SE TESLA E34L

[merlin el mago]

I have 2 tubes Tesla E34L without use & want to do two SE triode mono amps with only 1 tube per channel, I am looking nice design & schematics, any help will welcome.

[artosalo]

I am looking nice design & schematics, any help will welcome.

Here You are:





But I do not suggest triode connection as you wanted to build.

This circuit is an UL-connected output stage. It's sensitivity is some 0,5 Vrms for 50 mW out. So with a CD-player having 2 Vrms output voltage you can get some 0,5...0,6 W, while full capability of this circuit is some 10 to 11 W out. This requires some 8,7 Vrms input voltage.

If this circuit were triode connected the sensitivity would be much lower.
To get 50 mW out, some 1,7 Vrms input voltage is needed.
The full power of triode connection is about 6 W. To get this, you would need almost 19 Vrms input voltage.

To get a real SE-amplifier, a voltage amplifying stage must be added before the EL34. Then the triode connection would have some sense.

[merlin el mago]

Originally Posted by artosalo

Here You are:





But I do not suggest triode connection as you wanted to build.

This circuit is an UL-connected output stage. It's sensitivity is some 0,5 Vrms for 50 mW out. So with a CD-player having 2 Vrms output voltage you can get some 0,5...0,6 W, while full capability of this circuit is some 10 to 11 W out. This requires some 8,7 Vrms input voltage.

If this circuit were triode connected the sensitivity would be much lower.
To get 50 mW out, some 1,7 Vrms input voltage is needed.
The full power of triode connection is about 6 W. To get this, you would need almost 19 Vrms input voltage.

To get a real SE-amplifier, a voltage amplifying stage must be added before the EL34. Then the triode connection would have some sense.

Thanks for help, you are right will do a SE-amplifier with a 1st voltage amplifying stage so can be SE triode? I have on hand:

2 tubes Sovtek 12AX7WXT
2 tubes Sovtek 12AXTWA
2 tubes Sovtek 6922
4 tubes RSD ECC83
2 tubes Siemens E283CC
1 tube National ECC82
3 tubes EI long anode ECC81
4 tubes EI long anode ECC83
3 tubes EI long anode ECC82

Any suggestion will welcome, thanks.

[azazello]

ECC82 is more suitable for prestage with very good sound.

[artosalo]

Any suggestion will welcome, thanks.

Below is one option.





I calculated this amplifier with 12AX7 / ECC83. Connected as above the amplification of 1st stage is about 51. Therefore the sensitivity becomes 8,7 V / 51 = 170 mV. Then there is also some gain reserve to add suitable amount of negative feedback. I selected the input sensitivity of 0,5 Vrms for full output. Then the amount of feedback would be 20 log (0,5 V / 0,17 V) = 9,4 dB. This will give reasonable low output impedance, lower distortion and improved frequency response.

ECC82 is more suitable for prestage with very good sound.

ECC82 is also a good voltage amplifying tube, but in this case it's low gain
would lead to worse final result. The required input voltage would be essentially higher or there would be no spare gain to utilize NFB.

[azazello]

I, prefer IMO, tube with good sound, than tube with good gain....
For me, sound is more important than gain! And ECC82 is sounding
better and its gain is enough to drive E34L from every CD or cassette player or RIAA....

[artosalo]

And ECC82 is sounding
better and its gain is enough to drive E34L from every CD or cassette player or RIAA....

You hereby invited to present your version of the voltage amplifying stage. Please let us also know the input sensitivity and possible NFB your desing applies.

[merlin el mago]

Originally Posted by azazello

I, prefer IMO, tube with good sound, than tube with good gain....
For me, sound is more important than gain! And ECC82 is sounding
better and its gain is enough to drive E34L from every CD or cassette player or RIAA....

Could you post the schematic with ECC82?

[artosalo]

Could you post the schematic with ECC82?

I am waiting that too.

But the fact is that the gain of single ECC82-half is not sufficient.
The input sensitivity would be some 0,65 Vrms without negative feedback.
Although the 1 Vrms input level would be acceptable, there would be only some 3 dB left for NFB. This would lead to insufficient loudspeaker damping
and just average linearity.

However, as such, somebody could say that it sounds great.
But for me, the amplifier must sound good and perfomd good at tests.

[nicoch58]

el84 but some idee....

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