[grausch]

I'm sure it's not the source. PC to modi 2 uber with toslink, RCA to crack. Unplugging the RCA from the crack doesn't get rid of the noises. At one point, no RCA plugged in made the noise change from hissing to humming at full volume. After "shielding" the RCA to pot wires with aluminum, it's sometimes completely quiet at full volume, and other times scratchy. Definitely different than before adding the aluminum. The general background noises I'm also describing happens at any volume, but doesn't get louder if I turn the volume up.

Honestly, I'm completely confused about it. Sometimes I find a correlation between the noise and something, and then an hour later, they're no longer related. That was the case of the tube heat. At first it seemed like the colder tubes had more noise, now it seems they have less.

I'll do some research into attenuators later on. I'd like to try and solve the noise first, but thanks for the recommendations. I'll keep them in mind.

I have a feeling I'm going to be spending many hours poking connections and resoldering...

I would get a thread going on the Bottlehead site and post some pictures. The guys there are pretty good at the troubleshooting.
 
I have never had humming, so never needed to investigate potential causes for that. However, here is a helpful ground path check that can eliminate some potential problems (http://bottlehead.com/smf/index.php?topic=4812.0). If everything is properly grounded, you have no ground loop elsewhere and the RCA cables are properly braided / shielded then you should have no hum.
 
When I had static in my Crack, my first problem was a noisy USB port. Once that was fixed I also had another problem with the soldering at T13. Once that was fixed my amp was dead quiet. With the help of the Bottlehead crew, you should start eliminating problems until you find a solution. Might take a bit of time, but definitely worth it.
 
If your Modi 2 is running in 24-bit mode, you can decrease the volume on your PC without any loss in sound quality. Look for GUILT-FREE VOLUME ADJUSTMENT here - http://nwavguy.blogspot.lu/2012/04/odac-released.html. If you do not wish to go that route, then the Harrison Labs attentuators are the easiest solution. Just make sure you go for the -12db padding. The smaller values do not make enough of a difference.

 

[audiojun]

Well with enough evidence I am introducing the aluminum foil mod. Wrap a piece aluminum foil around 12au7 and ground it to the chasis. Easiest mod ever and it Eliminates noise from rfi interference.

Next I am going to try to use something else like chicken wire or something that can see through and can cage the tube. since aluminum foil looks ugly.




Now some proof:

I put my phone up to my 6080 power tube and just searched the web, it didn't make a sound.

I did the same to the 12au7 input tube and dang it picked up noise from my phone. So I did the aluminum foil mod. I tested again with my phone and yep zero noise at max volume.

Another project I did today:

asrock z97 motherboard had some computer noises from it's Headphone jack. After examining I noticed none of the wires from inside my case was actually grounded or shielded. I removed the wires that where not grounded from the case cause they can pick up noise like an antenna. I wrapped aluminum foil around the HD audio cable (goes to front headphone header) inside the computer then I wrapped a piece of paper around the foil (I don't want it to short my board with aluminum) then I attached an piece of aluminum from the shield to the case effectively grounding it. resulted in no noise from computer even when amped from crack.

Earlier I wrapped aluminum around the wires from rca input to the pot, it lowered noise more than just braiding.

Guys this mod is awesome! I am going to have a aluminum foil crack soon with my aluminum foil hat.

 

[mcandmar]

You are one step away from wearing a tinfoil hat

 
Seriously though, fit one of these http://www.ebay.co.uk/itm/390293225944

 

[Walderstorn]

  You are one step away from wearing a tinfoil hat

 
Seriously though, fit one of these http://www.ebay.co.uk/itm/390293225944

Cool, didnt know about those, are they easy to install?

 

[mcandmar]

They are a replacement tube socket, so you would have to unsolder the old socket, then resolder all the connections onto the new socket.  The two LED's would make it a fiddly job on a crack.
 
Another alternative is a slip on shield e.g. http://www.ebay.co.uk/itm/361225703724

 

[adydula]

Boy all this stuff on noises, hissing, pops, cracks, intermittents, chopsticks makes me laugh!! 
Being an old timer, growing up with tubes, building countless tube projects some which has 21 tubes, makes me smile alot!
 
Its like dealing with vinyl for years, hiss, pops, ticks, tracking etc..anti static guns, pads etc...terrible.
 
Then cd's come on the scene and they have bandwidth, silent, but still foreign! Many doubting thomas's, still today unless its a high sample
or high bit rate....
 
The Crack, and I do have one with Speedball, I built to see how it worked with my set of T90's. Having many solid state amps from many vendors and building three recent DIY SS amp. Which all are toatally silent and work very well..with none of the worts that many of you have gone thru with the Crack!
 
That said its still a great amp. If put together well, soldering, good tubes, keep away from interference, like dont put it next to your 2.4/5ghz wireless box, or your cell phone...it will give you thousands of hours of great performance!
 
But it will have its worts over time, mechanical  jolts, tapping on the tubes, jiggling tubes in sockets will drive you crazy chasing noise and hum.
 
Welcome to the world of tubes.....now where is my turntable micro micro tracking adjuster??
 
A.

 

[Jason Orlando]

  I don't know if you made a decision, but I'm listening to the HD700 + Crack with Speedball combo now.  It's fantastic in my opinion.  I can't really compare it to any other amp at the moment, but it is better than my memory of it with the Burson HA-160.  I don't really think the Crack will extend the bass very much, but the bass quality is excellent.  I have a hard time imagining someone describing the combo as having a "lack of bass."  I haven't encountered any sibilance so far.

Thanks for the feedback.  I ordered the standard crack during the leap-day sale.   From what i read, the standard crack alone seems to help the bass more than having the speedball installed.  Did you try it before and after the speedball upgrade?
 
I was able to get some bass out of my O2 by EQing it +20db.   Still looking forward to the crack.

 

[Jason Orlando]

asrock z97 motherboard had some computer noises from it's Headphone jack. After examining I noticed none of the wires from inside my case was actually grounded or shielded. I removed the wires that where not grounded from the case cause they can pick up noise like an antenna. I wrapped aluminum foil around the HD audio cable (goes to front headphone header) inside the computer then I wrapped a piece of paper around the foil (I don't want it to short my board with aluminum) then I attached an piece of aluminum from the shield to the case effectively grounding it. resulted in no noise from computer even when amped from crack.

Earlier I wrapped aluminum around the wires from rca input to the pot, it lowered noise more than just braiding.

Guys this mod is awesome! I am going to have a aluminum foil crack soon with my aluminum foil hat.

This is a common problem with computer builds.  Plugging into the rear port should eliminate most of the interference.  Otherwise an external dac is usually how people get around the issue.  

 

[Walderstorn]

  They are a replacement tube socket, so you would have to unsolder the old socket, then resolder all the connections onto the new socket.  The two LED's would make it a fiddly job on a crack.
 
Another alternative is a slip on shield e.g. http://www.ebay.co.uk/itm/361225703724

 
Im not much of a soldering guy but that doesnt seem hard, its just to copy basicly whats already done. Thanks

 

[audiojun]

I might do the slip on shield. It's a boutique part compared to aluminum foil

.
 

  This is a common problem with computer builds.  Plugging into the rear port should eliminate most of the interference.  Otherwise an external dac is usually how people get around the issue. 

 
What really helped was I removed a bunch of extra usb ports since they where not even shielded. Then I shielded/grounded the usb ports I was using. Now I get almost zero noise out of my motherboard analog outs yay! And Yes I have an external dac I have the Bifrost, I was just testing out the aluminum foil shielding and it works really well. I thinking people with noisy usb ports can do a simple aluminum foil shielding and ground it, then wrap the foil with an insulator so you don't short the motherboard.

 

[chuckwheat]

If your Modi 2 is running in 24-bit mode, you can decrease the volume on your PC without any loss in sound quality. Look for GUILT-FREE VOLUME ADJUSTMENT here - http://nwavguy.blogspot.lu/2012/04/odac-released.html. If you do not wish to go that route, then the Harrison Labs attentuators are the easiest solution. Just make sure you go for the -12db padding. The smaller values do not make enough of a difference.

Is that true? At least in the case of 44.1 16bit music? What % could I lower my PC volume if i'm using 192 24bit on the modi?

 

[Whit3Rav3n]

In case of 16 Bit music you can use 8 bit for volume control. You can lower the volume by 48 db without losing bit depth.

 

[chuckwheat]

  In case of 16 Bit music you can use 8 bit for volume control. You can lower the volume by 48 db without losing bit depth.

I have no idea how Windows 10 implements volume output for using a dac. I'm just wondering if I could lower whatever windows thinks the volume is to 50% or so, and not have any loss.
Question:
Could I plug the AMP output to the microphone input on my pc, with nothing connected, and try to capture the sounds it's creating by itself?

 

[audiojun]

I found some good info on how to lower the hum/noise for those of you who still have it.

http://www.diyaudio.com/forums/tubes-valves/211731-heater-wiring-good-bad-ugly.html

I am particularly interested in maybe converting my heater to dc. I just might do it in the future. My crack is dead silent though so obviously it isn't necessary at the moment. but i know 60hz harmonic is unavoidable due to the crack's ac heater design and I can feel the 60hz phase or something when it's cranked up to max though it's dead silent.

 

[Doc B.]

  You are one step away from wearing a tinfoil hat

 
Seriously though, fit one of these http://www.ebay.co.uk/itm/390293225944

Great shields. Very high price.