Connections of RCA Ground with separate mono blocks in same chassis

[rayma]

Those results will depend on the other "ground" connections, especially for the inputs.
But you cannot add resistance in series with the speaker.
What connections do you have directly to the chassis now?

 

[Sohal]

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:

View attachment 1292218

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.

One thing I read from hi-fi sonix that RCA input shall be shorted near to the input so that the ground loop shall not go out of the power amplifier and shall remain within the cabinet

 

[Ben Mah]

I have a dual mono amplifier connected as I had described and it do not hum.

 

[Sohal]

Those results will depend on the other "ground" connections, especially for the inputs.
What connections do you have directly to the chassis now?

No, input ground is connected to the potentiometer ground shorting the both channels ground

 

[Sohal]

I have a dual mono amplifier connected as I had described and it do not hum.

One thing is that the source ground is common, how to descriminate them, like source is a mobile phone, it's output is 3.5mm jack hence ground is common there how separate ground of amplifier input works?

 

[rayma]

No, input ground is connected to the potentiometer ground shorting the both channels ground

With mono blocks in the same chassis, do not connect anything to the shared chassis except the IEC ground.
Then add a network like in post #19 between each channel's audio common and the chassis, one per channel.

 

[rayma]

One thing is that the source ground is common, how to descriminate them, like source is a mobile phone, it's output is 3.5mm jack hence ground is common there how separate ground of amplifier input works?

That is not possible or necessary with properly configured mono blocks, as described in post #26.
There will be no common connection between the channels other than in the source, so there is no ground loop.
Do not connect the "grounds" of the amplifier input RCA sockets (or of the level controls) together, or to the chassis.

Of course, each channel can have other problems causing hum, due to power supply ripple coupling to other parts of the circuit.

 

[Sohal]

Agreed, I will do, please guide me one thing, I have common master volume potentiometer, that means I have to connect each RCA channel cable separately?

 

[rayma]

Yes, each RCA "ground" and pot "ground" only connect to their own channel's ground, but not to the other channel's ground.
This is part of the "dual mono" design. There is no need for the two amplifier channels' grounds to be connected together.
In two-chassis mono blocks there is no connection between their chassis. Same here (except for the post #26 networks).

 

[Sohal]

Thanks for your valuable inputs

 

[Sohal]

Any suggestions for Jean Hiraga amplifier

 

[Sohal]

The above mentioned all queries are regarding to Jean Hiraga monster amplifier

 

[rayma]

These points apply to any power amplifier with unbalanced inputs.

 

[Sohal]

Any low noise high gain transistor available equivalent to bc560c?

 

[ctrlx]

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

no joking, but i dont see it like that.

i see two separate grounds returned to the psu, i dont see any interference between the two.

 

[Sohal]

I have succeeded to kill the humm totally out, with below steps:
1) twisting all power wires together coming to amplifier.
2) Using ground lifting circuit.
3) At last for remaining humm - it is gone by using capacitance multiplier circuit
As there was a small amount of ripples percent due to class A amplifier (biasing at 1.27A). Now it is totally dead silent.