To learn things about electronics that you won't learn anywhere else, go to my Patreon page. Click this link: www.patreon.com/MrCarlsonsLab

I think this is why the internet was invented. Thank you so much, sir. You are such an inspirational and beautiful, beautiful person. So much knowledge and experience, no insecurities, humble, not judgemental, specific to every detail without being condescending and most importantly always honest and sincere. There's no other channel on youtube I enjoy more.

I've always told myself (imagined?) that I've worked on, designed and built so may amplifiers, tube and SS, but especially tube, that I can visualize pulsating magnetic fields and their couplings in a working amp, so naturally I was seriously enthralled watching your noise probe in action! Just WOW! what a great tool... what a wonderful invention. Kudos! and congratulations, and of course, thank you.

This is what my Electronics class is missing. Hands-on demonstration with the explanation and reason behind it. Not just a bunch of complicated formulas thrown at random.

"After all you did purchase an amplifier not a signal generator" - tremendous :)

Cool vid. I appreciate how you didn't trash tubes or the manufacturer. You actually made sure you were as complimentary as possible.

Amazing stuff,I just learned more in 40 min than I have in 15 years of reading books.You really have a way of making things make sense.I keep meaning to sign up for Patreon and believe me I'm usually not a fan of doing so.But in your case its a absolute bargain.Thanks for all you do too.I cant wait to get time to finish watching the rest of it.

I know that this will be way too long, but I feel compelled to say it. I find myself in amazement at Paul’s knowledge and physical skills. I have had a lot of experience along these lines. I am 82 years old, a military veteran (go 82nd Airborne) and for 35 years ran an electronics repair shop. Over that period, I worked with countless electronic techs and field engineers from various electronic companies like RCA, Magnavox, and Zenith. I was also a full-time hands-on tech doing service calls and bench repair on all makes and models of entertainment equipment including color TVs, stereos, security equipment, radios and electronic organs and keyboards. And, of course, I felt obligated to work on stuff for friends and family such as guitars and amps, dog fencing, and kitchen appliances. If it plugged in, we worked on it. I had to hire many dozens of craftsmen and oversee their skills and knowledge. Paul knows more and can do more than anyone that I have seen. Plus, he can explain it in a unique manner. Do you realize how many college graduate EE’s cannot look at a piece of equipment and then draw a schematic and explain what each component did? Maybe one in a thousand has his depth of knowledge and skills. I don't know where he accumulated this knowledge, but it is amazing to me. Paul, I think it would be interesting for you to make a video to explain where you got that experience and vast knowledge. How many years have you been working at it? Is it a hobby? Was it ever a full-time job? You seem to have a lot of experience with military and broadcast gear. Were you in military communications or have an FCC operators ticket? I see that you are a ham operator. What license level do you hold? I'm sure that a lot of your followers will find that information very interesting. Congratulations once again on your amazing dedication, knowledge, skills, and techniques.

Another awesome MCL vid. This was the coolest one yet IMO, I love when you get into the testing of audio gear! Whipping out the audio probe and everything! Hope everyone survived the ice storm with minimal damage, that had to be pretty stressful.

Paul, Sir Carlson of British Columbia, I hereby bestow upon you a knighthood for your services to electronic education. God bless you Sir Carlson. 😀

When I went to school, it was in '99. Needless to say, I pretty much did digital electronics only. It ended me up at an engineering job dealing mostly with PLCs and writing software; not as exciting. Knowing nothing about tubes, you make very nice videos for an analog layman. I appreciate your videos, and hope you will continue to make them for the foreseeable future.

To draw a schematic as intrinsic as the one we see here, and find a place in it for all the parts involved with all separate sub-functions is just such an art! It could easily take anyone 50 attempts sketching and one might still not get it right.

Mr Carlson you are an absolute jewel. There is virtually no other place from which to get a more advanced level of instruction. Almost everything out there is nothing but beginner level conversation. Also, you have all of the hallmarks of a fine electronics technician, especially your meticulous attention to detail and logically concice navigation through the diagnostic process. When I watch you do your work i almost feel like I am smart for a brief period of time. So invaluable are your instructions I promise to donate soon in some fashion to your cause as I hope others will as well. You deserve prosperity in return for your generosity to us. Thank you sir. P.S. Please more guitar amplifier repair and modification videos.

I cannot say that I fully understand the vid.At the age of 74,I am struggling.But I love your vids Paul.Love to “Try” and understand your vids.But there is no one, on you tube or Patrion, who can explain electronics like you.Awsome.

This is by far one of the best electronic channels on YT, Your teaching skills are off the charts!

I am glad to see there are people that still know how to really work electronics and old school tube equipment!

Wow, Paul. This was better than a classic spy movie.

I am always amazed at your knowledge, but even more impressed with how well you explain it.

Hey Paul! Thank you for another great repair video! As always, top-notch content! Regards, Phil

This right here, is exactly what KZfaq was created for! Educational video's like this are invaluable.. More people need to create video's like this.. Thank you so much for wonderful and informative video Sir.

Great video Paul. Good to see some of the equipment we are building on the Patreon site in action. Martin

Fantastic troubleshooting. It's amazing how people designing things forget about inductance and magnetic fields. Just a little moving around of the filter made a large difference.

Paul, another great tutorial on the amplifier. You explained the science of this unit to a tee., Well done. Enjoyed every minute of it.

I've been watching your channel for several years (?) now. I've gone from a complete novice to actually understanding (and anticipating) what you say in this video. Awesome.

I remember as a six year old kid being given an old Heathkit W-5M Mono Tube Amplifier, I remember being told it was obsolete junk, My brother and I played smashy smashy. I regret that now after watching your channel.

Finally I got time to watch this, and it was worth every second! Funny that you are talking about hi-efficiency horn speakers and hum, when I am listening with my Altec Lansing monster with 105 and 110dB/w sensitivity :D

Mr Carlson. I applaud you for doing this channel. It is the most informative channel I've come across in a Long time. I learn alot from you. Seriosly. It's like going to a classroom. Very serious stuff and no hassle. Keep on doing what you do!

Dr. Carlson is a walking encyclopedia of all electronics knowledge. Imagine reverse engineering an amp like this. Thanks for posting this Dr. Carlson

Thanks for making such great videos! I love how much detail you provide. You fill in every detail of the way you test things and then why and then what to look for. I typically have your videos on while I'm tinkering in the garage and I always learn something new.

Another excellent video, Paul. Beautiful amplifiers and your narration is excellent and informative as always. 👍🏻

Thanks, you have explained this very well. I have a pair of Six Pac’s, stock with the factory upgrades to better resisters, caps, wire, and connectors. The bias pot is a problem; it’s so sensitive that just touching it changes the bias. They put out a ton of heat, and a re-tube will cost you. One sweet sounding pair of amps.

As a very amateur hifi hobbiest I find a challenge in the practical matter of comparing the schematic to the unit. Watching you do it is most informative. In fact your series to date is just super. I watch uncle doug and a couple other similar tube channels .... Top notch tube stuff for us tubers. Thanks.

This is why I always like your channel. You always seem to know how to be careful enough to do the right thing.

i wish so badly i were younger....your teaching is the best there is!

You are the circuit whisperer. I wish I could see what you see when you look at these devices.

Thanks for this video! I, as many others, really enjoyed it. This is real quality education. I recently designed my first simple tube audio amp. Parts are mostly in. So the building process can start soon. Watching your video's delivers me a lot of tips & tricks which i can utilize during and after the build. Liked especially the zener cooling tip in this video :) Looking forward to future video's. Thanks a lot for sharing!

I can listen to this guy all day....Clearly and easily explains electronics. Good review / reminder / discovering electronic theory

He's a clever guy and good at showing things, like to watch these vids....

I know zero about electronics. I can find the circuit breaker box in my home and I know how to plug electrical cords into receptacles...and I can operate a power switch. But, I love to watch Paul's video because they are often like a good 'who-done-it' movie. You get to travel with Paul as he collects the evidence to find the miscreant part(s). And, he always gets the culprit.

That was very very informative, I am looking forward to your future videos. On a different note, seeing the wiring as standard in there makes me feel a whole lot better about the state of the 300b amp I built! Thank you.

Well done Sir. I miss working with tubes. “Dip the plate and peak the grid” is burned in my memory. Please keep the art alive as long as you can. I regret that I will have to live vicariously through your above and beyond, excellent instruction.

A newbie to the channel and I enjoyed every minute, now in catch up mode :)

oh, wonderful tube audio engineering with Paul and unlike other KZfaqrs, without being condescending about "tube sound"

I started in electronics when I was just 15 years old.My father was a TV Tech,and after only 3 jobs in my life I am now 62 years old.Great video Mr,Carlson,Steve.

I watched it as a thriller! Perfect! Clear and visible explanation! Thanks! Good luck!

Choices....ugly rainy day here....had to choose between vacuuming/dusting or Paul's video. Paul's video won.....vacuuming can bloody well wait! :-)

Great video, thanks! I'm a recently retired EE that has been designing solid state electronics for 42 years, but I've gotten interested in tube design. I built things with tubes as a HAM operator back in my teens, but never designed anything. Videos like this are very helpful. I'd like to build my son a tube guitar amp. BTW - They would get much more effective ripple rejection by placing the 1uF cap that's presently on the emitter of the voltage regulator on the base instead (or do both). The base is a high impedance, the emitter is a low impedance. It would also greatly reduce the momentary stress on the NPN, since there is a surge current into the 1uF at turn-on (depending on the rise time of the 400V B+ rail). Also, interesting that they didn't place any small caps across the series '5408's in the B+ rectifier to help equalize the voltage drop across them. The location of the B+ filter inductor certainly is a poor and curious one.

Top notch PhD coverage of an audio amp design from circuit to impact of layout.

Thanks for your tutorial on vacuum tubes amplifier ..it is definitely the simplest way to understand troubleshooting and also how to use basic instruments in a lab.

Many years ago I worked with an amplifier manufacture, on final test, the toroidal mains transformer was rotated to obtain a hum null, (50hZ of course) much like you did with that choke. To see minimum cross over distortion we used a 10khz tone and looked at the extracted distortion. One could very clearly see the glitch within the distortion which could be completely removed as the bias was increased. With total THD as low as 0.01% the cross ever glitch was almost the only visible distortion apart from low level noise. Needless to say this was a transistor amplifier!! Great video as always, thank you.

Thanks for another great video Paul! I would think about switching from choke input to CLC filtering for B+ with a full wave bridge rectifier connected to two 300v secondaries in parallel. This would allow to a) more effectively use both electrolytic capacitors with no risk of over voltage and b) greatly reduce hum and vibration from the choke which does not seem to fit for choke input application anyway. The risk of this mod is that some B+ voltage drop might occur which would be difficult to fix.

I know just enough about electronics to get myself in trouble, but learn something every time I watch your channel, thanks for sharing! Your friend is making me green with envy especially with your modifications to his amplifiers. I would probably never leave the house if I had a pair of those amps and a set of K horns....

I learned SO MUCH from this!!! Thank you for taking so much time and detail. You excel at teaching, as well as electronic diagnosis.

Just brilliant, fantastic and accurate in every way! I shall see you on patreon !

Wow I love your your videos. I am an audio fan from way back. Tubes rule!

Wow! Feature length video and it still didn't feel long enough. Great work!

Amazing.!! The best part of electronic engineering.. vacuum tube amplification.. keep up the good work.. thank you

I watched for over over an hour and i thought i was only 20 mins in. Love Love Love your vids.

No.1 ..... no words! Respect, Mr. Carlson!

There is a tremendous amount of knowledge in this video! Just what the doctor ordered! Great job Paul thank you!

I'am always impressed when I watch you work, I would love to have just 10% of your knowledge

Great Job Paul, this amp is a real beauty and your friend is a lucky guy, having you, working on his amp! Can't believe 1,5h are gone! I'd really appreciate to hear and see the final result. Many thanks for sharing this with us!

I know why the amplifier was humming! It didn't know the words :D

Man oh man, i know nothing about electronics yet i'm so fascinated just watching you trouble shoot and fix stuff, i'm binge watching all your videos now. I can only dream of building or restoring such beautiful amps myself. But hey we can't be good at everything right ? Thank's for sharing, cheers from Canada.

Thank you Mr Carlson, you said something in your video that helped me out a ton, thank you! We all wish we knew what you have forgotten. I'm revoicing a Sunn amp into a high gain machine (with only basic skills) you showed me that I may be mistakenly utilizing my heater power supply in AC, not half wave rectified DC, thank you again!

Great video! You check frequency response with the DSA without negative feedback against a dummy load. I think it would have been more interesting using a real speaker for that test because it would have introduced non-linearities (which maybe NFB would have corrected). Also at which output power was the plot performed?

I'm a bit late here. My first reaction at the beginning of the lecture was 'holly ... so much lab equipment, this guy must be very serious, maybe slightly nuts, why does he need so many scopes'. Definitely I would be in heaven with just a few of the lab pieces. This might be one of the best vacuum tube dissection video I have have seen. Strange, the designer(s) should be a bit more aware of magnetic coupling and other issues that you mentioned. But, many people this days usually own rather inefficient loudspeakers, my self included - maybe when they manufactured the amp it wasn't tested on 95dB+ 'real' speakers. A lot of people get a bit hyped up at prospect of purchasing tube gear. Not that I'm against tubes, but like you mentioned one should know what is he getting into, especially NOS tubes and tube rolling. I remember to use tube tester, because the Pro Audio place fixed a lot of tube gear, definitely a must for someone does for living. The probe is a really cool testing tool. Also some of Hi-end equipment back in the 80s, 90s had copper shielding or plating to fight RFI issues. Those Scandinavians, always up to something in audio. I will watch more of your videos, well worth the time and very informative. Thanks.

I love watching you fixing these things; amazing! Thank you.

I know nothing about electronics or valve tubes. I stumbled upon this video after looking up the numbers of some valves i have in a piece of art work someone made into a lamp to see if any of them could be suitable to make a guitar amp. Basically a desiccating jar filled with old valves and a light bulb in amongst them Cool effect. Anyway point is this is the most informative thing I've watched in i can't remember. Outstanding. Thank you for sharing. Im stuck here in New Zealand home Isolation because of the Covid 19 Virus. Will certainly be subscribing and watching more.

What amazes me is all the research into making that a great amp has been undone with bad component placement like that..........its like going 90% of the way and then slap happy for the last 10%.......crazy stuff.

Two six packs in 90 minutes! You Canadians! ;-p Very nice and informative. Thanks! :-)

Your videos are awesome. Most of the content is beyond me, so it's a stretch, but I always learn something. Thank you!

I really enjoy watching your videos. Thank you for sharing your knowledge. It's a real pleasure watching you work. Looking forward to seeing all of your videos.

Best quality picture on KZfaq

For audiable - see audible.

1) Congrats on another brilliant vidéo Paul 2) I always work with gloves now when the thing is live 3) you're super probe is the next thing I'm gonna build myself 👏👏

Thanks Mr Carlson for the nostalgic trip back to my world of Leek and Quad.

Absolutely glued to this video for the whole time, really informative and interesting and a great explanation of how it works .what is the drive voltage for the audio input for this type of amplifier, I would guess around 3-500 mV?

Love it!

The 'Noise Sniffer' was a great idea & product. - Yet another top class 'inside the case & mind' of Mr Carlson's lab. .

As always extremely interesting and well gone through! I learn something every time I watch your videos.

Where did the time go? Once again you have done an excellent job on this video. Perhaps as a follow up (sequel?) you could show us how and where you got that choke reinstalled. Secondly I wonder if you could include the description of the operation of the phase inverter tube circuit. Finally I wonder if a metal shield could be constructed around the choke as well as rotating it's mounted position. Again, very well done!

Whew! I thought you were going to electroboom yourself for a minute there. This video is Awesome!

I'm baffled by the numbers of KZfaqrs that talks in a radio voice. Very unnatural. This guy is an exception for sure - thank you.

Thanks again for the video and schooling Paul , I learn something new with every video you do.

Hmmm. Did you simply throw that switch on the back of the amp to the 4 ohms position to get 100W out of it? Great video as always, Paul! A joy to watch.

Wow... if you can’t find a Sam’s or a good schematic for your project just draw one of your own lol Geeesh!!! that schematic is so good it looks almost original... I would not know where to begin to draw one of those for a large complete circuit such as this... maybe a small one but not in that detail as you have Carlson.

Excellent video on what is likely a common problem with many of the lower priced tube amplifiers and amplifier kits.

I was having such a bad day...following a bad weekend. And then I saw this video was up...so much better now!

I haven't seen where anyone figured out the 100W mod. Those EL34 can take up to 800V, so my guess is that you added a cap on the input side of the choke to boost the B+ voltage.

Would be interesting to see the effect of copper shielding around the transformer coil for both hum and induction value.

Enjoyed this. You are very knowledgeable - more so than some of the original designers. Low noise is something I have a quest for as well. The alarm in my head sounded when I initially saw those chokes mounted where they are. Great job on reverse engineering and schematic drawing. Not easy!

You just showed all of us a simple and safe way to check capacitors for residule charge. Thank You.

To me it looks like the power supply filtering was never quite optimized in the design phase of this otherwise high performance amplifier. Clearly the ripple current trough the reactor is too high and the reactor is not correctly physically oriented related to the output transformer. I have an idea that redesigning to a lower ripple and re-orient the reactor, still located same place, would do almost the same as you moving it away from the input section out to the side. Moving the capacitor connection directly to the diodes through a low ohm current limit resistor, and then connecting 2 smaller capacitors in series on the output side of the reactor, would possibly get you close to the same result. But it would save you a major physical rebuild.

Would have like to see the final arrangement inside the chassis after you were done?

Always very good. Ya I learned my electronics the hands on blowing everything up first, then ask questions later method. Very cool to watch someone who's go it!

I can already see that it's going to take me a week to get through this video - taking copious notes for the near future work planned on rebuilding my pair of Bogen Challenger AC220 amps - little 8W jobs: (4) ECL82, (3) 12AX7, and a GZ34 power tube. Hoping to make a very retro quadraphonic system out of them. Thank you for the thorough detail, Paul.

I instructed Mil Std 2000 Category "C" soldering, wiring, and electronic assembly, as part of my job - for 17 long years. When I blinked, and you changed views to the underside of the chassis, I couldn't believe the rat's nest. Proper lead dress, and component placement were in no way primary considerations during the design phase of these unit's implementation. Shielding and ventilation were never taken into account. I could see taking short cuts with lower end "get it out the door" type merchandise, but not with anything sold with the intent of satisfying fussy audiophiles. Soapbox dismounted before going on a "pride of workmanship" rant. (sorry, I'm becoming an "habitual bitcher" - as I age like 'milk'.)

Is there no way to shield that reactor? Moving it looks like a difficult remedy.

One of the most well made and informative videos i’ve ever seen on youtube, and I’ve seen a lot of videos…