70W UL Super Reverb -- Bad JuJu?

[jbefumo]

Someone recently gave me a lovely 2X12 blond cabinet, sized for a Super Reverb chassis, in exchange for repairing his Epiphone Pathfinder. I was scouting around for a chassis when I came across a “blackface modded” Super Reverb at a really good price, so I grabbed it. Haven’t picked it up yet, so no clue what’s under the hood (will find out tomorrow), but my research indicates that it’s a late ‘ultralinear’ 70W model, so I’m sure it’s not a complete ”blackface mod.” That doesn’t really concern me, but the more I look into the topic, the more questions arise.

The one that seems most perplexing is the apparent disdain many people have for these amps, versus the favorable attitude toward the ‘SRV Mod’ attributed to the late Cesar Diaz. From what I can glean, this mod consisted largely of installing larger transformers, replacing the GZ34 with a solid state rectifier, and some various tone stack tweaks. Seems to me, at first glance anyway, this is largely what differentiates the 70W Supers from earlier models, right?

Then, of course, there’s the Ultralinear connections. I’ve built a few amps with 3-way Triode/Pentode/Ultralinear switches, and while I can definitely hear and feel the differences, none of them sounded totally awful to my ears. My point is that they’re just taps, and nobody is forcing one to USE them. The primary impedance of the transformer is the same as the older ones, though presumably it’s built to handle more power, so one should, in theory, be able to just add appropriate grid resistors and ignore the UL taps altogether.

Again, my initial plan was to just part it out for other projects, but am now thinking I may play with it for a while and see how it sounds. I’m guessing the B+ might be higher than I might like for a vintage Super Reverb tone, but I have a couple of Gold Lion KT88s on hand, and I bet I could make THEM feel right at home in that environment.

(That actually got me to thinking about what Jim Marshall might have come up with had he started with a Super Reverb instead of a tweed Bassman …)

If necessary, no reason not to punch a hole and install a tube rectifier, and/or go to cathode biasing to soften up the response a bit.

Of course, if some ham-handed ‘tech’ really messed it up, then the parts bin it is, but if it’s playing when I get it, which I’m assured it is, then it seems like there should be many cool solutions other than slavishly trying to turn it into a 100% correct BF clone…

Anyway, just thinking aloud and fishing for ideas, comments, potential gotchas, etc.

[eleventeen]

If you like the form factor of a 2 x 12 cabinet (that would be bigger than I want) and you like (in general) a Super Reverb, than as you suggest, you can turn it into Blackface with a fairly small number of changes.


You sure the cabinet fits 2 - 12"?


Like this? 1981ish? http://www.tdpri.com/forum/amp-central-station/330292-mystery-blackface-mv-ul-super-reverb.html


"4 knobs on the non-reverb channel clenches it. It's a UL 70 Watter. Loud, hard, clean."

[DummyLoad]

ya mon! bad juju mon!


--pete

[Willabe]

 

[jbefumo]

Someone recently gave me a lovely 2X12 blond ...]


Well DAMN!  After getting lost in Newark NJ for 3 hours, I finally located the Pawn Shop that was selling it, and the first thing I noticed was that it HAD a GZ34 installed already -- very optimistic!  Sounded pretty good, too.  Got it home, lugged it inside, and immediately installed a set of casters I had on hand.  While it was upside down, I noticed ... a complete set of what looked like brand new Mercury Magnetics ToneClone transformers!  Cabinet isn't too bad either - a bit of contact cement should be sufficient for most of it, thought the two back panes are just black-painted plywood & will be replaced.  Bad news is that the chassis is wider than the original blackface units, so it won't fit the blond cabinet I had slated for it, but by this time I'd already decided to leave it intact.  Only thing I will want to replace eventually are the 4 Italian-made ceramic Jensens for some original alnicos, but no rush on that ... Not bad for $356.  My guess is that the pawn shop probably paid some poor soul $50-$100 for it.

[eleventeen]

" Bad news is that the chassis is wider than the original blackface units"


Fender has worked this insidiously throughout their line. Oh yeah, one amp (can't remember what it is) will fit in a different cabinet but essentially, NO Fender will properly fit in another amps' cab. Some will fit with spacer blocks at the side. Other miss by 1/2" or some silly thing. I have a newish (but electrically dead) Deluxe 90 that I would consider popping for a mojo (or other) chassis for a build. The dimensions are just off everywhere.  I was skeptical that your cab would fit, but you seemed to have done OK.

[jbefumo]

So, after playing with this beast for several days, I am confident that it was converted well, though the cosmetics are a bit nasty.  Definitely a keeper, though.  Of course, I'm going to HAVE to change SOMETHING, so before I end up turning it into fodder for my ever growing parts bin, thought I'd toss up some ideas I'm toying with before I heat up the soldering iron ...


I had originally planned on replacing the faceplate with a real Blackface version, and in fact, went out and bought one, and only then discovered that it wasn't going to fit.  No problem there -- just ordered a proper sized chassis, and a eyelet board from Doug Hoffman, so .... when in doubt, build another amp!


As for the Fender ....


I'm thinking that rather than leave that nasty hold where the master volume used to be, I might just install a new one -- cross-line, post PI, with a push-pull to bypass it if desired.


Not sure about the hole where the mid control on the Normal channel used to be -- not like anyone is going to mistake it for a real blackface anyway, and I rarely use the normal channel anyway, so I might just put the tone stack back the way it was -- better than a hole ... but ... I have look at the board layout more closely, but am thinking of maybe building something like the old HiWatt tone stacks.  They're different than anything I've seen elsewhere, and the curves look pretty interesting in the simulator ...


Which brings me to my next idea --.  Have always been bothered by that extra channel that I never bothered using, and what a waste of two triodes!  Like an udder on a bull, to paraphrase that old quip...


My initial thought was, as has been discussed in various other places, to use a relay to turn the normal channel into a foot-switchable tube overdrive, but my preliminary sketching suggest this is probably going to be way more complicated than it initially seems. As I said, I really do like this amp, and am going to try hard not to turn it into junk...


Saw a post suggesting an A/B switch, and that sounds like a really low-impact possibility -- but maybe TOO simple for my feverish mind...


Thought about an internal solution to switch between the channels, but again, as I start to work though the ramifications, I vaguely see various gotchas down the road.


(Did I mention that I have a HUGE parts bin populated by former 'greatest idea ever's')


Someone in this forum mentioned jumpering the reverb tank to implement a gain boost -- brilliant!  Of course, I like my reverb, so maybe a foot-switchable relay control ....


Someone else mentioned revoicing the normal channel, and having reverb on both ... I like that idea as well.  I might toy with the idea of two separate reverb level controls so each could have different levels, or, combining with the internally switchable jumpering idea, but here again, I vaguely foresee a proliferation of relays, and sub-boards and .... (Did I mention that I have a HUGE parts bin populated by former 'greatest idea ever's')

Of course, if I could just leave it alone, but we all know that ain't gonna happen.


Getting back to my most basic user requirements -- I like to be able to show up to play, bearing only my guitar, a cord, and an amp -- two hands, two things to carry (though this amp may be a bit much for one-handed lugging as I close in on 64Y/O).


So that means reverb, which the amp has, and some way to switch on some additional gain when moving from chords to solos ...


The simplest solution, of course, is just have one extra patch cord, and my trusty Danelectro transparent overdrive in the guitar case, but again ... too simple, and besides, now that I'm playing an SG more and more and my Tele less and less, no room in that fitted case for even one little pedal.


Well, you get the idea ...


ANY observations, criticisms, suggestions are gratefully solicited ....

[Ritchie200]

If you are considering doing a total gut Hiwatt thing, it sounds like you are open to just about anything!  PLUS, you mentioned the KT88's you have laying around.  A few years ago, we had a really nice thread on building a two tube Mini Major complete with the one-wire mod and master.  (See Michael R/T soundclips for reference - not mine!) You didn't mention if the Mercury iron was still UL?  If it is, you are almost there!  Tubenit has layout and schematics in the library.  With all the Fender logos and cabinets, you would have to call it Mindbender! (If you are old enough to remember THAT tune....)

OR, if the iron is not UL...  Marshall/Park made the Park75 that was basically a small box Marshall 50 with KT88's.  They are tone monsters.

Both could very easily be plug and play with all the internal trimmings.

Just a few thoughts to bring another to the dark side!

Jim

[jojokeo]

...back to the lighter side. I've simply done some creative re-wiring on the normal channel where all you do is cascade the two triodes and put the tone stack behind them. You get a big gain increase and there is your lead channel. A simple A/B switch you throw in the back of the cab is all you need...

[jbefumo]

Actually, I have a 2X12 cabinet that a friend picked up at a music show and gave me -- lovely, blond, all wood --- and !/8" too narrow for a BF Super chassis .... Some careful work with a pull saw and a couple of finger planes, and a standard chassis will now fit it.  Still deciding what I want to do --


Some more follow up:


Once I turned the Super over, it was pretty clear that this was a professional, no expense spared job.  All new Mercury Magnetics iron, including the reverb and choke .... but then .... 4 X 16-ohm Italian Jensen/Fender speakers which I surmise had to have been the originals from that 70W amp.  Moreover, all the retaining nuts were loose.  Coming as it did from a pawn shop in Newark, NJ, one doesn't have to be Sherlock Holmes to deduce that before pawning it, somebody put the old speakers back in, especially since the OT is a single, 2-Ohm output, and those speakers present a net 4-Ohm load.  For the present, I've replaced them with 2 NOS UK Celestion 10s, a new Chinese Celestion 10-30, and a used Eminence Patriot Lil'Buddy. Not perfect, but WAY better and presenging a proper 2-ohm load.


Next, it struck me that, while it's been many years, my memory of Fenders was that they had way more lush reverbs.  I pulled the tank, and it turned out to be out of a Marshall, probably valvestate, and was supposed to have been mounted vertically, jacks upward.  I replaced it with my last US-Made Accutronics, and now .. .Surf City -- enough to make you seasick at abut 4 or 5 ...


As soon as I make some room on my bench, I'm going to pull the chassis, check all the voltages and bias, and likely install the pair of Genelex Gold Lion KT-66s I ordered about 30 minutes ago (already contacted Mercury Magnetics and confirmed that the PT has enough juice to handle the extra filament requirements.


It now sounds absolutely lovely -- like a black-face super should.


Where I go next -- still cogitating.


I have on hand my favorite speaker of all time -- a vintage Altec 417 15", 100W Alnico.  It will fit perfectly in that 2X12 cabinet (which has the 12s staggered, one higher than the other, like a later Twin), with just a new baffle board.  That, of course, will mean replacing the OT with one offering multiple outputs so as to match the 8-ohm speaker.  That may be a way to go.


On the other hand, I could also spring for a smaller, 4X10 BF style cabinet (already have a nice BF Super Reverb faceplate), which I would have covered with standard black tolex and aged proper grillcloth -- just to complete the vibe.


I ALSO have on hand a Doug Hoffman AB763 eyelet board, and a Tweed Overdrive turret board, which I may put into that new chassis and the blond cabinet. I have on hand a lightly used set of PT and OT from an old Sundown that came with 2X6550s making 100W, so would probably use those regardless.  No 5V output, so I'd have to add a small transformer if I want to use a tube rectifier, which I'd prefer in order to tame that power a bit.  Have a pair of Gold Lion KT88s to go with it.  I figure I could cathode bias it so it'll make ~60 Watts with the KT88s, or 30-ish with KT66s.  I could wire the speakers for 16-ohms, and use the 8-ohm output from the OT to raise the effective primary impedance to what's called for for cathode biasing either of those tube sets.


I'm leaning in the direction of doing that first -- either with the AB763 board, or with the Tweed Overdrive circuit, but adding reverb and foot-switchablility for the OD. (Having heard the audio clips, I'm sort of leaning in that direction.)  That way I won't start messing with a working amp until I have another one up and operating reliably.


Decisions decisions decisions!


 

If you like the form factor of a 2 x 12 cabinet (that would be bigger than I want) and you like (in general) a Super Reverb, than as you suggest, you can turn it into Blackface with a fairly small number of changes.


You sure the cabinet fits 2 - 12"?


Like this? 1981ish? http://www.tdpri.com/forum/amp-central-station/330292-mystery-blackface-mv-ul-super-reverb.html


"4 knobs on the non-reverb channel clenches it. It's a UL 70 Watter. Loud, hard, clean."

[jbefumo]

No, the Mercurys are ToneClone repros, with all original BF specs -- including the 2-ohm-only output (seem my last post).


On a side track, I've been in contact with Mercury several times, and am utterly blown away by their service, responsiveness, and overall help, especially since I haven't bought, nor am I about to buy anything from them.  I won't mention the name of the other US manufacturer that I've been dealing with for the past 7 years or so, but everytime I ask THEM about anything different, the standard response, after a rather lengthy wait, is .... "no, we don't make anything like THAT ..."


Not sure about the Hiwatt thing -- I that's probably something I may experiment with on the bench before trying to integrate it into an actual build, although I DO have one of those 4-pole Blond-style treble pots, and may try that out in the 'normal' channel of of the Super.


Joe

If you are considering doing a total gut Hiwatt thing, it sounds like you are open to just about anything!  PLUS, you mentioned the KT88's you have laying around.  A few years ago, we had a really nice thread on building a two tube Mini Major complete with the one-wire mod and master.  (See Michael R/T soundclips for reference - not mine!) You didn't mention if the Mercury iron was still UL?  If it is, you are almost there!  Tubenit has layout and schematics in the library.  With all the Fender logos and cabinets, you would have to call it Mindbender! (If you are old enough to remember THAT tune....)

OR, if the iron is not UL...  Marshall/Park made the Park75 that was basically a small box Marshall 50 with KT88's.  They are tone monsters.

Both could very easily be plug and play with all the internal trimmings.

Just a few thoughts to bring another to the dark side!

Jim