[Isaacc7]

Gotta say, I get a kick out of people using tubes engineered for high power output to power headphones. I’m sure the GEC engineers would be confused if they knew their high power tube was being used in single ended triode mode. Mind you, all those engineers probably switched over to solid state once the devices become good enough.

I have finally started using the GU50. This tube is one of the reasons I wanted to be able to use 12v output tubes. There really aren’t that many 12v output tubes that aren’t just 12v versions of 6v tubes so I don’t usually recommend spending the extra to have the abilty to do it. Sure, you can get 12aq5 or 12v6 cheaper than the 6v versions but the most desirable versions of the 6v versions weren’t made with 12v. The GU50 might be reason enough to get the option though, I’ve been really impressed.

The *av5 tubes are supposed to emulate a 2a3 when wired in triode. I do think that the Sylvania 12av5 did a pretty good imitation of a 2a3. I got a lot of the same impressions that I have gotten from 2a3 based amps in the past. I’ve never heard a 2a3 push pull amp before but there is a distinctive clarity and pure tone in the bass that I am getting with the 12av5 in triode. If you believe the internet, the GU50 is supposed to emulate a 300b when wired in triode. I’m trying not to let my preconceptions color my impressions but… What can I say? The audiophile’s mind is an easy thing to influence lol.

I’ve only got about 20 hours the the GU50 so far but they are opening up quite nicely. They are, like the 300b, giving me a presentation that emphasizes naturalness and tonal purity. Brand knew the bass was pretty loose but things have tightened up considerably since then. I’ll continue letting them break in over the next week. Currently driving them with a quad of Raytheon 12j5w GT.

 

[OctavianH]

Some photos for the thread: RCA 6L6. One of the pioneers.

And boxes with printing on all sides:

A detail on one of the tubes (all are similar):

 

[Xcalibur255]

Recently one of my Sophia EL34ST tubes has begun producing a snapping sound just as it comes on bias. About like snapping your fingers but faster and higher pitch. Do you think this is a cathode short developing? It's grown in intensity the last 3 power cycles as well so whatever it is it is worsening.

I've had the "loud pop of death" type of short in a tube before but this snapping noise seems a little different.

 

[LoryWiv]

Recently one of my Sophia EL34ST tubes has begun producing a snapping sound just as it comes on bias. About like snapping your fingers but faster and higher pitch. Do you think this is a cathode short developing? It's grown in intensity the last 3 power cycles as well so whatever it is it is worsening.

I've had the "loud pop of death" type of short in a tube before but this snapping noise seems a little different.

I had a similar noise in tubes recently that I think was RF interference and moving my router farther away eliminated it. Obviously may be different for you but worth a try as applicable.

 

[Xcalibur255]

This sounds almost exactly like the snapping sound of an electric starter on a grill. I'm pretty sure it's a short but was curious what other people thought too. The soldering on the pins on these always looked really iffy to me too. A shame since I think these tubes sound really good but the quality is pretty sketchy for the price.

 

[Isaacc7]

This sounds almost exactly like the snapping sound of an electric starter on a grill. I'm pretty sure it's a short but was curious what other people thought too. The soldering on the pins on these always looked really iffy to me too. A shame since I think these tubes sound really good but the quality is pretty sketchy for the price.

I don’t think I’d keep using that tube. Maybe you could resolder it?

 

[Isaacc7]

Finally listening to the kt81. I am using them in my single ended pentode amp. Had to rotate a few input tubes to find a good match and I think my Fivre made b36 is the best I can use in this amp. The kt81 is a kt61 with a loctal base. I have yet to be disappointed by an MOV (GEC, Osram, Marconi) tube so I was eager to try these.

Maybe it’s confirmation bias but I do think these are giving me as good a sound as I’ve ever had with this amp. It is giving me that elusive combo of warmth and clarity. Plus it offers a nice, rounded sense of bass. Kind of like a modern take of the classic tube sound I guess. Very satisfying. KT61 keep going up in price, the kt81 is still pretty reasonable when you can find them. They use the same adapter as the 7c5 which has some people saying that the kt81 is equivalent. It is not. The kt81 has slightly lower ratings so keep that in mind if you want to use them.

 

[Isaacc7]

I have now switched over to using the Sylvania 6bg6ga with the Fivre made b36 input tubes. This combo gives me a super solid sound, especially through the middle and low midrange. Super nice on voices, guitars, and string instruments in general. These are the ones with 7027a guts inside of them and supplied in government white boxes. I think I paid $10 A tube. Best 10 buck tube out there!

 

[Designsfx]

Not sure if the tube in question actually fits within the grouping of this thread but I’m wondering if anyone can provide insight as to the qualities of a tube known as the “E235L”.

 

[OctavianH]

Not sure if the tube in question actually fits within the grouping of this thread but I’m wondering if anyone can provide insight as to the qualities of a tube known as the “E235L”.

I wanted to try this E235L tube, made by Siemens, on my amp and had no success. It is normally an EL36 equivalent which has to work natively on 6V6/6L6 wired sockets. On the tube tester the tube behaved normally while on my amp behaved strange: currents raised to maximum in the first seconds. I use manual grid bias on my amp and this might have been the cause because this is a high transconductance tube. I have no idea how it sounds, I advise caution with it if nobody confirms it works on your amplifier or DAC (I think you want it for your Lampi).

This is the tube I am speaking of:

 

[Designsfx]

I wanted to try this E235L tube, made by Siemens, on my amp and had no success. It is normally an EL36 equivalent which has to work natively on 6V6/6L6 wired sockets. On the tube tester the tube behaved normally while on my amp behaved strange: currents raised to maximum in the first seconds. I use manual grid bias on my amp and this might have been the cause because this is a high transconductance tube. I have no idea how it sounds, I advise caution with it if nobody confirms it works on your amplifier or DAC (I think you want it for your Lampi).

This is the tube I am speaking of:

Thanks Octavian- when looking at your pics I realized I was looking at the exact same tube last night (same markings as in the lower picture). Per your comments I did read something regarding cathode bias vs manual which might have to due with your experience. It was in an online article regarding its use in a DIY amplifier.

 

[Designsfx]

Here’s a picture of the DIY amp project I was reading about- I’m not sure what to say about this.

 

[triod750]

Here’s a picture of the DIY amp project I was reading about- I’m not sure what to say about this.

Buy before you try .

I put a pair in my amp with cathode bias and the heaters lit up but the tube didn't draw any current and not a sound. First I waited less than a minute (the power tubes usually start to work within less than tweny seconds). Second try waited one minute. Third try three minutes. Same result.

 

[bcowen]

Here’s a picture of the DIY amp project I was reading about- I’m not sure what to say about this.

Have to give points for creativity if nothing else. Wonder how it sounds?

 

[Isaacc7]

Buy before you try .

I put a pair in my amp with cathode bias and the heaters lit up but the tube didn't draw any current and not a sound. First I waited less than a minute (the power tubes usually start to work within less than tweny seconds). Second try waited one minute. Third try three minutes. Same result.

That’s the thing about cathode bias. If it’s set too low the tube won’t start moving electrons. Cathode bias is great as long as the tube you’re using can function at the bias made for you. And then even if it “works “ it might be too far outside the optimal settings to sound good.