This series is an attempt at a video that will answer as many of your requests as possible. I never expected to see such a wide variety of requests for videos. In the end, I decided to build a very inexpensive amplifier kit purchased on eBay a while back. It has some interesting design features (or flaws, maybe) that will make for a very interesting learning experience. In this first part, I spend about 12 minutes talking about this channel and why I do some of the things I do in my videos. If you don't want to hear it, skip to 12:40 where I begin the actual project. In the following parts, we will study the circuit design and compare it to some of the more commonly found amplifiers out there, such as the Pioneer SX-450. We will then do some circuit testing using meters and oscilloscopes. Finally, we will try to modify or upgrade the existing circuit to improve performance. Hopefully by then, my covers for the Pioneer Spec 4 will be back from the powder coating facility! ☺
Dear Tony,maybe a helpfull thing is to get the thought proces in your head when you start on a project,resto or new build.Steps before you tackle a problem.(For electric pros this is daily stuff) Search for faults in a circuit is hard if you start at the wrong end.Look,smell, and understanding schematics will get you far.How we achive these is not relevant as long you work save and you solved the problem. Love your patience to explain to us,keep your vids up Dutch lover of tubes😂
There's camps? Of people? Haha. I've been watching for years, I like anything you do. Some of those people commenting might think they are smarter, they are bored lol! What I like about your channel, you don't use it as a platform to voice your political beliefs or complain about our country. I like your positivity. I wish more people were like that. They don't understand, this is our happy place, an outlet. Keep up the great content Tony.
Hey Tony. I think your videos are great and I really enjoy the longer ones. I do plumbing & heating by trade for the last 26 years. Before that I was a Chevrolet certified tech for about 9 years. I always had an interest in electronics but I am a total beginner at least for the most part. I have fixed a few amplifiers auto and home. Somebody gave me a 6 or 8 channel home Sherbourn. It needed every cap all 126 if I remember right. I was so happy when I powered it up and it worked lol. I still crank it in my garage with an Alpine auto deck feeding it. I have every channel hooked up with a crossover and 2 12” W6. It cranks! My head is everywhere I also have a lathe and Bridgeport mill lol. I just recently set up a spot on my bench for the oscilloscope and all the peak testers and my Fluke 88 I bought when I worked at Chevy. So anyway after all my blabbering now that everything is setup I’m getting back into it. I’ve learned a lot from you. Thank you and keep ‘em coming!
This hobby keeps me sane. You're so awesome. Make um Long and full of your knowledge. If you Saw My bench your influence is All over it. Short and sweet, I'm learning so much from you. Thanks man.
I get a kick of the various "soft start circuits" and mods to that circuit that you've done base on the amps topology and schematic. Especially since I've built SS circuits myself. Great innovations for different projects.
I've been watching your channel for years. Ive probably watched every video at least twice. :) I have a BSEET and I was fortunate to have a great instructors. You have that same passion and drive they had/have for teaching. Keep up the great work!
Learning by memorization or by imitation might seem great at first, but learning the concepts and techniques is much more rewarding in the long run. You are a great teacher sir and this hobby is thriving because of your contributions.
What a great idea! I pulled the trigger and bought one of these kits for myself and my son (12) to build. His first major project. Thanks for the inspiration.
@ 14:20 I would at the least, check the "budget" components supplied with the kit to make sure they are within tolerance, as that's the one variable that can lead to a LOT of head scratching when you apply power and signal and don't get the desired results. After that, you can at least leave it to a poor schematic design or "PEBCASI" , or "Problem Exists Between Chair And Soldering Iron" If I get parts that I know are going to sit for awhile before I get to an item, I will go through them to make sure I don't have any surprises later, even if they are from Mouser or Digikey. @ 21:00 , one could say, you created the electromechanical equivalent of "jock strapping".
You are not being fair to yourself. Yes, watching a video of a guy repairing and/or restoring an old amplifier will sound boring to many people, but I don't think anyone following your channel had ever fell asleep while watching any of your videos. I watched many of them as if I was watching an action movie. It is a matter of mindset that many people wouldn't understand. This is one of the top 10 channels I follow on RU-vid, in fact it is the only one that deals exclusively with audio amplifiers. My real passion is retro computers and if you can make me watch videos on analog audio circuits, then you must be doing something right!
My eyes lit up when I saw the thumbnail!!!! Yesss! It's back on the bench!! The force is strong with this one but resistance is futile up against the great master Tony! I have no problem assembling kit's when they are designed good enough! I'm not always in the copy camp although I do do it from time to time especially if I'm in uncharted waters, and even then, I will test and measure to see what happens to get a proper understanding of what happens under certain circumstances.... I'm really looking forward to this series, I fully understand that it's not a powerful amplifier and I don't mind this fact at all, I have in my possession two kit amplifier's that were built by someone else, one was out of the 1973 Electronics Australia Magazine and it is rated for 13rms per channel, through a pair of 15" 3 way Realistic speakers it's the best sounding amplifier I have and personally heard! There's enough power there to annoy the neighbours! The other more recent find was a Dyna Audio solid state amplifier, it was purchased and built by Telecom Australia (it was still government owned back then before it was privatised), I have no idea what a telephone exchange would be doing with such a beautiful amplifier but they did an amazing job putting it together and the hand wound inductors wrapped around the two very large capacitors is really something else, I have never seen this before in any other amplifier! If you ever get the chance to look at the building diagram for a solid state Dynaco amplifier, it's right there... The instructions are beautiful! US engineering at it's finest! I just hope that those very large capacitors aren't bad.... I'm going to use my Variac with a bridge rectifier and a micro amp meter to slowly bring up the voltage on the capacitors out of circuit naturally and see if they leak DC at any given point right up to their rated working voltage, none of the capacitor testers I own can test these things.... I will also have to add in a switch and resistor to dissipate the stored energy once the test is completed... I hope that they are still good, I fear that the inductor coil's wound around these capacitors would change in value if the same size can't be found.... I guess that I should measure their inductance and make a note so that I can work it out if new capacitors are needed.... It's a beautiful machine, I would love to see one on your bench one day.... But back to the amplifier on your bench now, patiently waiting for the next video.... I would love to know if it's possible to use a higher voltage transformer with it, I have lost of transformers to choose from but something in the range of 30V+ would net a few extra watts at the exhaust... I wouldn't complain... Through large and efficient speakers it could sound pretty good even if it's not too powerful.... Anyway, loved this video, full of wisdom as usual and useful hints and tips.... I may not comment as often as I should but I can assure you that I'm watching (and that just sounded creepy LoL).... Unless it's a tuner video, I have watched quite a few of your videos on tuners but have stopped watching them altogether, I'm not a tuner person, I never connected an antenna to my car systems for the fear that someone is going to ask to listen to sports, same thing at home! AM broadcast in Australia is almost dead, it's still there and some people still listen to it but I'm not one of them... I love music and I want to listen to it without some random people talking about crap that I didn't need to hear in the first place and all the commercials! In a 30 minute drive, you are doing well if you heard 2 songs! Aaaaaand I'm ranting...... Enough of that from me.... You just keep doing what you do... I'm going to be right here waiting... Thank you for everything.
@@marka1986 Dynaco Stereo 120 is exactly what's printed on the side of it! Have you ever had the pleasure of seeing it in person? I have yet to hear it, it's waiting for a full restoration before I will fire it up.... I want it as original as possible meaning that any components I replace need to look like the original parts.....
this is a super basic discrete amp, with a differential amp. they sell full soldered kits for there things @$5-6 at electronics markets here. 😊 obviously, not with highest quality components though.
Hello Tony,I can't beleve you picked this amp AGAIN! I bought this amp years ago just to study how it worked, this is more or less how it was explaned to me. Could you let me know if any of this is wrong. I can't wait to here what you have to say about this amp, I still have mine It was my first kit. The right channel, the input signal enters X3 connector and is AC coupled and biased to ground through R3. It goes to one Q1 of a differential pair which will have a large amount of signal gain. The differential pair uses R7 to deliver a fairly constant current which is split evenly between Q1 and Q3. The current through Q3 is entirely wasted as Q3 has no collector resistor. The amplified signal of this pair is developed across R5 and sent to the next stage Q5. Transistor Q5 is a common emitter stage with no emitter resistor so it also has a fair amount of gain. The collector current of Q5 develops Q5's output voltage across R13. Because this current also goes through two diodes,two output voltages are developed to be passed on the the output stages. These voltages are in-phase and the same amplitude but separated by about 1.4 V DC. This separation is necessary because the two output stages require their driving signals to be so separated so that the output stages are not simultaneously turned off with near-ground signal level. On positive excursions of the audio signal, Q7 and Q11 turn on and act as a conventional Darlington pair, or high-current-gain emitter follower and drive current into the load. During this time Q9 and Q13 are turned off. On negative excursions of the audio signal Q7 and Q11 are turned off and Q9 and Q13 turn on. They form a Sziklai pair. When Q9 conducts it develops signal voltage across R19 and pulls the base of Q13 higher (farther away from the negative rail). This turns Q13 on and delivers negative current to the load. If R17 and R19 are not chosen with care these transistors can burst into oscillation (usually 1 - 10 MHz) and waste a lot of power. R21 and C9 form an impedance -correcting network which can aid in making the power stage stable against spurious oscillations. This network is called a Zobel Network Not a very well understood concept. Their values also depend on what the load looks like impedance-wise. Now, lastly let's look at R11, R9 and C3. This is the feedback from the output to the other side of the differential pair. The differential pair subtracts the feedback voltage on the base of Q3 from the input signal on the base of Q1. This reduces the gain of the whole circuit by a lot and also reduces its signal distortion by the same amount. This whole circuit has the classical architecture of an op-amp. And, just like an op-amp it requires gain-setting feedback network. The gain set here is calculated just as with an op-amp as (Rf/Rg + 1). In this case it is (R9/R11 + 1) = 71. So with +/- .7V Pk signal in it should deliver about +/- 50V Pk out to speakers. C3 AC couples the feedback to the high-gain stage so that residual DC offsets in the circuit will not be amplified as much.
The next part in the series is already uploaded in two parts (part 2a and 2b). When I release them, they are all about what you are saying. Stay tuned!
You forgot about the 3rd group of people. People who just watch videos because they have something in common with you and might pick up a tip they missed along the years here and there or see some equipment we might never have come across before, the history etc. Just nice to see some decent gear restored and repaired or have something playing in the background.
Igen , ezt én is így gondolom, Nagyon sok mindent hasonlóan csinálunk a világ masik oldalán is, csak a mi felszerelésünk sokkal szerényebb. Ezt a szakmát nem lehet videókból megtanulni, ezt csinálni kell..
Tony, I ordered a kit of a range of cheap Chinese capacitors from EBay only to discover that they all test bad. What a waste of money, I suspect kits like this one are cheap because they use old surplus parts known to be bad or out of spec.
