Two audible problems with Crack build, all resistance and voltage readings ok

[Luxifer]

Hi all,

I just finished a Crack build last night, and was excited to give it a listen. All of my resistance and voltage readings were good, both sides of the 12AU7 are glowing, as well as the 6080, but I am encountering two problems. Music does play.

One: Even without a source plugged in, I hear extremely high noise from the unit, as in, even with the volume as loud as I would want to listen, it is still clearly audible on 300 ohm headphones. I have tried different outlets, but none have solved the problem.
Do I just have really bad wall power? Or might it just be a bad joint? Something else? I hear a much smaller but similar effect when past 75% volume on my Stax SRM-353X, but only when I have a source plugged in, in that case. If wall power is the issue here, what is the recommended course of action?

Two: This problem is more worrying to me, in terms of gear longevity. Whenever I plug a headphone into the Crack, an extremely loud pop comes from the drivers. Ear pain levels of loud. Any idea what could be causing this? I'd really love to get these two issues sorted so I can get listening, and eventually install my Speedball upgrade.

Any ideas or suggestions would be greatly appreciated! Thank you.

[Doc B.]

It will help if you are specific about the type of noise. Hum ? Buzz? Hiss? My hunch is your are hearing a buzz. It is most likely that there is a cold or missed solder joint at the headphone jack where the black wires are connected.

[Luxifer]

The first noise sounds like its oscillating, which is what made me think it may be mains related. I will look for a cold joint around the jack.

Definitely not a hiss, maybe somewhere between a hum and a buzz.

The other noise is between a loud pop and a crackle/snap (forgive the unfortunate rice crispies pun). Any idea what could be causing that? Do you think it's the same issue causing both?

[Paul Birkeland]

Definitely not a hiss, maybe somewhere between a hum and a buzz.

You can listen to a 60Hz and a 120Hz tone and let us know which one it sounds like.

The other noise is between a loud pop and a crackle/snap (forgive the unfortunate rice crispies pun). Any idea what could be causing that? Do you think it's the same issue causing both?

A poor solder joint or a joint that isn't soldered at all.

[Luxifer]

You guys are amazing. I touched up every joint on the jack, and both issues are solved! Thank you so much!

[Luxifer]

There is now more of a gentle buzz as I increase volume with inputs plugged in, although it's not really audible until about halfway on the pot. With no inputs, I have turn another 20% or so for it to come back, and the character changes from a static noise with some frequency hidden in it (inputs plugged in), to a more monotone buzz. I think this buzz sounds more like 120 Hz than 60.

[Paul Birkeland]

If the amp is quiet with the volume pot all the way down, then the amp is working properly.  If there is noise when the pot is up (especially turned way up), then that is just the amp picking up environmental noise.  We do also often find that taking audio directly from a PC or from a USB powered DAC will create a bit of noise as well.

[Luxifer]

Good to know. I'll see if maybe an isolator/conditioner/filter might give me a bit more headroom. Do you have any recommendations on that front?

In any case, this is 98% better than what was going on before. Thanks so much!

[Paul Birkeland]

What source are you using with your Crack?

[Luxifer]

An Oppo HA-1 (pre-amp and DAC), fed via USB from my computer.

[Paul Birkeland]

Just for the sake of experimentation, it's a good idea to try your phone (not plugged into the charger) as a source.

The Oppo should be quiet, but you may need to use the Toslink connection to break any noise traveling down the USB cable.