Marshall Popular model 1930, circa early 70's

Here's an amp you don't see every day, a Marshall Popular 1930 model. It's a 10 watt 2x10" speaker amp. I've probably worked on 4 of these in the last 25 years, they are quite uncommon though not as rare as the really sought after and far more costly 18 watt 1974 model.

These apparently were only made for the European market so you'll need to either buy a step up transformer or replace the power transformer for domestic use. I know. Replacing a transformer is sacrilege. Whatever. Stick the original in a box and put it away until the day you sell the amp.

This came through with a problem all of them seem to have. Noise. Particularly buzz and lots of hiss. This particular amp was, um, 'converted' to an 18 watt model. A 6CA4 tube was added in place of the silicon diode rectifiers, the output tubes are the more desirable 6BQ5/EL84 tubes rather than ECL86 and another 12AX7 tube was added. Nice thing is all the socket holes are already there as these seem to share the same chassis as the 1974 model.

The intention of the job was good, the execution not so good. I did like the normal channel, it broke up immediately as a result of there actually being an extra gain stage.

So first thing to address was the hum. That was easy. change the filter caps and cathode caps. Hum gone. The challenging parts were: dead tremolo and buzzzzzzzzzzz hisssssssssssssssssss. Un-useable at low volumes. Turn it up and rock out and it's heavenly. You stop playing and you want to turn the amp off.

The tremolo usually dies from dead caps. You know, those 3 in a row typically ceramic caps. Tried that and no life. In this amp the cap going to ground on the tremolo stage was a .1 from the factory. I changed that to a .047 and started getting some oscillation. But not good enough. I noticed when the person modded this amp they changed the power supply resistors to higher values. My guess was they were as frustrated as I was about the buzz and this was an attempt to clean it up. I used the stock values and voom voom voom voom. Tremolo is roaring back to life. And....more buzz and hiss than before.

Yes, already tried new preamp tubes. Also changed load resistors, took out gain stage to see if the stock circuit was quiet. Nope. It all comes from the tremolo oscillator / gain stage. Pull that tube or alligator clip the signal to ground and it's quiet like a dead fish.

Also pulled all the pots and sanded the front of the chassis to tighten up the signal grounds. A minor improvement. Marshall used mechanical grounding in those days. Sometimes maybe in certain conditions, corrosion can happen and you get noise.

But that didn't solve the problem. Worked like a charm in other amps. Rats......

Time to resort to the forums. Type in Marshall Popular noise hiss.... Took me a while to find this problem addressed but I did find it. Someone post this question, a discussion followed that got heated and ugly as forums can do. (These amps are crap! No they aren't! Piss off! Moderators shut this down!). One person attributed the issue to hearsay about the phase inverter. Bollocks. But one person said this: "It's a flawed design. There is no gain stage between your guitar and the volume/tone controls thus causing excess noise." My first reaction was "WRONG!" Add gain, you add noise. This makes zero sense to me. And his comment generated no other comments. So being that it generated nothing and I was bored of this amp I figured he was on the right path.

So I tried it. Moved some wires around so it's more like the 18 watt (I've built a dozen of those, they are quiet!) and lo and behold, QUIET! Minimal hiss, no buzz, great sound.

Amp is loaded with the original Ceslestion 10" speakers. Always a bonus. I did wind up swapping out the power transformer just for ease of use. Plus, my client has a nice house with beautiful things. Having a step up is just kind of ugly. Which part did I use? The Mojo 18 watt power transformer. I did add a 100 ohm 25 watt dropping resistor between the rectifier and the first filter stage. This got it from the 350V to 325V range which is close to original.

So my take on these? Stock they really aren't that good. And the price people ask for these is stupid. Modded they are great. The complaints about them, noisy and thin sounding, are well founded. I, like most of us, prefer quiet and full sounding. They have the potential for that. But don't pay $2500-$3k for one. I'd sooner buy an 18 watt clone for what I want and spend the rest on a ticket to Italy. I would love to see more sanity in the vintage market. If these were great out of the box I'd happily pay what people ask. They are a cute little recording and club amp. When you've spent a lot then you buy into the anxiety of "will making it functional make me lose all my money????" To me something is only worth anything if it's useful. Fortunately my client likes things that work and sound awesome over just things to look at. What rocks stays, what sucks goes away. That's just sane. In the end, I really like this amp now. I wouldn't think twice about taking it on a gig. It really does give up a beautiful sound that is right between a Marshall and a good Vox. With my Fender guitars it's good and clear. Humbuckers it goes into full bodied overdrive without ever getting mushy.

-J

1967 Marshall JMP "Bluesbreaker" 4x10" combo. One of the greatest amps of all time!

This was a fun project, and the 2nd most valuable amp I've ever worked on, the first being a Howard Dumble that belonged to a famous guitarist (not all that impressed with that amp, I would sell it and buy 5-10 of these!).

I've always wanted one of these. They are quite rare. I don't think any amp has surpassed the early 'plexi' Marshall era in terms of sound and style. Looks do matter and these amps are quite beautiful to look at. And of course, they have a special sound as well. Nothing quite like them. Clear, warm and beautiful overdriven sound when pushed. This amp is essentially a Tweed Bassman with tremolo circuit wise but with a much more present mid range.

When I received this amp it was quite a mess. It had been badly damaged in shipping. Poor packing? Maybe. Marshall combos are tricky to pack properly. These amps can command up to $15k so in my opinion it's best to ship the chassis separately. That is a weak part of these amps, how they are mounted.

It's heartbreaking when this happens. Fortunately, everything was fixable and my client decided not to send it back. The company he bought it from are good people and they payed the bill right away. No insurance battle for my client....

So this amp required quite a bit of gluing and clamping. Plenty of doweling as well. A couple filter cans were damaged and some components became unsoldered. The lovely Mullard 5AR4 tube was destroyed so I found a good deal on a NOS one. We're not going to load up a Rolls Royce like this with cheap new glass. No sir, not gonna happen!

Now the crux of this article. The unreasonable fear of 'originality' and 'collectibility' and what that does to a technician.......

Once I got into this amp, and it was gone through by what I assume is a good tech, I found a few issues. First, the Russian tubes were biased hot. 95ma each. These early models don't have a trim pot for bias. My opinion? Screw your 'originality' and put a trim pot in there! Running this amp this hot could kill the output transformer and possibly the power transformer! I was alarmed at seeing this but I've seen this many times before. The fear to alter something to make it ACTUALLY WORK properly. So I added a 22k trim pot. Took 5 minutes to install. Do it. If your customer freaks out about a change like this, you don't need to sell your amp to that person. He/she is unreasonable.

Had a private audience with George Gruhn last month. His words: "If it's old it's been worked on. Even a Stradivarius has a new fingerboard if it' been played." Enough said! My job is to keep important parts like your priceless transformers safe. In this amp the transformers and speakers are original and that is a miracle at 49 years.

Now the next problem. The speakers. At low volume you could hear this bzzzzzzzt as the note decayed. All 4 speakers were bad. One was not moving at all due to a frozen voice coil, the others were all rubbing. At higher volume one would think "oh this rocks". Inspect each speaker. It's important to do this! And it's worth having these re-coned. I had these done at Speaker Repair Pros in Los Angeles. I don't know of anyone here in New York that I trust to do these. One place I called after the third time the man on the phone said "you can just buy new ones cheaper" I finally said "you just don't get it, thank you for your time...." So off they went to Los Angeles. They did a fantastic job as usual!

So why was this amp sold with 4 bad speakers? I don't know. I attribute that to the same fear I wrote about above. In fact, in all honesty I refused to hear it myself. I was a bit afraid to tell my client he needed to get the speakers rebuilt cause I've dealt with many unreasonable clients who are so afraid their amp will lose all of its value. Bollocks to that! And fortunately my client knows better. He want's an amp that kicks it good, not one that will just be looked at!

I love the old logo on these speakers. Classy as can be.

Link to Speaker Repair Pros. They rock! https://www.speakerrepair.com/

So next was the output tubes. We went for Siemens EL34. This amp was built in the first year Marshall switched to EL34 tubes. My favorite year for the old Marshalls!

Biased this pair at 35ma each. Good safe place to run this amp. I also added a pair of 1k 5 watt resistors for the screen grid. The early Marshall amps didn't have them though curiously enough the JTM-45 loaded with 5881 or KT66 tubes had a 470 ohm resistor in this place. Trouble is when you blast this amp without those resistors in place the tubes draw a lot of current and you can pop a tube. You lose a negligible bit of tone by installing them but, it's worth it for the extended tube life. I think it was fine at one point when you had 800 volt Mullard El34 tubes available, but even the Siemens tubes should have those resistors in place.

The Siemens EL34 is by far my personal favorite EL34. Smooth and creamy, no harsh overtones like modern tubes. They were original equipment in 80's 800 Marshall amps and I've seen them go for over a decade being gigged with on a regular basis. And, amps back then were far more brutal on their gear......

Preamp tubes survived, and they are all Mullard long plate 12AX7. The finest for this amp!

One thing about the old Marshall amps the younger folks don't get is, they are 2 channel low gain amps. They evolved into the metal monsters we know and love or hate. These early ones are just as suitable for a jazz gig. In fact, they sound absolutely beautiful for those who want a nice clean tone. Jim Marshall supposedly hated his tremolo circuit but I found it to sound really nice.

These amps are probably the most guitar friendly versatile amps I know. A Tele, Strat, 335, Les Paul, big old Epiphone Jazz box, all sound great through one of these. The first Marshall I ever bought was a '77 JMP 2 input head. Got it for $200. Back in those days we didn't really have all this "true bypass' goodness. Pedals robbed your tone. But with that amp I didn't miss much. There was so much tone there I could stand to lose some. I was sold. My Fender Super Reverb was sold too. That amp was tough as could be. I wonder who has it now?

Amp sounds nice and tight now and is being loved in a happy home.

-JB

1974 Marshall 100 watt Super Lead (model 1959S)

Oh yes. The ticket to hell, or heaven depending on your point of view. This came to me with complaints of noise and poor volume. The owner runs it with only 2 of the 6550 tubes at 50 watts. He was certain it was dead tubes. These are big amps and I can make good dough on a tube sale for them. Caps too...

But the filters were all new and it's a good job too! And the tubes all tested great. Amp was only drawing about 6ma per output tube. So just a good cleaning and re-biasing is all it needed to get going. Also replaced the 100k cathode resistor in the cathode bias tone stack. It had drifted to 130k and this is common. Check that one if you have spits and crackles!

This particular one was modded to behave like a JCM800. Good job too. Nice, creamy and nasty distortion at any volume!

I was a 100 watt Marshall player for years. This is one of the last really attractive ones with the 60's styling. After that they went the way of the cheap looking President Ford/Carter suit. Boxy, ugly and ready for the CBGBs punk Los Angeles heavy metal era. Part of the early Marshall amplifiers appeal is it's beauty. They are some of the best looking amps on the planet. Notice how well it goes with my Persian carpet? Yes. Psychedelic all the way.

JB

1975 Marshall Super Lead!

 Well, here is the beast of rock nation.

  These amps are from the days when things were innocent to the point of being kinda dumb. Rock stars didn't wear ear plugs in these days.

  I was once coaching a group of kids for an after school program where they had a rock band. They played well. The final performance was to be for their parents at the end of the term. They were figuring out the order of the set and decided to put "Hotel California" 3rd out of 4th. I approved and said "yeah that's perfect timing for people to put their cigarette lighters in the air like this" They replied rather baffled: "people used to put their lighters in the air????"

  I said "oh man, you kids will never have any idea how disgusting a rock n roll concert once was." One of the fathers looked at me with a nod and said "yup."

  So these amps are some of the greatest inventions in modern history, or should I say, a great piece of evolution. Marshall merely copied Fender and his tweed Bassman amp and made it louder. Much, much louder. I've owned several of these, the first being a 1977 50 watter, the next being a 1974 100 watt Super Bass. Then I went through a series of Plexis. A 1966 Super Pa, '67 Super Lead, '67 JTM 50. These are hands down my favorite amps. The early ones simply look gorgeous. Heck, they made Jimi and Cream even more attractive to look at. That Gold face, black cabinet and silver grill along with Persian carpets screamed psychedelic.

  This one is a later model from '75. All original except someone added an fan which it doesn't really need. It's also been converted to 6550 tubes. Big sound with those tubes. I do prefer EL-34 tubes in these but, this is one ballsy amp.

The blue cap is from this amp, find me the date code:

  28th week of 1975. Now by this point in rock history, the stars were demanding amps to be brighter and have more distortion. This one isn't a Master Volume model, but it's dangerously bright. I don't like that. I prefer the sound of the earlier Plexi models. But, this is easy to alter. Just take out the damned bright cap across the volume knob on the bright channel. In this amp it's a .005. Try a 50pf or 100pf. Or leave it out so you can actually turn the treble knob up! I left the circuit alone cause this works for the owner.

  Also try taking a patch cord and putting between the low input on the bright channel and the high on the normal channel. I used to do this. I'd turn up the normal channel then add the bright channel for just a bit of hair.

  When this amp came to me it sounded terrible and had a nasty hum with plenty of crackly junk going on. I re-capped the power supply, changed a couple bad load resistors and cleaned it thoroughly. Also removed all the pots and cleaned the chassis where they are mounted to. This is routine. It gets gunky back there and causes problems cause this is where all of your signal path gets grounded to. Clean it. It will only take 5 minutes! Then make sure everything is nice and tight. Screws, nuts and bolts. Marshall amps, unlike Fender amps have mechanical grounds. In other words, the grounds aren't soldered to the chassis. They are soldered to lugs that are bolted to the chassis. For quietest operation, clean them all.

  I replaced the output tubes with Sovtek 6550 tubes. The plate voltage in this amp is 525V! I wouldn't trust any modern EL-34 tubes with that kind of juice. I'm running these at a conservative 35ma each. The preamp tubes, 2 were RCA, one was a Telefunken, all 12AX7 of course. I left them alone except for cleaning the pins which were filthy. They sound great and no modern tube can match these. I don't know what the good people at Telefunken were doing but, their 12AX7 had a 100k+ hour life span. And this was a smooth plate version, highly sought after. As per usual, that tube had both sides pretty close to being matched. I've sold dozens of these and use them in my own amps. It's rare that I get a mis-matched tube, even at this age!

  Also replaced the broken handle:

  Some before shots of the old caps:

  The filters are pretty easy to replace except for this one which feeds your preamp tubes. Fortunately by this point they put a longer ground lead on it so you can just pull it up from the chassis, unsolder it and solder in your new cap.

  In this particular amp I took some liberties with the power supply. The main filters rather than use the stock 50x50 caps I chose to use 350uf caps built by JJ. In series this gives you a total of 175uf. The next stage I went with the stock 50x50 caps followed by a 32x32 feeding the phase inverter and 16x16 for the preamp tubes. My customer wants that thunderous low end. JJ builds drop in replacements that go up to 800uf! That's pretty extreme. I've built a couple Plexi clones that used this high of a filter and gotta say, nothing wrong with a tight bottom. I chose to use a much smaller 16x16 for the preamps just cause that's what the old ones use. It's a bit faster response supposedly.

  So it was great to breathe life back into this fine amp. I miss the days when it was normal to rock one of these with a couple 4X12" cabinets. Voice of god I tell you! Nothing sounds this good to me. And the funny thing is for those who have a prejudice against these due to the years of bad music made by hair metal guys. These 4 input heads are actually a low gain amplifier. They can be FANTASTIC jazz amps. There is so much tone and they respond so well to your touch. I don't care for the later 900 and 2000 series at all. As my former boss Steve Melkisethian at Angela instruments said: "I know bad taste when I see it!" He refused to sell those 900 amps when they came out and he sold a lot of Marshall. I'm on the same page as he is.

  See.... what else can I say about these? I worked on a Dumble once. Belonged to Robben Ford. I couldn't understand for the life of me why people pay $40k for one of those when these just sound so much better! I'd take one, sell it and buy a few Plexis myself, or pay for a nice vacation.........yeah, that's what I'd do.

JB