[Doc B.]

Could just be dirty pins. Remove and replace the tube a couple of times, That may scrape off any contaminant.

 

[Klots]

@Klots that sounds like it could be a dodgy solder joint at the tube socket terminals. I'd recommend reheating each terminal to reflow the solder and see if that helps.

 
 

Could just be dirty pins. Remove and replace the tube a couple of times, That may scrape off any contaminant.

Did all that and nothing. Still high pitch squeal. I put my previous tube (GE 6AS7GA) into it and no squeal after 4 hours of listening. But the 5998 sounds better, only the high pitch squeal is a bit annoying. I just have to live with that squeal I guess. Made a little video with my phone so you can hear exactly what it sounds like.

 

[atomicbob]

I don't know if a tube damper would help, but it might make for a good experiment in the case of the squealing 5998.

 

[Loquah]

Maybe it's a dodgy tube?

 

[MattTCG]

Just an incredible experience...

 

[Klots]

Maybe it's a dodgy tube?

I think so yes. When I bought it (about 4 months ago) it was perfectly silent etc. And now a few weeks ago this squeal appeared. But I dont want to use other tubes, because I like the sound of 5998 

 

[diaBoliQu3]

Guys, care to suggest input tube replacement for my old 12AU7A? I need to figure out what's wrong with my Crack which I ask previously here:
 
http://www.head-fi.org/t/476650/crack-bottlehead-otl/6240#post_11080323
 
Kindly help me because it's been so long I don't listen from my Crack and it cracking me up.
 

Guys, my Crack got some hissing sound at the left side. Usually when I turn on the amp, it hiss only for few second than silent. However recently instead of disappear, the hissing became worst. I changed the large tube but no luck. I don't have the small tube to try with. Can faulty small tube caused this kind of issue? Or perhaps cracked soldering due to hot temp of the amp it self?

 

[atomicbob]

  Guys, care to suggest input tube replacement for my old 12AU7A? I need to figure out what's wrong with my Crack which I ask previously here:
 
http://www.head-fi.org/t/476650/crack-bottlehead-otl/6240#post_11080323
 
Kindly help me because it's been so long I don't listen from my Crack and it cracking me up.
 

I'd check the solder joints on the 12AU7 tube socket first. If that isn't the issue then find a replacement 12AU7.

 

[diaBoliQu3]

  I'd check the solder joints on the 12AU7 tube socket first. If that isn't the issue then find a replacement 12AU7.

Any suggestion for the replacement cum upgrade tube? Within $30 can get an upgrade or not in e-bay? I can't find suggested thread for this tube, unlike the output tube.

 

[dsound]

Just an incredible experience...
 

 
Did you just finish this build?  Very nice, is that a Blumenstein-bamboo base?

 

[MattTCG]

   
Did you just finish this build?  Very nice, is that a Blumenstein-bamboo base?

 
I was thinking about some new caps, but...I REALLY like how this sounds just as it is. Yesterday and today I was able spend some quality time with the Crack and hd800. Wow, it sounds much better than I remember. Could be the dac though. When I had the Crack/800 last, I believe that I was using the uberfrost. 

 

[skeptic]

 
Any suggestion for the replacement cum upgrade tube? Within $30 can get an upgrade or not in e-bay? I can't find suggested thread for this tube, unlike the output tube.

 
I think basic nos Tung Sol 12au7's are very nice balanced sounding tubes.  Not too lean or too warm.  Cheap too.  For example, here's a pair for $15.  http://www.ebay.com/itm/Pair-Tung-Sol-12AU7-12AU7A-ECC82-Vacuum-Tubes-Very-Strong-/321609528392?pt=Vintage_Electronics_R2&hash=item4ae16bf448
 
I run one of these frequently in my office rig.

 

[JamieMcC]

   
I think basic nos Tung Sol 12au7's are very nice balanced sounding tubes.  Not too lean or too warm.  Cheap too.  For example, here's a pair for $15.  http://www.ebay.com/itm/Pair-Tung-Sol-12AU7-12AU7A-ECC82-Vacuum-Tubes-Very-Strong-/321609528392?pt=Vintage_Electronics_R2&hash=item4ae16bf448
 
I run one of these frequently in my office rig.

 
I like the Tung-sol as well my favourites are the 1950's 12au7 JTL or the slightly earlier 12au7 black glass, nice sounding tubes and make for a good pairing with the HD650. 

 

[diaBoliQu3]

   
I think basic nos Tung Sol 12au7's are very nice balanced sounding tubes.  Not too lean or too warm.  Cheap too.  For example, here's a pair for $15.  http://www.ebay.com/itm/Pair-Tung-Sol-12AU7-12AU7A-ECC82-Vacuum-Tubes-Very-Strong-/321609528392?pt=Vintage_Electronics_R2&hash=item4ae16bf448
 
I run one of these frequently in my office rig.

Wow, thank you very much and that's a nice deal. Actually, my maximum budget for input tube is $40 but $31.25 inc shipping is really a good deal for me. So, does it need to be 12AU7A, or any 12AU7, or any ECC82. Confused with tubes...
 
Anyway, what is your main input tube? And how many Crack you own?

 

[atomicbob]

My current aural delight: