finished zen amp. How do I removed the hum?

[Lito]

Hi,

I am amatuer builder and I just finished the zen amp using the pcb board on Pass website . . How do I remove the hum? I have installed 60,000 mfd capacitors and I still have a hum even when nothing is connected to the amp. What could be the problem.? TIA

Lito

 

[AudioFreak]

The hum is almost certainly coming from the power supply .... the Zen has very poor PSRR (power supply noise rejection). Use a Pi filter .... 20,000uF then 2mH choke then the rest of the caps... should help alot or you could use the regulator from www.passdiy.com The Penultimate Zen Part 3

 

[Lisandro_P]

A good option is the capacitance multiplier. It's a bit more irksome than a capacitor bank, but's much simpler than a regulator and dissipates MUCH less heat. I think it should be mandatory for class-a amps 😀

 

[NickC]

go with the choke since you have that much of caps
2mh-15mh
with the choke the distribution of the caps is slightly different
i used 20000uf -15mh - 88000uf for one supply of + and the same number of caps and choke for the - part hence i have
220mf of caps. THe cap placement is critical when a pi filter is used
20000 is to smoothen voltage and the remain caps after the choke is for a resovoir
the optimimum number of capitance before the choke/resistor is less than the resovoir after the choke. there is a formula for calculating the neseccary caps for the smoothen part
it is sonically better to have a bigger cap at the end ot the ps
look around for the formula in forum
check for ground connection, might some problem there.

 

[grataku]

"when nothing is connected"
you mean when the input is open?
If so that's probably your problem.

 

[cp642]

Advice by Nelson in this thread might help......

http://www.diyaudio.com/forums/showthread.php?s=&threadid=1593

 

[Nelson Pass]

Nothing like a nice fat pi filter to take care of it.

 

[PedroPO]

I once had hum problems in my Son Of Zen and it was the location of the toroidal transformer. I moved it a little bit, rotated it and I found that the noise was gone!

I used only capacitors for filtering, no coils..

Pedro Oliveira