Building an ECL82 Single Ended Amp ...

[audiowize]

There is positive current feedback via the tap on the output tube cathode resistance back to the driver cathode. Pick the correct point & the output impedance of the amp is lowered. But there will be more distortion.

Yeah, adding distortion to a design like this seems very counter-intuitive, especially when the plate to plate local feedback should be able to do all the corrective work that needs to be done.

My only thought is that the designer may have been worried about reactive components in the feedback loop.

 

[nzoomed]

Can you explain more please? i am new to tubes. This particular circuit was assembled and demonstrated as an example of a simple and good ecl82 amp. I also have seen such a schematic from radio museum.org, Only change being that the plate to plate feedback resistor was 3.3M, whereas the new one shows 330k.

I built this circuit but with ultra linear transformers instead.
Works fine, it does distort when cranked up full, but considering you only get about 1 Watt of output without distortion, you cant really complain.

 

[tnvijay]

I did a quick rough rig up of the circuit that i attached in previous page, Its fine and has good bass,but as the volume is cranked up, I hear distortion. I believe as Forum member audiowise said,since this circuit values are more or less from old record players, The triode is wired for high gain. With modern sources whose output is easily 1v -2v, Is it possible to do a RHuniversal topology with ecl82? Triode plate resistor 100k, Rk triode 390 ohms,Grid to ground resistor in pentode is 220k. Plate to plate feedback 100k. Pentode cathode resistor 330 ohms, B+ 220 volt, Pentode screen grid drop resistor 1k from B+.

Will it work within parameters of the tube?
I am a tube newbie,hence all these doubts.

 

[feiyangdesixu]

I know this is a very old thread, but im looking at building a similar amp, but want to make a 2.1 sound system for my computer, whats the best way to go with this?
Should i add a third channel to the same amp chassis for the sub, or am i better adding a slightly more powerful channel for the sub with a single ended or even push pull pair of el84 tubes? I want to make the system as compact as possible.

1.ECL86 could be better.
2.sub channel 2a3 will be better.

 

[feiyangdesixu]

I did a quick rough rig up of the circuit that i attached in previous page, Its fine and has good bass,but as the volume is cranked up, I hear distortion. I believe as Forum member audiowise said,since this circuit values are more or less from old record players, The triode is wired for high gain. With modern sources whose output is easily 1v -2v, Is it possible to do a RHuniversal topology with ecl82? Triode plate resistor 100k, Rk triode 390 ohms,Grid to ground resistor in pentode is 220k. Plate to plate feedback 100k. Pentode cathode resistor 330 ohms, B+ 220 volt, Pentode screen grid drop resistor 1k from B+.

Will it work within parameters of the tube?
I am a tube newbie,hence all these doubts.

yes , that works ok,I tried it before

 

[tnvijay]

yes , that works ok,I tried it before

Thank-you. Are the values of the components correct? I also assume that one has to keep the Capacitor bypassed at Pentode cathode bias resistor as in original. Am I right? I will try to wire this in a couple of days and get back with results

 

[tnvijay]

I built this circuit but with ultra linear transformers instead.
Works fine, it does distort when cranked up full, but considering you only get about 1 Watt of output without distortion, you cant really complain.

Thank you