1940's Kalamazoo KEA

 Curious little bargain tube amp that I got to bring back from the dead..... a 1940's Kalamazoo KEA.

This is one circuit that I'll admit I have little idea of how it works. It has a single 6SJ7 driving a pair of 6V6 tubes. How this is achieved I do not know. It's not parallel single ended. Look at the schematic!

The other challenge was finding a 10" speaker that is shallow enough to fit in such a tight space. This project sat around and almost made the 'sold for parts as-is' pile. Nothing fit! But fortunately I was able to find an old CTS speaker in the bowels of Southside Guitars deep in the basement under discarded case parts...... It was dead so we had it re-coned. Speaker had the perfect holes to mount the output trasformer.

In the end it's a fantastic little amp. Not a fuzz box, very clear and defined. These are financially not worth the effort, you'll likely lose money doing what I did. But we were all so blown away by it's charming tone that an employee bought it and will be tracking with it! I have an affinity for the 6SJ7 tube. My favorite preamp of all time so it's not surprising how much I like this amp. 

Did the usual, changed the caps etc. Fortunately both transformers were good. I do not think this amp would work well without that odd asymmetrical output transformer. So make sure that part is happy before you commit to one of these. 

J

1950 (or so) Gibson BR6F

The first good small tube amp I bought was a Gibson BR6F. I found it at Guitar Exchange in Catonsville, Maryland back in 1992.

I....love....these....amps!

6SJ7 driving a 6SN7 phase inverter feeding 2 hungry little 6V6 tubes. 5Y3 rectifier. 10 watts into a 10" field coil speaker.

A word about the field coil speakers. They often sound lovely. Don't do what I did to mine: run a bunch of pedals into it and blast off for hours. I killed mine and once that speaker is dead, that's it. It'll never be the same. You want to treat the elderly nice and gentle, with respect. Leave those dumb ass pedals in the bag and learn to play better!

I probably could have had that speaker rebuilt, but I blew mine up in 1995. No internet in those days and tough to find someone to rebuild it properly

If you do blow it up, check these cats out:

http://www.thespeakershop.com/home/speakerrepair.html

his one was at Southside Guitars. It's long sold. I re-capped it and replaced the power cable. I hope the new owner just plugs in and plays it!

And a video of my friend Eric playing it.....

https://www.youtube.com/watch?v=_PUzJnwjELg

The amp:

40's - 50's Rickenbacher "Electro" amplifier

Here's an extremely rare amp. An old Rickenbacher metal amp from the 1940's.

No idea what model it is, there is one that looks like this called the M10 but this has a 12" Jensen PM speaker rather than a 10".

It looks like a space heater!



With this speaker grill and metal box we were expecting a not good sounding amp! Though the circuit is oddly similar to my main amp that I built: 2 6V6 tubes fed by a 6N7 phase inverter with a lovely 6SJ7 preamp. 5V4 rectifier tube.

What does it sound like? This was the closest we could get to the AC/DC sound. Raw, raunchy and open. I'm usually not a fan of the old Jensen PM speakers, too mellow for me, but not this one! It was perfect!

Re-capped it, changed the power cable and took out the death cap. This was another Indigo Ranch Studio amp that had been sitting on a shelf in Vermont for the last 2 decades. Now it's back in service.

I love that it lived in Cumberland Maryland and belonged to "Jaguars International"! I'm a Maryland native. I just wonder what music was made on this peculiar amp?





















Matching grey power transformer!







I'm a fan of the 6SJ7 preamp tube sound. They're cheap as chips for a good NOS one. Lots of harmonics and a big open sound. This is an amp I'd like to find another of for myself. But then again I can always visit my friends at Sonic Circus and cut tracks on this one anytime.

J

50's Russian 6SL7 and new 6SJ7 tubes, review. Nice glass!

Just a brief bit of impressions on some Russian glass I received recently from a great seller in Ukraine.

First up is the metal base Melz made 6SL7.

And the test LPs were Charlie Byrd Trio: Charlie's Choice and Stan Getz's Jazz Samba.

I usually have a set of run of the mill inexpensive nothing special RCA 6SL7 tubes burning away. I know how they sound as I spend hours listening to my setup. I'm also familiar with these records. They spend a good amount of time on my turntable.

My RCA tubes:

So how did they stack up against the RCA? The difference was pretty drastic. First let me say I wasn't expecting them to outshine what I have. I choose my hi-fi tubes carefully. If I don't like something it goes in my box to sell to guitar players.

The Melz has impressively low microphonics. Great for my phono stage. Sonically they are far more aggressive than my RCA. Very forward. Stan Getz's sometimes harsh tenor sound gets harsher, not in a bad way, just more in your face. I find the RCA tubes to be more clear and relaxed. Since I don't listen to much metal these days, the Melz tubes will go back in the box. I like to relax in my tiny universe.

I bet these will kick some ass in a guitar amp. I do have one Magnatone that used the 6SL7 tube. I have a new RCA in right now and prior to that I had a Sovtek there which I didn't find sounded objectionable at all. I have a feeling the Melz will melt some faces. I didn't find it objectionable for my hi fi either, I just prefer the RCA.

A word about 6SL7 tubes. The big octal 6SL7, 6SN7 tubes are my favorite for hi fi. They relax more for me than the more common and sought after 12AX7, 12AU7 which are obviously more in demand and more valuable. I built my own preamp to use 6SL7 tubes in the phono and line stage, 6SN7 for the cathode follower driving the power amp. I do not covet any vintage or modern preamps. I built mine 20 years ago from a Swedish schematic called "Remus". It's a fantastic circuit! Simple and honest. No Marantz 7 for me, this sounds better to my ears!

Ok next. A tube I'm really picky about. The 6SJ7. My 45 power amp uses these as a driver stage. Also my favorite guitar amps use these, Magnatone Varsity and "B" amplifier of my own design. They have something psychedelic about them, a shimmer, when in a guitar circuit. I thought it was an Echoplex I used to have but that's gone and that characteristic is still there on my recordings. I don't get it with other amps that don't use these.

So I have the fancy 5693 red RCA 6SJ7 tubes in mine. I love these for hi fi, guitar I prefer the standard 6SJ7. I have a set of metal base Sylvania 6SJ7s that I rejected in this circuit after 10 minutes. I missed the warmth and euphonic quality of these red tubes:

So I got these Russian babies. Cheap as a bag of fancy chips. No joke. A couple bucks each. How do they stack up?

I wasn't hopeful. But....they are pretty damned good! Again more forward and aggressive but not like the 6SL7 tubes. The sound was nice and round, not cold or harsh like my Sylvania tubes. In a pinch I would gladly burn these up. There is no markings on these, just a #7 in a box on the side. Charlie Byrd's guitar sounded nice and round, the percussion deep and warm with a nice top end. No, they don't beat my RCAs, but they don't offend me one bit either.

So, hope this was helpful! I will try these out in my guitar amps and do a bit about that as well. And remember just because something doesn't work for me doesn't mean it won't work for you. Give these a try if you are curious! I'd love to hear your impressions.

JB

Sprague Vitamin Q capacitors. Old school paper in oil magic for your hi fi!

Hello there tube amp heads.....

This is a little post about the legendary Sprague Vitamin Q paper in oil capacitors. I used to have dozens of these and at one point used to swap caps in and out of my hi fi amps when I had that kind of time. I was never all that impressed with the Vitamin Q caps in the past myself but decided to give them a go again now that I only have one system that I know quite well.

These arrived yesterday and I threw them in to my lovely single ended 45 tube amp.

When you have such a simple circuit like this, every little change makes a difference. For instance, the 6SJ7 driver tubes pictured lived in this amp for a day. They are Sylvania. Really nice tubes. I prefer my 5693 RCA Red series tubes by far so they went back in the box! The Sylvania version I love in a guitar amp. Big, open sound but for my hi fi I found them a bit harsh.

The signal caps were Sprague polyester PS type, .1@600V. I hate the 715P series that has been so popular for the last 30 years. The 716 is better but if I gotta use Orange Drops they gotta be PS types. I find them to be smooth, detailed and musical. Plus they are warm which I need and they don't sound harsh like the beloved 715.

Now the 715 in a mushy old amp? That can work. Not saying they are trash, remember, everything is a relationship so they work for some amps just great.

So when I audition a new cap, tube or transformer, the first thing I do is pick a record I've been listening to for many years of my life, preferably something with vocals. In this case it was "Rastaman Vibration" by Bob Marley. First question is how does Bobs voice sound? Can I make out the words clearly? Second is how does Aston "Family Man" Barrett sound? Does his bass sound natural.

First listen is terrible. No definition, crap bass. But, the amp had also been on a mere 3 minutes. When auditioning a cap let it burn at least an hour. When you rebuild an amp, you must give it time!

So I went about my business and came back to it after a few hours. Liquid.... That's the word I use. Bobs voice sounds clear and natural and the bass is big and fat. The bass however, does have a bit of flab I didn't notice before. These are bigger caps than what I had in there (.15 rather than .1) and I could go down to .05 and get my bass needs met. But I will continue to listen to records and see if it works itself out. As I recall, these Vitamin Q caps got better with weeks of use.

So the jury is still out. Do I spend $30 a cap on Jensen Paper in Oil? Are those worth it? (the answer is YES in my opinion. Those sound beautiful.) Or do I keep on keeping on with these surplus store gems? Time will tell and I will tell you later. For now I dig them about 85%.

And on a final note. Are paper in oil caps worth it in your guitar for tone caps? No.... Those merely bleed a little high end to the copper pipes in your walls. You can get a 50 cent ceramic to do that job. That's all marketing ladies and gentlemen......

JB



And instant update....That was fast!

Listening to my favorite Coltrane record, "Crescent". Side 2..... I wore out my first copy ,I love this side that much.

Jazz has a wonderful way of mixing itself. At least in a quartet fashion. The bass and low drums are the lows, the piano and sax are the mids and the ride cymbal are the highs. Coltrane sounds like he's hanging out in my little apartment playing. How the hell did he get that sound is beyond me! So warm and beautiful on this record. Jimmy Garrisons bass has authority and clarity and McCoy Tyner....crystal clear. The second song on side 2 is called "The Drum Thing". All about Elvin. Such a beautiful, dark drum sound. That piece moved me to change the way I make music. Oh yeah, this is about some caps.....they've been burning in all night. I'm in love.......

Magnatone Varsity

Not much to say about this little amp, I believe it to be made in the 40's, probably before it was called "Varsity". These are one of my all time favorite recording and yes, performing amps. I have a later mother of red toilet seat ones. Just lovely sounding. Not super gainy tweed Champ nasty, just a good sweet overdrive.

This one arrived DOA. Belongs to my friends in 75 Dollar Bill: (click invisible link below!)

https://75dollarbill.bandcamp.com/


Click here^^^^^^^^^^^^^^


They love these little amps and so do I.

Probably about 4 watts max. They have the classic 3 tube setup: 5Y3 rectifier, 6V6 power tube and a nice 6SJ7 pentode for the preamp.

The problem? Just dead caps. This amp is close to 70 years old. Caps die. Tubes were all NOS, I sold them to the band a few months ago and now this little amp simply rips. Has a new Jensen alnico speaker with barely enough room in the cabinet for the tubes to fit! But it works so.... And it sounds great. Not usually a fan of those new Jensens but in a darker sounding amp like one of these, they work really well.

Go try one, maybe buy one! These are a bargain. Not a "Champ Killer" or anything like that, they have their own thing going on. Perfect bedroom amp!

JB