This 1971 100W Super Lead has the most crazy mod you will ever see... headfirst.amplification@gmail.com headfirstamplification.com / headfirst.amplification / 225949122469679 / headfirstamps.jason
I’m thinking with a dummy load on the Marshall’s speaker out, it allowed the player to crank the Marshall to get power tube overdrive with the total overall volume controlled by the solid state power amp which then fed into the speaker cabinets. Eddie Van Halen did the same thing with his live rig in the 80s running his Marshalls, everything on 10, into H&H power amps, then into his cabs
This is the “Addition Mod” Anything you do, you add onto that. This one here takes ‘building the plane while you fly it’ -to the next level. Thst actually takes herds of skill to keep adding. & adding & adding and the amp to still function. It’s as if he created his own situation that needed something added right after he added whatever he just implemented. LOL man!! Cheers for YEARS🤘🏻 Cool video!
That wiring inside is wild! 😮 brings back memories of the first amp I built - I wasn’t good at building an amp 25 years ago so the wiring inside was a mess I eventually started referring to the wiring as a ‘rats nest’! Lol! You’ve no doubt brought it back to its original glory and tone Jason. Look forward to seeing the videos as it progresses.
What’s the issue? An amp is a piece of equipment, a tool. This amp had circuitry added to be able to function optimally in a certain setting/for a certain use. I have seen tube amps with small mixer consoles added to the head shell and wired directly to the preamp, tube screamers permanently wired into the preamp of the amp or parametric EQ circuit board lifted from another device and hardwired between the preamp and power amp.
If the amp doesn't do what you want it to in its current form, you're better off selling it and buying something else that will do what you want; or buy an amp with an effects loop and patch in whatever effects you like.
@@goodun2974or maybe build something yourself and implement these things into a custom design. At least find something besides an old Marshall to use as a Frankenstein
@@michaelknight4041 what if you can't build it yourself or a custom amp is waaay to expensive? Why do hotrodders build their hot rodded car on a chassis of a run of the mill car, like amps are run of the mill products? Why do people send amps in to be modded? It's one of Headfirst's branches of income...
On one hand what a nightmare, on the other it's kind of fun to see the kind of wild west solutions modders were coming up with solve problems players were coming up with back in the day. I wonder if that contraption ever worked the way it was supposed to?
It looks like an explosion took place at a spaghetti factory! I see some lousy soldering here, so whoever modified this probably didn't really know what the hell they were doing.....
@@jimbaxter8488 That's what I thought at first, too, but it seemed to be set up to come off of one of the original speaker outs, so maybe it was for splitting off some output signal for delay, reverb, stereo chorus, something like that? Or a jury-rigged "direct out," maybe? We're liable to find out, I reckon.
@@OgamiItto70 with that giant output transformer you are begging for loud hum…it might have looked good on paper but in practice it’s a really bad impractical idea
It's an auxiliary solidstate poweramp likely taken from a stereo rackmount unit judging by the box-like structure everything's mounted on. The transformers in these things were so massive that the circuitry had to be compacted onto these brackets to fit everything on as well as shielding it from the transformer to minimize noise.
My brain is blowing up because I can’t remember where I’ve seen that exact amp before! I’m gonna have to go back and look in my old messages or threads.
A good exercise would be to draw out that mod. Once you have a drawing of it, it will make sense enough to maybe leave it be, just fix it. It's a very tedious process but worth it to see if the mod is pure genius or pure sub-genius. If you plan on restoring it, as you mentioned? At least you can work off the new schematic. I once drew out a Jackson XLS-1000 schematic and man what I discovered.
It looks crazy now that these amps are valued in their original condition. I think the work looks skillfully done for its era, and appears to have been done with intent, (not a DIY experiment).
I suspect leaving that alone and making sure it functions would be my first response. It looks like a Wizard that knew what he was doing added Mad gain stages to it. Up to and including Diode clipping. I am only 2 mins in so... But I might want to leave it if it functions. But thats me. Ill keep watching.
The power transformer is a large dual C-core, we used to make 'em. -> As you can see from the Fluke on HT when playing, very low sag compared to standard Marshall PT. C-core traffos have about the lowest voltage sag of any transformer for a given power rating. The gotcha is they can have mechanical noise due to the cores 'chattering' where the join is if not joined, tension banded and varnished properly. It should be a pretty loud amp with decent tubes.
Interesting. I used to work for a magnetics manufacturer. I mostly did high frequency ferrite and powdered iron designs but also some 50 Hz transformers using E and I laminations. We never dealt with C-core types, though I was aware of them. Why does that core type offer less sag?
@@RedVulcan The core material is made from tightly wound, continuous strip GOSS (grain oriented silicon steel) / GOES (grain oriented electrical steel) There are various grades but they a/ have lower core losses for a given magnetization level and b/ can be run at a higher magnetization level (say 1.5 to 1.7 Tesla) than EI cores. This means fewer windings, so thicker wire for a given VA rating = lower winding resistance. Toroids a lighter and smaller for a given VA but will have more sag. You will often see them used for V H quality Hi Fi tube output transformers with much wider bandwidth than most guitar amp transformers. C-cores are also expensive.
My first impression was that the transformer looked beefy. Something I would want to keep for another build. Original E/I sag transformer sag would be desirable in a restoration. The C core would be great in a modern custom build.
Is there any resistive load in there? Perhaps it was supposed to be a way to reamp the loaded down signal for low volume playing. That’s my only idea of why someone would do that.
I thought this too. The external load would probably need to be external for size and thermal issues, but then, why not just design an external load + re-amp box?
@@Mark70609Look at the video of the prototype for the powersoak. Also has a relay on an out. Scholz was running a remote slave set up for volume control at one time, pre-Rockman. The age of the work looks right for the era, and whoever did it was purposeful.
Somebody just wanted to slightly modernize an amp which used tube technology which was totally obsolete already in the early 70's. And as we all can clearly see, that original design was not very compact either. Plenty of room inside the cabinet. So why not!👍
It looks like something an auto or hi-fi audio guy did. Everything's way oversized for the job because there's no real weight or size penalty in these applications. It's often the case the 'techs' installing this stuff over-do it because they lack the basic knowledge how to do things properly so they make everything as big as possible to ensure it doesn't fail. The top facing PCB appears to be the power supply going by the regulators on the board with the metal 'box' structure acting as a heatsink for the power transistors and mounting the rest of the circuit. I've seen this configuration before in older 4U-5U rackmount stereo poweramps (one 'box' per channel) so if I were to guess that's probably where it came from except with a smaller power transformer being it's only amplifying half of the signal. The size and weight of the EI transformers used in older class AB stereo rackmount poweramps amps are a sight to be seen. If it were a tube amp a power transformer it could easily support 500 watts or more they're that big, about 40-50lbs on or about. With modern class-D amplifiers being as efficient as they are, these older AB poweramps are functionally obsolete so unless there's a good reason to keep them operating (like a good vintage solidstate amp), swapping out the power section for a class-D configuration will eliminate the need for a large transformer or any transformer at all with a SMPS PCB module. So long as the preamp section gets the correct voltages you'd be hard pressed to hear any difference, your back will feel the difference though with an amp that's 80% lighter than it was before, no joke.
Christ mate!! What idiot put all that power circuitry down at the input jack end? No wonder she hums a bit.. and I noticed the little oscillation when you turned the treble up.. the best fix involves wire cutters!! Seriously though, it will be a satisfying job to rebuild it as stock... This is the only RU-vid amp video that left me speechless!!
