| 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 |
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| 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 |
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| 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 :D |
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| 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. |
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| grataku |
"when nothing is connected"
you mean when the input is open?
If so that's probably your problem. |
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| Nelson Pass |
| Nothing like a nice fat pi filter to take care of it. |
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| 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 |
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