finished zen amp. How do I removed the hum?

Lito · 26th June 2002, 06:05 AM

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 · 26th June 2002, 06:11 AM

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 · 26th June 2002, 07:59 AM

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 · 26th June 2002, 10:55 AM

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 · 26th June 2002, 03:12 PM

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

cp642 · 26th June 2002, 05:43 PM

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

Problems on ZEN amp

Nelson Pass · 26th June 2002, 07:51 PM

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

PedroPO · 28th June 2002, 03:53 PM

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

26th June 2002, 06:05 AM	#1
Lito diyAudio Member Join Date: Jun 2002 Location: philippines	finished zen amp. How do I removed the hum? 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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26th June 2002, 06:11 AM	#2
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	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

26th June 2002, 07:59 AM	#3
Lisandro_P diyAudio Member Join Date: Oct 2000 Location: Argentina	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

26th June 2002, 10:55 AM	#4
NickC diyAudio Member Join Date: Dec 2001 Location: Earth	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.

26th June 2002, 03:12 PM	#5
grataku diyAudio Member Join Date: Dec 2000 Location: -	"when nothing is connected" you mean when the input is open? If so that's probably your problem.

26th June 2002, 05:43 PM	#6
cp642 diyAudio Member Join Date: Aug 2001	Advice by Nelson in this thread might help...... Problems on ZEN amp

26th June 2002, 07:51 PM	#7
Nelson Pass The one and only Join Date: Mar 2001	Nothing like a nice fat pi filter to take care of it.

28th June 2002, 03:53 PM	#8
PedroPO diyAudio Member Join Date: Jan 2002 Location: Lisbon,Portugal	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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