I believe many misuderstand the rule. The outside-foil side is connected to the lower *impedance* side the the circuit, not (necessarily) the lower *voltage* .

Greetings from Mt. Lebanon. Another fine video. You are absolutely correct about the durability of the Weller 8200. I have one I bought in 1962, only issue is that it eats #222 bulbs.

Yet another fantastic video Tony remember all these people that bad mouth or sit behind their keyboard don't publicly air their work like you do its quite a talent to reveal yourself as you work and be honest with mistakes or mishaps as you go we all make them but some people pretend they don't and I personally find it so amazing that you are willing to open yourself up to the world as you work and share your knowledge with us, I have learned so much from watching your videos and letting me see how you approach certain electronic problems is priceless to me its very easy to watch something and say I would have done it this way but very hard to show someone that before watching someone else please keep the videos coming I love them

I didn't sleep well last night. Here I am just before noon watching this video. I put my feet up and leaned my chair back, and I feel asleep. I just had one of the most vivid dreams I've ever had. I was at a home I had just moved into (never seen this house in real life) and went over to my next door neighbor's house and it was you! Ha... So you and I started yapping about stuff and you came over and saw some of my projects setting around and I started telling you about one of tube radios that I had setting there with the top off of it (I actually own this but haven't worked on it yet). You said something about measuring the grid voltage, and as I went to grab a multimeter, one of my childhood teachers from grade school showed up (she was just as young as she was back then, so she was younger than I am now, continuity error??). She got on her facebook page (using my computer) and wanted to print a picture but she accidentally hit print all?? But the only printer I had hooked up to my computer was a Zebra Label printer and I don't actually own one of these, I do work on them quite a bit at work though. So like 100 pictures printed on my label printer, IN COLOR, on a black and white label printer. Then some random dude showed up (no clue who this guy was) with a broken CRT TV and wanted to give it to me? You asked if I would run you up to the store to grab a coke because you were thirsty and I was out of coke (this never happens at my house, I always have something to drink heh). So we left my teacher and random dude standing there and ran to the store, it was only 1/4 of a mile up the road to the store. In the dream I own some old rough looking Rover P5 from the 60's (I think perhaps that I watch "Cold War Motors" to much). On the way back I slid on some ice and went right past my house and we proceeded to slide down sideways on a dirt road (very steep hill) to finally stop at the bottom. Nothing horrible happened beyond both of us getting scared shitless. I asked it you were ok and you didn't say a thing, you looked as white as a ghost though. So I started back up the hill bouncing all over the place because the road was rough and the dream ended. I am no expert on such things but I interpret this as such. Either both you and I will win the lottery OR I need to stop watching youtube when I am tired.

Tip for the (Weller) soldering pistol: when you buy one, disconnect the tip, and measure the resistance with a mΩ meter. When you want to use a piece of copper wire in stead of the standard tip, be sure to match the resistance with that, so you get a 100% power conversion from the transformer inside; R-in must match R-out for that.

Nice work! Great education that you are passing on here. Have been enjoying all the sessions that you are passing on here. Leave the ego at the door and just pay attention. Thankyou!!!

I like the talk-and-solder segments the most.

love your explanation of the circuit and your assembly technique. Reminds me of when I built my first kit in 1967 (Allied Knight Kit Shortwave Radio).

@xraytonyb You are absolutely right with your observations on grounding - it is always a matter of "how many distance will the current have to travel" and the intended working frequency of the device you are working at. A very nice project (and BTW very well done as far as I would think - I like the project and how you did it, Tony!). THANK YOU for letting us taking part of it! :-D If it is an audio amp a few centimeters (or inches) is absolutely no problem, as you have to see the distance as factor of the wavelength of the operating frequency. Dealing with audio equipment and frequencies of no more than 20.000 Hertz (twenty-thousand cycles per second) you are ending up at an wavelength of round about 14.000 (14-thousand) meters or round about 0.9 miles (!) of wavelength. So, everyone, before talking of induction of hum and noise into the ground plane - think of what amount of noise could happen at your working frequency at a grounding distance of about 2.5cm up to 50 centimeters (1-2 inches)... Yes, there might happen RF stuff if you don't dampen it. Yes, in theory the shorter your connections to ground are the better. Yes, of course all resistances and impedances will add up to "something" that potentially will kind of spoil your results. But there are a lot of factors that are much more important than a few millimeters or fragments of an inch for the ground to travel. For example you maybe have to dampen radio frequency influences on your tubes by blocking capacitors. This may help to prevent your tube amp to oscillate when coming near to it with your mobile phone and you do not want to hear that characteristic sounds of your mobile phone connection as tubes are operating at high input impedances. And it definitely is a good idea to keep away strong electric or magnetic fields from your connection lines to avoid capacitive or magnetic coupling. I mean wire-to-wire coupling inbetween different signals! This helps to avoid unneeded noise from connection lines when signal has to travel from one stage to another. It is also a very good idea to have different stages separated either by shielding or at least having some physical distance - as Tony shows here perfectly: Having power supply as far off from audio stages as could be is best you could do, as it is prone to emit all sorts of humming and clicking noises up to the lower radio frequency range! Well done, Tony! Nice job done so far

Hi Tony. Will attest to the quality of the Weller 8200, mines is over 50 years old and with exception to a couple cracks on the Bakelite body has continued to operate flawlessly. Don’t waste electricity either because of instant heating with click switch, 140 watt for quick heat up and 100 watt to maintain temp. The tip last relatively long not being hot constantly and if maintained with a wet sponge to remove acid flux after heating.

I totally agree with you about armchair electricians and especially about the outside foil debate. I think a lot of people do watch other people's videos and then act like they're an authority on it and post disparaging comments on other people's videos, not based on what they know personally, but based on what they've watched in another video. I don't know if you remember Dennis Carter? He passed away a few years ago. He has a KZfaq channel that's still up. He was an electric engineer and he also made the point that the outside foil thing was completely wrong and he convinced me of it. He was an old-time EE and he knew the history of it better than a popular channel that has promoted the idea.

Xraytonyb building the second out put channel is cool

Fifty years ago buried two tea chests full of valves in the old mans back garden. They are now under a car park otherwise I might be tempted to do some midnight resurrection work. You never know maybe the vacuum held.

Another fun video, just chewing the fat and making something interesting. As an aside, one of the places my wife's business services does installation, removal and storage of large medical equipment. The noise the refrigerant pumps make is well etched into my brain. 😆

WELLER 8200D was the best, The cable on mine reeds replacing but still works but needs the replacement heads.

If you use the vacuum tubes with a 12V heater and a 12V B+ then a LT800 centre tapped Loudspeaker transformer should work and you don't have to worry about getting a 200-300V shock and can be run of a 12V Wall Wort.

I still have my Weller 8200 from back in the late 1960's, but has new bakelite case, original case broke from being dropped. Also have a Radio Shack gun, rebranded weller 8200.

i agree alot of outside foil talk is snakeoil

40:44 - With those blue bodies. brown and orange appear identical!

Those people who say that low voltage tubes don't put out a lot of power should experience the BUSH EMB60

I have been thinking about purchasing one of these kits :) everything you do is Great !

These are some detailed videos I believe anybody can build this amplifier following your videos and schematics

Hi Tony , just some advice on output tubes biasing.........here we have to do with automatic bias , bypassed with a capacitor which was and still is common practice. Normally it is a simple and safe way to bias tubes... The use of a common cathode resistor was once the rule in the past when tubes were simply user replaceable items.... In the long term........the imbalance du to aging will grow and ONE tube will end up in doing all the work and will finally red glow.! In the past era tubes were more consistent, reliable and stable ....but nevertheless .........I know that experience is hardly transmittable but I thought I may try to inform you about that.... Besides people liked the imbalance on the output tubes (PP ).....it creates a more Second harmonic which is reduced/cancelled by PP ... Safe is one cathode resistor per tube .........some original datasheet mention that ! Anyway .........I like your passion and your video's . I live with tubes for more than 65 years and repaired, build and worked with them up till today....for what it's worth 😀 Have a nice day.

In talking about grid resistors like the 470k, there is a limit on how large you can make these resistors that is stated on the tube datasheet. This should be emphasized in any discussion of them. If you make this resistor value too large, the tube becomes susceptible to going into runaway bias. And it's a different value for fixed bias. For the tubes you're using the maximum in cathode bias is 500k, so you're close to that, but in fixed bias it would be 100k. And it's different for different tubes. For example, the maximum in cathode bias for a KT88 is 220k.

Hi Tony nice build I love point to point wiring, I do it too. I wonder why the designer didn't use gridstopper resistors after the 0,1uf coupling cap to the grid of the 6P1. I use a 2k2 to avoid occilations. Maybe if you encounter this, you may add them. I use negative voltage to the grids of my end tubes to set its bias. I like to set the tubes exact with the bias. Yes they will drift after an hour then after 2 hours they will be very good stable also when it's cold and heat up again the next morning. I follow your build and you go your own way and it should be. Good information on your way to build. Appreciate that.

I like to think of cathode bypasses as eliminating a source of negative feedback and, thus, increasing the gain. In your circuit, with a single cathode resistor and two push-pull output tubes, the cathode bypass actually shouldn't do very much until the output stage crosses into AB1 operation. It's only once one tube shuts off and the other tube is conducting more than both tubes at idle that the output stage cathode bypass acts to stabilize cathode voltage. Without it, you would get compression of the audio signal because the cathode voltage would rise along with the control grid. And there were a few early guitar amps designed this way without cathode bypass capacitors on the output stage, probably to protect the low-wattage speakers of the time.

Great informative video. Thank you!

Great video Tony!!

hi tony thank you for another great video

If the filament wires were shielded,would that improve the induced hum situation?

If you guys don't want to use a soldering iron then what about Wires adhesive.

I think you need a bigger soldering iron....

someone said x-ray mchines first appeared in 1893

Sounds like tony is starting a new series "Sodda-Talk". (that's the NY version..)

Tony, can you share the part number for the teflon tubing? Mouser and digikey have a mind boggling assortment, mostly 100 feet, and expensive.

i put heatshrink over cartridge lead clips to insulate them

Super!

This amplifier needs a circuit board to have the inverter components and tone filters.

point to point doesn't present a problem of scorched circuit boards

i've seen taps like that. we have a tractor supply here

I'm not sure I understand how critical the cathode bypass capacitor is. A back of the envelope calculation shows that at frequencies as low as 50 Hz, the reactance of a 470 uF capacitor is less than 7 ohms which is considerably less than the 270 ohm cathode resistor (or the impedance presented by the cathode). So the capacitor is doing the job that was intended to do - hold the cathode voltage relatively constant despite the varying cathode current. A smaller capacitor would not bypass the lower frequencies and thus reduce the gain of the amplifier at those frequencies. Is this what you mean when you refer to "distortion"?

Tony, how do you find the MIEC capacitors ? Other forums are saying that they have high ESR. Where did you buy this kit ? Great series of videos.

Greetings: Do you have an OPINION about DC vs. AC filament power? Individual rectifier diodes or small rectifier bridges are inexpensive. Are we likely to still need to twist the leads in non-series string sets? What wiring style and filament power is appropriate for series string sets?

1:14:38 - Tony, do they sell a model of this for the home? :)

what tubes are used for the preamp section?

what gauge is that tube socket wire?

Well I tried to watch but your video has gone all Max Headroom, the virtual blotchyness from whatever KZfaq did to your video takes away any details, I will try to watch again after a router reset hoping it's on my end.