To learn electronics in a very different and effective way, and gain access to Mr Carlson's personal designs and inventions, visit the Mr Carlson's Lab Patreon page here: www.patreon.com/MrCarlsonsLab
The NE614 chip has a logarithmic signal level output, so that's why it is used in the amplifier - to make the meter have a log scale. This is quite cool.
Mr. Carlson, never in a million years have I ever considered using a pair of AR monoblocks as a welder. Really puts the output ability of these beasts into focus. My favorite quote from this episode would have to be "for those of you who like to drive dead shorts".
When I was competing in car audio I used to push 6KW of power through a 0,25 Ohm load, so 1 ohm is still pretty much resistance 🤣 The amps would pull over 700amps at 13volts then, sure when you push more than 60amps and over 100volts through a speaker the impedance goes up a little bit more, but the amps was linked making them see half the actual resistance of the load. I love those amps. But I do build tube amps and stuff from the ground up too for home hifi use these days
If you don't mind listening in mono while working in your shop, use one for audio, the other for welding together heavy-wheeled carts to move them around. :P - Fun and different video, thanks, Mr. C!
OMG these babies weight in at 72.2 kg ( 170 lbs) each! The physical and electronic design of the units are very well thought out. Impressive mid 1990's amplifier tech.
Great video. $34,000 a pair. Somebody has a lot of money. Back in the 80's I had the chance to listen to the ultra high end equipment. Now that I'm a lot older I couldn't tell the difference. Once again, love to seeing the innards of those !
This was one of my favorite videos you've done in a long time. I love it when you analyze the design and schematic of a piece of equipment. This amp demonstrated simple elegance in its design, which is a joy to behold.
I used to work for an Audio Research dealer of Montreal, by the end of 80's. One time, a costumer that moved from UK to Canada and took her pair of 300 Watts M-300 mono blocks and a SP-11 preamp. The only problem was the 220 V only main voltages. We ordered 120 V primary power transformers. They sent us 115/230 V universal models. I think they should had installed those transformers at the factory, but they may have a reason for that choice. I had the opportunity to listen this system with a pair of Martin Lpgan electrostatic speakers and a Velodine sub woofer. WOO !!! It sounded just AMAZING ! I felt like Keith Jarrett was THERE, in front of me on his Steinway grand piano. I could ear not only notes, put the subtile noises of wood hammers and felt mute between notes. I could also ear brass players breath before starting to play, in a symphony orchestra. That was absolutely delicious ! My bus was so happy of my job, that he let me listen whatever I wanted, on this system, for a full hour of my job time. In 1988, one M-300 mono block costed 5 000 $. I let you imagine the price of the whole system ... :-)
I greatly appreciate your review and analyses of the design. Calling out the ham radio engineering influences, wisdom in the parts selection and so on is very valuable. Bravo!
Oh the heady days of the comeback of serious audiophile tubes in the late 1980s. Audio Research were at the forefront, and these beasts set the benchmark in many ways. I had to console myself with a pair of Vacuum Tube Logic MB300 monoblocs. Only 8x 6550 on each side. No solid state control circuitry for a soft start, just a big thump and the odd trip of a breaker when powered on. They were supposedly 300W. They crossed the pond a few times, last one was to the UK ,and a ham radio guy, obviously, diid the voltage conversion, and replaced all the caps etc. He was impressed with the design, but told me that the 300W claim was wrong, they measured at 350W. But that was 20-20K Hz into a regular 4-8 ohm load, nothing like a crowbar at near DC that the AR monsters can manage. The VTL MB300s are my forever amps.
6:43 - I'll be VERY interested in how they achieve balanced inputs on a unit employing 'mono-polar' tubes! There are no 'PNP' tubes, that I'm aware of :)
They just build a diffential amplifier just like ypu would using transistors or Fet. May be common mode rejection is not that great as current design using special opamps for this task
@@InsideOfMyOwnMind Having setup and repaired just about every model of Mac back in the 70s while attending UMASS I'm curious as to what Mac circuitry design you think AR may have needed to "work around" in this amps design?
You are a very good teacher. I was surprised that you missed the opportunity to talk about "parallax" when describing the meter design. Actually, I was also surprised that these units didn't have the back-plate mirrors on these meters with so much meter function. Thanks for the continued teaching videos!
Well Mr. Carlson You win , that is the biggest the cleanest and coolest lab i ever seen. In my shop I've got 5 work benches with projects on everyone of them . And wires, cables, and antenna cable. You got a great show and a nice rack of equipment. Thanks garry
Mr C👍👍 I can see why you say "two thumbs up" to the designers and engineers at Audio Research for a job well done. These amps are obviously expensive to own and operate, probably not for your normal home theater use I'm guessing. Thanks for another great video. 73
Man, I really appreciate your videos. Im an audio guy, I wish I knew how to design something this special. But hey, knowledge doesn't come easy. Gotta work for it, earn it, which is respectable in its own sense. Not everyone can do this...
Mr Carlson your the smartest man in the world. Please teach younger people to carry on .I know your videos will live on forever. WHAT YOU DO WILL SAVE SO MUCH HISTORY. THAK YOU😊X
As a young ham radio operator just out of high school in 1972 Bose hired me and I worked testing and repairing Bose 901 Equalizers as they came off the production line and I would often assist the sound engineers in their large, state of the art sound room they had isolated out back. Here, we tested every other manufacturers speakers using a couple of audio amps, each powered by two 4CX1000A's capable of loafing at over 1000+ watts..! The idea was to test the speakers frequency response, efficiency, etc, and then lastly, their power handing capabilities. You haven't lived until you've seen the speaker coils of a JBL, KLH, Sansui, AR, Klipsh, etc, begin to glow dull red, turn bright red, smoke, and in some cases, actually catch fire..! I use to play Claptons Layla back there at unheard of sound levels using those old megawatt tube amps... My Central Electronics 100V Transmitter used two 6550 tubes as finals. Probably selected for the Audio Research amps due to its excellent linearity. Best regards!
You only got to look at a piece of electronic equipment, and it will scream at you if it's quality. As soon as I saw the notification for your video I knew we were in for a rare treat.
Wow much bigger lab! Brilliant Amplifiers, always had the utmost respect for this company. Always afraid of messing with the screws these top screws are so easy to break. DREAM AMP BTW
I own several Audio Research Amps and preamps. SP2, SP6, SP6B, D50 and D90. All working except for the D90 which has 4 6550's per channel and one in the power supply. It worked and sounded great when put in storage over 15 years ago. I got it out of storage and hooked it up but it didn't sound good and something went pop and a hum came out of both speakers. What went pop was the regulator pass transistor for the bias supply. What would cause excessive current draw from a bias supply ? I changed the transistor and it heated up and popped again. I bypassed the transistor with a resistor and it worked but it hummed. I decided to change all the output tube sockets but I lifted some traces when I pulled the first socket out so I've given up for now. Would love to hear that amp working again. I'm over 60 now but I may be even more sensitive to differences than I used to be. At least at certain frequencies.
It's videos like this on unique audio amplifiers that's exciting to watch and makes your RUclips channel one of the best on electronics. Amazing specs for a tube amplifier, the output transformer circuit design reminds me of the high end amplifiers built by a well known HiFi manufacture in Binghamton NY USA.
Very high end design. I would love to try them out for a week or two, they must sound incredible with the wide frequency range. I had to research these amps and a pair costs 32,000 sterling or $40,225.60 USD.
The latest are the Audio Research Reference 750 SEL at $42,500 each USD. Pair them with Radialstrahler System MBL 101X-Treme MKII at $398,000 USD per pair
33:30 I really wish the Marshall folks had thought of this feature! I own a Marshall 40W combo, and after reading elsewhere about adjusting bias in that amp, there's no way I'm doing that at home.
30:20 - I'm guessing it's in protection because no output load is connected, UPDATE: Oops, I was wrong. However, shouldn't a no-load condition be considered?
With no output signal on a tube amp, there's only a static DC current going through the primary winding of the output transformer, so, there's no consideration for any protection needed. I definitely wouldn't try driving any real power out of it without a load though, although most tube amps won't get damaged, the possibility of a oscillation happening is risky and could cause some real damage.
Beautiful amplifiers! I think those are the biggest I've seen with that many power tubes. And 6550s to boot! I believe you could use KT88s as well, if I'm not mistaken. I can't even imagine the cost. What are they like 20K-50K each? Even though I don't need that kind of power, I'm totally jealous! I'm only working with (2) 2-channel amps using 7868s in push-pull with around 35 watts each channel powering a pair of bi-amped speakers. The owner of those is a lucky person.
Great stuff. Even though you are quite particular about some things I appretiate that you know when to stop, like, don't expect perfect linearity out of an analogue meter. Decades ago I polished the daylights out of the clear window on an analogue meter, and after that it would react to static charges on the meter face. I learned that there is a coating on many of these meters. I ended up using a spray that was sold to remove the static charge from vinyl records. It worked on meters but I never used it on records. That makes me wonder if that was the coating you found on the one meter face?
41 minutes give or take.....this is some pretty cool engineeing at a high level. A friend of mine showed me the schematic of his AR amp that was only 120 w/ch or so and I saw something similar with the heater string I just couldn't understand. After seeing this video, NOW I get it :)
just WOW!!!! who in the world would actually NEED this kind of complicated audio gear? way over kills NO? sheeeesh never would i have imagined there was ever a reason for building such a thing!!! thanks for this cool vid...even if i am left wondering WHYYYY? lol!
I'm a long time watcher of your videos and I thank you, for what you do and the excellent recording/editing you put into your videos. I don't understand several things you talk about, but enjoy it just the same.
Man, I would love to have a pair of these for my horn subs. I just got a pair of VTL mb-300s that I had to repair, I think these are the only tube amps I've ever seen that offer more power! Beautiful amps.
Hello Mr. Carlson! I absolutely love your videos, they are so informative and I've learned so much from you. I do have one question though.. WOULD you consider doing a video on how to read electronics schematics and explain how to orient the schematic to the actual wiring and placements inside the electronic? I hope that I've asked that question in a way that concise. I am very curious on how to read those schematics and understand the layout inside the electronic from the schematic. Thank you so much!!
Man I love this, it makes me truly happy even though I know nothing about it. I just love electronics. Im a person that likes things way more than I like people lol.
Over several years I picked up two Quad tube mono amplifiers and and two Quad electrostatic speakers. Also a Quad tube stereo pre-amp. I sent them back to Quad where they re-tubed the amps and re-built the speakers. All for a reasonable price. There are not many companies the are willing to repair 30 year old equipment.
Reminds me of the 3-500Z audio amplifiers i built years ago with 811A drivers . it was also stupid heavy i used Plate transformers out of a collins .They are also handy in your shack in the winter time lol
The criticisms I have with these amps is the extended high frequency response that is speced as -3dB at 200K Hz! No reason to have an extended frequency response that is prone of oscillations in the amp depending upon the loudspeaker impedance load which varies widely between manufacturers. Also the damping factor is only 16 which is common with an all tube output amp which means bass will not be as controlled so things can get 'boomy". I'd use a solid state amp for the subwoofers. Haven't looked at the price but I'm betting I would go YIKES!!!. This amp probably will make a good heater in the winter time. Thanks for the video.
Apparently you have never heard of Harman Kardon "Citation A" pre-amp. This pre-amp (from 1964), had FLAT response to 1 megacycle (video frequency). The unit was designed by Stewart Hegeman who along with David Hafler, believed that an amplifier with extended response into the RF frequencies would sound audibly better in the audio range.
@@TheOzthewiz Which goes to show that it wasn't a valid design for "sounding better". Similar to the newer fad of high definition or extended frequency range of digital audio songs where all that does is make a mess of the sound quality by trying to include noise at higher frequencies. There is zero benefit of doing so past a certain point which common knowledge says is past 20KHz Like I said before , amps that have a very high frequency response are more prone to oscillations when driving certain speaker loads.
Great video. Love the audio vacume tube stuff. This makes want to start building again. I might!! Maybe you can tell something about the quality of audio output transformers sometime. Thanks!
Awesome tutorial... You mentioned around 10:30 about a device you use to safely discharge the capacitors. I did a search of your vdeos and could not find any reference to that device... could you or someone else point me in the right direction.. Thank you !
Once I tried to repair a meter with similar torsion mechanism. The main benefit of this coil mounting is that the torsion spring doesn't create friction(compared to the pivot needle type), therefore it enables much lower currents to be detected. The meter I tried to repair was a 10uA full scale meter from a soviet DP-5A dosimeter. Oh and also these tension wires don't like high heat, so factories used cadmium based solders.
We had to get a pair of those from London over to the Channel Island Alderney.. They went with an even bigger weight, a big pair of Wilsons and a Krell reference CD. They went by boat and I went by helicopter. A memorable install.
Those beasts are very nice. I really liked the design of the old 600’s vs the 610 - 750. Although the newer design is beautiful, the classic look is the best imo. Great amps, thanks for this video.
NICE SHOES! Thanks for sharing this with us. I learned some more about meters. I didn't know that wire is a counter balance for the needle. Now you can rock the house with your electric fiddle!
I would imagine these amps make good space heaters, with all the 6550 tubes in them. I have a power amp I built that only has four 6550 tubes and it generates a lot of heat. As you suggested, Paul, each 6550 is individually biased.
Most of us have transistor based amplifiers - a lot of them are already vintage if you are into stereo. What I would love is to have some guidance if they are still reliable or if I should have the caps exchanged - like on my beloved Yamaha p1050 and the even older Denon amp from the late 70s/early 80s 6:29
If they are from the 70s OR early 80s the Caps should absolutely be changed out as they are beyond its service life. They are only designed to have a 10-20-year lifespan.
I have a pair of the MKIII version. Very nice sounding amps even at low volume. They have a very good grip on low frequencies. Also, comparatively, they don't run hot. I've had solid state class A amps that run quite a bit hotter than these. Thank you for such a thorough demonstration.
That is undoubtedly the biggest tube power amp I've ever seen. Looking at the discoloration on the PCBs around the power tubes, you can get an idea of how much heat they generate.
An absolutely magnificent amp, should have a board with casters underneath just so that you can move it around your lab :). I like the split load design on the output transformer and the phase inverter with individual cathode followers for each output tube. What I dislike though is the CF tube grid and wiper on RV1...RV16 not having any failsafe resistor to the bottom end of the track, that would pull the output tube's bias as low as possible in case the pot has an intermittent contact. Elevating filaments has an additional advantage of preventing a diode from forming between the cathode and the heater, that would clip the signal asymmetrically. This diode wouldn't even be a problem with low voltage swings or low impedances in the cathodes (e.g. in output stages), but may be a problem in cathode followers driving the output tubes. I love electronic engineering using jellybean parts (for those who don't watch EEVBlog, it's just common, cheap and widely available parts like common transistors or ICs). It's not just serviceable, but also easy to analyze.
I (tubular Joe) was the last one to build Silver Seven 900 amplifiers for Bob Carver. They were redesigned to use KT120 tubes, originally KT88s, 9 up and 9 down, with two screen regulators. They put out at least 1000 watts RMS, and more peak power if your house wiring could handle it. They were beauties.
I guess these power amps would be use in theaters as opposed to home use. I used to have a pair of Dynakit amps using KT88 output tubes and a huge power transformer. The amp put out 60 Watts. I used two external whisper fans to cool them. I Paid $100 each on sale in the 1960's. I bought them ready built. They compared to the very high end amps at the time like Mc Intosh and Marantz. I wonder how these would compare to today's solid state high end solid state units. Of course a very good Pre amp would have to drive them. I also had a Dynakit Preamp and used AR 10AX speakers and an Empire Belt Driven turntable with a Shure Cartridge. Old Hi Fi equipment going back to the late '50s can compare to today's equipment. You have to have heard these. I was 18 and older at the time.
Based on my experience fixing a couple of tube tester meters, don't use any tools made of magnetic materials anywhere near the coil and magnet assembly, because the magnetic field is surprisingly strong and it can pull your tools right into the meter and cause you to bend or break fragile things.
Those are "suspension" type meters too, seeing that they had no bearing adjustment screw for the center, its just a hair fine wire at both sides of the meter pivot, tensioned by a spring band in front and back, and YES, are VERY fragile. It's the same kind of meter movement used in Triplett VOM's, and I know how fragile they are , because I broke one and needed to source a replacement parts meter to get it functional again.
Those are some crazy mono blocks, it would probably cost close to $5k just to replace the output tubes in each of them, but very cool to have a look inside.
Amazing amplifier in so many ways! Cool to see the inner workings. The meter repair and tips are spot on for 99% of the panel meters you come across but there are some types that *are not* to be mechanically set at zero. The HP 400L VTVM for example. If you zero that meter it will be wildly inaccurate. HP even disabled the zero adjust on some of them and now people think the meter is broken because it won't zero adjust. The needle normally rests left of the first tic mark. Just know the meter's design before adjusting! Curious about two things: why is there is a MAC224 TRIAC on the primary of T3 instead of a relay to do the switching? Note T2 primary is switched by a relay RY2. And in actual use how do you know how much to adjust the fan speed. There is no temperature indication and the amps run hot just idling. I would have thought the fans would be controlled automatically. -Erik
Not 100% sure but I think the Triac is operating when power switch is on standby... It limits the primary, which lowers voltage on some of the DC supplies... Enough to keep the valves heated? The Triac is disabled when switch is turned to operate. The fans should have some kind of thermal sensor in addition to the manual control ideally.
@@peterlarkin762 From what I see on the schematic the triac gate is switched on the same in normal and standby (SW3 and 100 ohm resistor). That is why I was curious. I don't see any phase control on the triac gate.
I live on the Gulf Coast, so tube amplifiers are not a reasonable option, but at a Chicago CES a long time ago, I remember hearing this beast's great grandfather: the ARC D-150. William Z Johnson's legacy is nice to look at. Many thanks.
@@chillinginthefrozennorth Not really, it's just the air conditioning load. A friend has a tube amp he plays during the winter. I guess one could spend some serious cash for an HVAC system that is super quiet even at max. Otherwise the noise spoils the listening experience.
Hreat video. Keep them coming! On the meter you zeroed, looks like someone opened the meter after it left the factory. One of the brass screws holding the meter together has a dinged up slot. I doubt a worker at the factory would have done this during assembly; if they did, quality control would have probably prevented it going out that way.
Execellent and interesting video Paul! It would have been nice to hear some music via a good set of speakers! Bach’s Tocatto and Fugue played by a pipe organ is a good test for an audio system. Many years ago I visited York Minster where this piece was being played and standing near the massive bass pipes was an experience I have never forgotten! You feel the bass pressure waves rather than hear them frequencies below 10 HZ I think! Pipes 32 ft and 64 ft if I remember correctly! Fraser.
Worked briefly in a Westinghouse meter lab many years ago, adjust and calibrate meter movements in the position they will be used, horizontal or vertical.
the torque on the meter leads is amazing...did the engineer happen to design FCS computers for Iowa class battleships...those are not going to vibrate loose no matter how much bass the cabinet is subjected too
I am going to refect on a detail I noticed , and one would have to compare it to the other meter to prove this right or wrong , given how the adjustment loop was bent offset to the side could some one have force rotated the meter adjustment to far rotating the adjustment pin "all the way around" to the upper quadrent and bending the loop to the left in the process ? , is it possable the adjustment pin orignaly was located in the lower part of the adjustment loop ? if the zero adjustment has a positive end to end stop in its adjustment range could someone have twisted past it ? just a thought .
Another excellent demo how to tune in already great equipment. 'Audio Research' are quality. That word 'quality'...getting harder to find. Oh its there at super high quailty prices. Peace ☮️ men ,and women enjoy your weekend
Need to purchase yourself some good lift tables for the really big stuff. don't go getting a hernia over those units. Also incredibly interesting video.
U know Ur in for a treat when the tubes have tubes Presumably the 2 hertz range is for audiophile pachyderms. But seriously that's something ive only ever encountered in scientific instruments. Kudos to the designers
The screw heads on the back of the meter were bunged up, so someone opened the meter for some reason. And then he didn't center the adjustment before reassembling it, which is how the arm got bent. My hardest meter lesson ever was when I had been using steel wool a few days before working on a meter. I did wipe the bench clean, but not clean enough, because the moment I opened the meter, little bits of steel wool jumped into the gap of the magnet. I was never able to get them all out, ruining the meter!
To learn electronics in a very different and effective way, and gain access to Mr Carlson's personal designs and inventions, visit the Mr Carlson's Lab Patreon page here: www.patreon.com/MrCarlsonsLab
Perhaps the best value per dollar of any Patreon I've seen to date. :)
Audio Research has always made quality audio equipment with great design engineering, reliability, and sound quality. No audioflake nonsense.
That does *indeed* look like a very well thought out design. Every aspect.
And made in USA
The NE614 chip has a logarithmic signal level output, so that's why it is used in the amplifier - to make the meter have a log scale. This is quite cool.
Yep. Probably the cheapest way to do it without messing with discrete diodes an op amps.
Thanks for info
Sweet. Ill start keeping them if I find any
On Bottom of Amp Chassis Should install Micro Wheels, Suspension and Steering System make them Easier to move around.🥸
Mr. Carlson, never in a million years have I ever considered using a pair of AR monoblocks as a welder. Really puts the output ability of these beasts into focus. My favorite quote from this episode would have to be "for those of you who like to drive dead shorts".
Krell used to demo their amps at audio shows driving an electric drill
When I was competing in car audio I used to push 6KW of power through a 0,25 Ohm load, so 1 ohm is still pretty much resistance 🤣 The amps would pull over 700amps at 13volts then, sure when you push more than 60amps and over 100volts through a speaker the impedance goes up a little bit more, but the amps was linked making them see half the actual resistance of the load. I love those amps. But I do build tube amps and stuff from the ground up too for home hifi use these days
If you don't mind listening in mono while working in your shop, use one for audio, the other for welding together heavy-wheeled carts to move them around. :P - Fun and different video, thanks, Mr. C!
I think I'll try using a welder as an amp.
OMG these babies weight in at 72.2 kg ( 170 lbs) each! The physical and electronic design of the units are very well
thought out. Impressive mid 1990's amplifier tech.
Great video. $34,000 a pair. Somebody has a lot of money. Back in the 80's I had the chance to listen to the ultra high end equipment. Now that I'm a lot older I couldn't tell the difference. Once again, love to seeing the innards of those !
Nothing to really "hate on" with those amps. The design is pretty classic, and that makes things fixable when needed. Very cool.
Actually very, very hot!
This was one of my favorite videos you've done in a long time. I love it when you analyze the design and schematic of a piece of equipment. This amp demonstrated simple elegance in its design, which is a joy to behold.
I used to work for an Audio Research dealer of Montreal, by the end of 80's. One time, a costumer that moved from UK to Canada and took her pair of 300 Watts M-300 mono blocks and a SP-11 preamp. The only problem was the 220 V only main voltages. We ordered 120 V primary power transformers. They sent us 115/230 V universal models. I think they should had installed those transformers at the factory, but they may have a reason for that choice.
I had the opportunity to listen this system with a pair of Martin Lpgan electrostatic speakers and a Velodine sub woofer. WOO !!! It sounded just AMAZING ! I felt like Keith Jarrett was THERE, in front of me on his Steinway grand piano. I could ear not only notes, put the subtile noises of wood hammers and felt mute between notes. I could also ear brass players breath before starting to play, in a symphony orchestra. That was absolutely delicious ! My bus was so happy of my job, that he let me listen whatever I wanted, on this system, for a full hour of my job time.
In 1988, one M-300 mono block costed 5 000 $. I let you imagine the price of the whole system ... :-)
Beautiful! AR is top dog! From Brooklyn Ctr/ Mpls.
Audio Research is world class in High End. Please post more high end audio. Cheers from Minnesota.
I look forward to every new release from "Carlson Studio's"
I've never learned as much in a short time.
Well done Paul!
I greatly appreciate your review and analyses of the design. Calling out the ham radio engineering influences, wisdom in the parts selection and so on is very valuable. Bravo!
Oh the heady days of the comeback of serious audiophile tubes in the late 1980s. Audio Research were at the forefront, and these beasts set the benchmark in many ways. I had to console myself with a pair of Vacuum Tube Logic MB300 monoblocs. Only 8x 6550 on each side. No solid state control circuitry for a soft start, just a big thump and the odd trip of a breaker when powered on. They were supposedly 300W. They crossed the pond a few times, last one was to the UK ,and a ham radio guy, obviously, diid the voltage conversion, and replaced all the caps etc. He was impressed with the design, but told me that the 300W claim was wrong, they measured at 350W. But that was 20-20K Hz into a regular 4-8 ohm load, nothing like a crowbar at near DC that the AR monsters can manage. The VTL MB300s are my forever amps.
6:43 - I'll be VERY interested in how they achieve balanced inputs on a unit employing 'mono-polar' tubes! There are no 'PNP' tubes, that I'm aware of :)
They just build a diffential amplifier just like ypu would using transistors or Fet. May be common mode rejection is not that great as current design using special opamps for this task
its two amps inside, one of each getting driven by either positve and negative xlr input
@@gamerpaddy it a fully symmetric amplifier, and build like a bridged amplfier, using a special output transformer
@@eDXTRe I suspect there are work arounds in there to avoid infringement on McIntosh.
@@InsideOfMyOwnMind Having setup and repaired just about every model of Mac back in the 70s while attending UMASS I'm curious as to what Mac circuitry design you think AR may have needed to "work around" in this amps design?
You are a very good teacher. I was surprised that you missed the opportunity to talk about "parallax" when describing the meter design. Actually, I was also surprised that these units didn't have the back-plate mirrors on these meters with so much meter function.
Thanks for the continued teaching videos!
Well Mr. Carlson
You win , that is the biggest the cleanest and coolest lab i ever seen. In my shop I've got 5 work benches with projects on everyone of them . And wires, cables, and antenna cable.
You got a great show and a nice rack of equipment.
Thanks garry
Mr C👍👍 I can see why you say "two thumbs up" to the designers and engineers at Audio Research for a job well done. These amps are obviously expensive to own and operate, probably not for your normal home theater use I'm guessing. Thanks for another great video. 73
I'm curious as to in what or where these would be used. I'm guessing in live concerts?
Man, I really appreciate your videos. Im an audio guy, I wish I knew how to design something this special. But hey, knowledge doesn't come easy. Gotta work for it, earn it, which is respectable in its own sense. Not everyone can do this...
Fantastic Video about a classic amplifier highly regarded in audio circles from a world class company ! Thanks Mr Carlson.
My pleasure!
Mr Carlson your the smartest man in the world. Please teach younger people to carry on .I know your videos will live on forever. WHAT YOU DO WILL SAVE SO MUCH HISTORY. THAK YOU😊X
As a young ham radio operator just out of high school in 1972 Bose hired me and I worked testing and repairing Bose 901 Equalizers as they came off the production line and I would often assist the sound engineers in their large, state of the art sound room they had isolated out back. Here, we tested every other manufacturers speakers using a couple of audio amps, each powered by two 4CX1000A's capable of loafing at over 1000+ watts..! The idea was to test the speakers frequency response, efficiency, etc, and then lastly, their power handing capabilities. You haven't lived until you've seen the speaker coils of a JBL, KLH, Sansui, AR, Klipsh, etc, begin to glow dull red, turn bright red, smoke, and in some cases, actually catch fire..! I use to play Claptons Layla back there at unheard of sound levels using those old megawatt tube amps... My Central Electronics 100V Transmitter used two 6550 tubes as finals. Probably selected for the Audio Research amps due to its excellent linearity. Best regards!
Thanks for sharing your story Adele!
You only got to look at a piece of electronic equipment, and it will scream at you if it's quality. As soon as I saw the notification for your video I knew we were in for a rare treat.
Wow much bigger lab! Brilliant Amplifiers, always had the utmost respect for this company. Always afraid of messing with the screws these top screws are so easy to break. DREAM AMP BTW
I own several Audio Research Amps and preamps. SP2, SP6, SP6B, D50 and D90. All working except for the D90 which has 4 6550's per channel and one in the power supply. It worked and sounded great when put in storage over 15 years ago. I got it out of storage and hooked it up but it didn't sound good and something went pop and a hum came out of both speakers. What went pop was the regulator pass transistor for the bias supply. What would cause excessive current draw from a bias supply ? I changed the transistor and it heated up and popped again. I bypassed the transistor with a resistor and it worked but it hummed. I decided to change all the output tube sockets but I lifted some traces when I pulled the first socket out so I've given up for now. Would love to hear that amp working again. I'm over 60 now but I may be even more sensitive to differences than I used to be. At least at certain frequencies.
It's videos like this on unique audio amplifiers that's exciting to watch and makes your RUclips channel one of the best on electronics. Amazing specs for a tube amplifier, the output transformer circuit design reminds me of the high end amplifiers built by a well known HiFi manufacture in Binghamton NY USA.
47 min of pure gold! Amazing video!!!
That is some serious amps.... Really beautiful made....
Thanks for taking the time to make the video and share it...
My pleasure!
I was totally geeking out on this video. I did a little research and learned that Audio Research has an even more powerful mono amp. Wow.
Multitaskers! Audio, welding, cooking and whole home heating.
Don't forget all that coal you will burn making electricity. Actually District heating is not a bad idea...
Very high end design. I would love to try them out for a week or two, they must sound incredible with the wide frequency range. I had to research these amps and a pair costs 32,000 sterling or $40,225.60 USD.
The latest are the Audio Research Reference 750 SEL at $42,500 each USD. Pair them with Radialstrahler System MBL 101X-Treme MKII at $398,000 USD per pair
I would just like to say holly guacamole! Would a cinema use something this big? I guess they would use transistors not tubes.
@@nicholaslittle2312 no, this is old tech, cinemas nowadays use class D amps in active speakers. They are far more reliable and efficient.
@@InXLsisDeo They also don't sound very good, which is kinda the focus of audiophile gear.
33:30 I really wish the Marshall folks had thought of this feature!
I own a Marshall 40W combo, and after reading elsewhere about adjusting bias in that amp, there's no way I'm doing that at home.
30:20 - I'm guessing it's in protection because no output load is connected,
UPDATE: Oops, I was wrong. However, shouldn't a no-load condition be considered?
With no output signal on a tube amp, there's only a static DC current going through the primary winding of the output transformer, so, there's no consideration for any protection needed. I definitely wouldn't try driving any real power out of it without a load though, although most tube amps won't get damaged, the possibility of a oscillation happening is risky and could cause some real damage.
Beautiful amplifiers! I think those are the biggest I've seen with that many power tubes. And 6550s to boot! I believe you could use KT88s as well, if I'm not mistaken. I can't even imagine the cost. What are they like 20K-50K each? Even though I don't need that kind of power, I'm totally jealous! I'm only working with (2) 2-channel amps using 7868s in push-pull with around 35 watts each channel powering a pair of bi-amped speakers. The owner of those is a lucky person.
Great stuff. Even though you are quite particular about some things I appretiate that you know when to stop, like, don't expect perfect linearity out of an analogue meter.
Decades ago I polished the daylights out of the clear window on an analogue meter, and after that it would react to static charges on the meter face. I learned that there is a coating on many of these meters. I ended up using a spray that was sold to remove the static charge from vinyl records. It worked on meters but I never used it on records. That makes me wonder if that was the coating you found on the one meter face?
Ah that's probably it! Its an old layer of something anti static thats gone gooey.
Now that’s more like it! I’ve been patiently waiting for some good audio equipment videos. Thanks Mr. Carlson!
You bet!
41 minutes give or take.....this is some pretty cool engineeing at a high level. A friend of mine showed me the schematic of his AR amp that was only 120 w/ch or so and I saw something similar with the heater string I just couldn't understand. After seeing this video, NOW I get it :)
just WOW!!!! who in the world would actually NEED this kind of complicated audio gear? way over kills NO? sheeeesh never would i have imagined there was ever a reason for building such a thing!!! thanks for this cool vid...even if i am left wondering WHYYYY? lol!
I'm a long time watcher of your videos and I thank you, for what you do and the excellent recording/editing you put into your videos. I don't understand several things you talk about, but enjoy it just the same.
Man, I would love to have a pair of these for my horn subs. I just got a pair of VTL mb-300s that I had to repair, I think these are the only tube amps I've ever seen that offer more power! Beautiful amps.
Hello Mr. Carlson! I absolutely love your videos, they are so informative and I've learned so much from you. I do have one question though..
WOULD you consider doing a video on how to read electronics schematics and explain how to orient the schematic to the actual wiring and placements inside the electronic? I hope that I've asked that question in a way that concise. I am very curious on how to read those schematics and understand the layout inside the electronic from the schematic. Thank you so much!!
And I've always felt so uppity with the two 6550s in my FrankenFender ... lol
Thx Mr. C!
Ok, those are pretty impressive. I’d like to set my EICO HF-14s next to them for scale. Really cool stuff!
Mr Carlson i wish i had 1% of you technical knowledge regards from UK
I was a little disappointed to see that this was just going to be a meter repair, but I really appreciate the deep dive into the schematics. Thanks!
Good Luck finding the 6550C tubes in years to come! Good video!
Man I love this, it makes me truly happy even though I know nothing about it. I just love electronics. Im a person that likes things way more than I like people lol.
yep. compliments to the meter design that it’s so serviceable
Over several years I picked up two Quad tube mono amplifiers and and two Quad electrostatic speakers.
Also a Quad tube stereo pre-amp.
I sent them back to Quad where they re-tubed the amps and re-built the speakers. All for a reasonable price.
There are not many companies the are willing to repair 30 year old equipment.
23:49 The same stuff you see on the inside of your car windshield. Is it from the plastics outgassing? Just like a vehicle does?
Reminds me of the 3-500Z audio amplifiers i built years ago with 811A drivers . it was also stupid heavy i used Plate transformers out of a collins .They are also handy in your shack in the winter time lol
These are cool,great video I see you getting one of these rolling lift tables,
What a Masterpiece of electrical engineering, would love to own those even if they a bit big. A 200 watt version I would buy though.
AR has made some very nice gear. It may be that these are the highest level. Lovely to see. Thank you for sharing
Not ham operators there, just the best audio amplifier engineers in the business for many years.
This is the kind of video your channel needs more of. Not some 50 year old radio nobody cares about anymore. Keep this up and your channel will grow.
i still enjoy the "old" stuff
Love this Classic Audio stuff !
The criticisms I have with these amps is the extended high frequency response that is speced as -3dB at 200K Hz! No reason to have an extended frequency response that is prone of oscillations in the amp depending upon the loudspeaker impedance load which varies widely between manufacturers. Also the damping factor is only 16 which is common with an all tube output amp which means bass will not be as controlled so things can get 'boomy". I'd use a solid state amp for the subwoofers. Haven't looked at the price but I'm betting I would go YIKES!!!. This amp probably will make a good heater in the winter time. Thanks for the video.
Apparently you have never heard of Harman Kardon "Citation A" pre-amp. This pre-amp (from 1964), had FLAT response to 1 megacycle (video frequency). The unit was designed by Stewart Hegeman who along with David Hafler, believed that an amplifier with extended response into the RF frequencies would sound audibly better in the audio range.
@@TheOzthewiz Which goes to show that it wasn't a valid design for "sounding better". Similar to the newer fad of high definition or extended frequency range of digital audio songs where all that does is make a mess of the sound quality by trying to include noise at higher frequencies. There is zero benefit of doing so past a certain point which common knowledge says is past 20KHz Like I said before , amps that have a very high frequency response are more prone to oscillations when driving certain speaker loads.
Great video. Love the audio vacume tube stuff. This makes want to start building again. I might!! Maybe you can tell something about the quality of audio output transformers sometime. Thanks!
Awesome tutorial... You mentioned around 10:30 about a device you use to safely discharge the capacitors. I did a search of your vdeos and could not find any reference to that device... could you or someone else point me in the right direction.. Thank you !
That is a project with all the plans released on Patreon. Thanks for your kind comment!
Once I tried to repair a meter with similar torsion mechanism. The main benefit of this coil mounting is that the torsion spring doesn't create friction(compared to the pivot needle type), therefore it enables much lower currents to be detected. The meter I tried to repair was a 10uA full scale meter from a soviet DP-5A dosimeter. Oh and also these tension wires don't like high heat, so factories used cadmium based solders.
those are called TAUT BAND meters, I've seen them in a couple of multimeters of good brands, they are unbreakable
*Respect for this great Audio Research* !!! 👍👍👍
Wow if you can do that.
Greetings from Hamburg, Germany,
Andre🤠😎
We had to get a pair of those from London over to the Channel Island Alderney.. They went with an even bigger weight, a big pair of Wilsons and a Krell reference CD. They went by boat and I went by helicopter. A memorable install.
Those beasts are very nice. I really liked the design of the old 600’s vs the 610 - 750. Although the newer design is beautiful, the classic look is the best imo. Great amps, thanks for this video.
Very interesting video. I myself just purchased the REF 750s. Along with having my REF 6 upgraded to the 6 SE.
NICE SHOES! Thanks for sharing this with us. I learned some more about meters. I didn't know that wire is a counter balance for the needle. Now you can rock the house with your electric fiddle!
WOW ! Thanks for the great video those things are insanity . What was the typical applicaiton of these?
I would imagine these amps make good space heaters, with all the 6550 tubes in them. I have a power amp I built that only has four 6550 tubes and it generates a lot of heat. As you suggested, Paul, each 6550 is individually biased.
Most of us have transistor based amplifiers - a lot of them are already vintage if you are into stereo. What I would love is to have some guidance if they are still reliable or if I should have the caps exchanged - like on my beloved Yamaha p1050 and the even older Denon amp from the late 70s/early 80s 6:29
If they are from the 70s OR early 80s the Caps should absolutely be changed out as they are beyond its service life. They are only designed to have a 10-20-year lifespan.
I have a pair of the MKIII version. Very nice sounding amps even at low volume. They have a very good grip on low frequencies. Also, comparatively, they don't run hot. I've had solid state class A amps that run quite a bit hotter than these. Thank you for such a thorough demonstration.
That is undoubtedly the biggest tube power amp I've ever seen. Looking at the discoloration on the PCBs around the power tubes, you can get an idea of how much heat they generate.
It's no wonder monoblock was/is a thing when it comes to high power tube. Those effing things are *massive* 🤣👍
5:12 - Screw-heads broken off? I can only surmise they have left-hand (LH) treads?
An absolutely magnificent amp, should have a board with casters underneath just so that you can move it around your lab :).
I like the split load design on the output transformer and the phase inverter with individual cathode followers for each output tube. What I dislike though is the CF tube grid and wiper on RV1...RV16 not having any failsafe resistor to the bottom end of the track, that would pull the output tube's bias as low as possible in case the pot has an intermittent contact.
Elevating filaments has an additional advantage of preventing a diode from forming between the cathode and the heater, that would clip the signal asymmetrically. This diode wouldn't even be a problem with low voltage swings or low impedances in the cathodes (e.g. in output stages), but may be a problem in cathode followers driving the output tubes.
I love electronic engineering using jellybean parts (for those who don't watch EEVBlog, it's just common, cheap and widely available parts like common transistors or ICs). It's not just serviceable, but also easy to analyze.
I enjoyed the big bad, almost overbuilt bi/mono amps. Thank you
I (tubular Joe) was the last one to build Silver Seven 900 amplifiers for Bob Carver. They were redesigned to use KT120 tubes, originally KT88s, 9 up and 9 down, with two screen regulators. They put out at least 1000 watts RMS, and more peak power if your house wiring could handle it. They were beauties.
I just want to hear them at work, great video Mr. C
I guess these power amps would be use in theaters as opposed to home use. I used to have a pair of Dynakit amps using KT88 output tubes and a huge power transformer. The amp put out 60 Watts. I used two external whisper fans to cool them. I Paid $100 each on sale in the 1960's. I bought them ready built. They compared to the very high end amps at the time like Mc Intosh and Marantz. I wonder how these would compare to today's solid state high end solid state units. Of course a very good Pre amp would have to drive them. I also had a Dynakit Preamp and used AR 10AX speakers and an Empire Belt Driven turntable with a Shure Cartridge. Old Hi Fi equipment going back to the late '50s can compare to today's equipment. You have to have heard these. I was 18 and older at the time.
Based on my experience fixing a couple of tube tester meters, don't use any tools made of magnetic materials anywhere near the coil and magnet assembly, because the magnetic field is surprisingly strong and it can pull your tools right into the meter and cause you to bend or break fragile things.
Those are "suspension" type meters too, seeing that they had no bearing adjustment screw for the center, its just a hair fine wire at both sides of the meter pivot, tensioned by a spring band in front and back, and YES, are VERY fragile. It's the same kind of meter movement used in Triplett VOM's, and I know how fragile they are , because I broke one and needed to source a replacement parts meter to get it functional again.
@@poormanselectronicsbench2021Sometimes called a taut band movement.
@@alistairmackintosh9412 Bingo! Thanks for the proper description.
@@poormanselectronicsbench2021 You're welcome.
Those are some crazy mono blocks, it would probably cost close to $5k just to replace the output tubes in each of them, but very cool to have a look inside.
Mr Carlsons lab your good at restoring vintage shortwave receivers and alignment of vintage shortwave receivers with ssb
His good what?
Incredible pieces of kit. I'd like to see the speaker system
Wow Carlson you found my dream amps congratulations
Amazing amplifier in so many ways! Cool to see the inner workings. The meter repair and tips are spot on for 99% of the panel meters you come across but there are some types that *are not* to be mechanically set at zero. The HP 400L VTVM for example. If you zero that meter it will be wildly inaccurate. HP even disabled the zero adjust on some of them and now people think the meter is broken because it won't zero adjust. The needle normally rests left of the first tic mark. Just know the meter's design before adjusting!
Curious about two things: why is there is a MAC224 TRIAC on the primary of T3 instead of a relay to do the switching? Note T2 primary is switched by a relay RY2.
And in actual use how do you know how much to adjust the fan speed. There is no temperature indication and the amps run hot just idling. I would have thought the fans would be controlled automatically. -Erik
Not 100% sure but I think the Triac is operating when power switch is on standby... It limits the primary, which lowers voltage on some of the DC supplies... Enough to keep the valves heated? The Triac is disabled when switch is turned to operate.
The fans should have some kind of thermal sensor in addition to the manual control ideally.
@@peterlarkin762 From what I see on the schematic the triac gate is switched on the same in normal and standby (SW3 and 100 ohm resistor). That is why I was curious. I don't see any phase control on the triac gate.
Too easy! It would have been nice to see some measurements of power and THD! Thank you for your content!
I live on the Gulf Coast, so tube amplifiers are not a reasonable option, but at a Chicago CES a long time ago, I remember hearing this beast's great grandfather: the ARC D-150. William Z Johnson's legacy is nice to look at. Many thanks.
@@chillinginthefrozennorth In a word, heat.
@@chillinginthefrozennorth Not really, it's just the air conditioning load. A friend has a tube amp he plays during the winter. I guess one could spend some serious cash for an HVAC system that is super quiet even at max. Otherwise the noise spoils the listening experience.
Hreat video. Keep them coming! On the meter you zeroed, looks like someone opened the meter after it left the factory. One of the brass screws holding the meter together has a dinged up slot. I doubt a worker at the factory would have done this during assembly; if they did, quality control would have probably prevented it going out that way.
Mr Carlsons lab your utube videos are awesome my best friend 🎉🎉🎉you mack my day 🎉🎉😊😊
Thanks for the video.
Would love to see what these where hooked up to.
Execellent and interesting video Paul! It would have been nice to hear some music via a good set of speakers! Bach’s Tocatto and Fugue played by a pipe organ is a good test for an audio system. Many years ago I visited York Minster where this piece was being played and standing near the massive bass pipes was an experience I have never forgotten! You feel the bass pressure waves rather than hear them frequencies below 10 HZ I think! Pipes 32 ft and 64 ft if I remember correctly! Fraser.
Worked briefly in a Westinghouse meter lab many years ago, adjust and calibrate meter movements in the position they will be used, horizontal or vertical.
the torque on the meter leads is amazing...did the engineer happen to design FCS computers for Iowa class battleships...those are not going to vibrate loose no matter how much bass the cabinet is subjected too
Awesome machines sir nice conditions. I really enjoyed the show Mr Carlson sir you are awesome Thanks for the sharing this video sir ❤❤😊😊
I am going to refect on a detail I noticed , and one would have to compare it to the other meter to prove this right or wrong , given how the adjustment loop was bent offset to the side could some one have force rotated the meter adjustment to far rotating the adjustment pin "all the way around" to the upper quadrent and bending the loop to the left in the process ? , is it possable the adjustment pin orignaly was located in the lower part of the adjustment loop ? if the zero adjustment has a positive end to end stop in its adjustment range could someone have twisted past it ? just a thought .
Another excellent demo how to tune in already great equipment.
'Audio Research' are quality.
That word 'quality'...getting harder to find. Oh its there at super high quailty prices.
Peace ☮️ men ,and women enjoy your weekend
You have NE614s in grocery stores? I need to move to Canada!
Need to purchase yourself some good lift tables for the really big stuff. don't go getting a hernia over those units. Also incredibly interesting video.
Another great one, Mr Carlson AR amps are nice you covered a lot of things great subject as normal thanks for sharing this one 👍from me
Glad you enjoyed it!
Now, that's a work of art just there :)
U know Ur in for a treat when the tubes have tubes
Presumably the 2 hertz range is for audiophile pachyderms. But seriously that's something ive only ever encountered in scientific instruments. Kudos to the designers
The screw heads on the back of the meter were bunged up, so someone opened the meter for some reason. And then he didn't center the adjustment before reassembling it, which is how the arm got bent.
My hardest meter lesson ever was when I had been using steel wool a few days before working on a meter. I did wipe the bench clean, but not clean enough, because the moment I opened the meter, little bits of steel wool jumped into the gap of the magnet. I was never able to get them all out, ruining the meter!
It would be nice to see the stark vt-9 vtvm restored that you showed a year ago. I have one with no cables like yours.