Hi all,
I am trying to build this simple amplifier and already done the preamplifier and the power stage. I'm having problems with the power supply. I managed to get a transfomer with 80mAat most and 280-0-280 in before the rectifier. Can't get to calculate the new resistors for my case.
Any help? 🙂
I am trying to build this simple amplifier and already done the preamplifier and the power stage. I'm having problems with the power supply. I managed to get a transfomer with 80mAat most and 280-0-280 in before the rectifier. Can't get to calculate the new resistors for my case.
Any help? 🙂
Attachments
Last edited:
In an AC coupled amp like yours, ±2% of tolerance in plate voltage causes minimum variations in the operating points, and distortion. Build it as you can, and adjust it when working. Take the usual precautions with the high voltages.
> 80mA at most
The amplifier appears to be a guitar amp? (That tone control will never be hi-fi flat.)
Guitar amps are "usually" single power output stage.
The one EL84 will suck about 43mA.
So as a one-channel power amp, your 45mA total is way less than the 80mA rating, and there is no problem.
If you are building a two power stage guitar amp, increase the 270 Ohm cathode resistors to maybe 330 Ohms, to reduce total current.
BTW: that 33K in the tone control is suspiciously small. Against the 25K MID pot it gives very little dip for the Bass and Treb knobs to add onto. Fender used 100K here. Be prepared to try his value, it works for many players.
The amplifier appears to be a guitar amp? (That tone control will never be hi-fi flat.)
Guitar amps are "usually" single power output stage.
The one EL84 will suck about 43mA.
So as a one-channel power amp, your 45mA total is way less than the 80mA rating, and there is no problem.
If you are building a two power stage guitar amp, increase the 270 Ohm cathode resistors to maybe 330 Ohms, to reduce total current.
BTW: that 33K in the tone control is suspiciously small. Against the 25K MID pot it gives very little dip for the Bass and Treb knobs to add onto. Fender used 100K here. Be prepared to try his value, it works for many players.
The filter capacitor connected to EZ80 pin 3 must be lowered to 47uF; 33uF is even better. 150uF will damage the tube quickly. If the resulting hum is too much, add a choke.
- Status
- Not open for further replies.