Tips to reduce noise?

[HaPpY]

So I just finished building and everything went better than expected. However there's various sources of noise which I've isolated to the following:

- the audio cable, which ill upgrade soon enuf
- the headphone cable which I havent actually isolated. its the stock Senn HD650 one. anyone notice a difference improving these? I have no problem keeping this away from trouble spots anyway.
- a WIFI router a few feet away! this is a HUGE culprit and I dont think a few feet more will help. i notice an obvious spike in noise soon as I start playing a utube/etc vid on my ipad.

so has anyone built some sort of faraday cage for their crack... or know of anything available I can fence around it? hopefully nothing too ugly/clunky

 

[Doc B]

You could try a tube shield over the 12AU7. It will need to be electrically attached to the chassis panel.

 

[HaPpY]

oh ok, so its the tubes getting the brunt of the inteference then... the rest of the crack circuits should be fine? i wouldnt think the wood casing blocks much...

 

[Doc B]

I don't know. Tubes are sometimes shielded from RFI in gear, particularly in circuits with much higher gain than the Crack has. So it might help, and it's something easy to try. Actually I think your router is the most likely problem since the tubes are not sensitive to the frequencies at which the router should normally be radiating. We don't have any issues with router noise in our lab and our router is in there. But my aim is to be a supportive manufacturer and thus I am willing to offer suggestions of things to try with our gear rather than sounding like I am trying to pass the buck.

You could also go back through and see if reflowing some (or all) joints helps. A less than perfect ground could make the amp more susceptible to noise pickup. And you could try covering the braided wires from the RCA jacks to the pot with some shield tape (aluminum or copper) that is connected to the chassis plate. Some users have reported that making a difference.

 

[HaPpY]

well to be specific with my setup in case you're interested in reviewing in your lab...

<tablet>---2ft---<crack>---2ft---<ap>

- audio cables are  UNplugged.
- headphones (sennhd650) plugged in
- tablet (ipad3) speakers off
- everything is sitting on a glass desk
- AP is 3 antenna. different settings like 2.4ghz(G) vs 5(N) and channel settings make little difference.
- position of tablet/AP doesnt really matter since its all broadcast anyway.

i hear noise relative to the current level of activity in the video being viewed on the tablet. turning off the tablet immediately stops the noise... what ill do next is find some block of copper or aluminum and position it inbetween the AP and crack entirely then just the tube(s) to narrow down a solution.

do you have any vendor recommendations or sell shielding directly yourself?

 

[ALL212]

"the headphone cable which I havent actually isolated. its the stock Senn HD650 one. anyone notice a difference improving these?"

I'd doubt that it's causing or picking up any noise (IMHO) but that stock cable is not the best.  I'm pretty sure you'll hear an improvement after replacement with something better.

 

[fullheadofnothing]

Your symptoms sound like the issue is with your iPad. You are amplifying its noise floor; most likely either the processor noise (as suggested by the sound changing with activity), or possibly the power supply (is anything else plugged into the iPad?). I suppose it could be data signals; try putting it into airplane mode and see if that resolves the issue.

Shielding wires / components or placing large blocks of metal around your home will not fix a noisy source.

 

[HaPpY]

it happens even with the ipad in another room... ive also turned turned off the 5ghz (802.11n) radio on my AP and it helped noticeably. just having this idling induced interference.

maybe its not the radio itself but whatever is happening inside the AP?

 

[Horatio]

I had something similar happen to me and it turned out I had my crack plugged into a power socket that was being interfered with by power line network adapters. Worth checking what else you have plugged in to the mains that could be contributing.

It drove me crazy checking every appliance in the house until I realised the power line network adapters were the cause.

 

[jaysbob]

I was plagued by weird RF noise issues with a number of my amps until I realized they only occurred when my cellphone was on my desk and using cellular data. I now put my phone on a shelf about 3 feet lower and I don't get any noticeable noise issues. I can reliably recreate it by making a call and moving my phone closer or further away from the amp. Sounds like morse code beeps and chirps.

I've also had noise issues from computer sound cards picking up clicks and noise from wireless adapters. That was remedied with higher quality network gear and an external power-isolated DAC.

I've found shielding can make a difference but you'll see the biggest improvement from physically moving sources of electronic noise (anything wireless) further away from your amplifier. Shielding is definitely worth trying if you can't actually move things around.

This is all assuming it's RF noise that's the issue.

 

[Surge]

Hmm, I highly suspect it's a problem with the assembly. My Crack is dead quiet. It's sitting on my nightstand with my iPhone literally touching it. And there is a router a few feet away. I also use it my iPad. No issues at all.

 

[pingping]

I find that I get quite a bit of mains induced noise. We have Ethernet over power from time to time, and you an hear them working sometimes through the headphones.

I also recently found that my original output valve had gone a bit (more) microphonic, and it showed me that the transformer mounting bolts needed tightening - made a big difference to the bass resolution even though I'd not really noticed the hum!

 

[HaPpY]

Hmm, I highly suspect it's a problem with the assembly. My Crack is dead quiet. It's sitting on my nightstand with my iPhone literally touching it. And there is a router a few feet away. I also use it my iPad. No issues at all.

so heres the thing... when i hear noise i know is due to my wifi router... i put my hand in between the router and the larger tube. noise instantly stops.

so ya... this is more apparent with 5gz than 2.4ghz (router is both, tested both).

maybe its not necessarily the actual signal rather whatever electric activity from the router's board.

either way its a problem

 

[attmci]

Follow Doc.  B's suggestions:


Cold Joints

Nope, we're not talking about arthritis, or rolling a blunt in the Seattle snow. We're talking about cold solder joints, that is, a solder joint that does not conduct properly. They are one of the most common reasons your new build doesn't measure right (along with mis-wired terminals).

Sometimes you can see a cold solder joint. It might look dull and crystallized or you might see that a wire hasn't been well covered with solder. But lots of times you can't see a cold joint. Don't trust your eyes. It takes all of a few seconds to reheat (or reflow, or rewet) a solder joint. And in fact when a kit arrives at our lab for repair it's pretty much standard operating procedure for our techs to 1) verify component and wire connections and 2) go through and reflow all the joints in a kit - before removing and replacing any components. Often that's all a build that isn't working right needs. Make sure your soldering iron tip is clean, otherwise you will be holding the tip to the work longer than necessary and possibly leaving more residue to further increase the resistance of the joint.

 

[Paul Birkeland]

so heres the thing... when i hear noise i know is due to my wifi router... i put my hand in between the router and the larger tube. noise instantly stops.

Add some distance between your router and the Crack.