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Kind: captionsLanguage: enHi there, I have something to confess, I doread all the comments underneath my videos.I know, I know it is a rarity among YouTubecreators but I cannot help it because I amalways looking for new video ideas and foryears now tons of viewers have been askingme to create a tube amplifier.

To answer that question we can firstly browsethrough the transistors datasheet in order to find this graph which describes the relationbetween the flowing collector current andthe collector emitter voltage.For an audio amplifier you want this lineto be very linear so that the amplified signaldoes not get distorted which is the case withthis BC637.Now let’s have a look at the lines of thevacuum tube which are also kind of linearbut feature noticeably more curves.That means that this tube will also createmore distortions than the transistor and whilethis sounds bad, the distortions are alsokind of the reason why tube amps are stillrelevant.

Supposedly tube amps do also not create highfrequency harmonics which might be anotherfavorable characteristic for their sound whichmakes people like them.The only real advantage they offer is thatthey do not clip like transistors when overdriven.And with those information now all in yourhead I can firmly state that the tube preamplifier of my bought product might add itsown distortions to the mix but I really donot care or hear them that much.

Anyway I hope you enjoyed this small historyclass and now understand why I have prettymuch no interest in creating my own propertube amplifier system.And by the way you can check out the videodescription to find more videos about the topic of different amplifier classes and transistorsjust in case you got confused once or twiceduring this video.

As always thank you very much for watching.Stay creative and I will see you next time.

WEBVTTKind: captionsLanguage: enHi there, I have something to confess, I doread all the comments underneath my videos.I know, I know it is a rarity among YouTubecreators but I cannot help it because I amalways looking for new video ideas and foryears now tons of viewers have been askingme to create a tube amplifier.In case you do not know with tubes they referto such vacuum tubes which kind of look likenixie tubes but are way more boring sincethey only light up a little bit.Such triode vacuum tubes were actually inventedin 1906 and they mostly have been replacedby the transistor which was firstly createdin 1947 and that basically makes vacuum tubesa relic of the past, right?Well, if you search for tube amp on eBay thenyou can actually still find lots productsthat feature those old school vacuum tubeswhich begs the question what makes them sospecial that after 100 years we still usethem.To find that out I actually ordered myselfsuch a tube amplifier and in this video wewill not only have a closer look at it, findout how vacuum tubes work and how to createa simple audio pre amplifier with them butalong the way we will also uncover whetherit truly makes sense to still use them.Let’s get started!This video is sponsored by Altium.I recently switched to their Altium Designersoftware in order to create a schematic formy guitar effects board and I have to saythat it is a pretty good piece of software.It comes with everything you need to createa schematic and what I really like is, thatyou can search for components from onlinesellers which makes sourcing components foryour project super simple.So feel free to test the Altium Designer byyourself by following the links in the videodescription.Firstly let’s have a closer look at thetube amplifier that I bought myself in thename of science for around 80€.I have to say that I really do like the factthat you can easily replace the tubes andthe all metal enclosure looks and feels prettyhigh quality.All the knobs and output/inputs also madea very good impression.For the input you can either connect a stereosignal through wires or connect to the ampvia Bluetooth.And for the output you can either hook upspeakers or simply plug in headphones.Now before taking anything apart I actuallyplayed back a couple of songs with this amplifierand then compared it to the audio output qualityof my phone.I am certainly no expert but by listing toboth devices side by side I have to say thatthe tube amp offers a more pleasant soundspectrum.And pleasant is the keyword here which besideswarm or natural is often used to promote suchtube amplifiers.So to determine whether those promotionalterms are truly correct, let’s unscrew allthe screws required to remove the PCB.And once again I was positively surprisedwith the product and its well-made PCB design.What I immediately noticed though, after unscrewinga big heatsink, is that there are tons ofICs on the PCB which are also amplifiers.We got operational amplifiers, a headphoneamplifier and also a powerful class D amplifier.The Class D one is used for the speaker outputand the headphone amplifier is obviously usedfor the headphone, so the only job the vacuumtubes fulfill is by pre amplifying the originalaudio signal, but why only that?Well the first reason comes to mind when googlingthe label 6J4 of the vacuum tube.As it turns out my tubes are triodes whosesymbol looks like this.They can only handle a maximum current of20mA which is certainly not enough to directlydrive any kind of speaker.That means, the real power amplification happenslater with the other amp types but why thenbother with pre amplification through thevacuum tubes?To find that out let’s have a look at themost important pins of our triode, calledplate which is the anode, cathode, grid andheater.As you might recall from your diode knowledge,current can only flow from the Anode to theCathode but not the other way around.That is the case for our triode as well; thecathode has an excess amount of electronsthat that can travel to the anode becausethere is a lack of electrons.To make that happen though we firstly haveto power our heater pins.According to the datasheet we have to apply6.3V to them and as you can see after doingjust that with my lab bench power supply,something starts glowing inside the tube andit becomes hotter.By the way this heat which is around 1.8Wof electrical power is an excess power lossthat for example transistors do not have todeal with.But anyway this heat is necessary to excitethe electrons and make the current flow happenwhich brings us to the last pin, the gridBy applying a control signal to it, we basicallypresent a negative charge to the electronpath which repels the electrons and thus reducesthe current flow.And just like that we can use a low powercontrol signal in order to control a higherpower current flow which is more or less thedefinition of amplification.To test the functionality of my tube we canbuild up such a simple class A amplifier designwith it.And in case you are wondering, creating aclass A amp with a bipolar junction transistorrequires pretty much the same circuit designbut there is one huge difference.While the BJT works with low voltages whichare safe to work with, the vacuum tube requiresaround 100 to 150V DC.And yes my bought product also uses 96V whichis why the average consumer should maybe nottinker around with it.But anyway to create such a high Dc voltageI will be using this high voltage dc converterwhich I originally ordered for my Nixie Clockproject.After hooking up my multimeter to its output,I connected the input to 12V and used theonboard trimmer in order to adjust the outputvoltage to around 100V.With that being done, it was finally timeto solder wires to the 7 pins of the 6J4 vacuumtube and connect them to the complementarycomponents which I showed you before in theschematic.And after a couple of minutes of soldering,the circuit was complete.For the signal input I will be using my functiongenerator whose sine wave frequency I cannotonly change but also its amplitude and offset.After connecting it to the input we can havea look at the output which offered a bit ofa surprise for me.If we look closely and play around with theinput frequency we can see that the amplificationdoes occur but why is there this weird waveformwhich apparently messes with the GND referencepotential.Well, if we zoom in on the waveform we candetermine a frequency of around 24.4kHz whichcoincidentally is the same frequency my highvoltage boost converter utilizes.So in a nutshell I got no suitable power supplyfor my tube amp but since my bought productuses a similar circuit design, we can simplyhave a look at it instead.As you can see the amplification works withoutany problems.But as a comparison let’s build up the sameclass A amplifier circuit with a BC637 NPNBJT.After connecting the input signal and powerwe can once again have a look at the outputin order to find out that we basically gotthe same waveform result as with the tube.So why should we bother with them since theyrequire high voltage and create excess powerlosses through heat.Well, maybe they create less distortion?To answer that question we can firstly browsethrough the transistors datasheet in orderto find this graph which describes the relationbetween the flowing collector current andthe collector emitter voltage.For an audio amplifier you want this lineto be very linear so that the amplified signaldoes not get distorted which is the case withthis BC637.Now let’s have a look at the lines of thevacuum tube which are also kind of linearbut feature noticeably more curves.That means that this tube will also createmore distortions than the transistor and whilethis sounds bad, the distortions are alsokind of the reason why tube amps are stillrelevant.You see some people just find those distortionsmore pleasant to hear and they describe itas warm or natural, it is pretty much subjective.Supposedly tube amps do also not create highfrequency harmonics which might be anotherfavorable characteristic for their sound whichmakes people like them.The only real advantage they offer is thatthey do not clip like transistors when overdriven.And with those information now all in yourhead I can firmly state that the tube preamplifier of my bought product might add itsown distortions to the mix but I really donot care or hear them that much.Anyway I hope you enjoyed this small historyclass and now understand why I have prettymuch no interest in creating my own propertube amplifier system.And by the way you can check out the videodescription to find more videos about thetopic of different amplifier classes and transistorsjust in case you got confused once or twiceduring this video.As always thank you very much for watching.Stay creative and I will see you next time.