I may have to watch this video a few times to let all the information sink in. I have been using Carver amplifiers for many years, and these videos really help me to understand how they work. Thank you for taking the time to make these great videos.
Hi Xraytonyb, I have an older carver receiver mxr130 and your videos on the 2000 #1,2,3 3a were very informative as my unit is pretty similar in the layout. I am trying to revive mine and am a beginner learning as I go. Thank you for the videos above. Mine does not have the sonic holographic stuff. Will search for your last two!!
I seem to remember in the Sales brochures some discussion of the Cube amp's ability to "borrow or steal" power from the weaker channel if the stronger channel needed some peak power to handle especially heavy bass demands, etc. - I have owned Carver Cubes, C-1 pre-amps and TX-11 tuners and other Carver stuff since it first came out in the early 1980s. Still have it all; and it all works great. Only a few minor fixes over the years. - Love your videos. Very informative. Keep it up!
I’ve 2 of these. 1 of the i’ve had since ‘80s. They both have been a pain in the rear, as they both have problems with the balance L/R going out/muting randomly. I then turn the speaker output off & crank the volume up to maximum on the side that cuts out, at which time it kicks on, so I turn down the volume re-establish the balance knob & unmute. At some point, once again, 1 side or the other will go out, making me go through the rebalance exercise all over.
(mars-2021) >>Fantastic and interesting video with comparison of those circuit-configurations AB+ _G and _H amps. (..if sources on internet still can't agree on which is which, maybe since the letter H comes after G then perhaps the 'H'-one can be considered the better design of those two, thereby the 'modulating' rail-controll config.) _>>Thanks again Tony. Love your videos (special those times with schematic reading&pondering) //br, from norway.
Thanks for taking the time to explore the Carver stuff. I enjoy all of your videos as you cover all of the brands I considered purchasing at one time or another. I remember buying my Carver TFM-25 in the 1990s? as it was so cheap compared to Adcom and other brands. I am always surprised by how light and cool it runs. And yes, it is still going. Wasn't there a Soundcraftsman Amplifier that you restored that used triacs as well?
Great videos Tony! Can you demonstrate how to measure ripple voltage of the high rail caps on this or the silver 9t? Basically looking to establish a baseline before cap replacement. Thank you for all your time and effort on these instructional videos.
With all these variable rail voltages and crossovers, how is this effecting the THD of the output? I see the benefit in cutting down power consumption and heat, but I am wondering if the audio quality is sacrificed.
A large part of the odd clipping behavior at low frequency is because of ripple on the bus. Unless the bus caps are infinite in size, this will happen with any amplifier without a tightly regulated power supply. Essentially the output is being modulated by the ripple on the bus during clipping because the output transistors are in saturation.
Kenwood dabbled in some class G designs. The KA-9X, a 120 wpc intergrated amplifier, M1A, M2A power amplifiers were split power rail designs. The M2A was a 220 wpc amplifier with a low output impedance and damping factor of 1000. It was not taken seriously because it only weighed around 30 lbs. Looked great on paper (spec wars) but sound was kind of clinical and cold IMHO. The KA-9X also had a gimmicky feature called "sigma drive". An extra pair of small sensor wires that ran back to the speaker output terminal that carried the signal back to the negative feedback. This was supposed to compensate for speaker wire would be my guess. It was discontinued because people would hook up the connections wrong and blow up the outputs.
As an electronics novice and a carver m200t owner I find this fascinating. I didn’t understand anything when I bought the amp in 1987 except that it was more power for less money and it ran cooler. From my layman’s perspective, the question would be, given these advantages why aren’t all amps designed this way? I’m sure there are downsides?
ca. 29:00... I think either the schematic or your explanation is wrong. Q1 isn't gonna just "turn on", but will act an emitter follower-following the signal. That makes sense...I think :-) D3 isn't switching-it's constantly conducting (I'm assuming it's a zener). It's "rail modulation".
wow another great video...your talking about the stuff ive been studing...best ab video out there....still...,I needed to see more...I may have to do my own video,,,...for instance, I wanted to the see the rail react to a audio programe input(music)...would it more closely resemble a dc voltage? that's what I would exspect to see...and , it would be neat to see high rail disabled,,,,does that cause clipping to happen earlier?, ,also I do not understand how emitter resistor does not burn up when the high rail is engaged...doesn't the speaker current go up thus the emitter currents? maybe measure rail with VOM on dc while putting in programe music....some music from ACDC would suffice
Regarding Class A/B amplifiers, you've mentioned what happens when the bias voltage is set too low: it creates crossover distortion. What is the result of the bias voltage being set too high? Loss of detail in the signal? If I have an amplifier in which the bias voltage is supposed to be 10mA +/- 1mA , but the actual reading is 13.4. I understand this is causing excessive heat by keeping the transistors turned on too much. What is the effect on the audio signal? Just so you know, I didn't leave the bias voltage that high! I brought it down to 10 mA as directed. It SEEMS like there is a lot more detail/separation in the stereo field now., or am I dreaming? Thanks Tony! You are the best teacher out there!
There is no real difference in sound on low to mid volume if your bias current is too high but you're burning your power supply (Transformer, regulators), your power-stage transistors by overheating. Plus the exceeding current will lead to higher likelihood of humm from your power supply. And as your storage caps would not store enough energy to deliver the additional energy (i. e. rail voltage x current drawn from power stage) on peak performance demands it also could lead to earlier clipping on high output levels. Did I miss something?
Slartibartfas042 Okay, thank you for your assistance. I realize the importance of correct bias current (thank you for correcting my terminology!) as it applies to component wear. I was reasoning that if the transistors were too far "on" (excessively high bias current ), low amplitude signal variations would be lost as the transistor was already turned on above the amount needed to detect those variations.
As already mentioned excess heat is a problem. But you also get what's called gm doubling, which slightly increases distortion above what is present at the optimum bias point.
While a novel way (for its time) to increase efficiency and use smaller parts, it really is an overengineered mess. I can't help but think a regular class A/B amplifier with properly sized parts would perform better and be less expensive. It would certainly have less to go wrong. I remember working on a 70's Pioneer 250x2 amp that was about the size of this thing. It has a weird current limit that was latching (think transistors connected as an SCR) and instead of limiting current on a fault, the output would fall to zero until the next zero crossing. Good thing that it was almost impossible to current limit it, because that sounded awful.
Creative Soundworks series was a large PC speaker system that used BASH, which is a patented version of a class H. They were very nice, but unreliable.
I had a few of those Cambridge Soundworks amps fail. Never thought they sounded very good. I was given a few of their desktop Bose Radio knock-offs; those are reliable but are heavy and sound lousy.
@xraytonyb: Did I miss something or is there a mistake in the circuit diagram at D709/D710 and D711/D712? I did not finish the video up to now, but it looks to me very strange that D709 and D710 are in parallel while D711/ D712 are anti-parallel!? Shouldn't be D711 the other way round?
You are correct. The schematic has a misprint. D711 should be the other way around. It is in the correct way in the actual amp. Thanks for catching that!
I would never connect my 30000$ B&W speaker to Carver amplifier , this Amplifier is not for Audiophile people with silver wire speaker , But it is good for sport hall or buss station as public amplifier to call people name .
That's incorrect when you say that in a normal power supply the transformer works the entire time. Whenever the output voltage is below that of the bus cap (the majority of the cycle) no current flows because the rectifier diodes are reverse biased.
I've watched all of your Carver repair videos, and as a retired professional engineer I get the sense that whoever designed these Carver audio products wanted to impress us all with his/her technical prowess by doing unnecessarily complex designs with little added real-world benefit to the user. The designs do provide Carver marketing people with opportunities to differentiate their products, but was that the reason for these overly complex designs or just a way to salvage some marketplace benefit from overly complex (and costly) designs?
Carver's Phase Linear 700 had heatsink issues. The FTC's 1/3 power preconditioning rule made that situation worse. Carver's way around that on his newer products was to vary the power supply rail voltage in such a way that the dissipation was not great and he could claim high power in a small size. On the cube amp he also used class G circuitry. When the cube came out I sarcastically said that "Bob Carver couldn't design a good heat sink so he designed an amp that didn't need one."
Carver was the first to bring to market an amp with a signal tracking power supply YEARS before anyone else. He was (and is still) known for solving problems that a lot of others either didn't think could be solved, or didn't bother trying. He gets a lot of flack for it from people who just don't get it. Humans ALWAYS attack what we do not understand.
Carver, in his patent US4218660A in 1978 recognized several tracking power supply patents ahead of him. Carvers method was different but various ways of tracking voltage to audio signal were known by then. If you consider class G a tracking power supply, Hitachi had the Dyanaharmony in 1977 in production.
Carver patented his continuously variable signal tracking power supply and then couldn't get it to work. So he came up with a sort of "half ass" compromise in the magnetic field power supply, which was a three rail stepped approach. Then a little over a decade later he took another fresh look at his patent and was able to make it work, because of some new technology-which didn't exist at the time of the patent-and something that he overlooked. There are multiple videos right here on RUclips in which he explains all of this. The name 'Magnetic Field Power Supply" had next to nothing to do with what it did. It was more catchy marketing. However that wasn't the only notable thing that he invented. The autocorrelator single ended noise reduction circuit Sonic Holography Asymmetrical Charge Coupled FM Detector circuit DC restorer circuit for his current Vacuum Tube amps This is only a partial list of things that I can think of off of the top of my head right now. My point is that there are a lot of haters out there, but anyone can acknowledge the fact that the man has had a HUGE impact on the audio industry which we know today. Just look at what he did for the subwoofer market with his Sunfire true subs.
![BLACK BAG - Official Trailer [HD] - Only in Theaters March 14](http://i.ytimg.com/vi/Du0Xp8WX_7I/mqdefault.jpg)
I may have to watch this video a few times to let all the information sink in. I have been using Carver amplifiers for many years, and these videos really help me to understand how they work. Thank you for taking the time to make these great videos.
Hi Xraytonyb,
I have an older carver receiver mxr130 and your videos on the 2000 #1,2,3 3a were very informative as my unit is pretty similar in the layout. I am trying to revive mine and am a beginner learning as I go. Thank you for the videos above. Mine does not have the sonic holographic stuff. Will search for your last two!!
Great series of videos Tony! I think the way you've taken the time to explain some of the design had been really useful. Thanks!
It looks like he got the idea from motor control and applied it to an amplifier. Bob was a genius.
I seem to remember in the Sales brochures some discussion of the Cube amp's ability to "borrow or steal" power from the weaker channel if the stronger channel needed some peak power to handle especially heavy bass demands, etc. - I have owned Carver Cubes, C-1 pre-amps and TX-11 tuners and other Carver stuff since it first came out in the early 1980s. Still have it all; and it all works great. Only a few minor fixes over the years. - Love your videos. Very informative. Keep it up!
Just out of highschool Carver was the first stereo equipment I bought and still own.
I’ve 2 of these. 1 of the i’ve had since ‘80s. They both have been a pain in the rear, as they both have problems with the balance L/R going out/muting randomly. I then turn the speaker output off & crank the volume up to maximum on the side that cuts out, at which time it kicks on, so I turn down the volume re-establish the balance knob & unmute. At some point, once again, 1 side or the other will go out, making me go through the rebalance exercise all over.
Fantastic explanation. Sadly, I don't think I could live with the noise. But so pleased you covered a little marvel.
Cool. Thanks Tony!
As usual, great explanations Tony!
HI, Thanks for these series. I know just enough to get the Ideas..Thank you.
(mars-2021) >>Fantastic and interesting video with comparison of those circuit-configurations AB+ _G and _H amps. (..if sources on internet still can't agree on which is which, maybe since the letter H comes after G then perhaps the 'H'-one can be considered the better design of those two, thereby the 'modulating' rail-controll config.) _>>Thanks again Tony. Love your videos (special those times with schematic reading&pondering) //br, from norway.
Thanks for taking the time to explore the Carver stuff. I enjoy all of your videos as you cover all of the brands I considered purchasing at one time or another. I remember buying my Carver TFM-25 in the 1990s? as it was so cheap compared to Adcom and other brands. I am always surprised by how light and cool it runs. And yes, it is still going. Wasn't there a Soundcraftsman Amplifier that you restored that used triacs as well?
Thanks for this series of video's, I love this more in-depth type of video. Don't suppose you could do one on amplifier stability? Cheers.
Great videos Tony!
Can you demonstrate how to measure ripple voltage of the high rail caps on this or the silver 9t? Basically looking to establish a baseline before cap replacement.
Thank you for all your time and effort on these instructional videos.
With all these variable rail voltages and crossovers, how is this effecting the THD of the output? I see the benefit in cutting down power consumption and heat, but I am wondering if the audio quality is sacrificed.
Not really. Essentially what Carver did was build a Class H amplifier using a triac based supply instead of a high frequency switcher.
A large part of the odd clipping behavior at low frequency is because of ripple on the bus. Unless the bus caps are infinite in size, this will happen with any amplifier without a tightly regulated power supply. Essentially the output is being modulated by the ripple on the bus during clipping because the output transistors are in saturation.
It's a high frequency transformer in the sense that the resulting non-sinusoidal power waveform has a lot of high frequency components?
Kenwood dabbled in some class G designs. The KA-9X, a 120 wpc intergrated amplifier, M1A, M2A power amplifiers were split power rail designs. The M2A was a 220 wpc amplifier with a low output impedance and damping factor of 1000.
It was not taken seriously because it only weighed around 30 lbs. Looked great on paper (spec wars) but sound was kind of clinical and cold IMHO.
The KA-9X also had a gimmicky feature called "sigma drive". An extra pair of small sensor wires that ran back to the speaker output terminal that carried the signal back to the negative feedback. This was supposed to compensate for speaker wire would be my guess. It was discontinued because people would hook up the connections wrong and blow up the outputs.
It would be convenient & get you more views if you put links to the 1st & second videos in the series in the more section
Is this an early class G amplifier ?
That's how Carver made their powered subs small and powerful. With this type of amplifier design.
As an electronics novice and a carver m200t owner I find this fascinating. I didn’t understand anything when I bought the amp in 1987 except that it was more power for less money and it ran cooler. From my layman’s perspective, the question would be, given these advantages why aren’t all amps designed this way? I’m sure there are downsides?
ca. 29:00... I think either the schematic or your explanation is wrong. Q1 isn't gonna just "turn on", but will act an emitter follower-following the signal. That makes sense...I think :-) D3 isn't switching-it's constantly conducting (I'm assuming it's a zener). It's "rail modulation".
wow another great video...your talking about the stuff ive been studing...best ab video out there....still...,I needed to see more...I may have to do my own video,,,...for instance, I wanted to the see the rail react to a audio programe input(music)...would it more closely resemble a dc voltage? that's what I would exspect to see...and , it would be neat to see high rail disabled,,,,does that cause clipping to happen earlier?, ,also I do not understand how emitter resistor does not burn up when the high rail is engaged...doesn't the speaker current go up thus the emitter currents? maybe measure rail with VOM on dc while putting in programe music....some music from ACDC would suffice
Your
I think Bob called it down tracking power supply.
Regarding Class A/B amplifiers, you've mentioned what happens when the bias voltage is set too low: it creates crossover distortion. What is the result of the bias voltage being set too high? Loss of detail in the signal? If I have an amplifier in which the bias voltage is supposed to be 10mA +/- 1mA , but the actual reading is 13.4. I understand this is causing excessive heat by keeping the transistors turned on too much. What is the effect on the audio signal? Just so you know, I didn't leave the bias voltage that high! I brought it down to 10 mA as directed. It SEEMS like there is a lot more detail/separation in the stereo field now., or am I dreaming? Thanks Tony! You are the best teacher out there!
There is no real difference in sound on low to mid volume if your bias current is too high but you're burning your power supply (Transformer, regulators), your power-stage transistors by overheating. Plus the exceeding current will lead to higher likelihood of humm from your power supply. And as your storage caps would not store enough energy to deliver the additional energy (i. e. rail voltage x current drawn from power stage) on peak performance demands it also could lead to earlier clipping on high output levels.
Did I miss something?
Slartibartfas042 Okay, thank you for your assistance. I realize the importance of correct bias current (thank you for correcting my terminology!) as it applies to component wear. I was reasoning that if the transistors were too far "on" (excessively high bias current ), low amplitude signal variations would be lost as the transistor was already turned on above the amount needed to detect those variations.
As already mentioned excess heat is a problem. But you also get what's called gm doubling, which slightly increases distortion above what is present at the optimum bias point.
Mister Hat So, there IS an audio effect to a bias current that is too high! Thanks for your information!!
matran47 Yes, but unless it's grossly misadjusted, you won't hear it.
While a novel way (for its time) to increase efficiency and use smaller parts, it really is an overengineered mess. I can't help but think a regular class A/B amplifier with properly sized parts would perform better and be less expensive. It would certainly have less to go wrong.
I remember working on a 70's Pioneer 250x2 amp that was about the size of this thing. It has a weird current limit that was latching (think transistors connected as an SCR) and instead of limiting current on a fault, the output would fall to zero until the next zero crossing. Good thing that it was almost impossible to current limit it, because that sounded awful.
Tony, what's with D 711-12 compared to D 709-10 is that a misprint?
D711 is misprinted in the schematic. It should be the other way around.
+xraytonyb I see. Thanks for responding. It was kinda confusing. Lol.
Creative Soundworks series was a large PC speaker system that used BASH, which is a patented version of a class H. They were very nice, but unreliable.
I had a few of those Cambridge Soundworks amps fail. Never thought they sounded very good. I was given a few of their desktop Bose Radio knock-offs; those are reliable but are heavy and sound lousy.
@xraytonyb: Did I miss something or is there a mistake in the circuit diagram at D709/D710 and D711/D712? I did not finish the video up to now, but it looks to me very strange that D709 and D710 are in parallel while D711/ D712 are anti-parallel!? Shouldn't be D711 the other way round?
You are correct. The schematic has a misprint. D711 should be the other way around. It is in the correct way in the actual amp. Thanks for catching that!
Never heard my Carver "grunt"
Voltage control using SCR device, the same way a light dimmer works. ...very noisy. Needs lots of filtering.
I would never connect my 30000$ B&W speaker to Carver amplifier , this Amplifier is not for Audiophile people with silver wire speaker , But it is good for sport hall or buss station as public amplifier to call people name .
That's incorrect when you say that in a normal power supply the transformer works the entire time. Whenever the output voltage is below that of the bus cap (the majority of the cycle) no current flows because the rectifier diodes are reverse biased.
I've watched all of your Carver repair videos, and as a retired professional engineer I get the sense that whoever designed these Carver audio products wanted to impress us all with his/her technical prowess by doing unnecessarily complex designs with little added real-world benefit to the user. The designs do provide Carver marketing people with opportunities to differentiate their products, but was that the reason for these overly complex designs or just a way to salvage some marketplace benefit from overly complex (and costly) designs?
Roger Mason , you've nailed it !!
Carver's Phase Linear 700 had heatsink issues. The FTC's 1/3 power preconditioning rule made that situation worse. Carver's way around that on his newer products was to vary the power supply rail voltage in such a way that the dissipation was not great and he could claim high power in a small size. On the cube amp he also used class G circuitry. When the cube came out I sarcastically said that "Bob Carver couldn't design a good heat sink so he designed an amp that didn't need one."
Carver was the first to bring to market an amp with a signal tracking power supply YEARS before anyone else. He was (and is still) known for solving problems that a lot of others either didn't think could be solved, or didn't bother trying. He gets a lot of flack for it from people who just don't get it. Humans ALWAYS attack what we do not understand.
Carver, in his patent US4218660A in 1978 recognized several tracking power supply patents ahead of him. Carvers method was different but various ways of tracking voltage to audio signal were known by then. If you consider class G a tracking power supply, Hitachi had the Dyanaharmony in 1977 in production.
Carver patented his continuously variable signal tracking power supply and then couldn't get it to work. So he came up with a sort of "half ass" compromise in the magnetic field power supply, which was a three rail stepped approach. Then a little over a decade later he took another fresh look at his patent and was able to make it work, because of some new technology-which didn't exist at the time of the patent-and something that he overlooked. There are multiple videos right here on RUclips in which he explains all of this. The name 'Magnetic Field Power Supply" had next to nothing to do with what it did. It was more catchy marketing. However that wasn't the only notable thing that he invented.
The autocorrelator single ended noise reduction circuit
Sonic Holography
Asymmetrical Charge Coupled FM Detector circuit
DC restorer circuit for his current Vacuum Tube amps
This is only a partial list of things that I can think of off of the top of my head right now.
My point is that there are a lot of haters out there, but anyone can acknowledge the fact that the man has had a HUGE impact on the audio industry which we know today. Just look at what he did for the subwoofer market with his Sunfire true subs.
You must be a MIT man.
I have a Carver 2000, bought it used untested off eBay of course it didn't work.