Tube Rolling w/Crack

[Grainger49]

Nick,

Well written and informational.  I don't have a Crack but I will expect that those who do have one will really appreciate all the time you have put into this.

[bmwr75]

I have an Amperex 6AS7G.  It looks very similar in construction to a 421A.  You ever seen or heard one of these tubes?

[Nick Tam]

Amperex 6AS7G is unfortunately a Russian rebrand.

The 421A is distinct to any other tubes in the 6AS7 family.
421A had spiral wound "pigtails" filament wiring and matte light grey (50's) or black (60's) dimpled "Domino" Plates, dual bottom halo/d getters

Here are photos of the 421A with halos, domino plates and a d getters variant.

Last photo is a picture of the 421A and 5998.

[Laudanum]

I have 3 5998's, two variations.   One is a grey plate, dual bottom D getter.  The other two are black plates, dual top D getter.  Sonically, they are the same.   I had another variation with both top and bottom getters that was noisy.    I have remained skeptical about any signifigant differences (sonic) between the 421A and the 5998 because of several reasons related mostly to internet "research".  But, I fully admit to never owning a 421A so I could very well be wrong.  But your photo of the Tungsol labeled 421A doesnt tend to change my thinking.   The biggest "issue" that I have is that Ive seen several of both the 5998 and 421A tubes with different internal contruction from one another, respectively.   The 5998's that I have/had that are different internally all sound essentially the same so it leaves me plenty skeptical enough to not have any desire to spend the money on a 421A.   Again though, I could be wrong and will probably never know for sure unless a 421A basically dropped in my lap.

Very nice post BTW.

[Nick Tam]

I admit even I don't have the 421A and I'm tired of trying to get my hands on one. The web consensus is that the 421A=5998 based on construction photos but people that claim this never really owned one so it's mostly a baseless assumption. But if people that have the 421A say so that there is a difference that is huge, then it probably explains the crazy dropping of wallets. Otherwise it just doesn't justify to pay big bucks for a step up from the 5998.

The 5998 has in fact, 4 variations including the Tung Sol 421A. Single top getter, dual top, dual bottom and top and bottom getters. The 421A however, always have dual bottom getters.
The "black" and "grey" plates however is very subjective, but I think I could firmly say that the 421A is easily distinguishable with it's matte grey plates whereas the 5998's plates give off a slight sheen. The early 5998 seems to have dark grey "black" plates whereas the later ones had a glossy black to it. I'm just skeptical if a well balanced 5998 sounds essentially the same as the 421A. EDIT: CONFIRMED THAT BOTH the 421A AND 5998 HAVE BLACK AND GREY PLATES

I've got a NOS 5998 for $60 off ebay some time ago and one new in factory box from local retails for $110. Does it sound different? Probably. Strangely I prefer the NOS one more and felt "burn in" in the sense that it sounds musical. On the other hand, the NIB one didn't sound as musical and sounded as if it had a deeper soundstage. I don't know if there really was a difference but I'm sure that both tubes were balanced. Subjective opinions anyways but I've stuck to the one I picked off ebay until now.

[Nick Tam]

I have 3 5998's, two variations.   One is a grey plate, dual bottom D getter.  The other two are black plates, dual top D getter.  

It appears that I was wrong about the plates: WE 421A had grey plates in the 50's and black plates in the 60's onwards. In other words, the 421A and 5998 are otherwise identical in plate construction as the 5998 was indifferent in the given production periods. See photo

Although we could now be sure that the Tung Sol 421A is otherwise just a rebranded 5998 with 421A specifications.

[Paul Joppa]

...
Although we could now be sure that the Tung Sol 421A is otherwise just a rebranded 5998.

Just noting here that "re-branding" might involve testing and selection as well - balanced sections,, tighter specs, lower noise, for instance. Or on the other hand, rejects from a quality-tested batch can show up under a different brand. The tube business has its dark side!

[Laudanum]

I agree with you Nick, without owning a 421A it's impossible to be certian if there is any signifigant sonic difference from the 5998.   Thats why all I can say is that I remain skeptical.  But I really appreciate you posting that Tungsol labeled 421A.  That kinda adds fuel to my own fire      I wish that top and bottom getter variation I had was a good tube.  I'd like to have 3 variations of them just to have them,  even though I couldnt hear any real differences.   

I have mentioned previously, what Paul has stated.   That maybe the WE 421A is a selected 5998 with some internal contruction differences.   Well, atleast for some of them, the Tungsol labeled 421A murkys the waters some more.   But the bottom O getters are the most obvious from your pictures and others I have seen.   Still, that doesnt necessarily make them signifigantly different, sonically.   I never really chased a WE, when I have seen them for sale it has been at too steep a price for me and it's likely to remain that way.   I know most of the folks who have one proclaim the WE is better but of course human nature has to be accounted for so I still remain skeptical.  But fact still remains that without one myself I will never know for sure.

[Nick Tam]

I know most of the folks who have one proclaim the WE is better but of course human nature has to be accounted for so I still remain skeptical.  But fact still remains that without one myself I will never know for sure.

Someone in the 421A camp bust this myth? I'm not willing to sponsor for the usage of your precious 421A and 5998 tube though!!!

[Nick Tam]

I bet a lot of people are kicking themselves for literally just throwing away their tubes now that there is a market where people will pay tons of money for such things.

I don't think anyone would do that... a little research on eBay is all you need to do if your dead tube is worth someone else' fortune. I was hunting for rare 421As and A1834s and the prices would always break the $150 barrier regardless... so I turned to hunting for rare 6SN7s for the input side instead. Turns out that, the average price of the "rare" 6SN7s like the Sylvania 6SN7W and British 6SN7s bunch aren't much better...

Well, I would throw out the stock 6AS7 anyways, unless it was the Tung Sol Westinghouse one.

Ultimately, we all have to draw a line for the $$$ barrier for the lone 6080/12AU7 combination we're using in the Crack though

[m17xr2b]

Would the SYLVANIA JHS 5814WA black plate tube work with the crack? I have found a pair of these for sale and I heard a lot of good things about them.

[Laudanum]

Yes, the 5814 is a direct sub.  Go for it, no problems at all.

[m17xr2b]

Also will the 6AS7GA work with the crack? On the list I only see 6AS7G.

[Paul Birkeland]

Also will the 6AS7GA work with the crack? On the list I only see 6AS7G.

The only difference between the two is the shape of the glass, so yes.

[blstrek]

At the moment, I am running;
Amperex 6085-PQ and Chatham/Tung-Sol 5998.

Also in my arsenal of tubes to roll are the following;

Input;
EH 12AU7
Sylvania 12AU7
RCA 12AU7A Cleartop
Raytheon 12AU7 Long Blackplate
Mullard 12AU7
RCA 12BH7 Blackplate
Sylvania 12BH7 Curved Plate

Output;
RCA 6080
Mullard 6080
Cetron 7236
GE 6AS7G

Regards,
Dave