Hello to all forum members, I am writing my first post so please be understanding! I would like to present my amplifier and get your opinion on the appearance and used lamps and other components.
The amplifier is a typical Single Ended based on EL34 tubes in the power stage operating in triode and pentode mode (change with a switch) and ECC82 in the preamplifier working as a white follower, EM84 as a drive indicator and one EAA91 as a signal rectifier for EM84 tubes. The amplifier has a semiconductor bridge rectifying to the anode voltage and it is the only semiconductor used in it. I decided to use a CLC filter for the power amplifier and a CLCRC filter for the preamplifier. The total capacity of the capacitors for the anode voltage is 362 uF. The capacity is sufficient because the only hum comes from the magnetic coupling between the loudspeaker and mains transformers (I checked). The choke has 8.1H and 140mA of allowable current, 20mA reserve. The anode voltage at the first electrolyte is 270V and about 245V at the EL34 anode. Ug1 = -14.5V.
Initially, it was powered by an Elpo stabilized power supply, and then from a network transformer scrolled on request, its power was about 100VA, Ua = 230V, Uż = 6.3V, measured under load. A loudspeaker from Telto, I had tubes.
The amplifier worked from the first start:
- hum is a single mV
- no excitation at low and above acoustic frequencies, measured with an oscilloscope
I did not measure the power and I will not say about the sound because it is the first tube amplifier I have ever heard, but it satisfies me (a bit weak bass but without exaggeration)
Here are photos from the completed project:
And here are photos from the formation and others:
And here are the diagrams from which I was based, but I changed them a bit (e.g. adding a triode / pentode switch)
If you have any questions, write to us.
Cool? Ranking DIY
