[Zachik]

Mischa will be building me an amp similar to the Solar Flare, but with KT66-150 + 6550 + EL34 + 5881 family, no superpowered 300b (or whatever that setting was for the Solar Flare, just regular 300b) and estat out though. I already have a ton of 6J5s so his recommended setup really appeals to me

@A2029 Mischa is awesome and his handy works sounds amazing! Cannot believe how good my Solar Flare sounds driving IEMs. Huge bonus

 

[ARCXENOS]

@A2029 Mischa is awesome and his handy works sounds amazing! Cannot believe how good my Solar Flare sounds driving IEMs. Huge bonus

I have went through every page in the 1101 thread, and he is certainly the person you want to make an amp!

Not to derail this thread any further and to bring it back to EL34 & co....I assume the cheaper Telefunken EL34s aren't likely the real deal, similarly to how the ECC802s have yugo made stuff? Not planning to get anything...yet, but thought I should educate myself beforehand

 

[UntilThen]

.I assume the cheaper Telefunken EL34s aren't likely the real deal

I don't think Telefunken EL34 metal base are cheaper. They can cost a bomb and imo they are very good. Any metal base EL34 are expensive when they are in good condition. Telefunkens in general are leaner in tone and as some will put it, clinical. I just find them to be superb with imaging, clarity and details and yet sounding very sweet.

 

[LoryWiv]

At times in this hobby it seems the more I learn the less I know. This statement is preamble to a question for the tube rolling veterans:

Is it prudent practice to use driver tubes with a lesser heater current than the installed powers tubes' heater current. For example, in my Euforia AE I currently have a pair of Philips EL3N powers (0.9A heater current) driven by a pair of Visseaux 6K6GT (0.4A heater current). I swapped their positions just for craps and giggles and actually quite liked the sonic result, but wonder if it Is it inherently unwise to run them this way from a circuit design / tube longevity perspective. Euforia AE has auto-bias. I understand that the correct answer may vary based on amp. topology and design, but would appreciate any general guidance.

 

[mordy]

At times in this hobby it seems the more I learn the less I know. This statement is preamble to a question for the tube rolling veterans:

Is it prudent practice to use driver tubes with a lesser heater current than the installed powers tubes' heater current. For example, in my Euforia AE I currently have a pair of Philips EL3N powers (0.9A heater current) driven by a pair of Visseaux 6K6GT (0.4A heater current). I swapped their positions just for craps and giggles and actually quite liked the sonic result, but wonder if it Is it inherently unwise to run them this way from a circuit design / tube longevity perspective. Euforia AE has auto-bias. I understand that the correct answer may vary based on amp. topology and design, but would appreciate any general guidance.

From what I learnt the main thing is not to exceed the total current draw that the Euforia amp was designed for. In other words, if the amp was designed for up to 7A, you add up the current draws of each tube, making sure that it does not exceed 7A.
As far as I know it does not matter the position of the tubes. In the event that you reach a little over 7A in this example, say 7.4A, the addition of cooling fans can extend the current capability a little but probably not more than 1/2A in this case.
All the above applies to the Feliks Euforia - a different make may have other limitations.

 

[LoryWiv]

From what I learnt the main thing is not to exceed the total current draw that the Euforia amp was designed for. In other words, if the amp was designed for up to 7A, you add up the current draws of each tube, making sure that it does not exceed 7A.
As far as I know it does not matter the position of the tubes. In the event that you reach a little over 7A in this example, say 7.4A, the addition of cooling fans can extend the current capability a little but probably not more than 1/2A in this case.
All the above applies to the Feliks Euforia - a different make may have other limitations.

Thanks @mordy, I know how experienced you including with Elise / Euforia are and your input means a lot to me. BTW currently listening to Philips EL3N driving Visseaux 6K6GT powers and the result is superb sound!!! Unless anyone indicates this "reversal" is not sound practice ("pun intended"), think I'll stick with this roll for a while!

 

[Xcalibur255]

At times in this hobby it seems the more I learn the less I know. This statement is preamble to a question for the tube rolling veterans:

Is it prudent practice to use driver tubes with a lesser heater current than the installed powers tubes' heater current. For example, in my Euforia AE I currently have a pair of Philips EL3N powers (0.9A heater current) driven by a pair of Visseaux 6K6GT (0.4A heater current). I swapped their positions just for craps and giggles and actually quite liked the sonic result, but wonder if it Is it inherently unwise to run them this way from a circuit design / tube longevity perspective. Euforia AE has auto-bias. I understand that the correct answer may vary based on amp. topology and design, but would appreciate any general guidance.

Auto-bias will take care of the bias current, but the important thing in this case is probably going to be your bias voltage. I don't know the details of the Euforia's design, but going by the driver the plate voltage for the driver socket is likely 250V. If the voltage on the output sockets is also 250V then you're fine, but it could be higher. I think 250V is typical for EL3N but I wouldn't make any assumptions. If your voltage is higher than intended the total heat dissipation of the tube will be higher and its life will be shortened.

As for power transformer requirements, you are likely fine there. All of these tubes have 6.3V heater filaments and likely share a tap on the transformer, so as far as the transformer is concerned nothing has changed and the total heater current draw is the same.

 

[mordy]

All I can say is that in the past I used EL3N tubes in the Elise/Euforia for hundreds of hours without any problems. The tubes ran very cool.

 

[triod750]

If your voltage is higher than intended the total heat dissipation of the tube will be higher and its life will be shortened.

This is what bothers me with these matters. I guess most of the heat from a tube comes from the heaters? Or am I wrong here? If so, the tube could be run too hard with a shortened life even if it is running comparably cool. Please say I'm wrong!

 

[LoryWiv]

All I can say is that in the past I used EL3N tubes in the Elise/Euforia for hundreds of hours without any problems. The tubes ran very cool.

As powers, @mordy?

 

[LoryWiv]

Auto-bias will take care of the bias current, but the important thing in this case is probably going to be your bias voltage. I don't know the details of the Euforia's design, but going by the driver the plate voltage for the driver socket is likely 250V. If the voltage on the output sockets is also 250V then you're fine, but it could be higher. I think 250V is typical for EL3N but I wouldn't make any assumptions. If your voltage is higher than intended the total heat dissipation of the tube will be higher and its life will be shortened.

As for power transformer requirements, you are likely fine there. All of these tubes have 6.3V heater filaments and likely share a tap on the transformer, so as far as the transformer is concerned nothing has changed and the total heater current draw is the same.

Thank you @Xcalibur255, that is very helpful. Note that the standard Powers in Euforia are 6AS7G, data sheet below indicates plate voltage 275 so shouldn't' be too far out of spec. using EL3N, correct?

 

[mordy]

As powers, @mordy?

Four or six of them.

 

[LoryWiv]

Four or six of them.

Interesting, @mordy, although I wonder if that mitigates risk of Euforia delivering excess voltage versus only 2, since the plate voltage is delivered across more tubes. I am probably overthinking things at this point!

 

[mordy]

Interesting, @mordy, although I wonder if that mitigates risk of Euforia delivering excess voltage versus only 2, since the plate voltage is delivered across more tubes. I am probably overthinking things at this point!

Personally, I don't know much about these things. Back in the days we mainly used the EL3N as drivers since it is a predecessor of the 6SN7. Some people were saying that you need some kind of circuitry so that all the power tubes receive equal power if you use a six socket adapter.
I know that Until Then experimented with the EL3N; maybe he can shed more light on the subject.
If you look carefully at the picture you will se six tubes in the power section. There wasn't room for more than four EL3N tubes so I put in two 6BX7 tubes as well.
Today I use six 0.9A tubes with external power as power tubes.

 

[Xcalibur255]

This is what bothers me with these matters. I guess most of the heat from a tube comes from the heaters? Or am I wrong here? If so, the tube could be run too hard with a shortened life even if it is running comparably cool. Please say I'm wrong!

Some of the heat is from the heater, but the dissipation rating refers to plate dissipation which would be from your bias current and voltage. Tubes have a specified maximum plate voltage and current, but they also have a specified maximum dissipation rating that can be arrived at through various combinations of voltage and current. Within reasonable limits you can be a little over on one and a little under on the other and still be okay because the total dissipation is still within the rating. Tubes, especially the really old DHTs, will also typically tolerate some degree of abuse over the maximum rating. This of course reduces lifespan. The reduction isn't linear either. Being just a little over is usually not a very big deal, but if you wind up, say, 20-30% over the max rating the reduction in lifespan becomes rather dramatic. This works in reverse too, with tubes that are operated gently lasting a very very long time in some cases. You can also get carried away enough and drive the tube so hard it actually fails. You usually have to be running a tube is very different than the one the amp was designed for to run into situations like that.