What’s up my friends, welcome back.
This is a vacuum tube amplifier and this time it has a lot more power.
I say this time because a few months back I made another project for a pre amplifier
board based on vacuum tubes.
That PCB had very low power and it only added the vacuum tubes harmonics but we had to use
another amplifier to increase the power.
This time this amplifier has enough power for some normal size speakers and is also
based on vacuum tubes.
This is not my design, I’ve ordered this kit online and in this video I will share
with you the schematic, the component list and how to assemble it.
At the end we will give it a test and see how it sounds.
So guys, let’s get started.
What’s up my friends, welcome back.
Now remember that my previous video on vacuum tubes amplifiers was with a low power one.
Actually, that was a so-called pre amplifier.
It was only adding the harmonics effects but the power output wasn’t high enough for
a speaker.
This time we will make a bigger one.
I’ve bought a kit from AliExpress and today we will check the part list, I will try to
make the schematic and then we assemble it and test it out with some speakers.
Let’s see what we need.
Remember that vacuum tubes can’t deliver power by themselves so we will need some powerful
transformers.
As you can see, these are very bulky.
They are also heavy, they can weigh between 1 and two kilos.
We have this big one for the main AC supply and the other two are for the right and left
audio channels.
The next main components are the vacuum tubes, obviously.
This time we have 5 tubes.
These two are 6P1.
These other two are 6Z4.
The last one is a 6N2 type.
I hope that you remember how a pentode works, and if not, check my previous video on the
vacuum tube preamplifier to learn more.
You can check the links below or the card right here.
Then we have a few bags of all sorts of passive components, screws and connectors.
We have two big capacitors, two smaller ones and two even smaller ones.
We also have two film capacitors like these ones.
Then we have the ceramic sockets for the tubes with the correct size we don’t have to solder
wires directly to the tubes, that would be ugly.
Then we have all sorts of power resistors from 1W up to 10W resistors.
We also get two potentiometers and the audio banana connectors for the input and output.
We get a switch and the main power connector.
The kit I’ve ordered also comes with a metal case but in the future video I would like
to design my own case.
But for today, this will be enough.
By the way, the kit also arrives with an MP3 player.
We can supply that player with 6 volts from the main transformer but we need to add a
rectifier in between in order to get DC voltage.
We connect the audio output from the player to the amplifier and like that we have a nice
music player.
Ok guys so that’s all we get with this kit.
Looks quite interesting, right, can’t wait to see how this works.
So let’s assemble it.
They give us this schematic but I will try to put below the video another one made by
me.
Actually, I will design a PCB for this and share it with you in the future.
So as you can see the connections are simple.
The main transformer will give us 240V, 15V and 6.3V, all AC.
With that we supply the vacuum tubes.
The audio input from the potentiometer is connected to pins 7 and 2 of the 6N2 tube.
Then the signal goes to the other 6P1 tubes.
We have some power limiting resistors and some output capacitors and at the output we
have the transformers.
To make the connections the kit has this connection support.
That’s why I would like to make a PCB for this project.
Because it would be a lot easier and better looking than some connections on this support.
Ok, I know we should do this last, but I first take out the protective film from the case.
Then we use this bracket, the socket and some screws and we add in place all the vacuum
tube supports.
Ok now all supports are in place.
Then I add the big transformer.
It has its own screws.
Then We add the other smaller transformers in place and make sure the wires are going
inside of the case.
On the inside, using a separator and some screws we fix in place the connection support
and later we will make all the solder connections here.
Then I also add all the banana connectors on the rear part.
We have 6 connectors for the audio output since this can work with 4 and 8 ohms speakers.
Then we have two more connectors for audio input which are a bit different.
Then we also add the main power input connector.
On the front part we add the switch, the potentiometer and in my case I also screw in place the mp3
player.
On top of the potentiometer we can add a plastic knob.
Now all the peripherals are in place, is time for the internal connections.
We have to follow the schematic and add all the components.
In my case I first solder all the power wires from the main transformer for 15V and 240V.
Then I solder the wires from the smaller transformers to the output banana connectors.
For the middle ones I’ve made this kind of connection because here we will have a
lot of wires connected.
Then I add all the capacitors.
as shown on the schematic.
Then the power resistors.
I connect everything to the vacuum tubes sockets.
I add the film capacitors connected to the resistors and the vacuum tube sockets.
I finish all the connections with wires to the audio jack, the vacuum tube sockets and
the output transformers for the left and right channel.
Ok, now pretty much everything is connected, we could give this a test.
I’m a bit of nervous since this is working with high voltage AC.
We add all the vacuum tubes.
I get a small speaker and connect it to the output.
I power the amplifier with 220V AC from the main outlet and flip the switch.
Good, nothing blew up so we can continue.
We can see the filament getting hot inside the tubes.
I put the player in Bluetooth mode and connect to it with my smartphone.
I play some free music from YouTube.
So guys as you can see behind me
the amplifier works, we can just lower the volume
And increase it
And as you can see is a lot more powerful than the pre amplifier
So this project works!
So guys, it works.
Before we make another sound test, let’s close the case and give it a better look.
The kit also has this wood sides and the bottom metal plate.
We use screws to close it and that’s it.
Then we have to add this cover for the tubes and the amplifier is ready.
Let's listen to some more music.
So guys, I now have a vacuum tube amplifier
with sufficient power for some speakers.
Supposably, each output could create 6W of power.
As you can see marked on the schematic we have an output for a 4 ohms speaker and another
one for 8 ohms speaker.
The transformer output is different depending on the speaker resistance.
I can’t really know for sure the exact power output.
Even if I measure the power input, that doesn’t tell us the power output since there are a
lot of losses.
But what do you think of the sound effects the vacuum tubes are giving to the music?
Obviously, for a higher price you can order even more powerful amplifiers and other designs.
This one is a relatively low cost one and it still has a vintage look.
Is crazy to know that this can output a maximum power of only 12W and it weighs more than
4Kg.
But on the other side, we can output more than 100W from two amplifier ICs with this
other board which is based on integrated circuits.
But is pretty cool to see how much technology has evolved.
What Im probably concerned about this kit is safety.
I mean this works at 220V AC and the case is made out of metal.
Any loose wire inside could injure you so we must think of something for that.
So guys, below you will find the schematic and in the near future I will make a PCB for
such project as I did with the preamplifier PCB.
I will also share all the needed components and other different schematics so check electronoobs.com
for more information.
I hope that you like this video and if so, consider giving me a like or comment below.
Thanks again and see you later guys.