Hum problem with pseude dual mono amp

[kin]

Thank you for the link, but I don't know how it applies to my problem. Could you expand on this a little bit?
I see(on your website) that you use the same psu configuration. How did you lay out the gnd?

 

[turnA_zpoint]

Hi !
According to the theory of introduced URL ,
but because I doesn't actually experiment though the effect is uncertain,(very very sorry) ,

two starground will be connected with two diodes in the opposite direction

Though my PSU is twin monoral composition
At first the hum noise was heard when making it to the stereo.
I did not hear the hum noise only by 1Ch.

I guessed because the timing of the rectification was not corresponding, the output transistor had been influenced from the cause though it became for my amp case.

So local feedback was given to the biasing circuit of the output transistor ,or when it used the constant-voltage regulater to amp circuit including the biasing circuit (not Power Regulater), did not hear the ham.

Of course, I think it was also effective to reduce the area of the loop that the ground line made as much as possible.

Regards!

 

[kin]

Thank you for your suggestions, but I don't really see how putting 2 back-to-back diodes would help? They have a quite low dynamic resistance(a few ohms) and the volt-drop between stages I think would worsen the situation. But I will try it nevertheless.

Meanwhile, I have modified my psu layut, in that the return current for all the smoothing caps is in the left side of the star gnd(I have used jumpers for that). I will attach the files for your review:

 

[kin]

and the top:

 

[AndrewT]

the diodes are not back to back. That would prevent any current flow in both directions.
The diodes are in parallel to each other but they are in opposite directions so that current can pass in either direction with a volts drop of Vf dependent of the value of current flowing.

 

[kin]

Yes, that's correct and that's what I meant too, just a linguistic error. I should have said anti-parallel(It's not the first time I mix these terms ).

 

[turnA_zpoint]

Hi ! KIN

I think two pair of diodes that in parallel to each other.
(According to the theory of introduced URL, one pair is ok too ...
but because I doesn't actually experiment ,so sorry )

If the hum sound is not like "BOON" but like " JI JI " , a situation one of the diode is broken is thought.

Regarads!