[OctavianH]

I wanted to take a break from EL3N+EL6 which I have listened for several days in a row. Because I wanted something good and interesting, I have decided to try an quite unusual combo and also to put to work my RCA 76 pair. So my try was the Philips PE06/40N with RCA 76. This is a very energetic output, hard to tame and in the past I had good results with it and lower gain input. A good moment for RCA 76 to shine.

A detail of the RCA 76:

This is a step back from the richness of the old european pentodes, but from time to time we need to go back to something else. And these are some of the best out there.

 

[OctavianH]

A morning with some good natural light. Summer is coming and most probably I'll recover some energy.

This PE06/40N was not good with 76, gain too low. I was around 2AM with the volume knob. So I had to do something if I want to understand something from these RCA 76. And solution was simple Mullard EL38 because it was here close to me.

I went around 12AM and now things are more in line. I'll leave these here for a while, the sound is decent. Mullard EL38 was always too polite for me, this was always for me a tube made for sweet mids, like KT66. But well, for mids it's good and RCA bass helps a little bit. Mullard 807 is better for my taste than Mullard EL38. Anyway, I'll spend more times with them because I might change my preferences.

 

[OctavianH]

I could not listen too much to EL38, I really tried, but in the end decided to fix the sound. LOL

So I switched to Philips Sittard ECC40 with Philips Sittard EL41 metal base disc getter. Oh, what a difference.

I said some time ago that old Philips sound killed british sound for me and since then all these famous british tubes sound veiled. It's true.

In order to ensure proper tube rolling I have put the EL38 in their boxes and adapters to storage. Otherwise they will be close and I'll loose another day of listening.

 

[OctavianH]

Today is free HINT day. So let me show you a beautiful datasheet: 6CL6. This tube looks to me very interesting. If I would be still interested in small pentodes, this 7.5W (some US datasheets mention 7.5W, CSF mentions 8.2W) one should be in my interest since it's cheap and might sound better than many others. Might be this one an EL84 alternative? Might be not? I have no idea, but I would look into this one if I would be interested in a nice power/output pentode.

Here:

The CSF datasheet for this one is very beautiful, if CSF manufactured these might be some very nice tubes. Might work digging.

PS. Needs adapter, does not work in EL84 but specwise, I have no idea why I think about that one when I see it.

 

[Isaacc7]

Today is free HINT day. So let me show you a beautiful datasheet: 6CL6. This tube looks to me very interesting. If I would be still interested in small pentodes, this 7.5W (some US datasheets mention 7.5W, CSF mentions 8.2W) one should be in my interest since it's cheap and might sound better than many others. Might be this one an EL84 alternative? Might be not? I have no idea, but I would look into this one if I would be interested in a nice power/output pentode.



Here:



The CSF datasheet for this one is very beautiful, if CSF manufactured these might be some very nice tubes. Might work digging.

PS. Needs adapter, does not work in EL84 but specwise, I have no idea why I think about that one when I see it.

Would be nice if it used the same adapter as the n78. Sigh. No more! Seriously, no more!

Wait, does it use the same adapter as the 6kg6? I have a bunch of those…

No! No more!

Probably…

 

[OctavianH]

Wait, does it use the same adapter as the 6kg6? I have a bunch of those…

That one is magnoval, this is noval. Speaking of which, you can use EL509, that seems to be a VERY interesting tube.

 

[hpamdr]

The CSF datasheet for this one is very beautiful, if CSF manufactured these might be some very nice tubes. Might work digging.

The CSF spec is very nice and in "French" it is also a tube where you have triode strapped curves and measure !
This should be a good sounding tube that last long in the area of 2W by channel. In eternity we bias at 20ma and this one seems a bit more linear in the 40-60ma area. But almost each tube is sounding good in eternity once you find the input tube that match with it.
For US brand, you can give a look at 6677 tube, same construction see Sylvania Spec.
About EL84 adapter and 6CL6 tube, both pinout are too different to work even with some strapping...

 

[Isaacc7]

That one is magnoval, this is noval. Speaking of which, you can use EL509, that seems to be a VERY interesting tube.

Haven’t looked into the el509 but have seen some at prices I wouldn’t want to pay lol. Wish more European tube makers embraced different heater voltages like the Americans did.

 

[Isaacc7]

That one is magnoval, this is noval. Speaking of which, you can use EL509, that seems to be a VERY interesting tube.

Whoops, I have the 6gk6 not the 6kg6. I was looking around and was so confused because they all had top caps. And now I know why they el509 is so expensive, they are, or were, a popular tube for OTL amps. Looks like they have been mostly bought up over the years.

 

[OctavianH]

I studied many tube types recently, but I will try only what has potential for my amplifier and personal preferences. For example EL300/6FN5, EL500 or 6CD6 are interesting for more powerful amplifiers. For me, I am happy that Eternity is able to bias safely older tubes so I can focus on my final and most ambitious project: the european pentode tribute amp. In short, I doubt I will ever try something else, except if it will be very cheap and I will be very bored. I do not need more, because I know what is better than everything I will ever find and I already have a big part of those. So the potential of surpassing my expectations is very low for the types I have not tried.

PS. Forgot about EL5000.

 

[OctavianH]

Product of the day: Vacuum tube puller/inserter.

 

[Isaacc7]

So my amp ordeal was really dumb but at least there is a happy ending.

I was going crazy. Since my Odyssey was giving me distorted sound and the bias meters were bouncing around I had it sidelined until I could get it back to the tech. He was befuddled since it worked fine at his place. In the meantime I was listening to my other amp.

Everything would be working fine and then after a day or two distortion started to creep into the sound eventually getting terrible. Swapped all the tubes in the amp and preamp, no difference. Well, let’s try the other preamp. It sounded good so it must have been the main preamp. But after a few days the distortion started again and got terrible. So then I was giving my amp the side eye but what could cause something like that? Then I remembered that one of the RCA cables was really loose. Hooked the DAC up the amp directly and it was fine for days. It was the damn cable! It must have slowly, slowly worked itself out of the socket by its own weight. I have never experienced this in all my days of doing audio gear. Got some better constructed cables and things are good.

Then I thought, huh, the distortion was the same on the Odyssey. You don’t think… Yup, with new cables my Odyssey is up and running sounding great. Why that would cause the bias to jump around I have no idea. I’m just glad I have my amp working again!

 

[Isaacc7]

Currently using the Russian Tung Sol 7581a in triode with some grey glass 14n7 inputs. Reveling in having my amps working again but will go back to a favorite tube combo in a few days while I put this through its paces. Sounds good but I wonder if part of that is the power 10 watts class A 24watts full out. This is the hardest I’ve run any tubes in the amp, 400v 50ma. I might do the same with the GU50 when I put them back in.

 

[OctavianH]

Then I remembered that one of the RCA cables was really loose. Hooked the DAC up the amp directly and it was fine for days. It was the damn cable!

If you ever find out why a loose cable influences your meters please let me know. By the way, to avoid such problems I use XLR connectors for headphone/interconnects even on SE amplifiers, I always want to have something like this.

 

[hpamdr]

Why that would cause the bias to jump around I have no idea. I’m just glad I have my amp working again!

If you have very bad cable with shortcut, this can cause the bias to bounce... Some tubes like 12E1 can also cause bouncing. But if Bias is swinging without any tube nor any input cable, this is likely you have capacitor ready to die...
I'm using very/building short RCA cable 30cm ~12ft with amphenol or neutrik plugs not too tight not too loose ! Also as said by @OctavianH the best is to use XLR also because the plug is better built and more robust. I have some Vovox sonorus cable on my main system and I'm very happy with it. They also have super long cables 3 - 5 m