[Dubstep Girl]

No one will ever convince me that the WE421a is anything other than a rebadged Tung-Sol 5998. At MOST, I will allow that it might be a "carefully selected" 5998.

Premium 5598

 

[hifimanrookie]

Premium 5598

 

[rosgr63]

Quote:

 
Have you tried the RCA with a high blood alcohol content? Guaranteed better.

 
Actually the RCA is one of my favourite tubes including the Black Base Osram.
 
With alcohol I would probably like the Svetlana.........

 

[hifimanrookie]

Actually the RCA is one of my favourite tubes including the Black Base Osram.

With alcohol I would probably like the Svetlana.........

I actually bought my 337 with svetlana powertubes... Oops... U can see them in my first pics in my profile.

 

[GrindingThud]

Wow...the thread was active today!

I'm a 5998A lover. I like their signature, dynamic punch, and depth of soundstage in single ended OTL amps (WA3). It sounds different than the 5998/2399 but to me very similar to the 7236. I'd call it a poor mans 7236. The 5998 biases up in a completely different spot on the curve (the warm nonlinear region) in a cathode biased amp designed for a 6080. 5998A and 7236 bias nearly the same. The tube has a serious drawback in my opinion. It is very vibration sensitive and can resonate (microphonics) in the audio band. Some do it, some do not. Ones that do it I find can be 'smacked' into compliance if subjected to a jolt while hot. Once quieted, mine have stayed that way. They also are known to arc sometimes in a woo3.

Just wondering what is the relationship between the 5998 vs 5998a vs 7236. Was thinking if it's possible to pay non premium price for the 5998 equivalence.

Thanks

 

[Xcalibur255]

As rosgr mentiond, and I have mentioned here in the past, there is factual data in the data sheets to show that the 421A is not identical to the 5998.  It is clearly a derivative and probably sounds nearly the same, but look at the transconductance..... it is 33% higher in the 421A.  If the tubes were electrically identical they would have the same transconductance, you can't get a 33% increase by cherry picking I'm thinking. 
 
The bottlehead link was a nice read.  I find myself pretty much agreeing with it for the tubes on the list I have owned.  The 6080 seems to get no love but I can think of several I would easily take over the RCA 6AS7G as suggested in that writeup.  I am rather fond of my Chatham 6080Ws and got them dirt cheap.  I'm tempted to get my hands on some Bendix someday too.

 

[Skylab]

The 421A data sheet lists the transconductance as being over 20,000 uS???? I've never seen the whole data sheet for the 421A.

 

[GrindingThud]

http://www.westernelectric.com/spec_sheets/421A.pdf

The 421A data sheet lists the transconductance as being over 20,000 uS???? I've never seen the whole data sheet for the 421A.

 

[Beefy]

Quote:

As rosgr mentiond, and I have mentioned here in the past, there is factual data in the data sheets to show that the 421A is not identical to the 5998.  It is clearly a derivative and probably sounds nearly the same, but look at the transconductance..... it is 33% higher in the 421A.  If the tubes were electrically identical they would have the same transconductance, you can't get a 33% increase by cherry picking I'm thinking. 

 
You absolutely can get that sort of change with cherrypicking, assuming the 421A don't outnumber the 5998.
 
The value in the datasheet is an average/typical value, and individual but identical tubes vary by a huge amount around that average. This is why there is such a big market in matched pairs and matched sections - and even then, matched pairs/sections are rarely closer than 5%.

 

[Skylab]

Not just that, but now looking at the data sheet, the higher transconductance is derived by specifying different operating values than the 5998 uses when it specifies 15.5K.

Sorry. I'm unconvinced. That and the fact that the WE data sheet itself says "5998/421A"...

The primary reason for my skepticism is that the odds of WE having manufactured such an uncommon tube type don't seem very high. It's possible that ER had Tung-Sol tweak the 5998 slightly for them when they supplied it to WE. But even that I'm skeptical of.

 

[GrindingThud]

Getter placement does vary. Chatham and TungSol 2339/5998 typically have top getters while 421A have doubles in the base or none at all. I've seen exceptions though. And then there are those green label side getters....those are cool. And the short/tall plate varieties:

 

[Skylab]

Yup, I have some bottom getter Tung-Sol 5998's.

 

[GrindingThud]

Of course while surfing for 421A pictures, I ran across this 6080.....never seen one like this before, now I have a new obscure tool to hunt down. Jeebus, it's sooooo cool. Wonder how it sounds

 

[Skylab]

Isn't that identical to the Bendix?

 

[GrindingThud]

No, looks more like a relabeled TS7236. The bendix have a different shape box supported with rods.

After looking at these for so long I'm beginning to think the labeling department put whatever they needed on the tubes to satisfy order demand.

Isn't that identical to the Bendix?