I can say that you are the best and pleasant in explanations, I watch many films about repairs in audio electronics, you are above all. I'm looking forward to a new project. Thank you for the pleasure you give me watching and learning!
"YEHAA" , really love the specs! You are really good on passing alot of knowledge to us, which I am quite grateful. Keep up the wonderful teaching you are doing on your channel. Thanks and ENJOYED!
In this video XrayTonyB proves that technical videos can be informational and humorous. Thanks xraytonyb for this video and all the others. Very precise and well explained. They give enough detail that I'm comfortable performing this work at home.
The relay trip with a 4hz signal was interesting. One wouldn’t want to drive that amp more than 50% power playing a vinyl record without a subsonic filter. Speakers (woofers) wouldn’t like that either. Power hungry Low frequency rumble.
Tony when you were playing the "music" I could clearly hear a premature drop in response at just below 79kHz. This was obvious even through my 1970s Sony amp. I believe this to be because you ran the cables past a large pile of non--audio grade tools on your bench. Do I win the file?
The specs show that distortion is rated at full output power. That is very good for any era, because normal listening levels would be much lower distortion on the Marantz. Modern mass market amps are typically tested at 1watt for distortion specs and output power at 10% distortion with only one channel driven. Basically, modern specs are useless info. Higher end companies still use real specs.
Hi Tony, Ive been watching your videos for years now. Its my first comment, I want to say thanks a lot for your great contents as those have given me the opportunity to learn a lot. Unfortunately blockheads cannot go away...lol. Continue with your good work. Cheers..Z
Excellent test. The slew rate is the time derivative of a sine wave d/dt[Vpsinωt]=ω×Vpcosωt = 2πf×Vpcosωt, and the highest slew rate is for cosωt=1, and as a result the minimum slew rate should be 2πf×Vp. If we use Vp-p we obtain a better sine wave, but I tink it's OK to use Vp instead of Vp-p. In this way the maximum undistorted frequency from calculus will be double.
Thanks for the comment! The only issue I see with just using half of the waveform is with the complementary design of these type of amplifiers. Technically speaking, the rise time and fall time of each side could be slightly different. Using only half of the waveform would not account for that. This is really nitpicking, as they are usually so close that this doesn't matter. One thing I love about electronics is the use of "close enough" math that is often much simpler than the more precise calculation that a math major would use. My son is currently attending college for EE and often has these discussions with his friends (math majors) as well as his professors about this. Very interesting!
Very enjoyable video! You could have shown the waveform (ramp, I suppose) of that "audio file" by rubbing it with a phono cartridge connected to the oscilloscope. 😜
The THD would be at least .01% better if he used cryogenically treated test leads. :) Also, I’m glad you skipped that destructive output-shorting test, it proves nothing and only hurts the outputs.
Thanks for the video Tony. That was a nice and challenging project. Besides expertise, you have a lot of patience and determination too. I also liked the "audiophile" remarks. Unless the music listener is a Gen Z person, it is proven that it is virtually impossible to hear frequencies even close to 20 kHz, but some people fall for the "snake oil" marketing bs and buy power cords and RCA cables that cost hundreds of dollars and produce zero audio improvement.
Amen. Been reading a review of my AudioLabs 6000 CDT CD transport, and a couple of posters are remarking about how much better it sounded after they replaced the AC Mains fuse with "Hi-FI grade AC fuses". I responded, what about the 75 ft of cheap 12g solid copper in the Romex that goes from the receptacle to the mains service box? "Oh, but the clarity! The stage presence! The improvement is amazing!" Bwaaaaaa!
@@richardmarshall6751 Exactly! I sympathize with the fact that some music listeners are not experts at all in the electrical or electronics areas, but the old saying "If it is too good to be true, it probably is." can be used. The person can do some research and ask some experts before spending money (usually hundreds of dollars) with those Pinocchios that claim miracles, as if the electrical utility company uses only 'audiophile grade' materials and components from the power grid, transmission lines, transformers, etc., until the person's house. Those Pinocchios should be reported to the Best Business Bureau so hopefully they stop stealing money from people who believe in their false claims. And I have heard ridiculous and false claims when shopping in major stores like Best Buy.
this question isn't about this project in particular: what is that Terminator that you have on your tectonic oscilloscope on I believe the external trigger input? it's a white square cube unit? I was watching another video and saw it on the Harman kardon protection circuit video. please keep up the great work I have learned so much from you Tony. thank you.
Dear Tony, thank you so much for the video, very informative, as always! I was wondering if you'd be interested in making a video (maybe even a series of) for those who can't afford a full set of equipment that you're using for taking the measurements. I'm talking about using a computer sound card (better an outboard interface) as a DAC/ADC with a proper voltage divider, in conjunction with a whole bunch of software to choose from: REW, Arta, TrueRTA, maybe even SpectraPlus, you name it. You get pretty much the same capabilities, if not more, only for a fraction of a price. I think it would be very helpful to those hobbyists who are not ready to invest thousands of dollars in all the hardware, which is the absolute majority. Also, it'd be great to hear your thoughts on things like what exactly we want (or don't want) to see in the trail of harmonics when we look at the spectrum, be it THD or IMD or square wave, you name it.
Tony you must live in a house where nobody appreciates your music, When you try to rock out , you get read the riot act," Hey we're tryin to watch the batchelorette up here!, Just last week I was sampling some Macallan 86 proof single malt, I was running the Radio Shack 125 at less than full power and Billy Wymans Bass line in the outro to Honky Tonk Women! was making the empty beer bottles dance across the glass coffee table!!
Hi Tony, I would have thought that the slew rates for Vp and Vp-p would be the same. It’s the same signal. The p-p voltage is double Vp, but it has twice the time to get there in the waveform.
In theory, it is. The one slight issue is that this is a complementary output design. This means that the NPN and PNP sides could have slightly different rise times or fall times, which could skew the results a bit. In the real world, the difference is usually so small that it really doesn't matter. Remember, no matter which side of the waveform you are looking at, you will be looking at a combination of the rise time of one side and the fall time of the other. There are four waveforms that make up the whole signal. Rising and falling edge of the NPN side and rising and falling edge of the PNP side. Again, the 4 waveforms are usually close enough to just use the Vp of one side.
I just think it's just terrible how they subject those poor electrons to oxygen deprivation and then force them through burned-in wires. Oh the humanity.....
That demo at the end was fantastic. I know, 'cos I played it through a £35 Beringer DAC, a Chinese kit-built valve preamp, and a £20 Chinese D-class power amp... Into Realistic Minimus 7 speakers.😁
Tony, this was helpful with explaining the testing procedures. Could you recommend a budget friendly way to measure distortion? Those Keathly meters are big$$$. Also how about a series on measuring a working, yet unrestored amp, and running the tests and then doing repairs one at a time to see how it changed/improved?
There are several software-based products that use your computer's sound card to do these tests. They do not have the resolution of a professional piece of test equipment and can be subject to noise artifacts if you don't set them up properly (but so can professional equipment), but they are more than adequate for testing audio gear. I have used TrueRTA software and it is pretty good, as long as you have a good sound card. Another popular one is ARTA, which I have not tried yet. It is shareware and seems to be very popular.
Excelente Tony, Marantz se caracterizo por hacer muy buenos equipos, poseo un Marantz modelo 300DC y este es de 150 vatios por canal, creo que es un poco mas nuevo que este, pero también es de la época dorada del audio creo que es de 1978. Este a diferencia de este, usa fuentes independientes para cada canal y usa un par diferencial de entrada con Fet. pero bastante robusto como este, claro su apariencia es bella con dos grandes meter en el panel frontal.
That Marantz 250 amp was conservatively rated for THD. Why did you not increase the output till you got to 0.1% THD and then see how many watts it delivered into an 8 ohm load?
My realisation that audio foolery was equal to my realisation that god didn't exist. I want everyone to be happy and I want everyone to listen to true hifi it's an eye opener.
Isn't the frequency response calculated off of the reactive components in the circuit and how they are set up? Another words, it could be possible for an amplifier to have a frequency cutoff at a much higher frequency than the transistor's slew rate could even allow. Not that it matters over 20kHz anyway, I'm just speculating. I know when I have went through all of the stages of amplifiers before and calculated what the frequency cutoffs were at each stage and coming up with an overall frequency response curve(Bode plot), I never factored in the fact that the outputs may not even be fast enough to duplicate a frequency range. Maybe that 100kHz spec was a calculated FR rather than a measured one?
Actually, we weren't measuring the slew rate of the transistors, but rather the slew rate of the entire amplifier, including the feedback loop and all of the reactive components. The transistors (even the so-called "slow" ones) have a transition frequency in the MHz range. What we were measuring was the slew rate at the amplifier's output, which is much slower than just the transistors by themselves. Negative feedback as well as the capacitors used to prevent oscillation have much more influence on SR than anything else. IN some of the "high speed DC" amps of the 1980's, manufacturers were working with designs that used very little feedback, almost no miller capacitors and very fast transistors in order to minimize TIM distortion (which is a debate in and of itself). The by-product of this was an amplifier with very high slew rate. The Sansui AU-X1 I restored could pass over 1MHz to the speakers with very little degradation of the signal. Crazy!
So if the slew rate wasn't up to the 20kHz test, wouldn't that show up in the IMD test? Slew rate, to my little mind, is akin to sampling rate. Humility with intelligence, is how I would characterize you. Well done. 👍
Just a thought; since distortion is visible on an oscilloscope only at higher percentage, wouldn't it be better to check the max. power at 0.1% THD, just like the spec sheet says?
Hi Tony, I am working on a Hitachi SR-604. I have replaced all the capacitors, all of the fuse resistors and 3 of the signal transistors that were causing shorts. The bias on the right is 8.8 mV where it should be but the left side is close to 19 Volts. There is no click from the protection relay and I assume it wont click until that bias voltage comes down to where it should be. Do you have any idea what could cause that high Bias voltage? Any help would be greatly appreciated. Thanks.. Carlos
If the 19 volts is across the emitter resistor, the emitter resistor is open! If the 19 volts is at the junction of the emitter resistors, then there is something wrong in the drive circuit to the bias circuit. Check for open junctions on all negative rail transistors. Also check for bad or open resistors.
@@RaulHernandez-lg5nw I found a shorted output transistor and replaced it. I powered up the receiver and the protection relay clicked. The right channel is fine but now the bias on the left channel is 54 mV and it wont adjust with the trimmer pot. There is a lot of distortion on the left channel speaker. Can this be a leaky transistor? I checked the other 3 output transistors of the left channel with my DMM and they seem ok. I have one of those cheap transistor testers from China would it tell me if one of the output transistors is leaky?
and you have to let the audiophile know that you’re solder does not contain silver made by virgin female elves cast & smelted on a blue full moon into spools of audiophile grade solder
