Ancient Gibson amplifier circa 1930's

Here we have a real gem, an ancient Gibson amp from the early or mid 1930's. I know very little about this one, I don't know what model it is. What I do know is it's ultra simple. No power switch, no volume control. And inside no signal capacitors either. It's 100% transformer based in the signal path.

I replaced the ancient electrolytic capacitors, put a grounded power cable on and left it at that. It has a lovely voice with it's 10" field coil speaker. It's about as loud as an old Gibson J45 being strummed good and hard so it's actually kind of perfect for playing in acoustic situations.

Silkscreened logo:





Ancient super cool "Goat" tube shield:





Speaker shots. Jensen field coil. I love wrinkle black paint. It's my favorite. 30's look!






Interior shot. Simple!



This was another amp from the legendary Indigo Ranch recording studio. It had been sitting for the last 20+ years at Sonic Circus in Vermont. Now it's cutting tracks again at their studio. Real blessing to be able to work on such a rare and interesting piece!

J

1955 Fender 3x10" Bandmaster, 5E7. Yes, rare as can be.

This was a fun project. A 1955 Fender Bandmaster with 3 10" Jensen P10R speakers. This is the first original one I've had the pleasure of playing, I built one when I had my shop in Portland and sold it soon after. If I ever need to go 'big' again, I may build another one of these for myself, this may be the candidate for what I need.

What do I like about these? They are raw and primitive. They are part of the evolution to the more refined legendary Bassman amp. They don't work nearly as well in other words. The tone controls are a bit weird and the transformer to speakers is a good mismatch! (4 ohm transformer into a 2.6 ohm load!) That's a part of the sound for better or worse. Plus, I love the size. A Bassman is just a bit too big for any of my needs.

Speaking of that mismatch, you almost never find one with the original output transformer. They simply burned out. A friend had an even more rare Brown 3x10" from the early 60's and that had it's transformer replaced just like this one. I believe only Mercury Magnetics makes a proper 2.6 ohm transformer for these. When I built one that's what I used. Great part but I was a little let down. It was a lot more iron than I expected. I think they call it the "Fat Stack" or something like that. I prefer to have a smaller part, I don't need all that clear bass! So hopefully someone out there makes a trashier part now. A great sounding amp is a mixture of excellent quality parts and frankly, crap. Too much of either direction and you lose me.

This amp belonged at one point to a rhythm guitarist who played with Muddy Waters. When it came to me I saw pictures or the insides and outsides. I could see it had Orange Drop Sprague capacitors throughout, not my favorite, and the work looked a bit sloppy.

It also had a solid state rectifier and just okay modern tubes:

Once I played it other than a bad distortion (one of the speakers had a bad voice coil) I had to wonder what could I do to improve it besides the obvious: better tubes and a proper tube rectifier.

Once I opened it I could see the Orange Drop caps weren't the icky 715 type, but old polyester. I like those. They are nice and warm. You can identify them by the black stripe on the outside foil side:

Notice the blue resistors and the 2 "Chocolate Drop" capacitors in the preamp. Those do have to go. Not acceptable parts in a Cadillac!

Those blue metal film resistors are ok for load resistors, in fact they work better and are more stable. But stable isn't what were after here, we want that extra push over the cliff into special!

The only drag with modern Carbon Composition resistors is they seldom have long enough leads. So I had to extend the 2 watt cathode follower resistor:

Tone stack complete:

I use Mojo Dijon caps as these are my favorites. I also opted for a 250pf 500V silver mica cap for the treble cap. For the phase inverter I left the Orange Drop caps intact. I like them there. The Mojo caps are more like an old cap. Nice soft edges, warm. Mixed with the polyester Orange Drops I think it's a good balance.

Next was the tone caps on the pots themselves:

These were really poorly soldered. In fact the one on the treble pot simply came off then I touched it with a chop stick! You really need to have a high quality iron to get that joint right. Don't cheap out with your economy iron! Buy a Weller already!!! Also hit the back of the pot with sandpaper and use rosin. You'll have a much easier time of it and some pots you simply can't solder on to the back without sanding or using a scratch awl!

The caps themselves here don't matter as much, they are only bleeding some signal to ground, but I replaced them anyway cause, why not? The Mojos look more like the original Astron caps so....

Now the switches. They were fine, just not a classy part in my opinion. I can't stand seeing some big ass disco switches on one of these amps. It just looks stupid!

The one on the right is the replacement. I'll use the old ones for a Plexi, which likes the big bats!

Also on the standby switch I needed to add a .047@600V cap to ground. Not entirely necessary but it's in the schematic so:

And if you notice in the above photo the original wire had oxidized badly. I needed to replace that length with some nice cloth stuff as well. If I wanted to be all picky I'd age the wire with coffee, but who is going to see it???

Then the bias circuit and the grid stop resistors. I did add a trim pot to adjust bias:

Next the sexy part... The tubes. These amps sell for a lot of dough. Sovteks are nice, and I do like the Chinese 12AX7 tubes it was loaded with but, let's reach for the top shelf. Sovtek 5881 tubes replaced with Tung Sol made RCA!

Also that blasphemous solid state rectifier replaced with a NOS Sylvania 5U4 made the same year as me, 1968:

Those scuzzy preamp tubes are replaced with Mullard made "Phillips" branded tubes. And the first gain stage replaced with an RCA 5751. A bit less gain but that's what Fender wanted. Want faster breakup? Use a 12AX7, or....just turn the volume knob up!

Photos of the transformers:

The power transformer and choke are original. The output is from 1961. It's a proper Schumacher Bandmaster transformer.

And a nice chassis shot:

I did use a bigger (30uf @ 500V) cap in the first stage of the power supply. Personal preference. The rest are proper 16uf and an 8uf for the preamp.

So how did it turn out? Was all this work worth it? The amp did sound great but yes, it sounds better now. That extra color to the tone, and it's a more defined. Warmer. So I say yeah, it was worth it!

So if you own one of these, you know how lovely they are. One of the most unique American made amps that ever was produced. It's unusual cause Fender knew how to build an amp like no other, so why the mis match with the transformer. As the drive to produce cleaner tones and more powerful amps to achieve this ensued, I wonder what he was thinking with this one?

For those of you who don't have the dough for an original, I see Fender is making them again. They are pricey but not as pricey. My opinion? Pay someone else like myself or maybe Victoria to build you one. We'll do you better!

-JB

1954 Fender Princeton 5C2 amp. Lovely warm jazzy sound.

Here's an interesting amp. A 1954 5C2 Wide Panel tweed Fender Princeton.

This was an internet purchase what was serviced by the previous owner. I didn't take any before pictures but, the amp worked fine but the work was comically sloppy. I get a lot of work cleaning up poor jobs.

The other bits: this is a really great amp. It was loaded with a cheap Electro Harmonix 4 ohm speaker and a cheap Triode Electronics output transformer. Not bad stuff, but to my ears, it was rather flat and uninteresting. It was also loaded with Sprague Orange Drop 715 caps. No, no, no. Filter caps were decent quality but sloppily installed.

So I loaded it with Mojo Dijon caps, a 60's 8 ohm Jensen C8R (I effing love these speakers!) and a Mercury Magnetics '55 8 ohm tweed Princeton transformer.

C8R: Brown is Beautiful!!!

I come across these speakers on EBay all the time. Best lil' secret though I suppose if I get more readers everyone will want one. Not useful for Champs, these are 8 ohms. But for my GA-5 and old Magnatone Varsity, it's a match made in heaven. They were often used in organs as midrange drivers so they are usually in great shape. People played polka and church music through these babies, not blues and rock n roll!

Yes I know it's not an alnico speaker. I do love a good alnico but as someone who plays out live on tiny amps, I like the way these project and hold together. I like the clarity I get. Try one! Couldn't hurt!!!


Better interior though not final:

I replaced the original 250k 2 watt load resistors which were noisy with new carbon composition 2 watters. Also replaced the cathode bias resistor and power resistors, typically they drift far out over time and these were no exception.

This particular amp has one transitional feature. They were loaded with a 6SC7 tube, then a 6SL7. In this amp the socket had an adapter to put in a 9 pin miniature socket so it could be loaded with the more modern 12AX7. This was factory. And not unusual is the tube chart simply has the 6SL7 tube crossed out with a ball point pen and 12AX7 written in. Leo Fender liked to use whatever parts he had left over till they were gone. Very much in line with his practical sensibilities.

I took out the "meh" output transformer and loaded it with a classy Mercury Magnetics FTPO-55-8. From my research on these amps, they were 8 ohms. Better to not be lazy and use your off the shelf 4 ohm Champ transformer if you are going to get this right. Just my opinion. More expensive, yes, but totally worth it. The amp came to life after installing this and the Jensen speaker. Big, warm and round. I fell in love with it right away. With a Les Paul or a big Jazz Box it's heaven.

The Mercury transformer is bigger than what was in there, and I suspect the original may have been mounted to the speaker. But the good thing, there are some factory 'mystery' holes in the chassis that mounted diagonally the transformer mounted perfectly.

These are quite different than the more sought after late 50's 5F2 model. This one is a 5C2.

The preamp arrangement is radically different than a 5F2 or 5E2. Between the first and second stage in the preamp you have a 250k resistor connected to a 75k resistor that is going to ground. It's a bit like having a potentiometer in that spot and it's set to 1/4 volume. Just for fun I tried opening this up to see if I could get more gain. The amp simply became unstable and started motorboating. BUMP BUMP BUMP BUMP.......  I put the resistors back the way they were. Looking at the schematic this may work with an additional stage to the power supply, this sound typically happens when you have a bad filter cap or too little filtering. Could go to all that trouble or...simply accept this is the way this amp is and what it is is not a later one. Why not have an amp that plays cleaner? It has such a beautiful tone. For my style, it's perfect and I kind of want to build one just for me.

You can see the evolution in this amp going from the old 6SJ7 circuit, which has little gain, to the later rock n roll nasty later 50's 12AX7 version. It sits right in the middle of that evolution. The tone is more relaxed than a later version, but has a bit more punch than the earlier version. Right now the owner claims it's his favorite. I can see having one and feeling the same way. Great little rare gem!

JB

Gibson GA-5 Les Paul Jr amp. My 2nd favorite small amp! And about "too big to care!"

This arrived in the mail today. An early 60's Gibson GA-5 Skylark. I love these amps. It's to me, a Champ killer. The Fender stuff is built much better but some of the late 50's to early 60's Gibson amps just have such a great thing going on.

Typical 3 tube 5 watt design: Single 12AX7, 6V6, and 5Y3 rectifier. This one came loaded with a nice RCA 6V6 and 5Y3 and a great nasty sounding GE 12AX7. It was also 100% original. I changed the electrolytic caps and installed a grounded power cable for safety.

I've bought a few of these as fixer uppers and flip them like a burger. They are easy for me to sell cause they are just that good. A bit wider and more open sounding than a tweed Champ and much less dough. I may keep this one, my last one I was bummed about selling.

Now, in the pictures. Notice how filthy this amp looks. Fresh from the barn. When I turned it on it crackled and popped, the pot was filthy. Not sellable in my opinion. I would have bought it at the asking price, no problem but that's cause I can fix it good and proper. If I was just a guy who didn't have those skills I would have turned away. I bought this from the worlds largest guitar store online. Won't mention the name but you know who I am talking about. I did a stint with said company and was baffled by their treatment of vintage gear, good vintage gear like this. No effort made to clean or improve. I suppose somewhere corporate sees that extra effort hurts that bottom line. I like to make money. I like to make as much as I can. It doesn't take much effort to clean something up. People like it when they don't need to worry and don't have to do anything except negotiate a price and be done with it.

But that's the nature of some big ass companies. Too big to care. It's okay to get big, but never give up the caring part! There's money to be made there and more importantly, there are people make happy.

And here's the schematic for you tech heads. Ultra simple signal path. LESS IS MORE!

So what do I like about these over a Tweed Champ? Well, first, I ain't gonna lie. The price! Tweed Champs to me are simply overpriced. No fun for me. Second? I just got back from playing this at my practice space for 2 hours. These amps tend to not fuzz out as much. The notes articulate better for me. Pick soft and you get a lovely clean sound, punch it and it sings, nasty distortion but....clear. I can hear all of the notes in each chord. It really sounds like a cranked Marshall in that respect.

This particular amp has the original .022 famous Bumble Bee Sprague capacitors. Yeah, they are leaking. Can tell by the fact that the volume pot scratches slightly from top to bottom. A little DC on that, and also by the way the notes decay. I may change them and sell those to a rabid Les Paul fanatic. But for now I don't care to change anything else. There is something I like about the slight trashiness.

So what is the difference between a GA-5 Les Paul Jr. amp and a GA-5 Skylark? Electrically, there is no difference. Same great Jensen 8" speaker too. The cabinet is slightly different and the Skylark says "Skylark" on it. The Les Paul Jr amp is a bit earlier, the Skylark was made in the early 60's.

Here's a Skylark I sold 2 years ago:

And the earlier Les Paul Jr amp:

If these amps were mint you would see that dapper Gibson logo on the front. The Skylark had it on the grill cloth, the Les Paul Jr amp has that lip across the top of the cabinet where the logo went.


 If you are considering one of those sad GA-5 Reissues, don't bother. You may find one of these for about the same money and these are simply better amps. And if you find a dead one cheap, they are so simple it won't cost much to get it going again. Even the higher priced ones are worth it as a tool. Nothing beats one of these in the studio. Pure, simple, direct and awesome sound.


JB