Wireless Interference???

[mackat]

Hi all!

I am new here, some of you might know I'm originally from head-fi, then went to audiokarma.

I am currently using an iMac 27 inch with a PS Audio Digital Link III DAC, connected to a non-speedballed Crack using a Beckman 6080 tube and a PhilipsECG 12au7 tube.

I have noticed some very low volume interference, e.g., I can;t hear it with music playing, but it's still annoying no less. I have figured out that I'm pretty sure it's the WiFi from my iMac. I have ruled out the bluetooth keyboard and trackpad.

I bought the Crack used assembled and am not technically advanced, but I am curious as to what you guys think.

The 6080 tube does ring a bit in the left channel is you tap on it, as well as in the past I have discovered some VERY slight ringing in the left channel too. I am using Sennheiser HD650 headphones.

Thanks!
Ben 

[Grainger49]

Computers of any manufacture are notoriously noisy.  They should be at least three feet away from your audio gear.  If this is not your problem, good.  Also, cell phones cause a lot of problems when close to audio gear.

Don't tap your tubes, they are just amplifiers not drums.    ;-)   That does indicate a little microphonics but it is not a problem.  

[mackat]

Ok, thank you! No, it's closer to 6 inches from the 'puter, so I'll figure out some way to move it.

Thanks!
Ben

[mackat]

Hello again!

I haven't done much other than get a new DAC (Schiit Gungnir). It still has the problem, mostly at night. Maybe that's when I'm most alert. I can't really move it away from the computer. Could a tube possibly be a culprit? If so, which one is more likely? Also, with the Gungnir, there is some white noise if I turn it all the way up, which then migrates into what sounds like very dirty power is I select an input that isn't being used on the Gungnir (optical, coax, different coax). Hmmmm...

Thanks a lot!
Ben

[Grainger49]

First, do as you said, try moving the computer.

I have noticed some very low volume interference, e.g., I can;t hear it with music playing, but it's still annoying no less. I have figured out that I'm pretty sure it's the WiFi from my iMac. I have ruled out the bluetooth keyboard and trackpad.   .   .   .

Ben  

Ben,

Can you describe the noise?  There are noises that are intrinsic to tubes.  There is a white noise that sounds like SSSSSSSS.  Sometimes there is a noise that is mostly low frequencies that sounds like ShShShSh.  Then there is hum, 60 Hz and 120 Hz.  Paul Joppa refers to 1/f noise which I think translates as the first sound.  This is tube rush and can be relieved by rolling tubes.  

If you haven't tried different tubes this is always a first step.  Not to mention you might find a tube that you like better.

[mrarroyo]

Are your cables shielded? If not install a ferrite in the power cord about 9 inches from the amp.

[mackat]

It's an "interference" type noise, one that goes in and out, kinda fuzzy, like I'm hearing data go somewhere.

[Paul Birkeland]

Ha ha, yeah, this will happen.  Doc B's phone is easily the worst offender at Bottlequarters.  We've actually gotten to the point where we see it on the scope and know what it is. 

I'm not so sure that tube shields help much, but distance seems to work nicely.

[mackat]

Glad to hear that, still going to get more toobs since I don't currently trust the 6080 too much. What toob would you think would be the easiest culprit? Or it is more of a "whole item" prenomenon, from what I'm hearing?

[Paul Birkeland]

The 12AU7 is the most likely culprit. 

[mackat]

Well, the new 6as7g has a very noticeable hum in the left channel and a slight whistle in the right, that doesn't happen on the 6080. I'm guessing a defective tube, right?

[Paul Birkeland]

Yup, there are some gnarly ones out there.