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The only issue I see is safety. Wiring direct through a bridge rectifier leaves the chassis connected to one side of the incoming power (neutral). If somebody were to connect the plug incorrectly, or into an incorrectly wired outlet, the chassis will be full live AC voltage. Switching power supplies get away with it because there's a high freq. transformer isolating from the source AC.

Interesting design. Sounds excellent. Well done, mate.

Thanks so much for sharing this, the video, the clear schematic and the slow-start circuit, which is pleasure to watch. I used a BC557 as the pnp transistor- I see that the value of the 240 ohm transistor needs to be quite precise to get to the 15 volts. I do find that the sound is lacking treble on low volume settings. Great instructions - thanks again.

Brilliant video - what is the spec of the o'/p transformers - Thx

I made my first tube amplifier after watching this video. Worked perfectly and sounded very good, for a while. Then the HV boost converter failed. Put in another converter and it failed after a few hours. Tried various Chinese boost converters from Aliexpress and other sources. They lasted from minutes to a few weeks. Then they all gave up the ghost. Got a standard linear power transformer replacing the last failed boost converter, amp has been working perfectly for years. Have since made 12 tube amplifiers, all using standard power transformers. None have failed. If people have used a boost converter and it has lasted, then I'm happy for them. And a little envious. I know a linear transformer costs more, but in my limited experience it's worth it. If you have made this amp with a boost converter and it's still working, let me know here!

I applaud your desire to get rid of power transformer, but you are opening up the whole system to all kinds of noise. The transistor amp you showed is almost certainly Class AB, not Class A (big difference). Your tube amplifier is likely 2-5 watts, subject to the quality of your output transformer. If you are "enthralled" by the performance of this small system, I would suggest it is the characteristics of the output transformer that is pleasing to your ears. I would suggest that your speakers have a whole lot more to do with the sound than the ancient tubes. Enjoy your system.

Loving Your approach, and I've just bought pretty much the same components for My project. Aww Maplins, what a shame they've gone. Anyway Best Wishes Dee : - )

Do you have a source or specs for the output transformer, please?

solid state less "bright" harmonics

I can hear its much clearer through the tubes. Love the old systems, made almost from raw elements. I think we have to face it - do we like the sound of electricity passed through rocks or a vacuum. I wonder if there is a third medium as yet untried. Tubes of the future?

The schematic shows R5 and R6 as being in series between pentode cathode and ground, with a connection between the two going to the triode cathode. In the video, the author connects R5 to the pentode cathode and earth, and R6 between the pentode and triode cathode, with no connection to R5, apart from the socket terminal (16:10 on the video). Can anyone enlighten me as to which is correct?

This is lovely. I am planning my first valve build and this really helps thanks.

Um ótimo trabalho, inspira tentar confeccionar um igual, de tão bem detalhado . Um amplificador assim ligado a caixas de alta sensibilidade é um deleite , ainda mais com mídias analógicas Parabéns e saudações do Brasil

I like both solid state and tube amplifiers. And honestly, the tube amp sounded fat and thick. The solid state amp sounded a bit thin in comparison to my ears.

Using OPT? You are only fooling yourself. Transformers are impedance matching devices --- period.

Unfortunately with all the compression on TH-cam videos, it was very difficult to tell the difference. A lot of people comparing tube amps to solid state have similar experinces to your verbal explanation, but as you said, music is a subjective thing and everyone has their own preference, and plecbo effect has a huge influence. I don't understand why people talk about "soft start" power. Tubes/Valves use to run AC heaters, the heaters got the power immediately when turned on, and there were numerous directly heated rectifier tubes. Soft start is not needed for Tubes/Valves at all. They really are not that sensitive. The indirect heated tubes don't conduct until they are warm so they do their own soft start anyway. The only thing is to make sure your filter caps can take the voltage of the unloaded power supply.

The tubes attenuate the "ringing highs"?

I'm a bit of a sound freak and I believe there is an analogue and natural aspect to tubes, vinyl records and tapes. Not sure it means anything now as we would get a 99.5% true copy of what happened in the recording (if we care about the whole thing.)

Hello, I would like to know from you very important point, so please answer :) You employed step up SMPS in your project. How is the reliability of this particular board/module you used? You build it 4 years ago if I see correct. Does the step up SMPS still work? I heard from couple people they are so low quality to survive only few weeks...

It might be better to start using TELEFUNKEN Space Charge Vacuum tubes that use a B+ of 12-90V and a H+ of 1.5-3V

Great video, am collecting the parts to build one myself. Just wondering what value of potentiometer did you use for the volume control? Thanks

고맙습니다 thanx a lot

Tube sounds better from high end of low pass all the way thru the audible limit. In comparison, the other two attenuate same frequencies, the transistor the better. I like how you approached the project; especially starting up. Thanks.

Great work! The kit companies will not be happy with this video, but us hobbyists are! Thank you.

Sound is always most affected by the output transformer. Buy the best one in your budget. Next are the caps and resistors in the direct positive voltage signal path. Go big with the mug size $100 polypros. Build your own speakers next. Commercial speakers spend most on marketing and the cabinet. The drivers are 20% of the retail price at most. A $300 full range on an OB is better quality than any speaker under $20k.

Excellent video on your build. Interesting using buck regulator for the 220v section . Think that type valve was sound in TVs , Thankyou for posting. I would love a valve amp again might copy your ideas , deffo easier to source the parts you used rather than trying to find an old mains transformer

I am really impressed.

Really brilliant video, thank you so much. I was inspired to build my own after watching it. The amplifier worked first time, which I consider to be a minor miracle. Could I ask a question please. Although the mids and highs were clear and sweet, the bass and low mid was really thin, and not warm and full, as described by others in the comments below. So I must have done something wrong!!! Do you have any suggestions to try and improve this. Thank you again

Enjoyed the video. You should make more.

To me tube audio sounds clearer in the highs. While solid state sounds a small amount muddied in the highs. However, neither sounds bad at all.

I image ECC83 and EL84 would adapt. I like the boost converter. R4 I guess is shunt feedback. ECC81 might work as higher Rp. R6/5 unusual as no bypass. The latter might give it better than average sound.

One word stands out : REALIRTY ! " And at leat being skeptic is not the same as believers in measurements ....you can NEVER argue with beliefs ....but you can trust you rears and your soul.. Reality means you can perceive and identify ..so you feel and understand the music.

Terima kasih, sangat detail, mudah mudahan saya bisa membuatnya

I would love if you put in the parts list and the schematic maybe on the next build great video

Awesome video!

Very much agreed. The Arduinos purpose is to give a non-programmer the illusion that he can program.

woah woah woah wtf. Picture at 1:45, Hayling Island bridge in winter taken from either the Royal Oak or Ship Inn. Really didn't expect to see my hometown in this random video!

Interested to know how you printed the plastic in an ink jet. It could be a useful thing that.

Thank you for sharing your little project. I just finished the left channel and tested it; it works! I used the original 3.3M R4 resistor because I did not see an explanation for the change in your schematic I do have 2 issues. R6 and R7 (both 1 watt resistors) are overheating. R7 is the worst and I do not understand why. I would not think that much current would be flowing through R7. Any suggestions?

Direct cut is the best.

Es posible me pueda compartir el diagrama???

Nice job man. Nice to see those high voltage modules in a working environment. Jack Ma would be proud!

Es posible me pueda compartir el diagrama???

Great, awesome build, I’d love to see some more of your videos. Shame this is the only one on your channel 😊

I loved the video - I've been looking for a easy to build valve amplifier to get me started and I thing that this amp is the one! One Question @Electrolark : what output transformer did you use ? I cant tell the specs from the schematic.

The tube sound is much richer, even in your short test example.

A really nice build. Kudos! It had to be a very enjoyable process and most satisfying result. I really enjoyed watching your video.

The Technics isn't a true Class A amplifier. It's what was called a non-switching circuit. They achieve this by putting the output transistors in what's called a linear state (not hard on). In a true Class A amplifier the transistors are switched hard on and generate lots of heat and draw lot's of current very inefficient but are said to be very high sound quality. The Technics system give you all the benefits of class A/B with just some of the benefits of Class A. Great video love to see people build equipment. My opinion is they do sound much better and warmer than transistors. I still have the two power amps and preamp my late father built in the late 50's. He rebuilt them and did some modifications on them when I showed an interest in the 1990's. They are still working perfectly today.

Really nice work!

This is a marvellously clear demonstration video! Very interesting even though I may never build one myself.