Hissing when connected to laptop

[benzxc]

Hi all,

I just built my crack w/ speedball upgrade.  Works perfectly and sounds great.  There is absolutely zero background noise/hum/hiss when I connect to my phone, even when I max out the volume (when not playing music).

However, when I connect my crack to my laptop, there is a very audible noise/hiss/hum once the potentiometer is about 25% of the way, and gets progressively louder.

I know that this is probably an issue with my laptop and not the crack as it is silent when connected to my phone.

Anybody have any experience with getting rid of the noise when connecting the crack to a laptop? As I mainly use my laptop for listening, it would be nice if there is a solution to this issue.   

Thanks!
Ben

[oguinn]

Are you using the same cable with the phone that you are with the laptop? If not, try that. If so, you might want to try a DAC to connect to the laptop.

[oguinn]

Oh also - what do you have the volume on the laptop set at? I'd recommend setting it to the highest possible and then using the Crack potentiometer to control the volume.

[benzxc]

Hi Jameson,

Thanks.  Yes I am using the same cables. I also am using a DAC with the laptop. The dragonfly red. And yes I have recently started to Max out the volume on my computer as well.

Thanks!
Ben

[Tom-s]

It's possible the laptop fans influence the PS of the DAC.
External USB dacs with a separate PS like some Schiit or DACS with optical input solve this issue.

[Paul Birkeland]

https://forum.bottlehead.com/index.php?topic=11676.0

[benzxc]

Thanks!

[benzxc]

So I spent the whole day tinkering with the crack.  Trimmed excesses and resoldered some bad joints.  The hissing is gone now and I had an enjoyable few hours.

However, I did notice this really strange high frequency hissing when I turn the volume to 0%.  It sounds kind of like what I imagine tinnitus to sound like.  Although it is barely audible, it is unignorable once I notice it.  It is not there all the time but rather comes and goes, stays for maybe 25 to 30 seconds and then disappears.

At first I thought it might be my wifi, electronics and the like, so I brought the crack into my bedroom away from all those applicances but it still seems to be present sometimes.  It doesn't go away if I play with the volume, or if I plug/unplug the RCA inputs.  It seems to be only with the headphone jack and power.

Has anyone had any experience with this?  Could this be a tube problem?  I'd be most grateful for any assistance!

Thanks to all!
Ben

[benzxc]

Oh - I might mention that this afternoon after I trimmed some excess I plugged in my headphones for a listen and somehow there was a loud pop in my right channel, and I saw a spark in the larger tube.  I thought I might have ruined my headphones so I turned it off and plugged my headphones into my phone and it worked fine.  I did the voltage tests (all fine) before I started using my crack again - all was fine after that.  Not sure what might have caused that.

[benzxc]

Also, the high freq hiss appears to be from the right ear.  Although this hiss happened before the pop happened...

[Paul Birkeland]

It might help to post some build photos.

[benzxc]

Thanks, Paul. Here are a few photos.

[Paul Birkeland]

You have a little more trimming to do.  It might help to get a good set of side cutters as opposed to wire cutters.

I also do not see the connection that I've circled in red in this photo.  Not having this connection could cause the pop and flash.

[benzxc]

Thanks, Paul!  Is this the connection that you are referring to? Might have been the angle of the last photo.

[Paul Birkeland]

Indeed.  In that photo it looks like the inboard side of the lower 2.49K resistor might've been cut.