1968 Marshall Model 1986 JMP-50 Bass Amp in Beautiful Original Condition
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- Опубліковано 28 вер 2024
- In this video we will first examine a really nice, original 1968 Marshall Model 1986 JMP-50 Bass amp, inside and out. Then we will review the circuit to see how it differs from a Model 1987 JMP-50 Lead amp. Finally, there will be a side-by-side audio comparison between this Model 1986 and the Model 1987 featured in a previous video, using a 1958 Gibson LP Jr. and a Marshall speaker cabinet.
Extra features include the opening of two gift boxes from generous viewers and a return to the car show at the War Eagles Air Museum.
If you enjoy advertising-free videos like this one, then please subscribe to our channel and consider becoming a Patreon patron at: / uncledougsvintageamps or making a PayPal donation to: dldcam@aol.com. Also please consider donating any unused tube gear or components, possibly to be featured in future videos. Thanks !!!
Once again a classy, tastefull video on not just wonderful vintage Marshall’s and the view/review of chassis, but then hot rods and their innards as well. You are impossible to compete with in many levels. I go to bed thinking about it and wake up with a cup of coffee and breakfast to view your videos....the best way to start the day. Thank you so much🙂
Thanks for your very nice comments, MP. We appreciate your viewership :)
Menu:
00:00 to 11:00 Examination of Amplifier, inside and out
11:00 to 29:35 Circuit Review and Comparison with 1987 (Lead) Model
29:35 to 31:48 Open Viewer Packages
31:48 to 42:00 Audio Demo and Closing Comments
42:00 to 50:19 Car Show
Errors: 1.) I say "EL 84's" at 25:15 and should have said "EL 34's". It has been brought to my attention that they may actually be 6CA7's despite the written designation. Here is a discussion of the differences between the two types of tube: www.marshallforum.com/threads/6ca7-vs-el34.16651/ 2.) I said that the Hunt's capacitor was a "Death Cap", but instead it was connected to the HV fuse (not the AC Fuse).....therefore it probably was a "snubber" to prevent popping when the Stand By switch was opened and closed.
Comments: 1.) Thanks to my good friend, Dean, who trusted me with close to $20,000 in precious vintage equipment, so that this video could be made. 2.) To those who think that the strong bass output of the Model 1986 would be better suited to a 4 x 12" cabinet, where it would less inclined to overpower the speakers.......I agree. 3.) The circuit could have been modified to more closely resemble that of the Lead amp, but why? It was pristine, and any alterations would border on heresy. 4.) The demo was performed at very high volume levels (bordering on the threshold of pain), which was challenging for the microphones, but they tended to compress rather than clip, so the audio is fairly accurate.
Link to previous Marshall video (1987 JMP-50 Lead Amp): ua-cam.com/video/k2EKNj4qtu4/v-deo.html
Really wish I could send you my vintage univox head would make a good video was told that it is pre Marshall when jim Marshall was with univox
the time you spent past present . late 60s early 70s you ever cross paths with Shawn Winklman ..one of the many Drummers Gerri Garcia had ? and another ? did you ever back up J Beck back in the late 60s early 70s ..you just to damn good to be an amp tec .that plays an Axe .
Wow..MUCH appreciated Doug! I purchased a 1986 Bass amp (made in 1974) many years ago when i was 19 years old. As the years past I thought I had screwed up because I bought that not knowing what I really purchased. Boy did I get lucky. I can imagine the guy setting around now wishing he had never sold it to me. I have a 1960A slant cab with greenbacks. Love the sound but Im not 19 anymore....hate the weight of lugging it around. Gotta get a small combo for gigs and practice and keep this jewel for the stadium gigs.
From the kitties to the coupes a very enjoyable video. I don't know why I was surprised to hear such a difference between the 68 and the 67. I would bet in a two guitar band situation with one sporting the 67 and the other the 68 they would compliment each other and just rock the place like the good ole' days.
Thanks, Jim. I agree......just like mixing ceramic and alnico speakers in a cabinet :)
That jumped-channel tone is TO DIE FOR....That JMP-50 is is in my top five greatest amps of all-time! 🎸
I would have to agree, Mike, now that I have had a chance to actually hear them in action.
A wonderful video Uncle Doug. I've worked on a few of these over the years, and have never seen one that original and in that good condition. You can tell how much your viewers appreciate your videos by the generous items they send you. Take care, and have a great day and beyond.
Thanks so much, GK. I really appreciate it.
Hi Uncle Doug, you are amazing!!! Thank you so much for sharing your wisdom with us!!!
You're welcome, F1. Thanks !!!
thanks uncle doug !! have a great day with you and the little 1's!!!!
You're welcome, Ken. I will :)
Two thumbs up Doug, another wonderful video, one of your best. Glad you came over to the Marshall camp.
Thanks so much, James. We like it here in Marshalltown.
It's just a shame I can only give one thumbs up. The rods at the end deserved a good three by themselves!
Thanks, Gerry. I wish you could too. It would help negate the idiot(s) who reflexively (and inexplicably) give a thumbs down ;)
@@UncleDoug I was just thinking the same thing having got to see the rest after my bed so rudley called me last night.
Wow! Two plexis in three weeks!! And both at the same time!! I just fell off my chair 😎👍🏼
I know right? I was blown away!
We beat the bushes to find new amps to feature, guys. Nothing is too good for our viewers :)
All I can say is, Rusty would be proud !!
Amen! Rest In Peace Rusty
He wouldn't like the noise.....but he would love sniffing those big transformers.
@@UncleDoug Yeah, I know what you mean! Psycho Kitty made it to about 5 on the volume with my floor standing Infinity speakers before she vamoosed. I must admit I never made it to 11 myself, lol.
Both the cats and the wife were hiding out during the demo's.
@@UncleDoug one time I had a mouse take off running from under a folded carpet when I played a single loud chord in my basement at full volume on my Bassman piggyback... Had to laugh.
Your videos are amazing. I used to assemble stage amps (Simms-Watts PA-150) many years ago (1970) before embarking on a career in computer programming - but I always kept my interest in electronics. I'm in the process of designing and building a 100+100 watt stereo unit for high fidelity applications including RIAA correction for the phono inputs and 4X KT88 output tubes (valves on this side of the pond). The 'refresher' information that I have learned from your videos has been indispensable.
Thanks so much, Michael. We're glad to hear that the videos were helpful and informative. Best of luck with your (very ambitious) project.
Hi Doug... these Marshall overviews are interesting to this Fender Freak... I feel that I can always learn something from them. Keep it up.
Since they are based so closely on the Bassman circuit, it's sort of like they are familiar, Bill, even though I have only worked on two, so far.
@@UncleDoug Just twins from seperate mothers...
And thanks for continuing to do the schematic to amp explanation. I really appreciate those.
You're welcome, Sean.
Nice to see Jack is still on the job with the cat scans.
He is a highly motivated sniffer :)
I dont know how to read a schematic, but i found myself enjoying every detail. Thanks again for another fun hour!
(Ps... i did catch one little mistake-at one point you called the EL34’s “EL84’s” , but we wont hold that against you!)
Glad you enjoyed it, BP :)
A neatly constructed, well-designed amplifier, which has been well loved and cared for. Having instructed Mil Std 2000, Category "C" Electronic/Electrical Assembly, Wiring, and Soldering, for 18 years, I must say that I have great respect for the layout and construction methods used to build these Marshall Amps.
I'm not usually one to scream "capacitors", I'm mostly in the 'radio and TV realm' of the restoration hobby/biz; here's the "however": I am of the understanding [my friends from the UK and Australia have told me] that "Hunts Capacitors" are even more notorious than "Black Beauty" and "Bumblebee" caps for shorting. BTW, this is coming from someone who installs 1-amp fast acting pigtails between the selenium rectifier and the power switch, in selenium rectifiers which have no corrosive issues, and test within reasonable parameters, versus the 1N4007/dropping resistor "shotgun" method. I believe there are justifications supportive of both views, by the way...
Thanks so much for your very helpful input, SE. Other viewers have expressed the same (low) opinion of Hunts Capacitors.
I love seeing you do Marshalls! Thanks! I love the 1987!
You're welcome, GL.
As always, The standard of these video's and the content are second to none......all my favorite things covered :)
Thanks so much, Harb :)
Loving both with the P90 equipped vintage Jr. Lester (I think Johnny Thunders would love the geetar)! If forced to choose, I'd take the 1986
I wish I could buy stock in you, In the next few months your going to be VERY POPULAR in other words your going to hit the big time my friend. congrats.
Wow, thanks so much, AA. I can't wait. Jack is already shopping for boutique catnip :)
Both are great sounding amps. It's hard to decide which one I like better!
That's very honest (and diplomatic) of you, MD. Thanks !!!
Fantastic circuit comparison Uncle Doug..!! Both of those JMPs sound fantastic.! Hartley Peavey told me a few funny stories on how he and Jim Marshall argued on who built amp circuits first. Thanks for the great content with added car show..!!
You're welcome, Mr. G. Thanks so much :)
Uncle Doug, you done it up good! Thanks for using the Marshall cab! I strongly preferred the sound of the 1986, I hear a bit of Malcolm Young in that amp.
You're welcome, Darren. High praise indeed......thanks !!!
Outstanding vid!!! Both amps are glorious!. 1987 sounded more open and 1986 abit 'snarky' at first. Funnily enough, i wound up liking this !
Thanks, GM:)
It's crazy how a bunch of wires and capacitors and resistors etc...can make such a beautiful noise.
Good point, Jeff.
Another awesome Uncle Doug Production!
Btw Doug, your playing is improving very nicely 😎
Thanks, John. It's because I turned the demo duties over to Jack & Ollie. They are a godsend to my amp demos :)
Love the 1986 model sound ! And nice to see such a clean circuit, thanks for this video.
Thanks, Erik. Most viewers preferred it. You're welcome.
what a gem! Time machine material.
They sound awesome, Nice work, I think the two have a place and value, depending on the sound you are looking for.
Thanks, Hack. That's an excellent observation.
Awesome amp & thanks for sharing the car show as well UD!
You're welcome, James.
Doug, If only we had teachers like yourself at my school I may have learnt a thing or two. Great job as usual
Thanks, Mark :)
I did a little research and ARS is now making those caps that are the same size and color as the original LCR caps. The F&T's are great, and their tone is great. I've been using them for years, but the ARS are the same size and color as the originals (the F&T's are much shorter). I will have to try some and see how they perform. Thanks for showing it Uncle Doug.
You're welcome, Bert. Good luck.
ARS is a distributor out of Van Nuys, California. Their labeled capacitors are very good quality and they have the original values available; ie. 50/50, 32/32, 16/16. They even have a 32/16 dual cap. I don't know who makes the caps for ARS but they are very good.
Thank you for the information. I will definitely try a set of 50/50's on a Marshall.
thanks a lot uncle Doug ... you rock ..from Quebec
You're welcome, Steeve. Thanks !!
The tone between the two is completely different......the 86 has the Duane Allman tone for sure..... thanks Doug your da bomb ....
Thanks, John :)
It was a great video.... what a treasure of gear, amps and guitar! Very enjoyable, thanks UD!
Thanks, K. We all benefited from the generosity and trust of the friend who loaned all the gear for the video.
Another great video Uncle Doug.
You are a very good guitar player as well as teacher. I liked your explanation of the amp at component level. This information is valuable to me with my current Marshall repair. The amp I have is a later model that has had the original board and top caps disabled, and a custom hand wired board put in place to reproduce a late 60’s model Super Lead Plexi.
My amp however is the 100W model using 4 EL34 output tubes.
After listening to both amps in your demonstration Uncle Doug, I would say the 1986 has a warmer richer sound. It sounds like the bridging of the two channels may have given the amps a bit of grit or dirtier sound from what I can tell on my iPhone’s speaker.
🍻 😎 👍 Cheers Uncle Doug !!
Likewise, Mike. Thanks !!!
Great Video Uncle Doug! It was nice to hear/see both amplifiers side by side.. also nice to hear them without all the knobs cranked to 10, with somewhat cleaner tones for Marshall's (also no Wha Wha's or Fuzz's/Overdrives/Distortion to mess with the tone).. I used a stock 72' Superbass with a 68' Basketweave 4x12 for years, and when I purchased my 1st Stratocaster 94' Plus Deluxe, I was surprised at the clean tones it could produce if wanted. Really enjoyed this one Master...
Thanks so much, Tom. I was surprised how clean Marshall amps really are. You have to go to ridiculous extremes to get any "fuzz"......which we did in the demo, especially the 1986 when jumpered.
Very nice! I am really learning from these comparative videos, thanks.
That's good to hear, Alan. You're welcome.
Thanks for another great video Uncle Doug..
You're welcome, Dave.
Outstanding. The 1986 is the mythical Duane Allman amp and it is easy to hear why. You can hear the difference, it is almost like one amp is Duane and the other is Dicky.
Good observations, Arnold. Thanks !!!
That is one lovely looking Marshall amplifier you have there Douglas. Whenever you spot a Hunts capacitor, serve an immediate eviction notice upon it. I remember how trashy Hunts capacitors were when they were new. Treat them like you would treat vermin.
Sprague capacitors have always been a favourite of mine, though I’m very impressed with IC capacitors.
I enjoyed watching this video, just as much as I enjoyed watching your last Marshall amplifier repair video ...thank you sir.
Regards, Phil.
Thanks so much, Phil. In this case, the Hunt's were successfully evicted.
....Thanks Uncle Doug ! Great videos, subject, info and your style ...
You're welcome, Jamie. Thanks !!!
Awesome comparison !!!!! Thanks Uncle Doug!
You're welcome, RR1
Always impressively educational and entertaining. Thanks UD!
You're welcome, FWR.
Nice tour through the amp, thank you. Beautiful cars!
Thanks, Andrew :)
Man I love the look of these era JTM45, 1959,1987/86 Marshall amps. I know the JCM 800 is a great sounding amp, but they look cheap when compared to these older ones....just my opinion. Keep up the good work Uncle Doug, I’m enjoying my education from Uncle Doug’s amp tech University. (UDAT University?) You have the rare gift that all great teachers possess, & you take pride in your work as a true craftsman should.
That's great to hear, VK. Thanks !!! Glad the videos are helpful.
Now that will cut through the mix with those V30's.
Wow
Yes, indeed :)
Both sound great ! As a kid i found a way to play through the family Grundig tube hi-fi ... its all i had, was terribly muddy and distorted . What i think I'm getting at is that we'll play through anything we can get our hands on even if it says bass amp on it 😃 turns out to be a real winner
Thanks, Ken :)
Good Stuff Uncle Doug always look forward to the next video!! Thank you sir!
You're welcome, CD. Thanks !!!
Both are great sounding Marshall amps and I’d be happy to use either of them. There is a slight tonal difference between them but that basic classic Marshall tone is there in both. I’ve seen inside more recent Tube Marshalls and they’re certainly not built like that these days, I guess that they must still be reliable as they’re widely used. I loved the old Les Paul junior, I’d happily watch a video just featuring that. They’re one of my favourite guitars. You’re a very fortunate man to own that and the nice sounding old Telecaster you have.
Thanks so much, Henry. I don't own any of the equipment in the video or demo......it was all borrowed for the purpose of making the video. I definitely agree with your comments and wish you the very best.
Thanks, Doug! Great stuff, both amps and cars.
You're welcome, GM. Thanks !!
I use to walk by these in used stores for 350.00 to buy a jcm 900. Now I prefer hand wired sound. Something in the big old capacitors. I'm playing a ceriatone 50 bass head now. Great amp.
Thanks for sharing, Dan.
Those tubes look like Sylvania production, Uncle Doug.
That's what several other viewers said, Ideal. I believe it.
@@UncleDoug They are Sylvania 6CA7, one just happens to be relabeled as an RCA which was a very common practice in the good old days ;)
Nice amp comparison, Uncle Doug !
The 1986 bass amp has more of that stiff high tension sizzle, ala "Paul Kossoff playing live with Free" sound then the 1987 guitar Marshall amp.
Another great video !
Thanks so much, Jay. Excellent observation.
oh my god you so much for letting me hear the holy grail of tone
The pleasure was all ours, J.
Cant deside which one I like better. They both sound great, I take one of each please!
Yes, sir. How about a nice Marshall speaker cab on the side :)
UD, I knew the engineer and manager of a Sylvania plant that made tubes and light bulbs. He told me that they would sometimes stop the production line of bulbs and switch the printer logo in order to run a batch for another bulb company. They may have done this for tubes as well, and manufactured a bunch for RCA. They would do this for a fee, or to settle up a patient infringement issue. Side note: this was the same Pennsylvania plant that made proximity fuzes, and the tiny super tough glass tubes within, for WWII artillery shells.
Thanks so much for the info MBG. I can't imagine how tough a glass tube would have to be in an artillery shell :O
@@UncleDoug , if you Google proximity fuses, there are numerous fascinating histories of their development and usage. Essentially, they were kind of like miniature radar devices that sent out radio waves and looked for the bouhced-back, time delayed return signal, such that the bombs or missiles could be set to explode at a desired distance from, or proximity to, the target, whether they be bombs dropped from the air or missiles fired at aircraft . Maximum damage wasn't necessarily even created by a direct hit, and a bomb detonating 50 feet above the ground could have much wider destructive effects than one that actually hit the ground before exploding. Similarly, you wanted the rocket or shell to be able to explode within a few hundred feet of an aircraft, rather than missing entirely and continuing until it ran out of fuel and momentum, and then falling on somebody's heads elsewhere. Better to have the missile or shell blow up in the air then to fall to the ground (where the enemy might capture it and reverse engineer the technology as well. During world war 2, proximity fuses were highly classified devices, critical to helping us beat the Germans, and the process of designing them greatly improved our Electronics technology as a side effect.
Very interesting. Thanks :)
Love the Jr!! Got my eye on a Hamer copy of a LP jr made out of korina for a great price. Your eye for taste shines again. Although I must admit I kinda liked the flames on the red Ford’s window ;-)
Thanks, William :)
Love your channel. All Victoria's are two doors. That first 34 is just a four door sedan, no Vic.
Thanks for the info, J.
The black (or dark brown) silver mica capacitor close to the phase inverter (between V3 and V4 tube sockets on the tag board) is not an original part to the amp. It's top quality, but they didn't exist back in 1968. I have a '68 Lead model 1987 with a serial number S/A 10540 and it was a thrill to watch this video and compare it to the photos I took of my amp. Cheers from Finland!
Thanks for your expert input, J.
1986 circuit all the way. Duane Allman and Dickey Betts both used 1986 50 watt Marshall's on Live at the Fillmore East and we all know the juicy killer warm lead tones they had on that album. Just richer and warmer when pushed a bit. I know a lot of guys change the 1987 circuit to the 86. Great video as always Doug.
Thanks 6S. It's interesting that they would go from lead to bass rather than the other way around......but having heard a 1986, I can see why now.
@@UncleDoug Yeah, it was just rich in harmonic content on your demo, nice full rich tone with a hint of breakup when you dug in. The 1987 just is too shrill and ice picky on the treble channel. If you jumper them they tame nicely but I think the the 1986 is so more similar to a Fender bassman and gets that same thick rich throaty sweetness just like it's American cousin.
@@SIXSTRING63 That's a great analysis, 6S. Thanks.
Those Allmans did things their own way :
Allegedly they ran their spkr cabs with No Backs ...
How about supposedly screwing the pick-ups down in to the body, whilst raising up the posts to Deliberately get a more microphonic sound ⁉ (i've never tried it)
@@lazyrrr2411 , I have also heard that Duane Allman had some kind of home built preamp mounted on the side or top of his Marshall amp.
OK THIS IS EPIC again, thanks UD!
Thanks so much, K :)
Doug! As always is your video's a great inspiration! Keep it up man :)
Thanks, Peder. We will :)
Such an awesome display of a timeless work of art. Interesting though with the 1986 bass amplifier during the demo and jumpering the guitar would have gone into distortion blocking but it seemed to have worked quite well.
Thanks, Eric :)
Another great video !
Thanks, David.
From Leo: Great review. I have performance matched tubes before and found similar results, that brand marking is not a important as in circuit measurements. Unfortunately some customers would rather pay for factory "matched pairs" that are sometimes not as close as the "matched strays".
Thanks, Barb. I agree completely.
@@UncleDoug From Leo: Sorry about any confusion, My wife (Barb) and I share a computer for social media to prevent any corruption on the business computer or the computer where I keep my research. I always get a kick out of your videos, and learn some along the way.
My Gibson Les Special in TV yellow would sound great through this amp!
We played a LPS through the amp.....and you're right.
I am watching some of the videos and it’s great trip down the memory lane.
Time before two Eurotube probes and SM57 microphone. Good old times.
Plexi amps are meant for stage use. They are designed to cut true the mix and be heard no matter what.
In home environment at low volumes and without band they can be sounding a bit shrill and thin.
V30 speakers do not help it either. They have pretty nasty hump in the top range. Again when on stage in the mix and at the volume it works. In house not so much.
Many single coil players went with the Bass models. That way they got more balanced tone.
Now everything at 11 really does work for the Plexi because part of its great tone comes from the power stage saturation. Only that happens at so high volume that many owners never have chance to experience it.
With Volume pot full on the bright cap is out off the circuit as well. That helps people who don’t like it.
This type of lead amplifiers behave almost as if they have integrated treble booster. At no compression they get to bright. But once the compression kicks in everything changes. When one part of the spectrum reaches certain maximum level it can’t be amplified any more. Requesting more volume just turns into more compression. Other parts of the spectrum get amplified and amplifier gets its final balanced tone. Middle and partially treble range cuts true the mix. Less bass heavy guitar amplifier often plays louder because low range requires way more energy. Marshall amplifiers with their closed cabinets control low end pretty good.
So once again they were designed to be played loud on the stage.
Even analyzing the tone stack you can see that it was designed to be loud. Less scooped EQ and less losses. More gain and more middle range. Middle range is perceived as loudest part of the audio spectrum we can hear.
There are always people removing the bright cap and saying it is necessary.
Well it is a matter of taste as number one and matter of volume as number two. Plus one can put it on the switch or what I do the most of the times I change the pot to a push pull pot. Than you have both options and you do not need to drill a hole in the peace of the rock history.
In my own amplifier designs bright cap is off as default. Pull activates it. I do not even mark it. I do not even tell that there is one. If someone misses top end then I tell them to pull the knob. With point to point builds with high quality components tone gets bright fast. Adding on top of it is not necessary. Some humbucker guitars are really dark. Then the bright cap can help.
Fender amplifiers can do lower volumes most of the time. Due to more lows they sound better played in the isolation and at the low volume. Not that they can’t get loud. Plus some of them have great overdrive sound. Most of them react great to pedals and those can shape the tone how ever you like. In some Fenders, at the full blast, top and bottom compress sooner and middle comes up. So they cut true better at high levels.
It’s tricky but louder is often perceived as better sounding. Tube amplifiers love high levels.
Thanks for sharing this with us, 9W.
@@UncleDoug thank you for learning everyone about wonderful world of the tube amplifiers. Your videos are real national treasure. They should be preserved in libraries and museums. When ever I need to reference something or help someone who wants to learn something, I point them to your videos. Way you explain stuff is very natural and easy to understand. Even for some stuff I knew for years I was able to start looking at them with a different approach thanks to your videos. Sometimes people miss understand some complex stuff and tend not to believe that they are wrong. Again all I need to do is to find your video and let them learn how stuff actually works. At your channel one can find almost every answer to any issue and almost every how things actually works video. It is worth revisiting your videos and enjoy them again. Thanks for your work. Greetings from Amsterdam.
@@NINEWALKING Thanks so much for your very kind comments, 9W. We really appreciate it......from the Sunny Southwest, U.S.A.
I managed to squeeze this video in during my bach dinner this evening. Loved the side-by-side comparison of schematic, amp and tone (Jack has stepped up his playing in the past 2 months). Seems silly that I didn't know but I now know why they call it a Plexi. Got a question about the death cap. We call it that because we have grounded outlets, what did they call it back in the 50s? Thanks Doug, I'm off to clean up before my wife gets home.
That's great, Craig. Thanks so much. I don't think anyone even noticed the "death cap" until fairly recently, now that society has gotten all weak and wimpy. In my day, if you didn't get the heck shocked out of you at least once a week, you were branded a sissy :)
I see that this particular Marshall amp still has it's original Bulgin 3-pin mains power socket, I read online on the Champ Electronics website (it's an amp servicing company located in the UK that services vintage guitar amps made by Vox, Marshall, Selmer, Fender, and etc) that the Bulgin mains power sockets are no longer regarded as safe for mains power, and have been de-rated to 50V AC.
Thanks for your helpful input, Simon. I will inform the owner of the amp.
I believe Marshall often just used whatever parts they had around, and there is some blending between model numbers, especially in their early years. Marshall really didn't have too many different models either, everything was based upon just copying the Fender Bassman circuit, and they modded it here and there to make it their own. That 1987 probably just used a leftover JTM45 power transformer. I've seen 1987's that had a chassis that's been punched out for a tube rectifier too, but they just put a cover plate on it and diode rectified it. It's important to remember that Leo Fender knew electronics and knew it well. Jim Marshall was a drummer, and really didn't know electronics. Those guys were really just winging it at the beginning, DIY style. Supposedly, the first Marshalls used KT66 power tubes and they only reason why they did was because the British military was getting rid of a giant stockpile of tube parts away and Marshall grabbed them up. Kinda amusing considering that them running out of these KT66's and switching to EL34's ended up being a big part of their signature sound.
Thanks for all the very informative input, Alva :)
Uncle Doug's Hot Rod Jams, I like the punch of the 1986 better and your playing has improved. We should start an internet band and cut a CD, not kidding.
Thanks, Mr. B. Jack and Ollie are ready :)
@@UncleDoug That's funny, you got me to smile, but what about you? ;-)
Heck, I'm always ready, Mr. B, as long as there is plenty of beer and deranged groupies :)
@@UncleDoug It's all work and no fun without them.
Amen, brother :)
Love the bass out from the 86 which is lacking on the 87. Both historic amps. Thanks for the travel in time.
Thanks, MT.
ARS( are) were in Van Nuys Ca they did sell tubes back in the day 1947. I have not been there in 30 yrs I saw one tube there once that was almost 2 foot tall
I understand they are still in business, Bob. Thanks !!!
WOW! That LP jr. sounds fantastic with both of those amps! Uncle Doug, is that the original P90? I can't get over the clarity.
Yes, it is, Bruce. Thanks !!!
Thanks,the 86 to my ears has a much fuller sound(not tinny). been playing over 45 years.
You're welcome, Frances. Most viewers agree with you.
Nice uncle Doug,,nice I'd be willing to bet that day gon thing barks. PS no luck on E150. O well
Thanks, Mark.
Good Morning Uncle Doug,
I am a bit less tardy with my comments this time. I figured you would appreciate that considering your background. I could definitely hear a much brighter sound from the 1987 amp as compared to the 1986. I also noticed a bit more 120 cycle AC hum on the 1986. I don't know if that has anything to do with the double 33 microfarad cap in place of a double 50 microfarad or not but I suspect that if you ran an audio sweep generator through the two amps you would find that the 1986 has a frequency response skewed toward the lower end of the audio spectrum. That would also explain the increased 120 cycle hum. The 1986 had a nice sound, definitely ”warmer” than the ”Birtish Bright” 1987. Both beautiful amps, some lucky owners out there. The output tubes of the 1986 were biased a bit cold so I don't know if that is having any effect on the frequency response. Great video. I look forward to the tube bias meter to manual method comparison in the future. I have always wondered if the added resistance, capacitance and inductance of the meter wiring harness would have any effect on the measurements. High impedance circuits can be so touchy to such things at times. I have seen that in tube type instrumentation amplifiers. In an old Honeywell chart recorder amplifier you did not dare move a laced wiring bundle anywhere in the chasis other than how the factory had it tied down. I have even seen that replacing a spade terminal on the end of a wire could throw the entire amp out of balance, simply because the wire was an eight inch shorter. I look forward to that. Some really nice cars and trucks at the car show, and a few ”what were they thinking when they did that too” Oh well to each his own. Another great video.
Thanks so much, Mark. I believe the buzz was due to the p-90 pickup, but it was more noticeable on the 1986.....possibly due, as you suggested, to it's lower frequency response (i.e. 60 Hz).
Rectification:I believe Marshall used whatever parts they had to hand so some earlier versions of the JMP 50 amplifier (which succeeded the JTM45) used some JTM45 components. hence although you might expect solid state rectification some earlier JMPs were using up JTM parts. This could apply to other components as well, but don't quote me on it. BTW my JTM45 came with KT66s in it. I didn't know any better at the time so I bunged a pair of EL34s in there and then wondered why the anodes glowed cherry red. Someone who knew better than I did fixed the bias. I think I've still got the KT66s somewhere.
Thanks for the input, Phil :)
Thanks! UD Not a speck of white paint!
Spiders know better than to poop on a Plexi :)
I'm going to move to Texas. You guys get the good stuff down there !
Now you're talking, William. Be sure to bring plenty of steaks and beer :)
Texas *needs* more steaks, and beer? Who'da thunk it? (In my head, I can hear Uncle Doug's reply: "Ya cain't never have too many steaks or too much beer!").
Actually, I don't care what Texas needs :) It's your old Uncle who needs the "refreshments" :):)
Hi marshall 1986 'bass' amp was not released until 1969. For this marshall 1968 was a transition year. In the beginning of `68 Marshall's had cathode shared and basically what became the `bass` amp. Later in the year marshall changed the cathode to make it split. Also the slope resistor and a couple of caps. What you have is an early 68 GUITAR amp.
Thanks for your input :)
Great rundown on the circuit layouts. Always good stuff there. I'm with you on the extra stuff on the cars. I can even do without the pinstripes on most. ( haters be kind )
Thanks, Carl.
I had a fender Mustang guitar with a racing stripe, I could have done without the racing stripe but I wish I still had the guitar. It was an unfortunate shade of original Orange, but it played and sounded great.
Excellent tutorial
Thanks, Jennifer :)
I like the super bass and bass model amps even more than the 1959 and 1987 lead models.
So do most of the viewers, Nemo. Thanks !!
@@UncleDoug I built a Superbass clone and added in the ability to have a split or shared cathode on V1 and a switch for adding in the cathode bypass cap to v2. I also have pull switches to change the tone stack from lead to bass. Makes an awesome amp.
Was there much difference between the split and shared cathode sound, Nemo ?
@@UncleDoug There is a difference in the bright channel. It really shows its self in the gain staging; the way it reacts to different guitars is most impressive.
I just dug out my pair of Sylvania 6CA7 valves to see if they are the same. As far as I can tell they are exactly the same as the ones in this video. Mine are labelled 6CA7/EL34, but if I understand correctly they are more like a 6L6 beam tetrode than a British EL34 that is a pentode (yes, I just wiki'd that and did not remember it off the top of my head).
The valves are known among Marshall enthusiasts as Big Bottles. In my old JCM 800 1987 model the 6CA7 valves would only give a total output just under 30 watts before they clip, even though they were in good shape when tested. EL34s in there would get nearly 50 watts. The amp guy explained why that is but I can not remember. I wonder if this is why that Eddie Van Halen fella liked them. Less output, which means less clean headroom and therefore overdrive at lower volumes.
My amp runs EL84s, so no use for these currently until I finally get around to building my Marshall clone amp. I have to begin with building a fuzz box and treble booster etc though, so I learn a few things before taking on the big job (probably should build a simpler Fender Champ or something first too). I also have a set of two Mullard and one Brimar ECC83s that the amp guy who tested them said were pristine examples. I don't use them apart from as a benchmark to compare against modern ones. The Chinese ones in my Laney are surprisingly good, but that is not the case for all of them these days unfortunately.
p.s. Thanks for making these videos.
Thanks so much for all your very detailed and helpful input, AR. We really appreciate it.
Hello Doug, I saw a Utube video with Dave Friedman in his factory and one of his chassis's was in view with glass tubes with ARS on them.I don't know the interem. Good day.
Apparently ARS is a company in Van Nuys, CA that is still in business, L2.
Okay so why oh why does the 1987 seem so profoundly more 'Hi-Fi'
than the 86? Izzit that treble bleed cap or mayhaps the response of
the 12AX7/ECC83's (where some swapping out could yield a clue)...
Hey Uncle Doug have you been woodshedding on the sly? You made
that Junior/P-90 TALK ta me laddie...
And the guitar parked next to that amp/speaker(?)
Twas the very picture of COOL. Thanx for that and for yet another
fabuloso videolah. For me your stuff is always the best...
the creme de la creme, the top of the pops... cheers
Marshall Lead amps just tend to be clean and clear-sounding, Jonny. They were intended for lead guitarists to cut through all the noise and devastate the audience.....thus, they sound best when accompanied by a bass and rhythm guitar. The Bass amp was not really intended for this purpose, and most likely due to the huge 0.1uf final coupling caps, it is a more universal amp, with massive amounts of bass frequencies, for ballsy rhythm (and lead) playing.
Sometimes the last word gets cut off in between clips like it was cut a second too soon. It is noticeable right before the guitar demo when talking about the LP Jr.
The editing program is at fault, Jason, but I have since found ways to prevent the problem.
Personally, I much prefer the 1986 model. I can see where the 1987 would be better suited for strictly lead and punching through the mix. The 1986 would be better for strictly bass/rhythm. Still, I'd use it for my lead. The jumpered demo on the 1986 confirms my preference.
Thanks, TM. The vast majority of viewers agree with you.
Great comparison video. There is a big difference between the two, but that wasn't exactly a surprise after you showed the two circuits side by side. I just wonder if Marshal had
engineering experience, hired one or broke out the capacitor and resistor "decade boxes" and tinkered until he got the characteristics he wanted. Remember those decade boxes?
I wonder if thy're even used anymore.
Sitting here watching the car show and wondering why people lower any vehicle. If one had no other choice but to drive a lowered vehicle in snow or other bad conditions, he or she
may regret the decision to slam the vehicle down so low. I live in snow country. Give me ground clearance. Another great video...on both ends(8-).
Thanks, Tom. I don't believe that Jim Marshall actually did any of the circuit design or construction. He was a drummer, with no electronics skills to speak of, but had associates who did have them. Lowering cars is quite common here in the great Southwest.....where it rarely rains and hardly ever snows :)
@@UncleDoug I hadn't a clue whether or not Marshall was even curious regarding how elecronics worked...but apparently he had and "Uncle Doug" type or two around(8-).
That'll work! I live in the rust belt...so people hear don't drive their "babies" in nasty weather...unless absolutely necessary. Many folks call their 4X4a their "babies" here.
Quoted from Wikipedia: "Jim Marshall wanted someone to produce a cheaper alternative to American-made guitar amplifiers, but as he had limited electrical-engineering experience he enlisted the help of his shop repairman, Ken Bran, a Pan American Airways technician, Dudley Craven, an EMI apprentice, and Ken Underwood, also an EMI apprentice. They most liked the sound of the 4×10-inch Fender Bassman and made several prototypes using the Fender Bassman amplifier as a model. The sixth prototype produced, in Jim's words, the "Marshall Sound", although at this time the only involvement Jim had was to sell the amps on a commission basis in his shop. As business increased, Marshall asked the three to work for him in his shop, as he had more space and capital to expand."
@@UncleDoug Great data, Thanks!
¿Curioso 1968 /1986 ? , cruzaron el 6 y el 8 y sale modelo 1986 .
Excelente amplificador aún hoy muy apreciado .
Muchas gracias , saludos desde España .
Yes, Marshall's model numbers are very confusing in that they sound like dates of manufacture.....but they are not. De nada Michel.
No Fender products were harmed in the making of this video, so 4 Fender employees had to hit the dislike button. Doug I'm enjoying the recent forays into Marshall-space. Nothing quite like the sound of those old 50 watt heads.
Thanks, Sooti. I agree :)
Surprising that Marshall uses serial numbers in sequence with guitar and bass model amps.
They were a small outfit in 1968, JD. As far as I know, the serial numbers were consecutive.
Yay! More Marshalls!
Yep :)
Another video very well done UD. I have made the decision to send my amp to you. I will send and email and give you some details... talk to you soon.
Thanks, Scott. I await your e-mail.
The bass amp every time for me. Warmer & fuller by far. The most boring things on UA-cam, by the way, are unboxing videos. A guy orders a guitar, a box arrives and who'd have guessed? It contains a guitar. Still my beating heart! The good Uncle's boxes though are surprises all the way. Well done all you Secret Santas. Don't even like to think about the freight charges...
Agreed, Bill. That and the audio demo consisting of 35 minutes of uninterrupted mediocrity.
Whoa, the hum buzzing on both rigs is notable!? Don't recall the previous Model 87 utube demo being so. Wondering about maybe a ground loop somewheres. If the guit is unplugged is it still buzzing? Or maybe some emi source close by. Just curious! As usual, entertaining as heck! (Oh man that quick glimpse of the Chevelle... sighhhh!)
The buzzing was caused by the P-90 pickup, Doc. When the guitar volume was zero, the buzz was gone.
@@UncleDoug ah that explains it. Thanks for the details as it puts the physics into proper perspective. Luv to hear these ole amps pumping out the shreadings. Its like 50 watts then aint 50 watts these days. But then again it depends what watts its been talked about.