Audio Research Reference 600 Mono Block Amplifier Troubleshooting And Repair!
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- Опубликовано: 9 июн 2023
- See this big audio amplifier come to life! Lets find the problem and fix this together. 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: / mrcarlsonslab
#restoration #electronics #repair 
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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.🥸
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.
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!
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!
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 !
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.
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.
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 ... :-)
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?
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.
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.
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...
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!
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!
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 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.
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!
Fantastic Video about a classic amplifier highly regarded in audio circles from a world class company ! Thanks Mr Carlson.
My pleasure!
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
47 min of pure gold! Amazing video!!!
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
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.
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.
And I've always felt so uppity with the two 6550s in my FrankenFender ... lol
Thx Mr. C!
Paul loves tube equipment and he's in heaven now.
That is some serious amps.... Really beautiful made....
Thanks for taking the time to make the video and share it...
My pleasure!
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.
Ok, those are pretty impressive. I’d like to set my EICO HF-14s next to them for scale. Really cool stuff!
Love this Classic Audio stuff !
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.
Now that’s more like it! I’ve been patiently waiting for some good audio equipment videos. Thanks Mr. Carlson!
You bet!
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* 🤣👍
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,
Very interesting video. I myself just purchased the REF 750s. Along with having my REF 6 upgraded to the 6 SE.
could be the worlds most beautiful electric room heater / audio amp
Those switch knobs on the front are beautiful too, you can hear the nice clicks and they just look solid.
That sure would heat a room. Leave a 1500w heater on without a thermostat and you'll be toasty, even in the middle of winter.
And the world’s most expensive 1600 watt room heater!
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.
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.
They are so well made. They are also very beautiful. ❤
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.
AR has made some very nice gear. It may be that these are the highest level. Lovely to see. Thank you for sharing
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
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.
Wow Carlson you found my dream amps congratulations
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.
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!!
Just looking at the internals makes my arms hurt, lol. Thanks for sharing!
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!
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!
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.
Incredible pieces of kit. I'd like to see the speaker system
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.
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 :)
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?
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.
7:09 Wow, now that looks GOOOOD
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!
Wow 😳 amazing 👍🤩, definitely a God amplifier 👏👏, thanks for sharing
Mr Carlson i wish i had 1% of you technical knowledge regards from UK
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!
*Respect for this great Audio Research* !!! 👍👍👍
Wow if you can do that.
Greetings from Hamburg, Germany,
Andre🤠😎
Good Luck finding the 6550C tubes in years to come! Good video!
Great stuff! Thanks!
I enjoyed the big bad, almost overbuilt bi/mono amps. Thank you
yep. compliments to the meter design that it’s so serviceable
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.
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.
awesome, thanks!
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.
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
I just want to hear them at work, great video Mr. C
Excellent video! Thank you!!!!!!!!!!
Very interesting video, Paul. Thanks
This is so great!
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.
Nice little piece of gear. One could embed those monoliths in some thick masonry walls, maybe in a recording studio to save space.
Nice Mr. C You made me blow coffee out my nose. Hook up welding leads and a stinger on the backside???
Beauties! Love the old design iron while the new gen hugs their Class D's
Mr. Carlson the jeweler/watchmaker! I have to say from my own equipment
when meters are a prominent component and they don't work properly it's a
real bummer.
I would LOVE to have one of these!
Awesome machines sir nice conditions. I really enjoyed the show Mr Carlson sir you are awesome Thanks for the sharing this video sir ❤❤😊😊
1200 watts of audio potential... Dance party at your house, Mr. Carlson?? I'd wait for the winter so the cast-off heat is actually useful. 😅 Really neat find. 👍
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.
Now, that's a work of art just there :)
A good reason for a hydraulic cart like the ones from harbor freight.
Excellent video like always..👍
Thanx..
Fascinating video.
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.
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
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.
Mr Carlsons lab your utube videos are awesome my best friend 🎉🎉🎉you mack my day 🎉🎉😊😊
Need popcorn for this video
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?
Thanks for the video.
Would love to see what these where hooked up to.
Replacing 40 6550's for a stereo pair would make me cry! Hell, I get teary-eyed thinking about the 4 I need for my Harmon/Kardon Citation 2!
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.
VERY nice! 👌