[gkg2k]

I got it for $60.00 from Ebay, so it is not a bad deal at all.

Good!

 

[VanHai]

And I am not sure if the GZ30 and 5G4V were actually manufactured by Mullard........

Yes, they manufactured in Blackburn by Mullard. I checked the codes.

 

[gkg2k]

If the tubes have identical construction and the only difference is the color of the base they should sound about the same. The brown base was introduced in the 1950's because it was more resistant to RF noise. But for most of us, our amplifiers are in very quiet and protected spaces. So the brown base is of no benefit in audio.

Very generally, tubes with black bases are older than tubes with brown bases, but not always. And some people think older tubes sound better. But again, not always.

Not always, I agree. There are exceptions, but not in this case IMHO. The earlier black plates and black base 53KU sounds better than the brown/grey one to my ears. Not by a large margin, of course. We're talking about details, but details count.

 

[gkg2k]

Just to be clear. The color of the base has absolutely no effect on the sound. Nonetheless, enjoy.

Gibosi, how do you think the 53KU would compare to the Takatsuki Denki TA-274B? Are there data that allow us to express an opinion?

Thanks!

 

[gibosi]

Gibosi, how do you think the 53KU would compare to the Takatsuki Denki TA-274B? Are there data that allow us to express an opinion?

Thanks!

The only way to know is to compare them in YOUR amp.

Takatsuki Denki TA-274B can provide at most 225mA, the same as a 5U4G.

https://www.takatsuki-denki.co.jp/en/products/ta-274b.html

My Glenn is very power hungry and I need at least 250mA. So even if I could get my hands on one, I dare not use it in my amp.

 

[gkg2k]

Here is a great review of the Takatsuki Denki TA-274B versus the KR Audio 5U4G "Riccardo Kron Anniversary Edition" by @ColSaulTigh :

https://www.head-fi.org/threads/rectifiers-why.305127/page-3#post-16963354

Many thanks to this guy for a very accurate comparison!

 

[VanHai]

Here are some pictures of the Cossor thin bottle 53KU/ GZ37. I think @gibosi is correct, it has characteristics of a Mullard built. Very sweet and smooth, Mid and vocal are beautiful.

 

[gibosi]

Here are some pictures of the Cossor thin bottle 53KU/ GZ37. I think @gibosi is correct, it has characteristics of a Mullard built. Very sweet and smooth, Mid and vocal are beautiful.

Yes indeed, that is a Mullard GZ37.

 

[Thaddy]

I read a bit about this tube earlier on in this thread and wanted to bring it up again. From what I understand there are two variants floating around: the older has a darker base with dual bottom 'D' getters, and the newer has a lighter base with a single bottom getter. I'm unable to make out the date code on my older 5R4GY, but the newer one is pretty clear. I'm assuming it's the 13th week of 1956? The logo definitely gives away it's military heritage.

 

[gibosi]

I read a bit about this tube earlier on in this thread and wanted to bring it up again. From what I understand there are two variants floating around: the older has a darker base with dual bottom 'D' getters, and the newer has a lighter base with a single bottom getter. I'm unable to make out the date code on my older 5R4GY, but the newer one is pretty clear. I'm assuming it's the 13th week of 1956? The logo definitely gives away it's military heritage.

I have never seen an 5R4GY from any manufacturer that didn't have two bottom getter holders, so yours is a new one for me.

Here's an "older" one with a dark base. H = 1944, 5 = the two-month period, Sep to Oct, and E = an Original Equipment Manufacturer, as opposed to a distributor.

 

[Thaddy]

Very cool, I'll have to inspect my double bottom getter a bit more closely to see if I can make out any codes. The single bottom getters appear to be fairly plentiful on eBay, probably worth picking one up to listen to. I believe I got both of mine from vacuumtubes.net, the single getter being a bit cheaper ($35 vs. $75).

Perhaps the single getter was related to the end customer being the US military? Quicker/cheaper to manufacture?

 

[gibosi]

Very cool, I'll have to inspect my double bottom getter a bit more closely to see if I can make out any codes. The single bottom getters appear to be fairly plentiful on eBay, probably worth picking one up to listen to. I believe I got both of mine from vacuumtubes.net, the single getter being a bit cheaper ($35 vs. $75).

Perhaps the single getter was related to the end customer being the US military? Quicker/cheaper to manufacture?

Well, a cheaper tube for use of the US military still had to meet minimum specifications. But manufacturing product more cheaply while still meeting spec is the natural order of business. So I'm inclined to think that due to technological advances, RCA found a way to meet spec with only one getter.

But still, I also have 5R4GY manufactured by NEC, Brimar, Fivre and La Radiotechnique and all of them have two bottom getter holders. So it is interesting that the later RCA has only one. Another mystery. lol

 

[Thaddy]

Well, a cheaper tube for use of the US military still had to meet minimum specifications. But manufacturing product more cheaply while still meeting spec is the natural order of business. So I'm inclined to think that due to technological advances, RCA found a way to meet spec with only one getter.

But still, I also have 5R4GY manufactured by NEC, Brimar, Fivre and La Radiotechnique and all of them have two bottom getter holders. So it is interesting that the later RCA has only one. Another mystery. lol

I think I'm barely able to make out a date code, but the first number appears to be a 6, leading me to believe my 5R4GY dual bottom getter is from 1946?

I also received an RCA 5V4G recently from VacuumTubes.net. Looks to be dated from December of 1948. Hopefully someone wasn't checked out for Christmas and New Years when assembling this one!

 

[gibosi]

I think I'm barely able to make out a date code, but the first number appears to be a 6, leading me to believe my 5R4GY dual bottom getter is from 1946?

I also received an RCA 5V4G recently from VacuumTubes.net. Looks to be dated from December of 1948. Hopefully someone wasn't checked out for Christmas and New Years when assembling this one!

Is the first digit on your 5R4GY a number? Or a letter? If a letter, the tube was likely manufactured before Jan, 1946. If the first digit is a number, then it was manufactured after Dec, 1945.

And so, if the first digit is a "6", it was manufactured in 1946, and the next two digits should be numbers indicating the month.

 

[Thaddy]

Is the first digit on your 5R4GY a number? Or a letter? If a letter, the tube was likely manufactured before Jan, 1946. If the first digit is a number, then it was manufactured after Dec, 1945.

And so, if the first digit is a "6", it was manufactured in 1946, and the next two digits should be numbers indicating the month.

The're all numbers, probably following RCA's "n-nn" scheme. The first digit appears to be a 6. The second two are very hard to make out but the second number appears to be an 8. So, 6-x8.