[john57]

Usually a curve tracer on a O'scope but this looks a bit different.

 

[rosgr63]

Quote:

Stavros, what tester is that?

 
Sofia Tube Tester.

 

[GalaxyGuy]

I picked up a pair of 2399 tubes via a group buy from Ultrainferno recently (thank you Ultrainferno and dminches!) and I installed the tubes yesterday.  Granted, they have not had any time to burn in yet, but I have noticed that there is a faint background hum in my HD650s, even with the volume turned all the way down.  Do you all think that this will diminish with time?  There are also some occasional pops.  I did not hear this with the stock tubes nor the Sylvania 7236s.
 
My initial impression of these tubes is that the bass seems to have a bit more punch than with the 7236 (although they are very close, imho).  Otherwise, they sound very clean across the spectrum.  I'm quite happy other than what's mentioned above.
 
Any feedback would be welcome.

 

[hodgjy]

It's my experience that the 6AS7/2399/5998/6080 family of tubes are just really prone to noise.  They were never intended to be audio tubes.  While it's possible the hum will decrease, I wouldn't bet on it.  I've run in all my noisy power tubes for hours in hope of this, and they never did get quiet.  I hope yours do because they really are glorious sounding tubes in OTL amps.
 
Quote:

I picked up a pair of 2399 tubes via a group buy from Ultrainferno recently (thank you Ultrainferno and dminches!) and I installed the tubes yesterday.  Granted, they have not had any time to burn in yet, but I have noticed that there is a faint background hum in my HD650s, even with the volume turned all the way down.  Do you all think that this will diminish with time?  I did not hear this with the stock tubes nor the Sylvania 7236s.
 
My initial impression of these tubes is that the bass seems to have a bit more punch than with the 7236 (although they are very close, imho).  Otherwise, they sound very clean across the spectrum.  I'm quite happy other than the hum.
 
Any feedback would be welcome.

 

[dminches]

Same here although with my current pair of 5998s in Glenn's OTL the hum is really quieted down.

 

[Dubstep Girl]

all my tubes including my 5998 are silent in my WA2. even more silent than the silentone 

 

[Silent One]

 

[GalaxyGuy]

Thanks for the feedback, all!  Hopefully the hum will diminish with time, we'll have to see.
 
One more quick question, just to show you how much of a newbie I am.  To burn in the tubes do I need to have music playing through the amp, or can I just leave the amp on with no music playing?

 

[GalaxyGuy]

Quote:

It's my experience that the 6AS7/2399/5998/6080 family of tubes are just really prone to noise.  They were never intended to be audio tubes.  While it's possible the hum will decrease, I wouldn't bet on it.  I've run in all my noisy power tubes for hours in hope of this, and they never did get quiet.  I hope yours do because they really are glorious sounding tubes in OTL amps.
 

What about WE 421a tubes? Are they intended for audio use?

 

[atomicbob]

There was a faint residual mains hum from my WA3+ with any high impedance headphones, HD600 and T90 here, for any of my 6AS7, 6080, 5998 and now 2399 tubes. I made an adapter cable that plugs into the amp and headphones plug into the adapter. This adapter parallels two 100K ohm resistors with the headphones. The resulting additional load dropped the residual hum to in-audible for me. A measurement mic shows the hum is still present but reduced significantly.

First 2399 rolled in had some static / machinery noises, and pings during warm-up. The pings still occur during first 10 minutes but other noises are gone. Pings are just part of thermal expansion until the tube equilibrates to 135 deg C. Enjoying an enhanced clarity of sound while retaining the magic mid-range. Bass is tight and accurately portrayed. Shortly to receive HD800 to audition; I'm sure this will move the reproduction sound to another level.

 

[hodgjy]

That is just a fancy rebadged TS 5998.  None of those tubes were ever designed with audio (home music) in mind.  They were designed to be voltage regulators, and often found their way into computers.  Some of them may have been intended for radio broadcast and radar, but that's a far cry from boutique audio.
 
Quote:

What about WE 421a tubes? Are they intended for audio use?

 

[rosgr63]

Quote:

What about WE 421a tubes? Are they intended for audio use?

 
They are an upgraded version of the 5998.
Closely matched plates tighter tolerances, better specs.

 

[GalaxyGuy]

Quote:

 
They are an upgraded version of the 5998.
Closely matched plates tighter tolerances, better specs.

 
 
Quote:

That is just a fancy rebadged TS 5998.  None of those tubes were ever designed with audio (home music) in mind.  They were designed to be voltage regulators, and often found their way into computers.  Some of them may have been intended for radio broadcast and radar, but that's a far cry from boutique audio.
 

Thanks!

 

[Ultrainferno]

Is it a ping or a pop?
I checked all tubes before sending, non had hum in my amp I tested them in and non popped.

 

[GalaxyGuy]

Quote:

Is it a ping or a pop?
I checked all tubes before sending, non had hum in my amp I tested them in and non popped.

It sounded like a pop to me, but I'm not sure that I know the difference...
 
What amp did you test them in?  I'm using them in my WA22.  I don't hear anything with my LCD2s, but with the HD650s there is a distinct hum that wasn't there with the 7236 tubes in place. I'm not worried, just wondering whether people thought it would prevail or whether it would diminish over time.