The Reference 6J5 Thread (L63, 6C5, 12J5, 6P5, etc.)

[RBoyd]

Had a Marconi L63 tube pop and die while adjusting the volume on my amp. Tube only had 49 hours on it.
I was curious to have a look inside. (posted this a couple of days ago and the post disappeared)

 

[nwavesailor]

Sorry to hear your Marconi L63 died.

I’m always amazed that we don’t lose more tubes when you consider when many of our NOS tubes were manufactured. You may have only put 49 hours on it (I don’t keep a log with my usage) but it is many decades old and has been holding vacuum for a long time.

 

[steve468]

Some of my favourite tubes are WWII surplus Ken-Rad 6C5 metal cans. All my cans are super quiet tubes, there’s definitely some advantages there. Sometime sound trumps tube glow!

6C5 tubes in general seem to me to be pretty even across the frequency range (except for RCA, they gots a fat bottom for sure), but definitely more intimate than expansive.

 

[mordy]

Some of my favourite tubes are WWII surplus Ken-Rad 6C5 metal cans. All my cans are super quiet tubes, there’s definitely some advantages there. Sometime sound trumps tube glow!

6C5 tubes in general seem to me to be pretty even across the frequency range (except for RCA, they gots a fat bottom for sure), but definitely more intimate than expansive.

I agree! To me the sound is more important than the aesthetics.
The black/rusty Ken-Rads may be ugly ducklings but they sound very good.
I also have some old GE 6C5 with orange print that sound nice.

 

[Xcalibur255]

There are two brands I've personally given up on because I've consistently had problems with them: the ST style Marconi L63 because they pop and develop shorts, and the Ken-Rads because they always have noise problems severe enough to make them unusable (usually the low pitch moooooooooaning hum).

Which is a terrible shame because both of these tubes sound fantastic and their tone matches up very well to my preferences. The Ken-Rads in particular are just lovely sounding tubes tonally, but I've gone through a bunch of them at this point and every single one has ended up unusable from noise problems.

I'm starting to develop a bit of a pragmatic side and just stick with tubes styles that have been reliable. I've been in this hobby long enough now to observe that some of the old brands definitely had better overall quality than others. For example I don't think I've ever had a bad or noisy Sylvania tube of any type. Tung-Sols are also consistently good for me. But, man, as much as I love the Ken-Rad sound I think I'm done playing the lottery for good at this point.

 

[shwnwllms]

But, man, as much as I love the Ken-Rad sound I think I'm done playing the lottery for good at this point.

I feel the same way about Fivre. Every tube I’ve bought has been significantly noisier than other manufacturers. Not specific to a certain type or time period either (even the rectifiers suffered from this). I feel cursed when it comes to Fivre so I avoid them like the plague (which is too bad since I do enjoy their house sound)

 

[shwnwllms]

And now back to our regularly scheduled programming…

 

[leftside]

And now back to our regularly scheduled programming…

When is a Cossor 6C5G not a Cossor 6C5G?

 

[shwnwllms]

When is a Cossor 6C5G not a Cossor 6C5G?

When it’s a GEC 6J5G L63

 

[triod750]

There are two brands I've personally given up on because I've consistently had problems with them: the ST style Marconi L63 because they pop and develop shorts, and the Ken-Rads because they always have noise problems severe enough to make them unusable (usually the low pitch moooooooooaning hum).

Which is a terrible shame because both of these tubes sound fantastic and their tone matches up very well to my preferences. The Ken-Rads in particular are just lovely sounding tubes tonally, but I've gone through a bunch of them at this point and every single one has ended up unusable from noise problems.

I'm starting to develop a bit of a pragmatic side and just stick with tubes styles that have been reliable. I've been in this hobby long enough now to observe that some of the old brands definitely had better overall quality than others. For example I don't think I've ever had a bad or noisy Sylvania tube of any type. Tung-Sols are also consistently good for me. But, man, as much as I love the Ken-Rad sound I think I'm done playing the lottery for good at this point.

I have Brimar branded Ken-Rad made 6J5GT/G that are completely silent, several pairs. My metal Ken-Rad 6C5 are also silent. I might be fortunate but if so, it is completely new for me. Do you mean 6J5G?

 

[triod750]

There is a first for most things. On Sunday I broke my first key pin, unfortunately on my Ken-Rad 6C5. I don't want to use it until I have repaired it so I put in a spare. SQ took a big blow but I tried to endure. Last night another first happened. The sound level suddenly raised considerably, so much so that I had to use the volume pot. The good thing was that the sound quality raised too.

A couple of hours ago I put in my pair of Westinghouse Canada made 6C5. They haven't been used much and didn't sound good this time either, rather small and compressed. I endured. You know it already, suddenly the sound level raised considerably, so much so that I had to use the volume pot. The good thing is that the sound quality raised too. Now I don't need to endure, just to enjoy. These beautiful black metal cans have nice print in orange as you can see in this post: https://www.head-fi.org/threads/the-reference-6j5-thread-l63-6c5-12j5-6p5-etc.934653/post-18043835 But most of their beauty reaches my ears, not my eyes. This is the reason for me to use headphones, not glasses. (Well, I use glasses too but often close my eyes when I listen).

The moral of this is that bad sounding tubes can actually be very good, but rarely from start. You weren't born as wonderful that you are today either. We all need time to flourish, tubes too. So don't jump to conclusions...

 

[mordy]

There is a first for most things. On Sunday I broke my first key pin, unfortunately on my Ken-Rad 6C5. I don't want to use it until I have repaired it so I put in a spare. SQ took a big blow but I tried to endure. Last night another first happened. The sound level suddenly raised considerably, so much so that I had to use the volume pot. The good thing was that the sound quality raised too.

A couple of hours ago I put in my pair of Westinghouse Canada made 6C5. They haven't been used much and didn't sound good this time either, rather small and compressed. I endured. You know it already, suddenly the sound level raised considerably, so much so that I had to use the volume pot. The good thing is that the sound quality raised too. Now I don't need to endure, just to enjoy. These beautiful black metal cans have nice print in orange as you can see in this post: https://www.head-fi.org/threads/the-reference-6j5-thread-l63-6c5-12j5-6p5-etc.934653/post-18043835 But most of their beauty reaches my ears, not my eyes. This is the reason for me to use headphones, not glasses. (Well, I use glasses too but often close my eyes when I listen).

The moral of this is that bad sounding tubes can actually be very good, but rarely from start. You weren't born as wonderful that you are today either. We all need time to flourish, tubes too. So don't jump to conclusions...

I have broken several guide pins, and even worse, on a couple of adapters as well. But no problem - I just put on a little sticker on the base to indicate the position of the notch on the guide pin. In the event you aren't sure where the notch was, you can usually see it as a small notch on the base where it was located.
I tried a few times to glue back the guide pin but wasn't able to make it hold. There are kits you can buy to add a guide pin in the place of a broken one but personally I don't have a need for it. And if the guide pin is stuck in the socket on the amp you can usually shake it out by turning the amp upside down.

 

[shwnwllms]

I have broken several guide pins, and even worse, on a couple of adapters as well. But no problem - I just put on a little sticker on the base to indicate the position of the notch on the guide pin.

White out pen works wonders as well

 

[AnyDave]

There is a first for most things. On Sunday I broke my first key pin, unfortunately on my Ken-Rad 6C5. I don't want to use it until I have repaired it so I put in a spare. SQ took a big blow but I tried to endure. Last night another first happened. The sound level suddenly raised considerably, so much so that I had to use the volume pot. The good thing was that the sound quality raised too.

A couple of hours ago I put in my pair of Westinghouse Canada made 6C5. They haven't been used much and didn't sound good this time either, rather small and compressed. I endured. You know it already, suddenly the sound level raised considerably, so much so that I had to use the volume pot. The good thing is that the sound quality raised too. Now I don't need to endure, just to enjoy. These beautiful black metal cans have nice print in orange as you can see in this post: https://www.head-fi.org/threads/the-reference-6j5-thread-l63-6c5-12j5-6p5-etc.934653/post-18043835 But most of their beauty reaches my ears, not my eyes. This is the reason for me to use headphones, not glasses. (Well, I use glasses too but often close my eyes when I listen).

The moral of this is that bad sounding tubes can actually be very good, but rarely from start. You weren't born as wonderful that you are today either. We all need time to flourish, tubes too. So don't jump to conclusions...

If you or one of your friends have a 3D printer, there are open source files for printing your own adapters to add the key back.

 

[triod750]

If you or one of your friends have a 3D printer, there are open source files for printing your own adapters to add the key back.

Good to know, thanks. Unfortunately my friends like myself are too old for such thingmajigs. I don't even use a 'smartphone'.

I worry about the unprotected glass protruding under the tube. It could break when I remove the tube from the double adapter next time. The grip in the socket is very firm so I have to use a tool to pry it loose. I guess this broke the key in the first place. There is a superglue, Permabond 920, that stands temps up to 250 degrees C. I will try to find this and also use it for a loose top contact.