• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

SE TESLA E34L

artosalo

Member
2010-02-16 9:00 am
I am looking nice design & schematics, any help will welcome.

Here You are:


[IMGDEAD]http://kuva.termiitti.com/image/14764.gif[/IMGDEAD]


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.
 
Here You are:


[IMGDEAD]http://kuva.termiitti.com/image/14764.gif[/IMGDEAD]


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.
 

artosalo

Member
2010-02-16 9:00 am
Any suggestion will welcome, thanks.

Below is one option.


[IMGDEAD]http://kuva.termiitti.com/image/14766.gif[/IMGDEAD]


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.
 

artosalo

Member
2010-02-16 9:00 am
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.
 

azazello

Member
2008-08-23 7:28 pm
USA
-U bias for EL34 is about 20-22 v and ECC82 with mu about 20 will allmost drive EL34
with input signal 1-1.5 v, that has every CD player. You can try and You will satisfacted. I don't need full driving, for me is important good sound, that has ECC80,82. ECC83 with his sharp sound is only, IMO, for guitar
amplifiers, but not for Hi-End.:) I don't like it and tubes with big mu. I prefer 80, 81, 82, 88, AU7, AT7.....
I make only SE without NFB and I haven't problems with sound, gain, noise, hummm from my 96 db F-x 206E...:)
Schematic is the same, Ra will= about 20 kohm, Rc depend from current, that will be about 5-8-ma. Try without FB.
The choice is Yours!
 

artosalo

Member
2010-02-16 9:00 am
ECC83 with his sharp sound is only, IMO, for guitar
amplifiers, but not for Hi-End.

ECC83 / 12AX7 / 6N2P have excellent linearity, frequency response and of course sound too. However all this reguires proper biasing and right component selection around it.

For sure one can make a bad sounding ECC83 amplifier, but it does not mean that the ECC83 tube has "bad sound" or worse that ECC82. If someone claims this, I would like to see his arguments.

If ECC83 had been a tube with "bad sound", then engineers at such companies like Dynaco, Harman-Kardon and Mac Intosh would have noticed this in time and ceased to use it.
But they did not, and used this type for few decades with the results we all know.
 

azazello

Member
2008-08-23 7:28 pm
USA
If ECC83 had been a tube with "bad sound", then engineers at such companies like Dynaco, Harman-Kardon and Mac Intosh would have noticed this in time and ceased to use it.
Of course....they make amplifiers for markets, for all people that like big gain and big power, with speakers with low sensitivity-83-88 db....This is econ. politic to selling
more stuff. Audionot produce only Hi-End, without 83 or AX7 for some audiophils,that like sound...../BTW, I compared Harman-K with my 2A3 RCA....my
won:)/
 

artosalo

Member
2010-02-16 9:00 am
I have fine-tuned the schematic a little and here it is:

[IMGDEAD]http://kuva.termiitti.com/image/14778.gif[/IMGDEAD]

I put a 470 ohms trimmer pot. at the NFB-loop so that the optimum value of NFB can be easily adjusted. After it is found, fixed resistors can be put instead.

This circuit would also be used with some 300 Volts supply voltage.
Actually with 2,5 kohms anode load (and Ub=300 V) the performance can be optimum. Then the cathode resistor of EL34 (now 120 ohms) must be adjusted to provide such bias that the cathode current do not exceed 90 mA. The value of the cathode resistor would be around 200 ohms, +/- something.
 

azazello

Member
2008-08-23 7:28 pm
USA
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