You ask about if you confuse the subject more then it helps. I can only say that I learned more about measuring amplifiers from your video then I have learned the last two month of looking other RUclips videos!! Thanks for sharing! :-)
Thanks Tony, now I can download the datasheet for those output transistors and literally geek out on their specifications, in particular their power handling (voltage, current and wattage) and their switching frequency (which is important to obtain the profile of square wave that you want, fast switching = perfect square, slower switching = less likely to oscillate) and lastly.... Their gain. It's interesting the choices that the designer makes when choosing transistors, some designers simply understand transistors better than others...
Great video! And thank you for the expertly explained way of reading, checking, and adjusting Bias and DC offset. Best I've ever heard it explained. I understood most of it before, but your rendition stuck like glue. You da man! Thanks again Tony!
As I watch your videos, I am increasingly realizing that you are a true professional in electronics and fine electricity. i am audiophile and music is what fills me but after all the explanations about the dynamics of music based on current calculations i now realize that most probably i am not listening to music as it should. I wish I could give you my power amplifier for a detailed review, but it's totally impossible because I'm on another continent. I love you channel and I want you to just keep going and make good videos.
Happy New Year Tony! Thank you very much for taking the time to make these highly informative and educational videos! I want you to know that I appreciate the effort, the work, and the time that you place into sharing your knowledge and techniques with us. God bless you Tony.
Great stuff as always, Tony! Many blessings! My amp made in the early 80s claims a slew rate of 250V/uS. It is easily the best sounding amp I've ever heard - highly detailed, yet smooth and easy to listen to, and watching this video is the first time I've paid any attention to slew rate. Maybe there's something to it. Now I have to go measure it and see if their claims are correct!
The amplitude at 60 kHz is less because the amplifier doesn't have the time to get up to the maximum amplitude. The more you raise the frequency, the more the amplifier finds it difficult to reach maximum amplitude. Thank you for all that information. I learned too much from your channel.
This has to be one of my top 5 favorite videos! It also helped me understand how my HP 5335A works to generate rise and fall times and slew rates automatically. 😉
Great video! I'm currently going through a pair of Crown ComTech 1610s. They are scary! 960 watts into 4 ohms, 58 pounds. They scare me much worse than being inside any TV I have serviced.
Hi Tony Really enjoyed this video. Slightly off topic but based on your fantastic videos I just bought myself a Fluke 179 meter and a Hakko soldering iron. I was never quite sure how accurate my basic meter was so can't wait to get using my new one! I know they are expensive but as the old saying goes, buy cheap buy twice. Andrew, UK.
Happy New Year Tony! Another terrific video! Thanks for demystifying slew rate, how to measure and what it means to amplifier performance. Have you done or could you possibly do something similar on damping factor?
Happy New Year Tony. You did it yet again another great video,very informative. So in a convoluted way you are saying this amp can go from about 0 to 60 (volts) in about 4.5 usec
11:10 - Those trimmers should be cleaned. The one on the first channel that you set the bias on (08:11) appeared to have a 'dead-spot' between 38mV and 42mV!
You can buy inexpensive kits with an assortment of blue Bourns-style ( knockoffs) multi-turn trimpots, direct from China. Best to buy an assortment of vertical mount pots as well as horizontal pots. The only drawback is that the leads are thin and kinda short, and might not match the footprint of the original trimmer. Retrofitting multi-turn trimpots into a vintage amp sometimes requiring lengthening the leads with jumper wires, or, better yet, drilling tiny holes in the PCB and modifying the foil side of the board with jumpers, or cut foils, to make the proper connections.
Good job! These amps are ready for another happy customer. Mitsubishi is one leading industrial Japanese giant, and produce many components for others. They can produce air planes, boats, cars and many other things. They're less known for their consumer electronics, but they've produced and sold some video and audio products. You can also find some Hitachi or Matsushita like these, but most were not sold outside Japan. It's a sort of proof of know-how demonstration force, say a company like Boeing or Bethlehem steel selling HiFi to it's best customers, as they can produce flight computers, car engine ECUs, medical hardware... One part you particularly noticed is the massive and effective heatsink. I guess it is not originally designed for this specific application, but perfectly match the needs (seen something like these in black boxes). Most of high end HiFi amps also use these, but you can notice the more expensive, the more "demonstrative" and massive they get. You can compare a Denon, a McIntosh or a Krell and bet the price! The most surprising seems the poor quality of the output connectors. You can guess they can suffer in transportation, as they effectively protude from the back. I've seen that so many times! This amp has external encased transformers, more common on high end of tube chassis. This way, it's said they suffer less from shocks. One of the most destroyed amp I've seen was a high end Yamaha PA7, fallen somewhere during transportation, with massive transformer loose "in the box", a torn and destroyed chassis... A transistor salad!
I've never seen or even heard of a Yamaha PA7, and I've worked on a *lot* of Yamaha gear. Are you sure you didnt mean a Nakamichi PA-7? Those frequently do get damaged in shipping, or transit...
@@goodun2974 You're right, cause I also had on of these pricey Nakamichi PA7! But also had a Yamaha M45 poweramp at the same period with same problem. 30 years later, I still remember the strange sound emitted by the relatively nice looking cardboard box, and the minute later, the look of my boss already thinking insurances, new delivery delays... Two layers of packaging, lower mass than Nakamichi, but some unhealthy heavy component mount resulting in broken hardware. The Yamaha also had a broken digital meter.
Another great video! If you ever find a source for the speaker terminals, please post a link. I am in need. I am having to share common grounds to make mine work. Not ideal. Thank you.
"you may be able to here". Yes, you will be able to hear....you even mention you could have with the sansui. Yes, that's what we are talking about. The faster slew rate allows for more fine detail of the overlaying frequencies. Violins, force of a piano,. Natural reverb, etc.
What is the difference between going through the hustle and calculating the slew rate from the 10% points and overlaying the input signal and the scaled output signal on top of each other using a 2 channel oscilloscope and directly observing the discrepancy?
55:30 : Is it possible to tell a slow blow fuse and a fast blow fuse apart by looking at them? 57:00 : How can one tell if the parts are fixed with the corrosive type of glue? On ATX PC power supplies many large parts are fixed with a white-ish glue. Is that one ok? Also, why are they using that glue in the first place? Is it to prevent parts coming loose or to minimize microphonic parts from picking up vibrations?
Would the slew rate of the signal generator not be a important factor to? How good/fast should the input signal be? The coax cable could allso influence the quality of the squarewave especially at high frequency.
Test equipment will have an effect on the slew rate, but most signal generators have a very short rise time by design. The generator I was using has a rise time of .004µS, including the attached cable! Remember, the amp in the video had a rise time of just over 4µS (1000 times slower), so it didn't have much influence on the test results. Thanks for the comment!
The worst style of orange caps for causing noise and electrical leakage are the low-mfd-value orange caps that are epoxy sealed at the bottom. Sometimes they leak and the leads visibly corrode, but often they look okay. Just replace them.
50mV is what they specify. This allows for a lot of error. If the transistors are fairly matched, you can reduce the idle current and still get no crossover distortion while allowing the amp to run a bit cooler.
I'm not sure what you mean by electron bounce? But as far as I know, the only way to bounce electrons is to aim the electrons at something which is non magnetic and cooled down to -190C, you will find at that temperature the non magnetic matter will not pass electrons and they will simply bounce off. Hope this helps :)
what about 2x 560k 20 turn pots that should solve a few problems, I have had to move away from Class A amplifier as they run very hot and after a while the electrolytic capacitors need replacing so I have moved to a DSP based system with a Class D output stage and actually the audio is actually quite good,
Nice amps, another great video. My mate has a Misubishi system including one of these amps, he speaks very highly of it. BTW, what caps or series of caps do you replace those low ESR orange electrolytics ? Cheers, DA.
If you can't get the value or don't have the space on the board for film caps, the KL series by Nichicon are really good. I also had pretty good luck with the UFG series, but KL is better for replacing the orange electrolytics. The best choice is a stacked film by WIMA or Kemet, but you can't always get them in the higher values without them being huge in size.
Some of the lower-end amps from the 1970's had a fixed-resistor DC offset. You would check offset and if it was out of spec, there was a provision to install a jumper across the fixed resistor. If that didn't bring it in, you were supposed to check the transistors for leakage or low gain. If they were OK, you had to swap out the resistor for another value. Very rarely did you ever have to install or remove the jumper. If the amp had DC offset, you usually had a bad transistor. Bigger amps with paralleled outputs and more complex circuitry usually had adjustable offset.
If you have modest DC offset ( not enough to trigger the protection circuit), replace the feedback capacitor in the differential input circuit (use a bipolar electrolytic!) And check or replace the differential transistors, they need to have matching gain and if one is leaky you will have offset. If the leads of those devices are oxidized and blackened, replace them!
Have you ever seen an output impedance-matching transformer (like the one used on McIntosh amp) on a bipolar amplifier? and do you think it is a good idea to use one, even on a class-D switching amp.
@@NICK-uy3nl -- Incorrect on all counts. First of all, terminology cannot be "patented." Second, "autoformer" -- essentially a shorter version of "autotransformer" -- is an accepted generic term and is not exclusive to any particular manufacturer (see en.wikipedia.org/wiki/Autotransformer) or to audio applications -- McIntosh apparently claims a trademark on the term "autoformer," but that trademark has never been registered and the term is openly used by other companies. Third, McIntosh solid-state amplifiers use autoformers -- check out Tony's recent video series about restoring an MC-2100.
Thanks for the comment! An amplifier needs to be designed for an autotransformer in order for it to take advantage of their benefits. For instance, the target impedance designed into the McIntosh 2100 is around 2.5 ohms. The autoformer matches speakers of other impedance to 2.5 ohms. This makes the design more current dependent rather than voltage dependent. This is why the power supply has such oversized filter capacitors and power transformer for only a 100 watt amp. To drive higher impedance loads to full power, the autotransformer converts some of that current to a higher voltage. This, of course causes the outputs to deliver higher current. The "Sentinel Circuit" (the two darlington transistors) are designed to limit the current on the output transistors so that they can't be overloaded by the speakers/autoformer. Most amps would not be capable of delivering the extra current required to achieve the same wattage at higher speaker impedances, if using an autotransformer. A rather long-winded explanation, but I hope that helps.
@@xraytonyb - Thanks for the description. Seems to me that only prohibiting factors are COST and the SIZE of the autoformer (besides any Intellectual property issues claimed by McIntosh). Designing an output stage to deliver high currents into a constant 2.5 ohms load (the autoformer) is fairly straightforward.
That's what I would think, but the service manual has you do it bass-ackwards ;) You really should go back and check bias afterwards, just for good measure. Thanks for the comment!
Mic's a little fuzzy but basically all right. If you get ambitious, consider the Rode wireless Go system, available on Amazon and I assume elsewhere. Gives really transparently good results.
If you listen to Tony he explains why this is desirable. Yes everything can be improved but this is a deliberate design choice for the reasons discussed.
You ask about if you confuse the subject more then it helps. I can only say that I learned more about measuring amplifiers from your video then I have learned the last two month of looking other RUclips videos!! Thanks for sharing! :-)
Thanks Tony, now I can download the datasheet for those output transistors and literally geek out on their specifications, in particular their power handling (voltage, current and wattage) and their switching frequency (which is important to obtain the profile of square wave that you want, fast switching = perfect square, slower switching = less likely to oscillate) and lastly.... Their gain. It's interesting the choices that the designer makes when choosing transistors, some designers simply understand transistors better than others...
Great video! And thank you for the expertly explained way of reading, checking, and adjusting Bias and DC offset. Best I've ever heard it explained. I understood most of it before, but your rendition stuck like glue. You da man! Thanks again Tony!
Hot cup of coffee and a fresh xraytonb video...starting the day off right!
Me three!
Me four!
@@electronicengineer Me five
As I watch your videos, I am increasingly realizing that you are a true professional in electronics and fine electricity. i am audiophile and music is what fills me but after all the explanations about the dynamics of music based on current calculations i now realize that most probably i am not listening to music as it should. I wish I could give you my power amplifier for a detailed review, but it's totally impossible because I'm on another continent. I love you channel and I want you to just keep going and make good videos.
Man, u make things more clear than any one that I have come across! Videos like this are absolutely valuable.
Happy New Year Tony! Thank you very much for taking the time to make these highly informative and educational videos! I want you to know that I appreciate the effort, the work, and the time that you place into sharing your knowledge and techniques with us. God bless you Tony.
Great stuff as always, Tony! Many blessings!
My amp made in the early 80s claims a slew rate of 250V/uS. It is easily the best sounding amp I've ever heard - highly detailed, yet smooth and easy to listen to, and watching this video is the first time I've paid any attention to slew rate. Maybe there's something to it.
Now I have to go measure it and see if their claims are correct!
Another excellent and informative video. Your time and patience with the explanations is sincerely appreciated, thank you Tony.
Love it when things work out, brilliant lesson on slew rate. Thanks for sharing 🙏
The amplitude at 60 kHz is less because the amplifier doesn't have the time to get up to the maximum amplitude. The more you raise the frequency, the more the amplifier finds it difficult to reach maximum amplitude.
Thank you for all that information. I learned too much from your channel.
This has to be one of my top 5 favorite videos! It also helped me understand how my HP 5335A works to generate rise and fall times and slew rates automatically. 😉
The new mic is working properly and thanks for all you do
Great video! I'm currently going through a pair of Crown ComTech 1610s. They are scary! 960 watts into 4 ohms, 58 pounds. They scare me much worse than being inside any TV I have serviced.
Nice little hot rod your working on there Tony. Looks like lots of fun to work on. 👍
Hi Tony
Really enjoyed this video.
Slightly off topic but based on your fantastic videos I just bought myself a Fluke 179 meter and a Hakko soldering iron. I was never quite sure how accurate my basic meter was so can't wait to get using my new one! I know they are expensive but as the old saying goes, buy cheap buy twice.
Andrew, UK.
Happy New Year Tony! Another terrific video! Thanks for demystifying slew rate, how to measure and what it means to amplifier performance. Have you done or could you possibly do something similar on damping factor?
Happy New Year Tony. You did it yet again another great video,very informative. So in a convoluted way you are saying this amp can go from about 0 to 60 (volts) in about 4.5 usec
I guess this amp would rule on the drag strip ;)
A very informative and interesting video, thanks for sharing Tony.
16:50 - Tony, I believe using a s'cope would be better for this kind of adjustment!
11:10 - Those trimmers should be cleaned. The one on the first channel that you set the bias on (08:11) appeared to have a 'dead-spot' between 38mV and 42mV!
47:07- I'm guessing that 'small-signal slew rate' would be the MAXIMUM slope of the waveform (-1V to 0V).
You can buy inexpensive kits with an assortment of blue Bourns-style ( knockoffs) multi-turn trimpots, direct from China. Best to buy an assortment of vertical mount pots as well as horizontal pots. The only drawback is that the leads are thin and kinda short, and might not match the footprint of the original trimmer. Retrofitting multi-turn trimpots into a vintage amp sometimes requiring lengthening the leads with jumper wires, or, better yet, drilling tiny holes in the PCB and modifying the foil side of the board with jumpers, or cut foils, to make the proper connections.
Good job! These amps are ready for another happy customer. Mitsubishi is one leading industrial Japanese giant, and produce many components for others. They can produce air planes, boats, cars and many other things. They're less known for their consumer electronics, but they've produced and sold some video and audio products. You can also find some Hitachi or Matsushita like these, but most were not sold outside Japan. It's a sort of proof of know-how demonstration force, say a company like Boeing or Bethlehem steel selling HiFi to it's best customers, as they can produce flight computers, car engine ECUs, medical hardware...
One part you particularly noticed is the massive and effective heatsink. I guess it is not originally designed for this specific application, but perfectly match the needs (seen something like these in black boxes). Most of high end HiFi amps also use these, but you can notice the more expensive, the more "demonstrative" and massive they get. You can compare a Denon, a McIntosh or a Krell and bet the price!
The most surprising seems the poor quality of the output connectors. You can guess they can suffer in transportation, as they effectively protude from the back. I've seen that so many times! This amp has external encased transformers, more common on high end of tube chassis. This way, it's said they suffer less from shocks. One of the most destroyed amp I've seen was a high end Yamaha PA7, fallen somewhere during transportation, with massive transformer loose "in the box", a torn and destroyed chassis... A transistor salad!
I've never seen or even heard of a Yamaha PA7, and I've worked on a *lot* of Yamaha gear. Are you sure you didnt mean a Nakamichi PA-7? Those frequently do get damaged in shipping, or transit...
@@goodun2974 You're right, cause I also had on of these pricey Nakamichi PA7! But also had a Yamaha M45 poweramp at the same period with same problem. 30 years later, I still remember the strange sound emitted by the relatively nice looking cardboard box, and the minute later, the look of my boss already thinking insurances, new delivery delays... Two layers of packaging, lower mass than Nakamichi, but some unhealthy heavy component mount resulting in broken hardware. The Yamaha also had a broken digital meter.
Thanks Tony! Looks like they used non-acidic glue on those boards. The lapel mic sounds good.
I am totally with you on sloo rate
Another great video!
If you ever find a source for the speaker terminals, please post a link. I am in need. I am having to share common grounds to make mine work. Not ideal.
Thank you.
Stay tuned for the next couple videos. I think you'll have your answer ;)
Tony - the new mic sounds great.
Are these amps easily bridgable I wonder?.... can You do a little tutorial on that. Happy new year from Canada All.!
"you may be able to here". Yes, you will be able to hear....you even mention you could have with the sansui. Yes, that's what we are talking about. The faster slew rate allows for more fine detail of the overlaying frequencies. Violins, force of a piano,. Natural reverb, etc.
Nice amps, it seems to be a little known fact that most of the cheap Teleton equipment was manufactured by Mitsubishi.
What is the difference between going through the hustle and calculating the slew rate from the 10% points and overlaying the input signal and the scaled output signal on top of each other using a 2 channel oscilloscope and directly observing the discrepancy?
55:30 : Is it possible to tell a slow blow fuse and a fast blow fuse apart by looking at them?
57:00 : How can one tell if the parts are fixed with the corrosive type of glue? On ATX PC power supplies many large parts are fixed with a white-ish glue. Is that one ok? Also, why are they using that glue in the first place? Is it to prevent parts coming loose or to minimize microphonic parts from picking up vibrations?
Would the slew rate of the signal generator not be a important factor to? How good/fast should the input signal be? The coax cable could allso influence the quality of the squarewave especially at high frequency.
Test equipment will have an effect on the slew rate, but most signal generators have a very short rise time by design. The generator I was using has a rise time of .004µS, including the attached cable! Remember, the amp in the video had a rise time of just over 4µS (1000 times slower), so it didn't have much influence on the test results. Thanks for the comment!
43:50 : What's your take on the various types of valve amps regarding that matter (i.e. T.I.M)? Have any typical measurements at hand?
Does the signal generator have a measurable (or even published) slew rate that you have to take into account? (and does the scope?)
Check out the video on the DA-M10. I address this and demonstrate it. I actually had several viewers ask this same question. Thanks for the comment!
The worst style of orange caps for causing noise and electrical leakage are the low-mfd-value orange caps that are epoxy sealed at the bottom. Sometimes they leak and the leads visibly corrode, but often they look okay. Just replace them.
I'da been tempted to order and install 4 10-turn pots, so that the adjustments could be less fiddly.
Hi Tony,excuse me,but are you sure that the 90% of the upper portion of the square wave is in that position?
The service manual at Hifiengine says 50mv for idle current. What manual do you have that says 42mv. Tony you rock keep the videos comming.
50mV is what they specify. This allows for a lot of error. If the transistors are fairly matched, you can reduce the idle current and still get no crossover distortion while allowing the amp to run a bit cooler.
Hi tony! Do you think you could do a segment on the electron bounce something that's not discussed in plain English
I'm not sure what you mean by electron bounce? But as far as I know, the only way to bounce electrons is to aim the electrons at something which is non magnetic and cooled down to -190C, you will find at that temperature the non magnetic matter will not pass electrons and they will simply bounce off. Hope this helps :)
Tony, does it look feasible to unscrew the speaker terminals fully and insert regular 4mm speaker binding posts into the holes?
Current cut is always faster than current rise in transistors.
what about 2x 560k 20 turn pots that should solve a few problems, I have had to move away from Class A amplifier as they run very hot and after a while the electrolytic capacitors need replacing so I have moved to a DSP based system with a Class D output stage and actually the audio is actually quite good,
Nice amps, another great video. My mate has a Misubishi system including one of these amps, he speaks very highly of it. BTW, what caps or series of caps do you replace those low ESR orange electrolytics ? Cheers, DA.
Nichicon KL are low leakage or you can use something like Wima stacked film (if they'll fit) which are far lower leakage than any electrolytic.
If you can't get the value or don't have the space on the board for film caps, the KL series by Nichicon are really good. I also had pretty good luck with the UFG series, but KL is better for replacing the orange electrolytics. The best choice is a stacked film by WIMA or Kemet, but you can't always get them in the higher values without them being huge in size.
How do you alter the dc offset on an amp with no pots on the board to adjust it, without changing components? I suspect you can't.
Some of the lower-end amps from the 1970's had a fixed-resistor DC offset. You would check offset and if it was out of spec, there was a provision to install a jumper across the fixed resistor. If that didn't bring it in, you were supposed to check the transistors for leakage or low gain. If they were OK, you had to swap out the resistor for another value. Very rarely did you ever have to install or remove the jumper. If the amp had DC offset, you usually had a bad transistor. Bigger amps with paralleled outputs and more complex circuitry usually had adjustable offset.
You could identify the resistors that set the offset and replace them with a pot.
If you have modest DC offset ( not enough to trigger the protection circuit), replace the feedback capacitor in the differential input circuit (use a bipolar electrolytic!) And check or replace the differential transistors, they need to have matching gain and if one is leaky you will have offset. If the leads of those devices are oxidized and blackened, replace them!
Did you find out who sells the IMPROVED speaker terminals? Please share.
Have you ever seen an output impedance-matching transformer (like the one used on McIntosh amp) on a bipolar amplifier? and do you think it is a good idea to use one, even on a class-D switching amp.
McIntosh uses an autoformer (multi-tapped single-coil inductor) on their solid-state power amps, not a transformer per se.
"Autoformer" is their patented brand name for the single-coil transformer - and as far as I know they only use it in their tube amplifiers...
@@NICK-uy3nl -- Incorrect on all counts. First of all, terminology cannot be "patented." Second, "autoformer" -- essentially a shorter version of "autotransformer" -- is an accepted generic term and is not exclusive to any particular manufacturer (see en.wikipedia.org/wiki/Autotransformer) or to audio applications -- McIntosh apparently claims a trademark on the term "autoformer," but that trademark has never been registered and the term is openly used by other companies. Third, McIntosh solid-state amplifiers use autoformers -- check out Tony's recent video series about restoring an MC-2100.
Thanks for the comment! An amplifier needs to be designed for an autotransformer in order for it to take advantage of their benefits. For instance, the target impedance designed into the McIntosh 2100 is around 2.5 ohms. The autoformer matches speakers of other impedance to 2.5 ohms. This makes the design more current dependent rather than voltage dependent. This is why the power supply has such oversized filter capacitors and power transformer for only a 100 watt amp. To drive higher impedance loads to full power, the autotransformer converts some of that current to a higher voltage. This, of course causes the outputs to deliver higher current. The "Sentinel Circuit" (the two darlington transistors) are designed to limit the current on the output transistors so that they can't be overloaded by the speakers/autoformer. Most amps would not be capable of delivering the extra current required to achieve the same wattage at higher speaker impedances, if using an autotransformer. A rather long-winded explanation, but I hope that helps.
@@xraytonyb - Thanks for the description. Seems to me that only prohibiting factors are COST and the SIZE of the autoformer (besides any Intellectual property issues claimed by McIntosh). Designing an output stage to deliver high currents into a constant 2.5 ohms load (the autoformer) is fairly straightforward.
Can I have the name of the speaker terminal company, please
Shouldn't you align DC offset prior to BIAS? That is how it reads in most service manuals. Unless this amp is an exception?
That's what I would think, but the service manual has you do it bass-ackwards ;) You really should go back and check bias afterwards, just for good measure. Thanks for the comment!
Mic's a little fuzzy but basically all right. If you get ambitious, consider the Rode wireless Go system, available on Amazon and I assume elsewhere. Gives really transparently good results.
The new mic sounds like it is on the inside of your shirt.
Crappy slew-rate at 28:10 asymmetrical... is not good.
If you listen to Tony he explains why this is desirable. Yes everything can be improved but this is a deliberate design choice for the reasons discussed.
I juat fell asleep while watching youre video
Thank you! this was awesome. ruclips.net/video/mk9FsFPaL5w/видео.html
Great discussion and demonstration. Lots of info to digest, thanks.