Hi All,
I did a search and didn't find ant similar thread about oscillation.
I built the Pass Zen 4 and noticed a 100mVpp oscillation at output either with/without load around 43kHz with 2nd harm. 96kHz.
It looks weird it is close to 48k but I'm sure no others gear is hooked to the main that can generate the noise.
Power supply not an issue as I use a Farnell linear psu and double checked that the regulator around Q5 is not an issue by bypassing it. Did anyone experienced similar one?
If I increase C12 to 10pF it decreases to 50mVpp but no benefit if I increase more ....any hint? Thanks!
I did a search and didn't find ant similar thread about oscillation.
I built the Pass Zen 4 and noticed a 100mVpp oscillation at output either with/without load around 43kHz with 2nd harm. 96kHz.
It looks weird it is close to 48k but I'm sure no others gear is hooked to the main that can generate the noise.
Power supply not an issue as I use a Farnell linear psu and double checked that the regulator around Q5 is not an issue by bypassing it. Did anyone experienced similar one?
If I increase C12 to 10pF it decreases to 50mVpp but no benefit if I increase more ....any hint? Thanks!
Attachments
Is this with the inputs open, or shorted?
Are you using the Pass designed pcb? Where did you buy the semis from?
Are you using the Pass designed pcb? Where did you buy the semis from?
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I tried both shorted and open input...nothing change.
PCB according Pass I made a visual cross-check of track.
Comps are all from digikey, no fake...
PCB according Pass I made a visual cross-check of track.
Comps are all from digikey, no fake...
1. You could try to solder a 0.1uF SMD capacitor right between the C7 pins... where the C7 pins are soldered to the PCB.
2. Try to use 1nF disc ceramic cap for C3 and move to as close as possible to R7
3. You may have overloaded Q4 with a high pp input signal/spike...? Replace it with a brand new part.
2. Try to use 1nF disc ceramic cap for C3 and move to as close as possible to R7
3. You may have overloaded Q4 with a high pp input signal/spike...? Replace it with a brand new part.
If the Zen were to oscillate it would pick a much higher frequency.
Nevertheless, poking around with a capacitor to see what happens
would be the way to go.
Nevertheless, poking around with a capacitor to see what happens
would be the way to go.
Thanks a lot all of you and special Thanks to Mr.Pass who made possible all of us to enjoy such a nice and simple electronics. I promise I will post the solution as soon as I have time to get finger on!
It's been a long time since I built this amp and when I checked the date, 2002 😱 nearly 20 years ago. I did have a brief revisit of this lovely amp about 2 years ago repairing a blown the input buffer (Q3 or Q4).
https://i.imgur.com/Ogn6HsD.jpg?1
I've built 2 of these monoblocs, dual boarded for balanced operation and higher PoWaH. In SE mode the amp works very well too if I crave 4 channels.
https://i.imgur.com/Ogn6HsD.jpg?1
I've built 2 of these monoblocs, dual boarded for balanced operation and higher PoWaH. In SE mode the amp works very well too if I crave 4 channels.
Thanks for sharing, I'm doing exactly the same and just built the first module and got the issue.
For the last 12 years I've been listening to one powering Jordans on my desktop.
Next week it goes to a new home with a pair of Fostex.
Plural is Fostices?
Next week it goes to a new home with a pair of Fostex.
Plural is Fostices?