each through a safety network
of parallel R, C, and high current diodes. The latter connection may yield less hum in the complete system.
Regardless, each audio channel can only be connected to the chassis at one point.
Yes, it is true that most stereo components have such an inherent ground loop.
However, if you use the second option of connecting an impedance in each power ground connection to the chassis,
the ground loop due to the source will not be completed.
But the grounds of the input RCA connectors also must be isolated both from chassis ground, and from each other.
However, if you use the second option of connecting an impedance in each power ground connection to the chassis,
the ground loop due to the source will not be completed.
But the grounds of the input RCA connectors also must be isolated both from chassis ground, and from each other.
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Try a thermistor like this from each power amplifier power ground to the chassis (one per channel).
Otherwise there should be no connections to the chassis other than the AC line IEC safety ground.
Either part is fine.
https://www.digikey.com/en/products/detail/epcos-tdk-electronics/B57234S0100M000/3500293
https://www.digikey.com/en/products/detail/amphenol-advanced-sensors/CL-60/19756
Otherwise there should be no connections to the chassis other than the AC line IEC safety ground.
Either part is fine.
https://www.digikey.com/en/products/detail/epcos-tdk-electronics/B57234S0100M000/3500293
https://www.digikey.com/en/products/detail/amphenol-advanced-sensors/CL-60/19756
If it's really 10k ohms, that's too large. You want around 10 ohms instead.
For testing you can use a 10 ohm, 2W resistor.
A thermistor is used for safety. If there is a problem like a short to ground, it will conduct fault current
and become a low resistance by heating up. Then the AC line fuse will blow.
For testing you can use a 10 ohm, 2W resistor.
A thermistor is used for safety. If there is a problem like a short to ground, it will conduct fault current
and become a low resistance by heating up. Then the AC line fuse will blow.
Don't return the speaker ground to the PS ground, but to the amp ground.
As it is drawn, it is easy to see that the hum and noise voltage across the wire from PS ground to amp ground is put in series with the speaker. You don't want that junk in the speaker signal.
Jan
Dear Sir, in my assembly I used two different power supply blocks, when I connect one PSU ground with chassis then it's ok, but ASAP I connect the other supply ground to the chassis humming started that' s why I only connected one Ground and the other one is open, and the input RCA ground is common at volume potentiometer
rayma and jan.didden have given good advice.
Use a "ground lift" - either a 10 Ohm thermistor such as a CL60 at each power supply ground to chassis/safety ground. An alternate to the CL60 is this:
Secondly, connect each RCA input ground separately to its respective amplifier channel's audio board ground. Do not tie the two channel audio grounds together.
For lowest noise, connect each channel's speaker ground to the audio board ground.
Also for lowest noise, at each channel twist together the V+, V-, and G wires to from the power supply to the audio board. Twist together the signal positive and ground wires from the RCA jack to the audio board, and twist together the speaker positive and ground wires from the speaker terminals to the audio board.
Also make sure that the RCA jacks are isolated from the chassis with plastic washers.
Use a "ground lift" - either a 10 Ohm thermistor such as a CL60 at each power supply ground to chassis/safety ground. An alternate to the CL60 is this:
Secondly, connect each RCA input ground separately to its respective amplifier channel's audio board ground. Do not tie the two channel audio grounds together.
For lowest noise, connect each channel's speaker ground to the audio board ground.
Also for lowest noise, at each channel twist together the V+, V-, and G wires to from the power supply to the audio board. Twist together the signal positive and ground wires from the RCA jack to the audio board, and twist together the speaker positive and ground wires from the speaker terminals to the audio board.
Also make sure that the RCA jacks are isolated from the chassis with plastic washers.
Thanks for your valuable inputs, I will try as suggested, one thing I faced as mentioned below :
One thing I came across, when checking in amplifier for speaker ground wire location,
1) when connected to speaker terminal there is a little humm audible
2) when I connect the speaker wire ground direct to PCB ground speaker terminal then noise increased
3) when connected speaker ground wire to power ground same noise there
4) then connected speaker wire on terminal again and added a 4.7 ohms resistance in series with ground terminal of speaker terminal, the minor humm in sr no. 1 almost diminished
One thing I came across, when checking in amplifier for speaker ground wire location,
1) when connected to speaker terminal there is a little humm audible
2) when I connect the speaker wire ground direct to PCB ground speaker terminal then noise increased
3) when connected speaker ground wire to power ground same noise there
4) then connected speaker wire on terminal again and added a 4.7 ohms resistance in series with ground terminal of speaker terminal, the minor humm in sr no. 1 almost diminished