307A VT-225 Single End Amplifier (Low Budget Project)

Step 1.

Go to flea market and buy few old tube type radios. You need all of them to be the same type, because we will use their power and out transformers. If you are lucky one, you’ll find some of stereo tube receivers, try to avoid models with ECL tubes, because trafos are too tiny for more than 3-4 watts. Try to find something like this:

or like this one:

Both of them were made by RR Zavodi Nis (EI – Elektronska
Industija ). I am really lucky guy, cause my country was abandoned a bit :), just in
this field, so we used tube type radios a long after transistor era was begun in
EU or US. It’s still easy to find them for few euros, even in perfect working condition like this one:


This is like new, mint condition, EI Simfonija with UHF unit, so I decided to keep it like collection item.

Step 2.

Still at junk yard, finding chassis and box for SE amplifier. This one seems to be suitable, also product by EI, AF generator.

A lot of parts could be used in AF tube amplifiers constructions.
Sometimes you can find really nice MKP condensators, quality sockets with golden pins which is impossible to buy new these days.

And tubes … of course 🙂

Step 3.

Matching of transformers could start. You first need to check
them with ohm meter, after that you need to input 6-7 volts to speaker
connectors and measure out. I have more than 50 transformers like these, so it
easy to find two of them with almost perfect / identical characteristics.

To be continued …

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