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Music Man RP 65: Repair, analysis, bias setting and sound demo
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- čas přidán 13. 12. 2023
- Eric Clapton, Albert Lee, Marc Knopfler, Johnny Winter and Muddy Waters- they all played Music Man Amps in the eighties for a short period of time.
Leo Fender was involved, when these amps where developed. So for shure, there must be something exceptional with these amps.
Let’s find out, what it is. Look over my shoulder, while I’m doing a repair and service, take a look at the uncommon circuit. Learn how to bias this early hybrid amp, and listen to a few sound samples, when it comes back to life.
Wow, that phaser at 25:20 is just right! The sound of the 70s.
I bought a really clean used. 112. 65 watt recently at a pawn shop for $150. Late 70s or early 80s. Speaker had been replaced with a cerwin vega. Loud and proud. A fender made better !!! Clean great for most styles. Clean lead amp
That’s a real bargain! I wouldn’t hesitate either! Congrats.
Your guitar playing didn"t torture my ears, all th opposite. Very pleasant, well done, sir !
Thank you!
Thanks for sharing. Great to have more info about these amps.
It’s my pleasure!!!!!
I just stumbled across your channel. Nice to see a fellow tech giving MM amps some love. I think they’re wonderful. I got one just because of Johnny Winter. He said in an interview once that he always kept the Bass and Middle controls on zero, and the treble turned to 10 on his MM amps. That’s insane.
Like I mentioned: they can’t be bad. People like Johnny Winter, E.C, and all the others had a good reason to choose them. And as a fellow tech: let’s preserve these jewels for generations yet to come.
Greetings from Germany
There was one of these in a rehearsal space I used to frequent. Favourite amp ever.
First time viewer here, thanks for putting this up. Not many tube amp guys want anything to do with op amps or transistors.
It’s my pleasure! Welcome to my channel.
I had one of those in the early eighties. I loved it. Worked great with the few pedals we had then. Very loud. Durable, never let me down, not once. Very well made. Wanted a Marshall, got a Marshall. Loved that Amp though. 30 years later I got another one. It's here now next to my Marshall
I have this exact amp model and the original speaker had a blue/silver Music Man logo on the sticker, so the Celestion one is a replacement for sure.
Clapton played a Musicman HD-130 reverb modded for a bit more gain than stock. The early version had a 12ax7 phase inverter tube and no reverb, like a fender bassman. I have both, the earlier one sounds better to my ear. They came with sylvania 6CA7 output tubes.
I have one of these. It’s worthy of being a collector.
Yes, totally underrated, build like a tank and traded for a reasonable price.
Thanks for this! A MM RD210 2 x 6CA7 and square Eminence 10" were my first "real" amp and served me well through many recordings and occasional live performances. I often recorded in my flat and had to play quiet but the built-in distortion circuit did a great job to mimic a "swetting" amp, at least in my recordings.
A viewer from Sweden! Welcome! Amp nerds of the world-unite!😎
Hey Martin, good to see a MM maintenance video, they are quite unique and fantastic pedal platform amps nowadays at a still accessible price on the used market. MM's never came with Celestions. Early on they came with Ceramic Jensen's. Then Ceramic square back eminence (most common). Sometimes with Eminence alnicos. The JBL DF's and EV 12L were available as upgrades. They would buy these speakers as OEM and slap a music man sticker on them usually. If you goto reverb and search up music man combos, you'll see the array of speakers they came with 👍
Thanks for these extensive informations. Would be interesting to hear that thing with all the different speakers! At least it is in deed a very versatile, high quality amp for a reasonable price. Definitely worth to consider when somebody is looking for the Fender sound on a low budget.
Don't forget about the hybrid amp Vox made in 1966 the UL730 amp.
@@bobbystereo936
Allright. Had the Vox a solidstate preamp or Poweramp?
@@martinstubeampworkbench2299 I think they were solid state front end tube power section. I always thought that was the reason the music man logo had the 2 beatle looking guys as the Big M. That's supposed to be Lennon & McCartney.
@@martinstubeampworkbench2299 Unfortunately, these music man amps are not so cheap anymore on the used market.
I had 2 Music Man amps back in the day (mid 80's). A 65 Reverb head and an HD 130 head . Both were crazy reliable and sounded great thru my 4x12 marshall cabs. I wish I still had them.Today I have a Mesa Boogie V combo and a Fender Blues Jr.
Yep. You are not the first one, who regrets the loss of an MM. And you won’t be the last.
My friend bought a 112RP back in Pittsburgh , Pa . It was brand new . I think it was around $350 .
Nice work, glad I found your video 👍🏽
My first real amp was a RP 100 head- wish I still had it
I have owned two MM amps...both the 212 HD model....and I believe both were either 120 watt or 130 watt....mine had a huge amount of headroom and were impossible to push into distortion because they were so FKN LOUD....I eventually bought a Soldano 2 channel foot switchable pre-amp and had an extra input that sent the Soldano straight to the MM's output section.....both MM amps had broken reverb when I bought them...the first had the entire reverb unit and enclosure bag removed from the bottom of the combo enclosure.....the second had the entire reverb still intact , but I discovered that the reverb pan had a small half moon cut into it for some of the circuitry wiring to pass through.....the reverb pan itself was being hung on springs , my guess is to lessen stage vibrations from transferring to the springs carrying the guitar signal , but when the amps were in a bumpy van with bad shocks on the way to a gig , or being mishandled by idiots , the reverb pan would shake like a hammock on a boat in a storm , and the sharp half -moon edge on the side would slice the circuitry wire because they were being thrifty and used short wires that had tension on them....a longer wire without the tension would just get pushed aside by the swinging reverb tank....I then understood why the first one I bought had the entire reverb unit removed ....I bought an Alessis microverb that I patched in after the Soldano instead of rescuing the original reverb.....both amps had Celestion Vintage 30's in them .....this rig sounded absolutely amazing !
Wow, that sounds gooood. :)
thnx
I have a 2-12-65 pre amp was a Leo design his last one 8m gold. But I've never seen any literature on that model.
I had a 65 watt, 2X10 and it was the flattest sounding, most toneless amp I've ever owned.
I owned the 2x12 version of this amp. The salesman at the music store talked me out of buying the Fender Twin Reverb that I’d always wanted. I regretted that decision every single day until I finally sold it to buy a Marshall JTM30 30 watt 2x10 combo amp which absolutely blew the door off this amp.
Interesting. What exactly did you find was was lacking in the MusicMan that you were after from a Twin Reverb?
@@darwinsaye for starters it did not have that Fender "sparkle". To me it sounded like "just another amp". And when I jammed with friends it had no power to cut through. What I hadn't realized when I auditioned it at a comfortable room volume in the music store was that as you turned up the volume there wasn't much more available. It got buried onstage. A Fender Twin was the beast that could dominate any stage and still can.
My mate had a 50w 1x 12...cream tolex though. Lovely amp heavy as, but built to handle the back of vans...
Joe Strummer used em too.
Nice job mate!
Thanks a lot! Joe Strummer??? Punk rock??? That’s interesting!
@@martinstubeampworkbench2299 Definitely mate.. l dunno what model, but he was using MusicMan by 79/80.
Mates 50w.. whack a Tele through it & there's that sound.
Like the channel mate, lve subbed.. so lve got a bit of catching up to do
@@martinstubeampworkbench2299 Apologies mate, thought ld replied!
Yeah definitely, Strummer was using MusicMan...
Edit: repeated myself!
Like the channel mate, have a great Xmas!
@@baabaabaa-yp2jh
Thanks mate ( are you located down under??) take care.
@@martinstubeampworkbench2299 Yeah Martin, Sth Australia... hour or so out of Adelaide.
Unfortunately the prices we pay for guitars and gear here is ridiculous.
I've subbed mate, so no doubt we'll chat again...oh, you were getting some nice tones out of the MM!
First time at your channel. Thanks for sharing. I hit the subscribe button too.
Welcome! Amp nerds of the world - unite!!✊
Very nice video. 👍
I had a MM amp 20 years ago. It had a SS preamp with quite nice tremolo and a pair of 6L6 tubes as output stage. No phaser. It sounded very nice and balanced. I cannot recall the exact model number, or what speakers it had.
AFAIK EL34 tubes surely can be run at those very high 800V plate voltages, and you can get almost 100W out of a push and pull pair, but they usually were supposed to run at almost pure class B and were used for example as PA amp output stage. The EL34 tube can handle that kind of voltages but bad quality or dirty tube sockets can't without arcing because of the pin order which is not optimal for ultra high voltages. 🤓
Thanks for your comment. I’m shure the engineers of MM wouldn’t run tubes with such a high voltage, if they (the tubes 😆) couldn’t stand it. But in a long period of time, it might strain the tubes and shorten their lifespan. Tubemanufacturer required a conservative platevoltage to make shure, the tubes life is as long as possible. People like Leo F. never gave a damn and created legends! But I did a few Valco/National amplifiers in the past. They run their output tubes with an exeptional low voltage, sometimes less than 300 V and the tubes where healthy after 60 years. But a comparison between an MM and a vintage Valco is at least questionable. Thanks again for your informations and take care.
@@martinstubeampworkbench2299 The Achilles heel of EL34 is that plate pin 3 and one heater pin 2 are next to each other and prone to arcing. Of course that 800V B+ is often just kinderspiel compared to voltage spikes which could come from a OT of a clipping output stage to output tube plates. 🤓
I have this amp. Has a MM labeled Rola ceramic speaker.
Stanton-Gibsons were hybrid, 60's design I think. They're kind of neat, built in Maestro effect kind of phaser? Reverb tank too.
Very interesting. Never heard of, never had one on the bench. Will definitely do some research.
I remember when they came out nobody wanted them. Marshall ruled the day.
Interesting, and effective testing. I've got a Music Man 112 RD. Nice sound, but I always thought it had a bit too much self noise. After hearing how quiet you got the Amp on your bench, I think there's probably something wrong with mine.
What kind of noise is it? In case of hum, new filtercapacitors might do the trick. They are 40 years old. It’s like worn out tyres or brakes on your car. You wouldn’t hesitate to change them, either. If it is white noise (hiss) new op amps could help. You need LM 1458 op amps. Swapping them is easy, because they are mounted in sockets. And they are dirtcheap. Worth a try.
@@martinstubeampworkbench2299 The noise has a little bit of hiss, more low hum, sort of the sound when blowing out air with your mouth in the shape of an "O" or what one might think that powerful electricity would make when surging through a circuit. The Amp is 100 Watts. I was shocked when you swapped out the op amps in the video, and how much difference that made. Thanks for advice.
@@picksalot1
Your welcome!
Joan Jett's choice too!
The schematic that you showed is for a different amp that is using 6L6 output tubes. These can't be operated with plate voltages near 800V. The RP 65 runs the output tubes in class B, with 25mV across 3.9 Ohms the quiescent plate current is only 6.5mA. Did you measure the voltage at the cathodes? I bet it is at least +50V. So the output tubes are stressed lower than in class AB amps.
By the way, the phase splitting is done by IC8, not by the cathode driver transistors.
I own a MM HD130 (the early version with a phase inverter tube) since 1980, the original EL34s were labeled Telefunken.
Thank you for these information, very helpful. I know, I showed a schematic with 6l6 OT, but the bias circuit is the same, for EL 34. There is a service manual Ernie Ball/Music Man provides with different schematics. All the same bias circuit no matter what kind of output tubes. I showed this schematic, because details are more obvious to see, rather than the other ones, that look like hand drawn.
Brilliant amps had this model just got to heavy over the years 👍
Peavey made hybrids before MM.
I have one with 2 10" speakers
The voltage across the resistor (the bias setting) on that and other Music Man amps varies depending on the master volume setting.
That soldering iron I would use for rain pipes on the roof
Well, technically tube amps and rain pipes are very close 😂
@@martinstubeampworkbench2299
Cool answer; I personally prefer a much smaller soldering iron (30W,Ersa)
@@martinstubeampworkbench2299😅😅
Fenders are great! Only prob valves/tubes upside down and components above get roasted! Bad for components! Fras
The Celestion is definitely not original. These came eminence custom order speakers.
Your job was ok, but your analysis of the power amp is wrong, sorry to say that.
I am the owner of the model 2165 rp. It contains the pcb named "GP2". My amp was made in January 1980.
The pcb of your amp looks different; it may be the "GP3" version. There ist not much difference electronically.
I call these amps the "NEW", the "MODERN" MusicMan powerAmps.
These amps are not anymore "hot", the powertubes are surprisingly "cold".
These amps don't copy anymore the "Williamson" design, the basis of all the Fender and Marshall Power-Amps since the end of the 1940s. They use a new invention - a power transistor working as a "floating cathode resistor".
The old Williamson design was used in the "early" MM Amps. These amps had a "normal" phase-splitting-design, featuring both triodes of a 12AX7 (ECC83). The splitted signals were fed into the CONTROL GRID of the EL34 (6CA7) or 6L6; this control grid had to be very negative (depending what type of tube was used) to control the "bias" (the current through the tube in idle state). The current through a 6CA7 or 6L6 in a typical "Williamson-Amps" is something between 30 to 40 mA.
The new design is revolutionary different:
The control grid is not used anymore. A positive voltage of +22 Volts is there (look at the 220 Ohm resistor, it is there for safety reasons).
The signal is splitted by the two op_amps in IC8.
The Motorola Power transistors JE 1692 act as "floating cathode resistors". The current through the Emitter-Collector path is "dancing" depending on the signal-voltage at the BASIS of these transistors.
This was a VERY NEW design - possible because of the availability of these new transistors.
The "bias" (the current through the power-tubes in idle state) is only between 6 to 7 mA (25 mA / 3,9).
The "new design" is also found in amps with 6L6 power tubes - for example in my second MM Amp, the 2475-75 amp with two 12 inch speakers.
Very interesting explanation! Thank you. And I have to admit: I didn’t knew that, this new amp design is new for me as well. Surprising, that other manufacturers never picked up this revolutionary technology. They rather stuck to the traditional way of phase splitting.
But anyhow, I appreciate your comment.
definitely not the original speaker