I'm now the keeper of Jazzkritter's amp menagerie

[nevershouldhavesoldit]

I'm honored to have been entrusted with the care and feeding of Jazzkritter's trio of mongrel amps. All 3 are products of his fertile imagination, foraging skills, ingenuity, and experience (he was a long time amateur radio operator). They all need some combination of rejuvenation, restoration, and love. With no documentation, no schematics, and enough repairs and mods over the years to cloud the origins, they're all enigmatic enough to make an interesting story. I'll try to piece it together as I work on them. There's a Twin, a Princeton, and what appears to have started life as some kind of 2x6L6 Bandmaster or Pro kit clone in a 2x10 cab.

The Twin was first on the operating schedule. It has a decent looking three pronged grounded plug on a nice cord, and the ground switch, cap etc were removed. The PS caps weren't visibly leaking, although 2 were originals. So I plugged it in, and it warmed up without incident, had the right B+ voltage, and amplified a guitar weakly and badly. There was major hum, and it had unbelievable IM distortion - when I hit the bottom 2 strings, I got a weird chord! It was not usable, but it was viable and at least I knew that the transformers etc were working and it was salvagable. The pots, switches, reverb, and vibrato all worked too. So I jumped right in with an exploratory procedure, sending biopsies to figure out what it is / was. I have schematics and original layout diagrams for every possible version it could have been (763, 769, 568 and 270). I hope to be able to define both its origin and what's been done to it, but I wanted to make sure it was sound and salvageable first.

As you can see from the pic, it's a Canadian chassis (CSA sticker instead of UL) that's had a very hard life. Both the front and the back of the chassis are concave, like a giant grabbed it in a huge fist and squeezed it in the middle. There are no markings of any kind inside the cabinet or the chassis. There's no glue, discoloration or other evidence that a tube chart was ever in the cab. It looks to me like the cab was either recovered or replaced - you can see small gaps between the top corner covering and the side covering in the pic below of the bent faceplate. The speakers are 1st gen Jensen Neo 12-100s (wired out of phase!). The complete amp weighs 59 pounds with the 5 lb neos.



There's no master volume, and it has a vestige of a numeric serial number that seems to date it to 1971 - but there's no letter in front of the numbers. Although I haven't yet traced everything against the schematics, it looks like it was either an early SF with 763 circuit or it was "blackfaced". It could have been an early enough SF to still have the BF circuitry, but that wouldn't jive with what looks like a partial '71 production number (if that's what I'm seeing in the metal). The power transformer is a replacement, so I can't date it from that. It came to me with a bent '63-'65 pre-CBS "Fender Elect Inst" blackface panel. But when I took it apart, I found a '68-'70 SF panel in the bottom underneath the very recent replacement Accutronics reverb tank (another clue that it could well have been one of the early SF Twins with a 763 circuit):





So I can't yet say with any certainty what it was when it left Fender. I have to clean off all the pots very carefully to see if I can find any codes to help date it more accurately. It has no cathode bias resistors, and someone moved what appears to be a bias pot to the hole where the ground switch used to be. I still have to trace this out to be sure it's not a balance pot (which it wouldn't be if it's a 763) when I check the bias and change resistance to reset it if necessary.

There was a service sticker on the doghouse dated 2006 with the name John Gurley on it. When I opened it, I discovered that said John Gurley (whom I've not been able to identify or locate) had a very warped sense of humor. He apparently changed 3 of the 5 original PS caps and left a sticker on the aggregate that has "old" written on it instead of a date.



Long story short: I did a cap job, looked for burned or otherwise suspicious resistors, checked all the solder joints, cleaned out the gross grunge, and decided not to try to straighen the bent chassis alone (since I was far more likely to cause a problem in the circuitry than I was to get great benefit from the minimal cosmetic improvement I might make). The third output tube socket from the left is a replacement. Here are the new caps (F&T from Germany) in the PS:



I used wood blocks to straighten out the blackface panel, which looked like this when I got it:



Here's the finished chassis:



The grille is also a replacement. If it were a '67 to mid '69, it would have an aluminum edge around it (the so-called "drip edge" grille). And I think this cloth is a later color than '71. IIRC a SF just after the "drip edge" years should have some turquoise threads in it. Also, the Fender logo on the grille should have had a "tail" - this one with no tail came along in 1973. I was able to clean and vacuum the grillecloth back to life without stretching or pulling it much, and the Tolex (which is is in very good shape) cleaned up beautifully. Here's the amp now:



It now sounds like a Twin should (this is my 4th one) except for a bit of hum that makes me want to check the preamp tubes. There's no static, and the plate resistors (which look too new to be original) measure about 100K. Yes, the Jensen Neo 12-100s sound fine. I'm only using it at home, so I want to keep it exactly as JK had it but in good working order. I assume he was physically unable to maintain these once his illness took hold, since he was a meticulous guy who knew his way around electronics. Once I finish detailing it (which can wait until after I go through the other two), it will live under the piano. Now that it can stay put, I love having a Twin again - my Henriksen is great, but I have to say "Wintermoon, you're right - there's nothing like a Twin!" as long as I never have to pick it up .

I recorded the first tune I played after putting it back together last week (Eastman 810CE7), all EQ flat, reverb on 3, mic'ed from about 18" with the onboard mics in my TASCAM DR-40x digital recorder. I really feel a connection to Jazzkritter when I play through this!



And here's the next patient - stay tuned.................

[wintermoon]

"but I have to say "Wintermoon, you're right - there's nothing like a Twin!" as long as I never have to pick it up"

Welcome back to the dark side nshsi!
And to think after going back to my Vibrolux last year after eons (no pun intended) of using a Twin exclusively I've been using a Twin again lately.
The only question that remains for you is when the Mrs demands you remove that behemoth from her home.

[nevershouldhavesoldit]

"but I have to say "Wintermoon, you're right - there's nothing like a Twin!" as long as I never have to pick it up"

Welcome back to the dark side nshsi!
And to think after going back to my Vibrolux last year after eons (no pun intended) of using a Twin exclusively I've been using a Twin again lately.
The only question that remains for you is when the Mrs demands you remove that behemoth from her home.

Aha! I’ve lucked out. There’s a short rack holding my audio amp and a few small components (DAC, Raspberry Pi, and power strip) under the piano against the back wall. The Twin sits in front of the rack wearing its black cover, so she can no longer see the rack. This pleases her!

I’ve been using the Vibrolux at the club for a few years now. It’s very good, but I’ve never been truly thrilled with the sound. I’ve even brought my Henriksen a few times and think it sounds better (as does the rest of the band). This week I went back to the DV Mark Jazz 12 because it also sounds better (although not as great as the Henriksen). But now that I have a Twin again, I realize how truly wonderful it is. I won’t gig with it for many reasons, but it really is the sonic standard for jazz guitar and I’ll enjoy it every day at home. Being a true mutt makes it special. The fact that it was my friend’s amp makes it extra special.

[wintermoon]

Aha! I’ve lucked out. There’s a short rack holding my audio amp and a few small components (DAC, Raspberry Pi, and power strip) under the piano against the back wall. The Twin sits in front of the rack wearing its black cover, so she can no longer see the rack. This pleases her!

I’ve been using the Vibrolux at the club for a few years now. It’s very good, but I’ve never been truly thrilled with the sound. I’ve even brought my Henriksen a few times and think it sounds better (as does the rest of the band). This week I went back to the DV Mark Jazz 12 because it also sounds better (although not as great as the Henriksen). But now that I have a Twin again, I realize how truly wonderful it is. I won’t gig with it for many reasons, but it really is the sonic standard for jazz guitar and I’ll enjoy it every day at home. Being a true mutt makes it special. The fact that it was my friend’s amp makes it extra special.

No offense to the club, its wonderful Jaime has a great back line and I know you owned a 'real' one at some point but one day I'll bring my '66 by the club to reacquaint you w how a Vibrolux is supposed to sound
Warning: you may not let me leave with it!

[nevershouldhavesoldit]

No offense to the club, its wonderful Jaime has a great back line and I know you owned a 'real' one at some point but one day I'll bring my '66 by the club to reacquaint you w how a Vibrolux is supposed to sound
Warning: you may not let me leave with it!

The best sounding amp I ever played through was Ron Kraemer’s early BF Vibrolux. Not only was it a fabulous amplifier, but it also felt like it weighed about 6 pounds next to my Boogie or my Twin. Ron left our neck of the woods for Florida years ago, and I assume he still has it. I tried to buy it for crazy money many times, but he wasn’t interested in selling.

The Vibrolux at the club is a production line “reissue” SF and I agree with you. None of the modern versions of BF or SF amps sounds or feels like the real thing. I think our CS Princeton Reverb is very close to an average original - it’s built well with good components hand wired on turret boards and a solid pine cabinet. To me, it sounds right. I don’t know if I could tell it from a real ‘66 by sound or playing feel. But these list for $2800 when I last looked, and that’s also serious coin.

Having a backline is like having a good small amp - it’s a compromise. I may not have the best tone in the region, but it’s pretty good. I just grab my gig bag, jump in the car, walk in, plug in, and play. It’s easy to get spoiled - just the freedom from worrying about hurting myself lifting a Twin out of the trunk is addicting

As a result, I’m happy using my Blu or my Toob with a Superblock US on gigs out of the club. For bigger shows, I take the 4 pound DV Mark EG250 and an 8” or 10” cab. If the Quilter OD202 coming tomorrow sounds great, II’ll use that when I need big power. But I don’t drag no anchors no mo’ - I’ll enjoy the Twin at home.

[jim777]

No offense to the club, its wonderful Jaime has a great back line and I know you owned a 'real' one at some point but one day I'll bring my '66 by the club to reacquaint you w how a Vibrolux is supposed to sound
Warning: you may not let me leave with it!

You two need to let us know when that day is coming so we can get out there to see it!

[wintermoon]

The best sounding amp I ever played through was Ron Kraemer’s early BF Vibrolux. Not only was it a fabulous amplifier, but it also felt like it weighed about 6 pounds next to my Boogie or my Twin. Ron left our neck of the woods for Florida years ago, and I assume he still has it. I tried to buy it for crazy money many times, but he wasn’t interested in selling.

The Vibrolux at the club is a production line “reissue” SF and I agree with you. None of the modern versions of BF or SF amps sounds or feels like the real thing. I think our CS Princeton Reverb is very close to an average original - it’s built well with good components hand wired on turret boards and a solid pine cabinet. To me, it sounds right. I don’t know if I could tell it from a real ‘66 by sound or playing feel. But these list for $2800 when I last looked, and that’s also serious coin.

Having a backline is like having a good small amp - it’s a compromise. I may not have the best tone in the region, but it’s pretty good. I just grab my gig bag, jump in the car, walk in, plug in, and play. It’s easy to get spoiled - just the freedom from worrying about hurting myself lifting a Twin out of the trunk is addicting

As a result, I’m happy using my Blu or my Toob with a Superblock US on gigs out of the club. For bigger shows, I take the 4 pound DV Mark EG250 and an 8” or 10” cab. If the Quilter OD202 coming tomorrow sounds great, II’ll use that when I need big power. But I don’t drag no anchors no mo’ - I’ll enjoy the Twin at home.

When you were nice enough to let me sub for you a few times I used the PR once and the Lux the others. Agreed the reissue PR sounds closer to an orig than the VR.

[nevershouldhavesoldit]

When you were nice enough to let me sub for you a few times I used the PR once and the Lux the others. Agreed the reissue PR sounds closer to an orig than the VR.

Let’s clear the air. You were kind enough to help us out by playing when I couldn’t be there, despite being underpaid. Everybody was thrilled with your playing. I (and the club owner, if he has any sense) owe you a debt of gratitude for sure!

Many thanks once again, my friend.

[wintermoon]

Let’s clear the air. You were kind enough to help us out by playing when I couldn’t be there, despite being underpaid. Everybody was thrilled with your playing. I (and the club owner, if he has any sense) owe you a debt of gratitude for sure!

Many thanks once again, my friend.

Well I sure as heck don't know about all that but what an exceedingly kind comment from one of the best players and classiest cats on the forum. I've long had you in mind to hopefully return the favor when the situation presents itself and hope you'd be available. It would certainly be one less thing I'd need to worry about, well, other than losing my gig!
p.s. check's in the mail, just let me know when it clears

[DawgBone]

Damn that thing sounds amazing and really beautiful playing. The Neo's sound absolutely great doing what you are doing with your settings. I am enthused by this because there are very few capab!e players demoing neos in a Twin out there, so thank you for sharing it.

59lbs is the portable version. Mine are like 80 and 94lbs cause I like big clean speakers. I have been really tempted to try a set of Eminence EM12N or Lil' Texas neos in one of mine. it would be nice to have a grab and go version. Since I don't really get deep into pedals I am always browsing stuff like speakers. There are a lot of nice speakers to choose from out there right now, never mind the classics like jbl and EV. I have more speakers than Twin Reverbs to put them in, lol.

Free Twin's are the best kind. I just had both of mine recapped also, one of them completely, with some of those same German caps and some orange drops (I am not amp savvy) but still breaking in a set of speakers and getting it all burned in. One of them had a loose choke. The heavy speakers were causing baffle flex on both of them which was exacerbated at max volume operation, and rubbing the chassis, making noise. So I cut a strip on the table saw and screwed it to the back of the baffles at the top so it's much more rigid and it solved my problem.

That is obviously a well loved amp, glad to see you keeping it alive. That transformer has leaked a bit of blood it looks like, which I would guess would mean some pretty hard use over the years. Survivor of countless incursions behind enemy lines haha.

I have a '69 drip edge that was a SF circuit once I got into it. The chipboard baffle had to be replaced with a mojotone. I think by 69 and 70 everything was basically SF, the 67-68 more likely to be a question, but even that is a speculative statement. My old man has a 70 and it was also SF before getting the BF at the tech. Yeah I even got my pop to buy a Twin.

I think you should get a nice cart and gig that puppy. It's beat up, it needs to be nicknamed "Kritter" in honor of your friend. The rough chassis kind of fits that name. Just an idea. Looking forward to any more clips. Sorry for the long post, I like Twins. Fantastic!

[nevershouldhavesoldit]

Damn that thing sounds amazing and really beautiful playing.

Thanks so much!!

I think you should get a nice cart and gig that puppy.

75 is in the rear view mirror and I'm looking at 80's rear as I catch up to her. The song lies - they don't all look better at closing time.

I sold my last BF Twin, the original Boogie hunree with EVM that I got in '78, the Boogie Thiele EVM 1x12 cab I used under it when I needed more), my Bassman 50 head and 2x12 cab, and a host of other monster pieces over the last 10 years. I love being able to walk in and out with my gig bag on my shoulder and my amp in my hand. In fact, I love being able to walk - I survived all those years with a fully functional body (including my back) and no replacement parts. I'm planning to go out a winner when I go.

it needs to be nicknamed "Kritter" in honor of your friend.

That name is aleady taken by JK's kit built 40W blond I'm now pulling apart and restoring. I'm having a new etched metal faceplate made up, along with a matching Boogie-style grille badge that says JK210 (the model number it would have had if Leo made it as a MusicMan combo).



I call the Twin "Wes".