Vermes
Advanced Member level 4
It is a tube amplifier push-pull in Ultra Linear system. It was modified – there is additional tone adjustment system, described below:https://www.angelfire.com/electronic/funwithtubes/images/Amp-Tone-5-A-B_thumb.jpg]/img][/url]
And the result is shown below:
[url=https://obrazki.elektroda.pl/11_1275652530.jpg][img]https://obrazki.elektroda.pl/11_1275652530_thumb.jpg
Signal goes to the tone system and then to volume regulator and the system of amplifier from Audioton. The PCB was redesigned so that it can fit an additional tube per channel.
To limit the buzz, you need to apply anode voltage stabilization and voltage powering the heaters. Both voltages are stabilized by systems of stabilizers with MOSFET transistor and Zener diode to eliminate hum.
How does the power supply work:
- After turning on the supply, capacitor C16 is loaded with a delay, what causes that the glow voltage does not rise rapidly and there is no current peak (cold heaters have lower resistance) and you det 6,3V DC at the output.
- For about 45 seconds from the activation of supply, system U1 has high state at the output, what causes that the transistor Q4 shorts the Zener diode D2. As a result, anode voltage does not appear until heating the heaters of tubes. System U2 operates simultaneously and causes flashing of the diode indicating the supply state.
- After 40 seconds Q4 stops shorting diode D2 and anode voltage 300V appears at the output. U2 goes into the reset state. Supply diode is lit continuously.
AVT2829B was used as a driver of the amplifier. It allows you to turn on the amplifier and adjust the volume from a remote control.
Link to original thread (useful attachment) - Wzmacniacz lampowy EL84, ECC83 push-pull