An externally hosted image should be here but it was not working when we last tested it.
11v output of more appalling, though not the maximum output, but the waveform has been difficult to read, both up and down the clipping. Then the output power 15.18w. But fully consistent EL153 characteristic Degen given by the manufacturer with the original set of impedance 2.5k load line situation. Full power output up and down has clipping.
Yeah, right, sure..... Throw away your 6SN7's too they are mixer/multivibrators.
el153 via the output transformer as a load, via the load curve can be seen EL153 anode output voltage p-p550v, via 16.7v transformer turns ratio, P-P33V about theoretical output voltage. That is 11.67vRMS. In this case the theoretical maximum output power RMS = 17w. 14.83v given value for the calculation software standard tolerance. Transformer design efficiency of about 87%, in theory, the circuit output 12-14wRMS without any problems. 90 F, the full power output of the test results, 8 ohms RMS ended output voltage up to 12v, the output 11vRMS still very high fidelity. Output Power Output RMS12v time is 18w.
With simulation, circuit came out. Circuit in the device values are estimated values, the specific use of the device value will be adjusted according to the test after completion.
1. Why is the EF80 G2 Voltage so low? In the datasheet, the minimum shown in examples is 170 V.
2. Why is the load resistor so high? If you look at the graph, you will see load resistances of 8,, 27 K Ohms look more normal.
3.What are the cathode and G2 currents of the 1st stage? I suspect they are too low, and the Rout is too high. Can it drive the input capacitance of the EL153 well , in high frequencies?
Thank you for sharing your DIY
First of all, I feel you have to understand how to interpret tube triode curves. Pentode, a second gate, a third have access to the anode gate, the curve on the same tube triode. The isolated individual link power when it will produce great changes. The change is not the same as the voltage is different. The following figure shows ef80 tube G3 = 0v, G1 = 0v, G2 curves at different voltages. It can be seen as the G2 voltage reduction to change its operating point.
Flexible application G2 \ G3 voltage can make pentode work in the best area to minimize distortion, or to better fit the tube stage to achieve the purpose of minimum distortion.
Master G2 \ G3 application through the following means:
1, simulation software
2, illustrating characteristics of tube instrument
3, the oscilloscope with FFT function
4, experience and explore
It is not in itself a problem of quality tubes, which can be used both side. Correctly grasp, flexible use, it is the essence.
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About 2,3 answer your question:
Because it reduced voltage operating point G2 dramatically changed. Resistive anode, a cathode resistor, the current selection is determined based on 100V when G2 =.
I am sorry, I expected more facts and justification. Playing around in simulation with circuit values until distortion looks good is not a path I take. It also depends a lot on the quality of the modelling. I go with the published curves.
In post #61, your output voltage is clipped on the bottom side only. You need to correct your biasing to get symmetric clipping.
In post #61, your output voltage is clipped on the bottom side only. You need to correct your biasing to get symmetric clipping.
The figure is not considered an output distortion of oscilloscope image , and manufacturers to provide consistent parameter map. If the state at this time to adjust the upper and lower waveforms consistent, it will affect the EL153 working conditions in other states.
The way the EF80 is biased, it seems somewhat non-linear, even if the overall response is fixed with gNFB, what's the reason for doing so?
This is not just rely on imagination, simulation and graphical characteristics meter, distortion meter has told us the real answer. Good tube amp once again proven the point I chose to work with excellent linearity.
If you want to know more, please yourself. But not in others unfounded accusations here,or ask for the data to others.
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