what's the problem with fender's ultra-linear amps?

Discussion in 'Amp Central Station' started by skeksis, Apr 24, 2008.

  1. skeksis

    skeksis Tele-Afflicted

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    I've not had the opportunity to play one of the late 70's/early 80's SF models with the much maligned ultralinear output...

    a clean 81-82 Twin w/ JBL's showed up on the local craigslist yesterday, but I've been holding out for a non-MV SF twin or pro (i'd take vibrolux, too). wondering about the arguments against the later amps. I'm probably not going to pull the trigger on this one, but maybe someone can explain why they're at the bottom of the 'vintage fender' pecking order?
     
  2. Paul G.

    Paul G. Friend of Leo's

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    Currently the fashion is that an amp must "break up", and do it at club volumes.

    The UL amps do not. They have a powerful, deep voice--but are clean to high, or in the case of a Twin with JBLs, ridiculous levels.

    If you are looking for a good clean sound, with tremendous headroom in a well-made amp, you can do worse.

    If you're for crunch, compression or somewhat distorted "lead" tones, look elsewhere.

    P.
     
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  3. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    Ultralinear mode is a really neat thing if you're after high-fidelity, clean tones. Fender (both the man and the company) were striving for more and more usable headroom, and UL was the next logical step. Wouldn't hurt to see how good of a deal you can get on the amp. You can always rewire it to leave the UL taps unused. Of course, with a Twin, I'd never be playing at the volume levels necessary for it to make a difference. :lol:

    - Scott
     
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  4. marshman

    marshman Poster Extraordinaire

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    So, would a nutball like me be able to use a UL Twin as a convoluted bass amp? Dial back the 'verb, let 'er rip?

    Is there any way to recognize one of these beasties from the outside?
     
  5. backalleyblues

    backalleyblues Friend of Leo's Silver Supporter

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    Well, if you want to play "Wichita Lineman" a UL twin would certainly be a great choice...

    The other big thing with the UL series in general, is how much stress the design put onto the power tubes. 135 watts out of a quartet of 6L6s is pushing it to say the least, as is 70 watts out of a pair, as seen in the Pro and Super Reverbs... if I'm not mistaken, Fender had a STR (Special Tube Request) that was tied to this amp design (was it the Sylvania 7591? please correct me if I'm wrong) so that the tubes wouldn't blow so often (a friend of mine had UL Pro Reverb that ate 6L6s for lunch, almost daily!).

    The easiest way to recognize a UL amp is by the output wattage listed on the back panel. 70 watts for 2 6L6 amps, and 135 watts for the 4 6L6 version.

    Franc Robert
    Back Alley Blues Band
     
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  6. marshman

    marshman Poster Extraordinaire

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    I feel like I'm maybe hijacking someones' thread, but would stepping up to 6550s, with the appropriate bias correections, make bass use a more realistic venture?

    I'm not even sure why I'm following this train of thought, it's not like we're tripping over silverfaced high-powered amps around here--though I guess a SF UL Bassman head would be more proper. Though I did just remember that my drummer inherited a SFTR from his stepfather a few years ago. It's been sitting unused for years (as in well over a decade), and he's not inclined to sell it, but it might be interesting to talk to him about. I told him when he showed it to me that firing it up was probably a bad idea, given the probable condition of the caps, but I didn't know much else about amps back then.

    Crickey, what a cerebral trainwreck this post turned into!
     
  7. Ringo

    Ringo Poster Extraordinaire Silver Supporter

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    135 watt Twin

    I had one of those back 26 years ago when I got married, loud, clean, HEAVY! but a great amp IMHO, just get a really good distortion / od pedal and you're set.

    One of my friends bought a late 70's 135 watt Twin last year, it had a bad speaker so he replaced both of them with some of the Warehouse Guitar Speaker 80 watt Celestion clones, and it is a killer amp! There is just something about the tone and reverb on a Twin that no other Fender amp captures IMHO, if you can deal with the power and weight, they are hard to beat, and a great value too for vintage Fender amps, ( sounds funny calling a late 70's Fender Twin vintage, but they are !)
    You can buy a Twin for much less than a comparable Super , Deluxe, or Vibrolux.

    As mentioned, if you're looking for amp distortion, break up, a Twin ain't gonna do it, at least not without hurting someone, but if you want a great clean tone, they are hard to beat!
     
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  8. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    Oh yeah... if I'm reading the schematic correctly, the 135W TR is putting 500V on the plates. 6550s, with their maximum of 600V on the plates, and 35W dissipation, would be perfect. 8417s would be a hip choice, too.

    The open-backed cab would cost you somelow-end response, but heck, if my 5E7 can sound good with a bass, I'm sure a Twin would too! :D

    - Scott
     
  9. Dacious

    Dacious Poster Extraordinaire

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    Fender did make a 135 watt Bassman. I know someone who has one, is not particular about tone - don't know whether the fuzziness is the result of his mismatched tubes (!) or the way he plays. Might work at limited volume, just don't expect it to compete with professional rigs for punch.

    Problem with 6550s might be heater current draw, 1.6 amp per tube (roughly double 6L6), for a 6-amp 6.3 volt supply which also has to drive six preamp tubes. Might work, might toast the P/T, especially after you bias it up to pull decent power.

    The other issue would be the preamp voicing which can be changed - some Silverface Bassmans had a switch for 'Normal' or 'Deep' so you could use it with guitar or bass.

    And the speakers would need to be considered. 12's in an open back cabinet wouldn't last long if you drive them especially with active pickups.

    I had an ultralinear Pro Reverb. Nice glassy Fender clean, lots of it, tons of it. Very piercing nuclear deterent treble/harshness if tone controls mismanaged. Great reverb, great tremolo - not bad sounding just CLEAN with a capital 'CL'
     
  10. Paul G.

    Paul G. Friend of Leo's

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    The Fender Bassman "Deep" switch did nothing for the voicing of the amp when it was on the Deep setting. In that position it is actually out of the circuit.

    On the Normal setting it attenuated the low end dramatically (cut the bass in layman's terms).

    I think it was just there to let you flip it up and down in the store and think you were getting more low end with the "Deep" circuit.

    There is no real difference in the tone stack of a Bassman and any Fender Guitar amp.

    P.
     
    Last edited: Apr 25, 2008
  11. frank4001

    frank4001 Tele-Meister

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    Well my tech just got done with my 70 watt Super Reverb and its one of the best amps I've ever played...Breaks nicely around 6. I have a 5751 in the PI tube slot but whatever he did was a mere $40.00 bucks. My friend, who is a great but broke player, loves the thing too...It aint too loud either...loud but bery managable....Flame on....oh wait, I'm not on the TGP.
     
  12. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    Ooh, good point. Adding a dedicated filament transformer for the power tubes would be a good idea in that scenario. They're pretty affordable.

    - Scott
     
  13. EMan

    EMan Tele-Holic

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    I used a 135W UL Twin for almost a decade. I sold it around '89 as I was out of the band biz.

    Had a hankerin' for another one a few years ago...and the guy I had sold the amp to still had it!....and tripletts...so I got my old amp back.

    However, I digress - Any 6L6GC will live for a long time in these amps. The OEM tubes in mine lasted well over 10 years, and were still in it when I bought it back. They were getting a little thin sounding, so a set/quad of JJs went in - a cap job - and two Eminence Alpha 12s.

    The 135W chassis was used for a number of amps, and if you hook up the right speakers, it works fine for bass. I had an old Dual Showman 2X15 cab that I used for bass, and a 4X12 cab for guitar ( who needs 6 12 inch speakers?! ... me!)

    RE - the big power: The UL's don't 'really' make any more power than the 100W versions. The difference is that the output power is less distributed over frequency. IOW, A output signal with 10% distortion distributes a portion of its power into harmonics, and that's subtracted from the fundamental. With a UL amp, the distributed power is kept in the fundamental.

    Summary - I think the 135W UL Twin is the best amp Fender ever made....and as mentioned, with a good DIST pedal, you can get a really nice tone. I used mine with an old Ross DIST, and a EchoTron delay....incredible!
     
  14. Wally

    Wally Telefied Ad Free Member

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    UL TR ....great clean amp, great steel amp, I can see where it would work for bass in a sensible volume situation. They are also easily modded if one wants.
    The amp works with good pedals. If you want that power, you could do a lot worse than one of these.
     
  15. Marcusin

    Marcusin TDPRI Member

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    yes it will have a hum balance and a line out recording jack on the back panel of the amp ,
     
  16. brookdalebill

    brookdalebill Tele Axpert Ad Free Member

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    I’ve owned many Twins, roughly a dozen, since the late 1970s.
    I like the ultralinear (130W) models best.
    My back likes them the least, but they do the “clean pedal platform” thing the best.
    Yes, they’re loud and HEAVY!
    They’re the cleanest sounding combo amps I ever owned.
    Alas, I cannot move one by myself any more.
    If my body wasn’t wrecked from my various mis-adventures, I’d still have one.
     
  17. Greenmachine

    Greenmachine Tele-Holic

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    Cool thread!

    I have an ultralinear SF Super Reverb. At first I thought I was settling for less. But I learned that I was indeed after a loud, clean amp with no breakup. I LOVE my UL amp!

    I play with a band and I always have a great clean tone. I dirty up with a King of Tone.
     
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  18. printer2

    printer2 Poster Extraordinaire

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    The thing about UL is it operates the tubes between pentode and triode operation. Pentodes have high impedance and the amp operates more as a current source and tries pushing more power through the speaker than if the amp was operating as a voltage source. Triode operation (strapping the pentode's screen to the plate, has the amp operate more as a voltage source, the amp only pushes as much power through the load as dictated by the output voltage (a transistor amp is a voltage source. But then when the realized the 'tube' sound might be due to the pentodes impedance they started adding current feedback to SS amps to make them sound more like tubes. At least hoe the output reacts to the speaker).

    Ultralinear operation has the pentodes operating in between triode and pentode operation. So close to the same power out as pentodes (the same pentode operated in triode makes less power than in pentode) but with lower output impedance, operating more like a voltage source. It works better as a bass amp as it controls the cone better at resonance, for a guitar it may not be as good with speakers that are darker, no pushing more power into the rising impedance of the voice coil. Keep in mind it is always a case of 'it depends' which is better where, depending on the type of speaker and cabinet.

    I doubt I would haul around that much weight now days for bass, get a switching amp unless you need a workout.
     
  19. mudbelly

    mudbelly Tele-Meister

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    I have the late 70s bass man 70 UL. I bought it early 80s with what I think is original cab with a 15" speaker. Played many a bass gig and it's a monster with a guitar and a fuzz pedal.
     
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  20. Milspec

    Milspec Poster Extraordinaire Silver Supporter

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    I currently run a '79 Twin with Altec speakers and it is my top 3 favorite amps. If you add a bias adjuster so you can dial it back to BF specs, you end up with a great amplifier for cleans. If you are a clean fan who only uses a little bit of OD in the mix, the UL Twin is one of the best out there....and not very expensive.

    They are heavy though, even with lighter speakers they are heavy due to the size of that transformer.
     
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