Crack buzz for Certain Audio only? [resolved]

[Baskevyl]

So, when turning up the crack roughly 1/3 of the way there are the hum and higher pitch hiss noises that happen, but that's normal apparently. Thing is, for certain audio a very distinct buzz is noticeable while the hiss and hum either disappear or are masked by it's prominence. In essence, some audio from things like Spotify, Youtube, and a few thing games like SupCom or Stellaris there's no issue. For some other ones like XCOM2 and PUBG the buzz is fairly loud and distracting.

I've order some shortening plugs to see if maybe it's my RCA cables? Other then that both tops of the 12AU7 glow and so do the small LEDS underneath the 9-pin. Everything should be wired right since it passed all voltage and resistance tests, and the only point of concern is the A3 solder. It's not nearly as bad as the example of a cold joint, but it is a bit dull and crystallized.

If it's of any relevance, maybe around the second time I powered the amp, the 6080 tube had a small (seemed 2-3 mm in width), brightly flashing discharge in it for a moment right when it turned on. Worked like normal though (I think), both coils light up over time.

Any idea what might be causing the buzz?

[fullheadofnothing]

If you play a Led Zepplin song, you will hear an electric guitar. If you play Mozart, you will not hear electric guitar. The reason for this is not related to the amplifier, it is what is in the source material.

If some source material has a noise in it, you will hear that noise when it is amplified. If you do not wish to hear that noise, then do not select the noisy source material.

[Baskevyl]

Well, there's definitely a certain satisfaction in the idea that it isn't the kit or my assembly, but I didn't think some audio would have such unintentional noises in it that only show up when amplified.

[Paul Birkeland]

I'd try a different source to see how the noise is.  Playing audio from your phone into the Crack via a 1/8" to RCA cable should provide an adequately quiet source.

-PB

[Baskevyl]

I'd try a different source to see how the noise is.  Playing audio from your phone into the Crack via a 1/8" to RCA cable should provide an adequately quiet source.

-PB

I'll get a cable and check it out.

So I tried some more source (not the phone yet), but I decided to turn down the volume in each but not the amp and see what happens. Apparently, the buzzing noise is there in everything, overpowering the normal hum/hiss (while nothing is playing such as being on desktop there's no buzz just the regular hum and hiss), even though in certain sources it's not quite strong enough to be noticed over say the intended ambience/music. So I guess something might be wrong after all, just not sure what.

[Paul Birkeland]

Your idea to make shorting plugs is a good way to go.

Something that's often overlooked that can cause this problem is loose hardware on the amp. I'd give everything an extra 1/4 turn just to be sure.

[Baskevyl]

Wow, I just noticed what the problem is by luck. It really was an issue with the ground connection, but not due to a bad solder on the safety ground lug, I literally forgot to solder the 16L wire, it's just been dangling there and sorta-contacting to the 5-lug terminal. Now comes one last question. In the instructions, this wire in 16L does not touch the bolt directly behind it. When I installed the transformer, I tightened the bolts just a bit too much, and bent the overall 5-lung terminal to be close enough to the bolts that at recommended wire length it will touch. Is this ok, since the terminal support is metallic and itself touching the bolt? If it's not ok, can I instead connect the wire to 16U where it won't touch the bolt, and still be on the some part of the terminal?

[Paul Birkeland]

It's OK if the ground wire touches the bolt.

-PB

[Baskevyl]

Soldered the input to 16L, buzz is still there    Not sure what else there is to do.

[Paul Birkeland]

This noise is in both channels?

I'd make yourself some shorting plugs to make diagnosis easier.

-PB

[fullheadofnothing]

So I tried some more source (not the phone yet), but I decided to turn down the volume in each but not the amp and see what happens.

Can you explain what this means more fully...?

When you originally posted, it sounded like you were using your computer as your source. You have not explained what other source(s) you have access to, nor what the computer setup is. It sounded like you were using the word "source" to describe software on that computer, rather than a source component. What it seems like you are trying to do here is turn down the output level from your computer and compensate for that by turning up your Crack. When you turn your Crack up, it will amplify whatever is coming into its inputs—signal and noise. The more you turn it up, the louder BOTH get. If you feed it a nice strong signal, you don't have to turn it up as far, so the noise is not intrusive. This post provides a good overview of the issues here.

What is unclear here is if you are simply listening to the basic noise floor of your setup, or if your setup is making extra noise (probably some aspect of the computer hardware).

What is the DAC?

How is it connected?

Do you have access to any non-computer source components (i.e. CD player, DVD player, phono stage, tape deck, MP3 player, cell phone, different DAC, et cetera) that you are able to connect to your Crack?

[Baskevyl]

So I inserted shortening plugs into the input jacks and, well no noise at all. Not entirely sure what that means.

Can you explain what this means more fully...?

Sorry if I wasn't being clear enough. Yes, my PC motherboard is the audio source. When I said "other sources", I meant a variety of programs and websites, not physically different audio sources. Again, sorry, I was indeed using "source" for software. Some of those "other sources" included things like Youtube & Spotify, and also some games I have like XCOM2 and CIV5, since I wanted to see if the buzz was just for a single program or for multiple ones.

I wasn't trying to turn down output and compensate for it by cranking the crack. I never turn it up beyond 1/3 of the way, or even 1/4, that's loud enough for most listening purposes. I wanted to make sure if the buzz (which sounded distinct from the regular expected hum and hiss) was actually there in more then 1 program and thus not just one programs issue. I'd turn down programs output to check because a few times I didn't notice the buzz because it was being masked under very loud default audio settings (Stellaris has some pretty loud intro music, it kinda blasts you). It turned out to be present in some programs but not others, which is odd.

To the other questions:

I am not using a DAC right now.

My setup is currently motherboard's line-in jack ---> Crack input jacks ----> Sennheiser HD600s.

I also finally got the wires delivered to connect my Crack to my phone; Besides there being more or less zero hiss or hum even with the cracked turned up to max (which surprised me),  there was also zero buzz, from any programs or music on my phone. So if all the wires stayed the same but the only thing that changed was my physical audio source, does that mean it's just my motherboard that's causing the buzz?

[Alonzo]

My guess would be coil whine in either your video card or power supply.  Could also by EMI from either of these manifesting in the cord to the Crack or the input tube.

[Paul Birkeland]

So if all the wires stayed the same but the only thing that changed was my physical audio source, does that mean it's just my motherboard that's causing the buzz?

Yes.  Does your motherboard have a toslink output?  An inexpensive DAC connected with a toslink cable will be nice and quiet.

-PB

[Baskevyl]

Ya my motherboard has a toslink output. So if I'm understanding, toslink is made for regular audio to be lossless and because it's using light, not deal with EMI. Simultaneously, it can't pass Hi-def lossless audio like HDMI can (which will possibly have EMI). Guess you can't have it all. Thank you very much for the advice, time to find an inexpensive toslink DAC then.