[dude_500]

Quote:

Originally Posted by dude_500 /img/forum/go_quote.gif Over the last few weeks I've noticed a quiet hiss that lasts for maybe a tenth of a second and occurs every few seconds (not at a constant rate, seemingly random in occurrence and exact sound). It doesn't occur all the time, sometimes it does it a lot, usually not at all, sometimes just a little. It is volume knob related and when the volume is at zero it's totally silent, and at max the noise is very loud. At listening volumes it's quite quiet but definitely there. Does this mean it's outside of the volume knob? Even with source unplugged it does it and I don't understand how the wire from the knob to the RCA jacks could do this. I didn't change anything, It's just started doing it recently.

I haven't had much time to troubleshoot this over the last few weeks so I've kind of just left it, and it slowly has been getting worse. Before today, it would just happen randomly, usually during late afternoon at a similar time. As of today, it started becoming periodic (~1 short click per second), and it is doing it constantly now, has been all day. It is also getting louder. Right now it interferes with listening.

It's identical in both channels so I don't think it's a solder joint in the volume knob. Also it is still fully volume knob dependent and cuts out with no volume. Continues with source unplugged from the amp. It is not dependent on the placement of the amp within my room or even house.

Any ideas here? I'm stumped since it's volume knob dependent.

 

[amb]

Cell phone interference?
Or some other interference from elsewhere?
The fact that it's silent when the volume is down means that it's not coming from the amp's electronics. It's from some external source.

 

[dude_500]

Is it possible to get some sort of feedback RF loop coming out of the amp electronics back to the input? The fact that it happens equally in both channels at the same level and period in various rooms of my house seems to rule out external interference. Does it without cellphones nearby.

 

[digger945]

The only other thing that I can think of would be a problem with grounding within the amp, especially between the attenuator and boards. Turning the volume down and noticing that it seems to get quieter or go away doesn't necessarily mean the problem isn't there, it could mean that it isn't amplified enough to hear.
To suggest an RF problem means that something would have to be oscillating. Do you have a scope(I can't remember?) You might be able to pick up some AC with a DMM.
Does it sound like a 60Hz tone? Tried moving the PS around?
I'm not sure if you could be getting some trash from the wall outlet. I suppose moving the amp to another location might rule out some possible things.

 

[Anonanimal]

I'd try things like unplugging any wireless routers, etc. to see if you can eliminate it- as those signals will permeate mostly your entire house and possibly create the non room-specific symptoms that you're seeing.

Or maybe try taking it w/ you to a friend's house or work or something and see if the problem "follows" you. That might help you narrow it down more rapidly. Good luck!

 

[dude_500]

Tried unplugging wireless devices, no effect.

I earthed the ground of the amp and it got significantly quieter (though still existent). The problem is, after I then turned it off and solidly attached the earth ground and turned it back on, the positive rail of the power supply promptly burned out. Is this normal when earthed?

I do have a scope and will look at the output after I repair the power supply.

It's not 60hz, it's a short pop every second

 

[digger945]

I wasn't referring to earth ground, but the daisy chain or star grounding of the inputs/attenuator/boards, but having a good earth ground is not a bad idea for more than one reason. What you're experiencing doesn't sound like that is the problem though, and given the interval you're getting the popping noise I doubt that a scope will do anything to help. A steady ~1 second interval sounds like a device doing a check or update, like a modem or cell phone or cordless phone perhaps. I've had similar problems with USB at times that would never be consistent, but you've made it clear that it persists even with no input to the amp.

 

[pistolsnipe]

hey, i am looking for 1.5 inch heatsinks on mouser without pins (so i can thread and screw them down.) i have found everything else but those. amb specefies them as Aavid-Thermalloy 529802B00000, but i cant seem to find them. has anyone found these from mouser?

 

[UKToecutter]

I think I got mine from digikey.....

Quote:

Originally Posted by pistolsnipe /img/forum/go_quote.gif hey, i am looking for 1.5 inch heatsinks on mouser without pins (so i can thread and screw them down.) i have found everything else but those. amb specefies them as Aavid-Thermalloy 529802B00000, but i cant seem to find them. has anyone found these from mouser?

 

[oneplustwo]

Not sure if you have a reason to prefer those or not, but personally, I found the ones with pins much more straight forward. No threading and no fear of over tightening. And I didn't see myself needing to remove the heatsinks ever. Just my $0.02.

 

[quattro98]

You can buy them directly from the AMB store.

AMB audio shop

Quote:

Originally Posted by pistolsnipe /img/forum/go_quote.gif hey, i am looking for 1.5 inch heatsinks on mouser without pins (so i can thread and screw them down.) i have found everything else but those. amb specefies them as Aavid-Thermalloy 529802B00000, but i cant seem to find them. has anyone found these from mouser?

 

[digger945]

Quote:

Originally Posted by pistolsnipe /img/forum/go_quote.gif hey, i am looking for 1.5 inch heatsinks on mouser without pins (so i can thread and screw them down.) i have found everything else but those. amb specefies them as Aavid-Thermalloy 529802B00000, but i cant seem to find them. has anyone found these from mouser?

Quote:

Originally Posted by UKToecutter /img/forum/go_quote.gif I think I got mine from digikey.....

http://dkc3.digikey.com/PDF/US2010/P2477.pdf<<<Figure 17.

Digi-Key - HS276-ND (Manufacturer - 529802B00000)

 

[pistolsnipe]

Quote:

Originally Posted by oneplustwo /img/forum/go_quote.gif Not sure if you have a reason to prefer those or not, but personally, I found the ones with pins much more straight forward. No threading and no fear of over tightening. And I didn't see myself needing to remove the heatsinks ever. Just my $0.02.

yeah i would totally agree with you, however i already have some that are tap/screw mount, so i would like to make them all match


Quote:

Originally Posted by quattro98 /img/forum/go_quote.gif You can buy them directly from the AMB store. AMB audio shop

Quote:

Originally Posted by digger945 /img/forum/go_quote.gif http://dkc3.digikey.com/PDF/US2010/P2477.pdf<<<Figure 17. Digi-Key - HS276-ND (Manufacturer - 529802B00000)

yeah, i was hoping to find them at mouser to avoid extra shipping, however i will probably end up getting them there, sucks because mouser has 1 and 1.75 inch but no 1.5 inch (at least that i can find) but i do appreciate the input

 

[digger945]

Quote:

Originally Posted by pistolsnipe /img/forum/go_quote.gif yeah i would totally agree with you, however i already have some that are tap/screw mount, so i would like to make them all match yeah, i was hoping to find them at mouser to avoid extra shipping, however i will probably end up getting them there, sucks because mouser has 1 and 1.75 inch but no 1.5 inch (at least that i can find) but i do appreciate the input

529802B02500G Aavid Thermalloy Heatsinks
They have pins. If you search HF you can find how others have removed the pins and tapped them, but for the trouble you might be better off ordering from Digikey.

 

[Anonanimal]

Quote:

Originally Posted by dude_500 /img/forum/go_quote.gif Tried unplugging wireless devices, no effect. I earthed the ground of the amp and it got significantly quieter (though still existent). The problem is, after I then turned it off and solidly attached the earth ground and turned it back on, the positive rail of the power supply promptly burned out. Is this normal when earthed? I do have a scope and will look at the output after I repair the power supply. It's not 60hz, it's a short pop every second

Which ground did you tie to earth? How many boards did you use in your Beta?

If it's an active ground (3ch+) and you tied the output to earth ground I can see that causing problems. Either that or I'm not 100% understanding what you tested.