Двухтактный ламповый усилитель для <<тяжелых>> колонок на ГУ-50 | Техника и Программы
2400 turns and 120 turns do 3,2kΩ 8Ω . Voltage is 400v
2400 turns and 120 turns do 3,2kΩ 8Ω . Voltage is 400v
I noticed at post #18 that you have -108 Vdc as bias voltage ??
My results are at class A. Attached the plate current of one GU50 at full drive.
As you see the plate current do not drop below some 60 mA.
The drive voltage at g1 is 68 Vpp. DC-bias at g1 = -68 V.
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104 mA is plate current + screen grid current (=cathode current) at idle (no signal condition).
Look at my post #24. There is the plot of plate current.
The max. value of the cathode current at full drive is 310 mA and min. 65 mA.
Working point ?? It is the idle condition.
Look at the schematic: Ua/Ug2 = 428 V, Ik = 104 mA, Ug1 = -68 V.
That kind from you.I save them.
I have my schematics,i will use 6n8s for drivers and Schmitt phase spliter.
Here's a schematic of an idea using PP GU-50 in triode and two 6N8S (= 6SN7).
The B+ is 400V and it uses fixed bias for the PP GU-50 pair.
The simulation predicts very low distortion and about 17 watts max power out to the speaker.
It's a 'Williamson' driver circuit.
The 4.7k ohm global feedback resistor is just an approximation to get about 6dB NFB.
It's just an idea. But it looks pretty good in theory.
PS - The output transformer model used is for a Dyna A470, which has an approx. 5k primary impedance.
The B+ is 400V and it uses fixed bias for the PP GU-50 pair.
The simulation predicts very low distortion and about 17 watts max power out to the speaker.
It's a 'Williamson' driver circuit.
The 4.7k ohm global feedback resistor is just an approximation to get about 6dB NFB.
It's just an idea. But it looks pretty good in theory.
PS - The output transformer model used is for a Dyna A470, which has an approx. 5k primary impedance.
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The concertina doesn't swing that many volts. It's followed by a differential pair that swings lots of volts.
All the concertina does is split phase. That way the differential pair does not split phase, so that stage can be a more effective driver. The differential pair receives a balanced input, after the phase splitter.
One of the problems with using a long-tail pair (LTP) as a combined phase splitter and driver is that it has both those jobs to do.
I think what you're looking to use is commonly called a 'Mullard driver', named after the Mullard 5-20 amplifier. That will work, and will be more stable with negative feedback applied since it has fewer low frequency pole points in the signal path. However, it will be less linear, so you'll be tempted to apply more negative feedback, which might cause instability.
Everything is a compromise between this and that. Nothing is perfect.
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All the concertina does is split phase. That way the differential pair does not split phase, so that stage can be a more effective driver. The differential pair receives a balanced input, after the phase splitter.
One of the problems with using a long-tail pair (LTP) as a combined phase splitter and driver is that it has both those jobs to do.
I think what you're looking to use is commonly called a 'Mullard driver', named after the Mullard 5-20 amplifier. That will work, and will be more stable with negative feedback applied since it has fewer low frequency pole points in the signal path. However, it will be less linear, so you'll be tempted to apply more negative feedback, which might cause instability.
Everything is a compromise between this and that. Nothing is perfect.
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