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

1951 Fender Pro.... terrible looking, sounds like gold!

This was a fun and interesting project. Came from Division Street Guitars in Peekskill, a great lil' shop run by my good friend Paul Decourcey. When it came to me it was, well, truly a barn find. Translation: absolutely disgusting. Barns are no places for instruments and definitely not a place to store an amplifier. This amp was badly water damaged on the bottom with plenty of mud to prove it. Some of the plywood had separated so much gluing and clamping was needed. Very time consuming and rather educational. I never realized how many layers of stuff are between the wood and the tweed exterior. More than I thought! And I also know, I'm not the man to do a re-cover job. Used a lotta Simple Green on this one.

He bought it on Reverb from a store in the midwest as a project amp. At least 2 other very good techs turned down working on it. I don't blame them either. If I wasn't a little nutty myself, I may have made the same choice. Amp was full of dead egg sacs from some unknown bugs and some of the wires had been chewed by mice. First order of business was to use a couple cans of compressed air outside just to get the nasties out. Next was the black mold. That and the mud is where I used a lot of Simple Green and a lot of towels, old toothbrushes.....gross man.

It also came with a replacement output transformer that was nice, but the wrong type. This amp had the transformer mounted to the speaker originally, but that old Jensen was long gone. So since this amp is so ugly and we're not re-tweeding it, we decided to just make it player friendly. I replaced the output transformer with a Heyboer tweed 8 ohm Bandmaster transformer availble through Mojo Musical Supply. Not terribly expensive and they are fantastic sounding transformers. I believe Mercury makes the proper '51 Pro part but it's much more expensive and we want to keep this amp affordable for re-sale. And truthfully, I like the Heyboer Iron I've used a bit better though my own amps are loaded with Mercury.

Power transformer was the original Triad. Bakelite fuse holder was broken in half and the power cable and switch were done. Replaced all that and grounded the poor thing!

No tubes came with it. Had to buy 3 6SC7 tubes. A word about those: at this stage of the game, they are risky to purchase. Most of the remaining tubes suck. A decade ago when I was really doing this I could buy a dozen for $60, reject 1/2 of them and still make my money of the remaining ones. Now they set me back at least $18 a bottle. Most I come across are microphonic or have a good hum going on. This one 2 outta 3 were passable, the third I used as the phase inverter. RING! It works but I advised Paul to get another one or buy a 6SC7 to 12AX7 converter on EBay. Other octal preamp tubes are plentiful, like the 6SL7 or 6SN7. For some old Gibson amps 6SJ7 tubes are cheap and plentiful. But, I'm not rewiring this amp for those.

The filter caps were all leaking. They had to go. Don't even bother turning an amp on with those old caps still in it. Throw them away right away. All the electrolytic caps had exploded in this amp. Also the original signal caps were all leaking, badly. I use polyester Orange Drop Spragues in the phase inverter and my favorite Mojo Dijon caps in the preamp. The input caps I left alone. No DC on those so why bother. I'm sure they leaked when they were new but that's a part of the sound so, leave them be!

Also replaced the power resistors with 10k 5 watt wire wound types and the load resistors with carbon composition like the originals. Amp was making those telltale spitting sounds. It's dead quiet now.

When he got the amp it had one of those ugly ass 70's Disco square magnet heavy 15" CTS speakers that belong in an Ampeg cabinet. Nope! Not for a tweed amp! Paul fortunately had this beautiful sounding and great looking Jensen from a 60's rather useless Epiphone amp that lives in his window. He bought the thing for the "someday I may need this speaker" factor. That someday is today and this amps just gives up a beautiful tone now....

It really needs a Telecaster. That is what this amp was built for. My '58 Jazzmaster loves this amp as well. That's a combination from heaven. Big, warm with lots of bite.

Nice and simple 2 channel amp with a single tone control. One channel is nice and dark and is set up for a microphone, the other has plenty of bite. Whenever I get a chance to show a Mesa Channel Switch reared youngster one of these amps I take it. They usually plug in and wonder where the 27 other knobs are but when they start playing something always happens: they start playing better. More grit? Turn the tone knob up and play harder. More clean, back off that pick.

I wound up bolting the new output transformer to the chassis and adding a 1/4" Switchcraft jack so you can plug this amp into any 8 ohm cabinet of your choosing. Also this amp is cathode/self biasing. You can simply drop in any matched pair of 5881, 6L6 or KT66 tubes of your choice and jam out. That's the fun/madness of these early tweed amps. Endless choices! You can make decisions about your tone on the fly. New amps they pretty much make the choices for you. No thanks. But ya know, those new amps are good for getting you there. A real amp like this is good for the one who has already arrived dig?


                                                         Mandatory photo with a Tele:

So if you want to see this amp, hang ten and make the drive to Division Street Guitars in Peekskill NY. Great shop and Paul may even sell it to you!

JB 

Late 50's Ampeg 518 "Dolphin Special"

 This may very well be my favorite rare amp. The absolutely beautiful sounding Ampeg Dolphin. Model number 518. I'm becoming a bigger fan of the early Ampeg amps the more I get to see them. Here in NY I see more oddball Ampegs such as this probably cause they were built nearby. Go to Michaels Music in Freeport, Long Island if you want to see and buy some rarities. He's often loaded with great old Ampeg product.

  Here's a link to his page:  http://www.michaelsmusic.com/

Ok, just click next to the word page! I know it's invisible. I work on old amps that should be in the landfill, not on computers so bear with me!!!

  Anyway, I couldn't find a schematic for this amp. The unusual bits are it was originally loaded with the famous Mullard EL-37 tubes. You can sub them out with common 6L6 tubes though. These amps are cathode biased so you don't need to fiddle with that, just drop them in and gig away.

  Also the original preamp tube is a 6CG7. This amp had corrections from the factory:

The 6CG7 tube was actually a 12BH7 in this case, and my eyes and experience says it came wired from the factory this way even though it says otherwise on the chart. Cool thing is, I can just drop in whatever 12A tube I like. 12AT7, 12AX7 or 12AU7 which is what I chose and my customer is way happy with his sound. The 12AX7 made this amp buck like a wild horse!

  I found a catalog picture of this amp from 1960 and the first preamp tube was listed as a 6SN7. They were obviously experimenting greatly at this point in the company history. The 6SN7 is a low/medium mu dual triode with an amplification factor of 20 just like a 12AU7.

  This amp has a very old school way of construction. The preamp and the power amp are separate. This allows for the preamp to have minimal noise entering it from the power supply. The only AC entering the preamp is the filament voltage. You could easily convert that to DC but why bother? When I finished the re-cap this amp became dead quiet!

     Shots of the power amp:

  And shots of the preamp:

Notice the beautiful old ceramic Jensen speaker! I don't know if it's original to this amp but I don't care either. It's a terrific match! I repaired a hole in the cone. There was one other repair from long ago as well. Sounds heavenly!

  One of the fun facts about these amps is the power amp was possibly a copy of an Acrosound high fidelity schematic. I know this cause the first amp I built was this one:

  I've built this amp using 6L6 tubes and 2A3 tubes as well. Great circuit. Ampegs have a lovely midrange to them, a bit fuller than a Fender. This I really like. Later Ampeg amps become too mid heavy for me but these early ones are right up there with my favorite Fenders and Gibsons of the day. I hate to use the word 'undervalued' but these amps, well, they aren't quite as sought after, and that's not a bad thing for those who dare to be different! One sold recently on Reverb for $495. My client who bought this paid $80 on Craigslist! Yeah, needed a lot of work but still, that's a lot of wonderful sound for the money!

  Here's one last shot of the super cool "Jet Age" styled control panel:

  Volume, treble, bass and 'ultra high' for you to enjoy the jet stream with!

  While I certainly don't need another amp, if I built anything new I may follow this path. No one else is and I think this is a great amp for a jazz player who likes a little bit of hair to their tone! I'm starting to hear more jazzers play through amps such as the Blues Jr. by Fender and it makes me really happy after nearly 45 years of Polytone and Roland Jazz Chorus blandness. Acoustic instruments such as my roommates oud would absolutely kill through this thing!

  JB

1959-60 Ampeg M-15! This is a great amp!

Mercury must have been in retrograde and taking its toll on out of date gear. This old Ampeg M-15 showed up a few weeks back. It was blowing fuses. Once againI hoped it was just a dead tube but alas, it was a burnt power transformer. You could smell it!

These early Ampegs are really likable in the sense that they are really well made and use fairly common tubes unlike the later models. This one has 3 6SL7 tubes, a pair of 6L6 tubes in cathode bias and a 5U4 rectifier. All are easily sourced and not terribly expensive.


Here's a shot of the back:

Amp has the original 15" speaker though it was re-coned in 1999. The filter can was replaced in 1994, it's dated. I usually like to replace filters after 20 years but the amp after it was fixed has no hum and a lovely voice.

So first, the transformer replacement. Again I could have purchased an expensive Mercury Magnetics part or Hammond makes a suitable one as well. But we're on a bit of a budget so I used a nice US built part supplied by a company on Ebay. It's slightly smaller but has the 140ma I need to feel good about this job.

So first the burnt out culprit:

Remove it. Unsolder everything first:

The second shot is the rectifier tube socket. The unused pins have the 2 black wires from the power transformer to the wall, 120 VAC. I don't like this arrangement. I doubt it's factory. So I found a solution. Simply put one of the 120 V in wires on the fuse, the other on the power switch. Makes for a tidier amp!

Next measure:

Simple. Use the new part as your guide. The new part has wires coming out both sides whereas the old part only one side. I'll need to drill a hole for that side, hence the blue dot on the left towards the middle.

  Next drill away! Start with 1/8" pilot holes. Use oil on your drill bit if needed.

The big hole I made with a step drill bit. I think I paid about $60 for it and thought I was crazy. But the first job using it the thing paid for itself. No more filing and wasting time!

Once it's in, start wiring it up:

Now before you get your collector panties up in a bunch about drilling a chassis, here's the deal. This is a beat up old Ampeg. They sell for about $450-$750. They're great player amps and you aren't going to hurt the value by making them playable!

So next, put it on the Variac with no tubes in it and see if that pilot light comes on:

Next, drop in that rectifier tube and bring it up slowly again and test the B+, or pin 8 on that 5U4:

Yup. 471 volts. Not for the weak. Don't mess with a tube amp if you like to drink while you work. Can be fatal.

Once I got this amp working another couple issues arose. The tremolo was weak. 3 out of 4 of the tremolo caps were replaced but they were replaced with some real crap. So I replaced all of them along with some other dead caps and cheap craps. I also replaced the tremolo feed resistor (470K on the schematic feeding the intensity knob) with a 220k. It's good to experiment. Too high a value and you have some weak ass tremolo. Too low and you have a 'WOOF WOOF WOOF THUD THUD THUD' sound. And that can actually damage your speaker. I've seen it happen. Rare, but possible!

Here is a beautiful schematic drawn by Joe Piazza. The tremolo circuit is in the lower left corner.

All in all, this is a really great amp. Ampegs have a totally different thing going on that Fender or Gibson. They lack the 'bite' but the mids make up for it. Lovely, warm sound, euphonic. This model had 5 inputs going into 2 channels. Accordion or Instrument. I prefer the bigger and deeper sound of the Accordion channel myself. Makes my Esquire sound bigger than one would expect.

So if you find one of these at a good price, these are a good deal. Like a tweed Pro with tremolo, more interesting of a choice. They are hand wired with a board not unlike a Fender amp. I imagine a pedal steel would be a great fit for this amp. My friend plays her violin and guitar through this amp. Lovely choice for a fiddle! Big and warm, that's what you want!

JB