[leftside]

Drooling all over myself. Love that design @leftside

Thanks. I will take credit for the design (you can see the history of the build over on the 1101 thread), and yes I "borrowed" features/ideas from Glenn's amps, but the actual build was performed by the highly skilled @A2029

 

[Hansotek]

Thanks. I will take credit for the design (you can see the history of the build over on the 1101 thread), and yes I "borrowed" features/ideas from Glenn's amps, but the actual build was performed by the highly skilled @A2029

Oh don't worry, I took the liberty of cyberstalking your amp already.

 

[chrisdrop]

GEC L63/ CV1067 Straight Tubes

These are going to be next to go in.

I believe the codes on them are:

• Ut for the date code. That makes this tube 1963, but still not clear on the lowercase t...
• Z for the Plant = MO Valve Co. Hammersmith

I got a good deal on these so I grabbed them. I will update the post when I get > 50h or so on them to talk sound...

EDIT #1: Interesting that these tubes sound pretty good right away. One hour in the amp and they already sound nice. I'm surprised also because my coke-bottle GEC 6J5Gs took FOREVER to change/calm. Will these change or stay?

 

[leftside]

GEC L63/ CV1067 Straight Tubes

These are going to be next to go in.

I believe the codes on them are:

• Ut for the date code I found this via google "Prior to 1969 the they were two digits using letters rather than numbers....the first is the year and second is the month. The months started at A for January, and the year started at A for 1939.". The 2nd digit somewhat confounds me (lowercase t for the month?). I guess that makes this tube ~1960, but still not clear on the lowercase t...
• Z for the Plant = MO Valve Co. Hammersmith

I got a good deal on these so I grabbed them. I will update the post when I get > 50h or so on them to talk sound...

EDIT #1: Interesting that these tubes sound pretty good right away. One hour in the amp and they already sound nice. I'm surprised also because my coke-bottle GEC 6J5Gs took FOREVER to change/calm. Will these change or stay?

A = 1945 for the year. Good luck figuring out the date codes before 1945...

Those GEC L63 come in two slight variations - the rarer earlier 'D' getter and the latter 'O' getter. I can't tell if there's any difference in sound though. The versions before these had black base and either cup getter (first version) or 'D' getter:
https://www.ebay.co.uk/itm/2-x-L63-MARCONI-6J5G-MWT-BRAND-TUBE-NOS-NIB-RCB383/133404627942

 

[chrisdrop]

A = 1945 for the year. Good luck figuring out the date codes before 1945...
Those GEC L63 come in two slight variations - the rarer earlier 'D' getter and the latter 'O' getter. I can't tell if there's any difference in sound though. The versions before these had black base and either cup getter (first version) or 'D' getter:
https://www.ebay.co.uk/itm/2-x-L63-MARCONI-6J5G-MWT-BRAND-TUBE-NOS-NIB-RCB383/133404627942

Hey there. How sure are you w/ the A=1945 vs A=1939?
Googling gave A=1939 and they switch date code styles in 1969.

@leftside - now for dumb question-time. When you say getter type, are you referring to the inner getter structure shape or the silvery flashing shape?

 

[leftside]

Hey there. How sure are you w/ the A=1945 vs A=1939?
Googling gave A=1939 and they switch date code styles in 1969.

@leftside - now for dumb question-time. When you say getter type, are you referring to the inner getter structure shape or the silvery flashing shape?

Google again Also do the math of 'A' starting from 1945 to 1969 (with a couple of letters/years missed out)
https://www.diyaudio.com/forums/tubes-valves/16854-gec-date-codes.html

The getter is the piece of wire that looks like a 'D', 'O' (or halo) and earlier getters look like a piece of foil/spade, inverted tray, inverted cup, flat saucer, etc. For a surprising change, most tube manufacturers seemed to use the different getters around the same time, so it's relatively easy to spot an earlier tube. Of course companies like GEC would occasionally use spare parts lying around - so you might see one of the earlier getters in one of the latter tubes!

A lot of the 6J5 tubes I've seen have the earlier foil/spade getters - especially the ones with the metal base. If you're wondering why a particular tube goes for more than a very similar looking tube - it's often because the more expensive tube has one of the earlier getters and black plates. Not always the case... but more often than not. Edit: the 6J5 metal base seem to be an exception to the norm - grab them while you can

 

[mordy]

Sylvania 6J5GT/VT-94D (metal base)

As per @leftside's comment, I rolled in some Sylvania 6J5GTs today.

These tubes were, for some period of time (probably during Christmas this past year) my most reliable, oft returned to inputs. It is nice to have them back for listening today. Rolling from the Fivres pictured above, a few things are noticeable. By contrast, the Sylvanias are a bit warmer and fuller in the lower end. They have solid representation across the spectrum. They don't sparkle quite like the Fivres, but that is their key trait. I could happily live with these for some time. I consider them neutral to slightly warm with a good sized stage.

These are not expensive tubes FYI. I think they can be had for $10-$20 each NOS.

I don't know the date of these things. I don't have good notes on Sylvania date codes.

Hi Chrisdrop,
Enjoyed reading through your posts!
Re dating the Sylvania: The VT designation is a US military designation and very hard to decipher lol - it means Vacuum Tube. Usually VT means from around WW2.
The SC 966 A probably is a quality inspection stamp (like the Russian OTK stamp) and possibly means Signal Corps Inspector 966A.
What about the date code? Well, you already have the calculator with you - your fingers! One tube has silk screened on the glass K 4 and the other G 4. The letters denote the month. Counting the alphabet on my fingers G is the 7th letter = July; K is a little more difficult (lol); let's see - 11th letter = November (Did I get it right?)
The 4 should be 1944.
JAN is military: Joint Army and Navy. It also means that the tube has to meet some more exacting military tolerances.
CHS is the military designation for Sylvania.

 

[L0rdGwyn]

I have been meaning to contribute something to this thread, thought I'd post some pictures of my Fivre 6C5G collection.

Here are the earliest model, black base, mesh shields, wire spacers. The bottle of these tubes is a bit taller and skinnier than the later models, have some interesting decals as well. All of these tubes are early makes with foil getters, the getters are suspended from the internal shields, which are grounded through pin 1.



Next are the somewhat more common type, brown bases, shorter bottle, mesh shields, wires are replaced by mica. It is a common misconception that the earlier makes of European tubes (Mullard, GEC, Fivre, etc.) have brown bases, but it is actually the black bases that came first.



Last type is somewhat unique, at least I have only ever seen one pair, with brown bases and solid shields.



Here are some of the earliest type in my amplifier. Very nice smooth Fivre midrange, slightly warm, very nice tubes.

 

[leftside]

I have been meaning to contribute something to this thread, thought I'd post some pictures of my Fivre 6C5G collection.

Here are the earliest model, black base, mesh shields, wire spacers. The bottle of these tubes is a bit taller and skinnier than the later models, have some interesting decals as well. All of these tubes are early makes with foil getters, the getters are suspended from the internal shields, which are grounded through pin 1.



Next are the somewhat more common type, brown bases, shorter bottle, mesh shields, wires are replaced by mica. It is a common misconception that the earlier makes of European tubes (Mullard, GEC, Fivre, etc.) have brown bases, but it is actually the black bases that came first.



Last type is somewhat unique, at least I have only ever seen one pair, with brown bases and solid shields.



Here are some of the earliest type in my amplifier. Very nice smooth Fivre midrange, slightly warm, very nice tubes.

Very nice! I find the 6C5 to be very similar to the 76 in my amp. Lighter/airy/spacious sound. Great to have in your arsenal of tubes.

 

[chrisdrop]

I have been meaning to contribute something to this thread, thought I'd post some pictures of my Fivre 6C5G collection.

Here are the earliest model, black base, mesh shields, wire spacers. The bottle of these tubes is a bit taller and skinnier than the later models, have some interesting decals as well. All of these tubes are early makes with foil getters, the getters are suspended from the internal shields, which are grounded through pin 1.



Next are the somewhat more common type, brown bases, shorter bottle, mesh shields, wires are replaced by mica. It is a common misconception that the earlier makes of European tubes (Mullard, GEC, Fivre, etc.) have brown bases, but it is actually the black bases that came first.



Last type is somewhat unique, at least I have only ever seen one pair, with brown bases and solid shields.



Here are some of the earliest type in my amplifier. Very nice smooth Fivre midrange, slightly warm, very nice tubes.

All of those are beautiful. I think Fivres in general are physically lovely. The labels make them look ... Italian I guess - LOL. I am sad I will not be heading over to Italy for a normal summer break I must admit, so perhaps I'll have to import some more Italian tube-charm.

Posts like yours make me want to collect these little beauties even more. I had been on a multi-month metal casing tube listening. Posts like this make me want aesthetically beautiful tubes that sound great and look great too.

Here are the earliest model, black base, mesh shields, wire spacers.

Regarding the dating/age; are they labelled/dated, or do you know the history of construction? It reminds me of @leftside's comments above on getters; you can infer the age/era based on the getter style. The base style, getter style, etc all give you info on the age. Fascinating.

 

[L0rdGwyn]

Very nice! I find the 6C5 to be very similar to the 76 in my amp. Lighter/airy/spacious sound. Great to have in your arsenal of tubes.

Nice looking tubes and still widely available I'll put them on the short list to try out some day.

Regarding the dating/age; are they labelled/dated, or do you know the history of construction? It reminds me of @leftside's comments above on getters; you can infer the age/era based on the getter style. The base style, getter style, etc all give you info on the age. Fascinating.

Hey Chris - they have codes, but no explicit dates, I can't make sense of them and have never found a resource on Fivre. For instance, one says 7/F, another 1/B, but then another says 3/6 (I think? hard to make out the second character). Perhaps the first is the year the second the month, 7/F could be June of 1947, for example, and 1/B February 1951.

This is a nice summary of the Italian tube manufacturers from Radiomuseum: https://www.radiomuseum.org/forum/a...largest all,by distinctive violet-glass bulbs.

Specific information on Fivre is somewhat sparse it seems.

 

[mordy]

I have been meaning to contribute something to this thread, thought I'd post some pictures of my Fivre 6C5G collection.

Here are the earliest model, black base, mesh shields, wire spacers. The bottle of these tubes is a bit taller and skinnier than the later models, have some interesting decals as well. All of these tubes are early makes with foil getters, the getters are suspended from the internal shields, which are grounded through pin 1.



Next are the somewhat more common type, brown bases, shorter bottle, mesh shields, wires are replaced by mica. It is a common misconception that the earlier makes of European tubes (Mullard, GEC, Fivre, etc.) have brown bases, but it is actually the black bases that came first.



Last type is somewhat unique, at least I have only ever seen one pair, with brown bases and solid shields.



Here are some of the earliest type in my amplifier. Very nice smooth Fivre midrange, slightly warm, very nice tubes.

Hi LG,
Are there any differences in the sound between the different Fivre variations of the 6C5G?
Re the brown and black bases, I read somewhere that the brown bases was a development with better characteristics but I think that this only refers to US made (Tung Sol (?) tubes - found this quote:
According to the TungSol manual, the difference is the brown micanol base, which minimized leakage and gas currents
Cannot verify if there is any substance to this claim.

 

[L0rdGwyn]

Hi LG,
Are there any differences in the sound between the different Fivre variations of the 6C5G?
Re the brown and black bases, I read somewhere that the brown bases was a development with better characteristics but I think that this only refers to US made (Tung Sol (?) tubes - found this quote:
According to the TungSol manual, the difference is the brown micanol base, which minimized leakage and gas currents
Cannot verify if there is any substance to this claim.

Did a little A-Bing on the different Fivre 6C5G builds, I had not compared them critically before. There are easily discernible differences, the early black base are more airy and detailed than the brown, smoother, the brown base are a little more "up front and personal" in the midrange, the black base seem more even across the frequency spectrum, handle greater complexity of music with more ease, larger soundstage, more diffuse whereas the brown base staging is more round with more clearly defined boundaries.

Been doing a lot of tube comparisons today, it has been a while since I have. I acquired about half this collection of Fivre 6C5G while working on other things and never got around to doing any critical listening with the black bases. Since I already had them in and I was so impressed, I kept going and compared them to the gray glass GEC L63, can't believe it, maybe tastes are changing, but I prefer the black base Fivre...so they stay. Guess I have a new daily driver, maybe it is tube synergy or just my mood, I am seeking a sort of "easy on the ears" sound lately, which isn't to say the L63 aren't, but the Fivre are very chill and smooth. I'll double back in a few days to be sure.

 

[CAJames]

Black gold:

Adapters in Never-Never-Land so I can't tell you how they sound, but the tubes are starting to arrive. Tung-Sol 6C5s across the top and a smorgasbord of 6J5s on the bottom. I'm surprised how small the tubes are, they are adorable!

 

[mordy]

Great condition und rost-frei! I have all of these, and you will be very pleased with them!