ELEKIT TU8100 Class A Tube Amp Build Part 2 in 4K

[@seelafever]

Thank you for the theory explanation while describing it on the schematic. Very good.

[@sman222222]

Thank you very much for these videos.I was very interested in getting one of these from tube depot instead of buying one from China but never have done any soldering or anything like this before. this video has really help me realize that it doesn't look very difficult at all but I'm sure you make it look easy. 👍🏼

[@zx8401ztv]

I am supprised that they use a switchmode to produce the h.v, switchmodes are normally very noisey with harmonics. Perhaps the pic chip tailors the drive waveform to minimise the noise perhaps?. Im not deep into switchmodes, except they are capacitor killers LOL :-D Its a nice kit :-D, you look like you're enjoying the build, i hope the presents of the camera hasnt taken away any enjoyment.

[@manne3d]

great vid and interesting theory talk. Thanks

[@joohop]

nice work bud May you have a good Christmas over in BC

[@williamstaten8102]

This question is off topic but started thinking about it while watching your vids. Do have a good place on the web for cross referencing SK transistors? I have a few receivers from the 80s that's full of them and I'm at dead ends finding anything on them.

[@metroboytartu]

Maybe ebay can help you to get more good old 80s era solder with lots of lead isnside. Yes environment suffers from use of that, but C'mon. You are worth it!

[@thattubesound2214]

Does all that switching to create the square (pseudo-sine) wave cause noise? If I were to run an AM tuner through this amp, would there be a bunch of buzzing similar to what comes from wall warts?

[@12voltvids]

I haven't heard any, but I will go plug my AM radio into it, and see if it has any noise generated and let you know.

[@Γεώργιος.Παπαδόπουλος]

Ποιό πρόγραμμα χρησιμοποιήτε για την κατασκευή τοῦ τυπωμενου;

[@geojor]

always good stuff ...

[@dmcintosh1967]

I hop your two tube radios that your planning to restore don't have sliver mica disease . if your radio do you will have fun taking apart if can and digging out the mica capacitor. none of my radios have CMD. radios form 40s don't get CMD.

[@12voltvids]

They could have asbestos in them for all I know. Won't know until I get them apart. It was common to place asbestos sleeves on wires that were in contact with large resistors to prevent the heat from melting the insulation on the wires. Of course back then asbestos was safe right.

[@jaywalt1311]

Just looked at the specs. THD is 10% Is that typical of tube amplifiers?

[@12voltvids]

Yes most tube amplifiers have a fair bit of distortion at max power however that type of distortion that tubes produce is even order harmonic distortion, which actually sounds very pleasant to the ear. It warms the wound up, and takes the harshness off MP3 for example.Odd order harmonic distortion on the other hand is terrible, and the ear can hear it as lot as .12%. Guitarists crave even harmonics, and that is why so many use tube amps. Each harmonic is an octave above the frequency, and this is why they sound so good.Odd order are in the 3rd 5th 7th multiple of the tone, and are very objectionable.So when you see tube gear distortion is not generally a bad thing. Also when tubes saturate they do not clip like transistor gear.With a transistor amp when the transistor saturates the waveform clips, and produces very harsh odd order harmonics that will blow speakers.Tubes on the other hand do not clip. The waveform will max out, but the peaks of the waveform are not flat clipped. By the nature of the output transformer, the sharp edges of the square wave that would result from clipping is rounded off, and softened.So 10% distortion is not a bad thing. I have listened to one of these amps on demo in the shop and it sounded wonderful.

[@pcno2832]

Also, you can rate the power of any amp at 10% THD just by over-driving it, so it would be interesting to know at what power the THD rating hits the minimum and what maximum power it can produce at a more reasonable distortion level like 1%.

[@12voltvids]

Captain Cuntonese single ended amplifiers sound even better. I keep astonishing my friends on how much better it sounds. this little amp has by far the best sound of any that I own at background music levels vocals are especially clear. was listening to Sheryl crow and it sounded like she was in the room. it's hard to put into words to someone that has never experienced this. as a musician I have used tube amps for years because of the sound quality but these were always push pull class ab. there is as big a difference going to a single ended amp as there is from going from solid state to tube in terms of music listening pleasure. THD means absolutely nothing in the tube world because all the harmonics are even order and they ear does not hear these types of distortion like odd harmonics.

[@Nirky]

The general practice is to measure distortion at 1 watt @ 1 kHz. A good distortion number for 1 kHz is around 0.25% THD or less. When output distortion just crosses over 1%, that is commonly listed as maximum output. IMHO 10% THD would not really be listenable over time, that's the kind of distortion (and more) guitarists aim for.

[@bryanlatimer-davies1222]

I think it might have been worth bending the lugs on the transformers to secure them before soldering

[@12voltvids]

I considered that, but the unit isn't going to be transported.Solder will hold them in place just fine. I may do that before final assembly as the unit isn't done yet. All the boards are complete, just need to put it in the cabinet. Of course you need to wait for part 3 and 4 to see that.

[@DAVIDGREGORYKERR]

There are tiny wire-ended Russian Vacuum tubes which are designed for battery operation, Resin-core solder should be available in any hardware store, but why do try and source the solder from some where in California.

[@12voltvids]

I can get 60/40 solder where I bought this kit, but it is Chinese crap, and well we all know how well that crap flows.

[@12voltvids]

Way back, when I was a kid Radio Shack made kits.One that I built was the 1 tube radio.It used a single AA battery for the filament heater, and a 22V battery for the plate voltage. I remember that the AA battery would only last a few hours but the 22 volt battery lasted a few months of use. I often wondered what happened to that old kit and all the other ones I built as a kid.www.google.com/search?q=radio+shack+science+fair+1+tube+radio&biw=1188&bih=640&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwiahKr5ltvQAhUUz2MKHU8TCicQsAQIGg#imgrc=3fRqbXjrSQCHcM%3A

[@thattubesound2214]

I have a source of American-made 60/40 solder here in Salt Lake City. I did a video on the place. I'll bet if you contact them, they would mail order some to you. The store is called RA Elco. They are in the 801 area code on Main Street in Salt Lake.

[@umajunkcollector]

The price is too high. The most expensive parts are the three transformers though, could be well over 50% of the price for quality. The PCBs, tubes and caps etc., aren't that bad. But if it had the larger el34's, kt88's, or 6l6's, the tubes can be over 50$ each. I found a Lafayette PA675 with two el34's for under 200$, more fun to restore / rebuild than build a newer kit for me. It's a gamble from ebay, but that's part of the challenge. Hint, old tube public address (PA). organ, and movie projector amps can be found to be pretty cheaply still. But large tube guitar amps and hifi with kt88's can go well into the thousands of $. Don

[@12voltvids]

My home stereo amp uses 4 EL34B and 4 12ax7 and yes I know the price of those tubes as I have replaced a set. I haven't opened the box with the tubes in it yet so I don't know what they are, but the display kit in the shop where I bought it had NOS Mullards in it.I have 2 tube radios to restore. One is a Nordmende AM/SW with a record player (that part is missing and I am looking for one for it) and the other is just a chassis. WIll be working on them at some point.Was in a car accident, and have whiplash now, so I am not feeling like doing much today.

[@umajunkcollector]

sheesh, back pain sux, I know from years... hope you feel better soon, I try to avoid pain pills. I have an old late 50s tube Philips Jupiter table radio, I like German rigs. I made a vid about it. Still on the back burner for restore, but it works. There are many German SW radios from the iron curton days; Grundig, Telefunken, Blaupunkt, Nordmende, Philips, Graetz, Saba, etc., they all look similar. I'd like to find an old Unitra Polish radio, uma Polock too. Don