5U4G vs 5U4GB

[tubeswell]

I recently brought a Sovtek 5U4G for a recto valve for a 5G9 build.

Upon taking to random googling tonight, I notice that the Sovtek 5U4G is claimed to be a substitute for the 5U4GB here and here

http://thetubestore.com/sovtek5u4g.html

http://www.tubedepot.com/so-5u4g.html

So I'm almost convinced, when I happen to see this page (Read Note 4):

http://www.emissionlabs.com/datasheets/EML5U4G.htm

So is the Sovtek "5U4G" not a 5U4G (since it is supposedly a substitute for a 5U4GB), and can I get away with it in my 5G9 build (which has a 40uF first filter stage followed by a choke)?

Or is the Emission Labs 5U4G another beastie?

Or should I be filtering the Sovtek 5U4G the way that Emission Labs suggest filtering their 5U4G? (i.e. with first cap no bigger than 33uF and a choke between the next cap etc).

Can anyone shed any light on my confusion please?

[Le Basseur]

We're talking three different tubes here.
The Emmision Labs is a Czech-made tube and it resembles the Kron/Vaic "steroids" philosophy of building tubes (google a little for the two names from above and you'll see what were they up to...usually,these names are very popular in the Hi-Fi world).Yes,you're right,the EML is a beast in terms of construction details AND size.Unfortunately,I never had such a piece so I really can't comment it in any way.Though,if you wish,the Kron's and Alessa Vaic's versions of tubes such as 300B,2A3,6SN7,etc,are very noticeable (and specific,for that matter) in every aspect.
The Russian 5U4 under the original name: (read phonetically) 5Tz3,as seen @ thetubestore link you posted,is a close relative of the Western/American original 5U4 BUT,if I remember correctly,it has some slightly different data.One is that the Russian drops less voltage than the original 5U4 and the other is a significantly smaller first-cap value.At this moment,I cannot remember exactly the parameters but if you're interested,I'll search for the original Russian spec sheet (the factory one,not the BS posted by different sellers).
Regards,

[stokes]

The 5U4GB is a later version of the 5U4G.You can sub one for the other,there is a slight difference in the ratings.i.e. the G version will drop about 45volts at about 240 ma's while the GB version will drop about 50volts at about 275ma's,these numbers are off the top of my head and are close but not exact.Anyway any difference in the performance or sound will not be very noticeable,if at all.

[tubeswell]

At this moment,I cannot remember exactly the parameters but if you're interested,I'll search for the original Russian spec sheet (the factory one,not the BS posted by different sellers).
Regards,

Puno vam hvala Le Basseur (my grandparents were from Racisce, Korcula).

If you could find that Sovtek 5U4G data sheet, that might help solve the riddle. I've been looking for ages, (can see several data sheets for 5U4GB but can't find a dang thing for Sovtek 5U4G)

Uzdravlje

[Enzo]

I just posted some pages from my old Sylvania 1959 book. Graphs compare the 5U5G and 5U4GB. Look on www.ampix.org in the Enzo collection.

I think anything made today with 5U4 on it should work. ANy differences would be in performance nuance, just as in swapping brands of 6L6 or 12AX7 You may prefer one, but all will work.

[tubeswell]

I just posted some pages from my old Sylvania 1959 book. Look on www.ampix.org in the Enzo collection.

many thanks Enzo :-)

[Enzo]

Just don't assume in this day and age that the distinctions between tube numbers have the same meaning they did 50 years ago. For example there really was a difference between a 12AX7 and a 7025. Now they are just two different numbers for the same tube so it is easier to market them. 6L6GB was an earler 6L6 than the 6L6GC. But now when you see a 6L6GB it is just that brands attemp to make their 6L6 look retro and cool so you'll buy it.