Akarakrit Uamkruea, blogger and audio gear maker who passionate in vacuum tube, audio & music.
Producing electronics projects since high school. Seriously upgrade and modify vintage audio equipment for “Real Sound” concept.
He is a co-founder of Soundaries, all audio solution provider.
Experienced and lively explore the listening rooms & audio shops in Japan as his most favorite to do.

Thursday, May 6, 2021

Telefunken ELA V311 Transformation Part 1

I've got the first version of V311 power amplifiers more than 10 years. 

Already took out microphone transformers (2 channels in 1 can, using as stereo) 

to use as MC step up transformer, match with many cartridges especially Ortofon SPU.

Very good sound indeed, good dynamic and musical.

But the rest has been keeping like trash until now.

(Maybe) because many reasons that hard to bring them to life.

It is too high power (100W)/ It has 100V line output (not 16/8/4 ohm)/ It's heavy 😆/

It's using expensive power tube (2 of EL156)/ I'm too lazy (maybe the main reason 😁)

So I plan to re-design circuit, make it can exchangeable between EL12 & EL156.

Bypass microphone amplifier stage also tone control stage too.

Change to fully balanced circuit with input transformer and 1 high gain tube driver stage.

And finally using switching power supply instead of all parts in rectifier stage.

It will get about 20W output power, enough for me & my friend's speakers.

Let's see in next chapter but check the original before doing anything below.

Inside with German built... (from 1950's)

Many parts need custom to fit with standard components but interesting to make it possible.


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