Super Champ 1983 - Optimizing

Discussion in 'Amp Tech Center' started by Bendyha, Mar 29, 2014.

  1. Dacious

    Dacious Doctor of Teleocity

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    http://www.tdpri.com/threads/noad-fender-1980s-superchamp.820470/ here's my thread, there's a pic of my speaker and the Emi some others have. 064121 appears to be a Fender part number and it appears on the small magnet Emi, Pyle and this large magnet version.

    I used to work in an OEM supplier and I know we put their part number and brand stamps on stuff to go in their vehicles or parts boxes - sometimes to fill an order we supplied a better part i.e. better linings on a clutch plate than the customer wanted to pay for. Maybe Eminence started supplying the better speakers for all Fender orders to simplify production? Or maybe a batch got mislabelled?

    Maybe Fender got complaints or respecified it, or Musicman or another customer and Eminence rationalised their line?

    Either way - it's not a terrible speaker.
     
    Last edited: May 30, 2018
  2. hapsong

    hapsong TDPRI Member

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    got it - mine is a much smaller magnet than yours - it does have part # 064121 on it ..
     
  3. Mudman32

    Mudman32 Tele-Meister

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    What app are you using for the ipad? And is there a way to make it not fall asleep?
     
  4. LudwigvonBirk

    LudwigvonBirk Tele-Holic

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    iRealbook Pro (mostly). It has a keep-awake mode, iirc I didn't do anything in settings to keep it awake.
     
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  5. hapsong

    hapsong TDPRI Member

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    ok - first mod done - new cab and speaker .. I had an extra 12" Vintage 30 so I started with that. Big improvement, way less boxy but still super bright compared to my '72 Deluxe Reverb.. now weighs in at 31 pounds, up from 28. Gut shots attached. Any suggestions on which mods to start with to warm this thing up?
     

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  6. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    Looking good.
    [QUOTE="hapsong, post: 8398598, member: 141674"Any suggestions on which mods to start with to warm this thing up?[/QUOTE]
    The speaker has a very large effect on brightness perception of course, and I have never tried a Vintage 30, so can not comment on it.
    But as to possible small mods to the amp to warm it up a bit....then I would start here;

    Taken from post #75 - And edited somewhat;

    The Mixing Bridge
    , ..........To set the amps over-all voicing/character and degree of the brightness.


    The parallel "RC" network of 47pF capacitor and 3.3M resistor has a -3db frequency that can be calculated by f = 1/ (2 x pi x R x C). This gives us a -3db = 1026Hz. Up to this frequency the response is dictated by the 3.3M resistor and the voltage divider setting that it is part of. Above this frequency the capacitor provides a boost by letting the highs bleed through relatively unattenuated.

    So why have this treble boost?
    ............... The 47pF cap is not there to compensate for treble loss, this is a deliberate boost, and at just over 1kHz it is like having a presence control that is set quite high.
    ............... there are several ways of re adjusting this mix, remembering that all the components are to varying degrees interacting with each-other, and at the same time fulfilling more than one function.
    ................Reduce the 47pF capacitance so that the-3dB frequency of the boost rises. Popular values are either 10pF, to make it like the standard Fender set-up, or 5pF, which gives pretty much unity-gain by just making up for the treble loss inherent in the stage.


    Keeping the 3.3M resistor, but changing the value of the capacitance, shifts the -3dB point as follows;

    3.3M //47pF = 1kHz........22pF = 2k2Hz........15pF = 3k2Hz........12pF = 4kHz.......7.5pF = 6K4Hz.........5pF = 9k6Hz

    .........And if you change the resistor down to 2.2M, then you get........ a bit less reverb, then one could try a 2.2M//7.5pF combination for a smoother tone with a touch more drive potential added to the clean channel.

    2.2M //68pF = 1kHz........47pF = 1k5Hz........22pF = 3k2Hz........18pF = 4kHz........12pF = 6kHz.........7.5pF = 9k6Hz

    ..........Testing my amp with the 3.3M//47pF and signal generator, I found the boost at 1kHz sounded only very slight, by 2kHz it was more obvious, and from 2.5kHz upwards, quite noticeable. When you get up to 10kHz, without the cap the signal is much attenuated.

    ...........Even if one decides to leave the 3.3m resistor, it is a good idea to check it if you have the amp open, because is likely that it has with time drifted up in value, and it might have been high to start with. Mine reads 3.6M which is still acceptable, although I might try a 2.2M sometime to see if I like it.
     
  7. dcoyle

    dcoyle TDPRI Member

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    Thought I'd add a little info about a Super Champ I am working on for a friend. It's first serial numbers are F2. I have read that is the year 1982. The complaint was it doesn't work now, and the boost pedal never did.

    The reason the boost pedal didn't work was that the two 70u/100v electrolytics in the bias/pedal supply had gone south, and the 6.2v zener was only presented with 5v, so the optocoupler wasn't really open. Visual tip was the clear coating of the ends of the caps was cracked from expansion.

    The power tubes had died and things worked with replacement, giving 30v p/p, 15w into my 7.5 ohm load. The cathodyne phase inverter of this design is so much better balanced than the typical long tail pair of the big amps. To me, this amp is a Rivera modded Princeton Reverb, with bigger power supply caps (except the compression-inducing 4ud first stage), higher B+, much less bandwidth, a thin reverb and an over the top boost that today we would put in a pedal. It runs the 6V6 screens pretty brutally, but that's part of the sound.

    Thanks very much Bendyha for sharing your knowledge, taste and time. I am grateful for the information of how the pedal circuit works. Great cabinet you made. For the benefit of other SC owners thinking about these mods... do be aware, they migrate this amp very far away from what a Super Champ sounds like.

    Rivera's voicing is a complete package. A given mod may well suit your purposes, and I first met this amp years ago because the owner thought it sounded too thin, but (very) modded is not a better Super Champ, it's a (very) different amp. The solution for thin was to increase the .001u coupling cap between v1b and the 3m3 reverb resistor to .022u.

    With regard to production variation, this amp was factory fitted (all the orange drops in this amp have a "418" marking, sideways to the value code) with a 1200pf cap shunting V1a, instead of the 500pf. Also, the grid stopper R coming into V1a was a 39K, not the 68K . Unlike Bendyha's amp, this one had the called for value of .001u for the coupling cap coming off the reverb send, going to the boost.

    Dan
     
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  8. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    Hi Dan, welcome to the sight, I hope you post more than this once.

    This is a good tip for hapsong.

    Thanks for the info.

    I agree that any mod will change the amp, therefor I am prone to state that "such and such" is a must do. I sort of had a sound I was chaseing, and there after just tried lots of things out in switchable A-B comparisons, always choosing the one I liked best. I have tried and discarded many ideas that others have claimed to be "Good" or "Usefull" mods...just didn't suit me. But many I have mentioned here in the thread for others to be aware of the possibilities.

    I have a backlog of half written posts for extending this thread that I should finish off sometime, and post.
     
    Last edited: Jun 1, 2018
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  9. hapsong

    hapsong TDPRI Member

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    yes - got it - that coupling cap increase may do the trick as well..
     
  10. dcoyle

    dcoyle TDPRI Member

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    The owner said change what I think , so here are the mods I thought were useful but didn't morph the amp too much. YMMV.

    My guess is that the ceramic caps in the SC are there on purpose. I bet it was Rivera, not a bean-counter that made the ceramic call. The orange drops aren't cheap, and yet they are used for all but four places: the input and output of reverb, the bypass of the lead volume pot and the bypass of the reverb 3m3 resistor. Changing them is not an upgrade, but a voicing change. The ceramics have a slight grit and coarseness, IMO.

    Having said that, I choose to change out the ceramic reverb input and output coupling caps for the same value film. I also reduced the .0022 film that shunts the treble output of the reverb to a 1000pf film. I perceive the reverb now as a little less metallic and more useful.

    I heard the treble cut from the .003uf ceramic shunt across the lead volume pot as too much, so I changed it to .0022uf film.

    I added a 250pf silver mica across the .001uf film coupling cap from the reverb driver to the lead boost for a bit more girth in lead.

    I added a 15K resistor to the 39K grid stopper for V1a to net 10K, for ?less noise? and slightly more treble.

    As I mentioned, I had already changed the .001uf film coupling cap from V1b to the 3m3 reverb resistor for a .022uf film because the amp seemed thin.

    Dan
     
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  11. dcoyle

    dcoyle TDPRI Member

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    I have also added a 510K grid stopper to the cathodyne input and 9K1 grid stoppers to the power tubes. Got rid of the dread nipple distortion, cleaned up a bit of the nastiness of the lead drive. Not sure if it's too different, yet.

    Dan
     
  12. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    I found this, plus adding screen-grid resistors to the power-tubes, to be wise choice when playing full-tilt......which the amp then masters with bravo, and rewards by singing.
     
  13. Dacious

    Dacious Doctor of Teleocity

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    I just recorded this to demo the Sakai SG I just bought and cleaned up. I haven't made any circuit changes or recapped yet.

    It does have a NOS Phillips 12AU7 as V2.

    This is with the large-magnet Eminence speaker discussed elsewhere.

    Here the volume is 5, master '6', treble 7, bass 6, lead on 5.

    It is Sunday evening so I can't crank it.

    I want to debuzz the drive a bit - hoping the bypass cap change will make it less throaty.

     
    Last edited: Jun 3, 2018
  14. dcoyle

    dcoyle TDPRI Member

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    Adding screen resistors is a voicing change, though. I like the sag and the protection of screen resistors, but it is a slightly harsher sound than none. The grid stoppers seem neutral till overdrive.

    Dan
     
  15. ExpeditionElec

    ExpeditionElec TDPRI Member

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    Bendyha, going all the way back to your analysis of the pedal induced "tone suck", you mention that the 470k to ground through the vactrol is low enough to roll off some bass frequencies but I don't see how. The output cap from the previous stage is seeing at least 3.3M regardless. The added load will definitely cause a volume drop across the board though.

    I find it interesting that blackface classics like the Super Reverb have a 220k in this position fulltime connected to ground. Besides setting the overall gain into the next triode, lower values here make the dry gain less sensitive to reverb level adjustments. Not many complain about the tone of Super Reverbs so I wonder if this is just a case of quieter being perceived as worse tone.

    Also on Page 1 there's mention of using a 12AU7 for reverb/gain driver. When my 6C10 rolled off the table and smashed (doh!) I decided to see if it could be subbed. I made an adapter out of a stainless washer for a 9 pin in V3. Changed V2 to a 12DW7 (half AU7, half AX7). Used the AU7 half to drive the reverb and AX7 half as reverb recovery. Then I could use a plain 12AX7 in the adapted V3 spot. Upsides: no drilling required, no expensive 6C10 required. Reverb and boost still sound good (possibly better depending on taste). Downsides: requires some socket rewiring. Not a lot of DW7 options available for tweaking lead channel tone. I don't use the boost much so that doesn't bother me and what you lose in options for V2 you gain in options for V3.

    Another possibility would be to use one 12AU7 and one 12AX7, using the other 12AU7 side for the cathodyne splitter, but would require some component tweaks as well as more rewiring.

    Dave
     
  16. Wally

    Wally Telefied Ad Free Member

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    Dacious, ime, the bass cannot be run that high if one wants the overdrive to hang together in the Lead mode....the low end goes to pieces in the preamp....as we hear in your demo when you go to the Lead mode. This is typical of AB763 type of preamps. Mesa Boogies manuals for the MK amps has been cautioning folks about this for over 40 years now.
    Yes, this can tend to take the amp to the bright side of things so I don’t push the treble, either....and I run speakers that have good full range response and a smooth high end for distortion. Fwiw, I like my gain controls all at 10...treble around 4-5, bass at 3. The BF sounds, the tweed thing with the mods boosted, and the lead mode all occur at the same volume level due to that compression thing...run it from the guitar.
     
  17. Wally

    Wally Telefied Ad Free Member

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    Regarding that 6C10, there are three triodes there. You describe an adapter that provides only two triodes...if I am understanding you correctly. ??? Explanation, please.

    And...fwiw...there are other 12pin compactrons that have different triodes there that can be used....perhaps with rewiring. I keep a stash of the opti9ns.....plus more 6C10’s than I will ever need. Bendyha has built a double Noval adapter to utilize 2 x 12A-7’s in place of the Compactron tube.
     
  18. ExpeditionElec

    ExpeditionElec TDPRI Member

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    The stock reverb drive circuit uses both halves of a 12AT7. With the sub I'm only using one half of the 12DW7 for reverb drive, so I've gained the half stage I lost from the 6C10. If there's not enough drive you can always bypass the cathode of the reverb drive stage (which many Fender classics do), but if you use the boost you have to compare the differences of each change for its effect on boost and reverb. For my taste, there's too much reverb (on almost all fenders) and too much boost, so the sub works well at taming both somewhat.
     
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  19. Dacious

    Dacious Doctor of Teleocity

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    Actually it's also because the drive level was so low. It is notably better with lead level at 6 or so. That phone recording was a bit muddy, too I think. And I'm still tweaking this old SG.

    At prac the other night, gain 8, master 8 with treb 6, bass 4 and lead on 6-7 it's much more a Mesa tone. I think the mica cap change along with the .022 bypass caps might just lighten the tone enough. It's a modern sound, but that works for the modern band I'm in.

    The speaker hangs in pretty good, but I don't think it's high enough efficiency. Will be going Legend I think.

    Reverb was also a bit high, was on 5.

    I'd love to get the mid boost footswitchable.

    It needs the electro caps changed I think.
     
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  20. dcoyle

    dcoyle TDPRI Member

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    On further listening, the grid stoppers on the P.I. and the power tubes are great.

    I really must say, the cathodyne with a giant grid stopper, operating into the 220K grid leaks with 9K grid stoppers is far sweeter than any stinkin' LTP . :)

    I also went with 270 ohm screen resistors for safety sake. This thing sounds great dimed, and it needs some protection, although 270 ohms is not much.

    I settled on a 1330 pF for the cap that shunts the reverb tray output, in parallel with the original 220k resistor. The reverb still has less treble than the dry, but there seems to be a little more detail than the stock 2200 pF shunt.

    There is quite a bit of reverb early on the dial, as others have noted. Were this my amp I would explore changing the 3m3 reverb isolating resistor to ? 2M5 ?.

    The good side of the Rivera boost is that it will get an almost feedback-like sustain going, but if I owned the amp I would explore backing the gain off a bit. In Rivera's Deluxe II of the time, he used the same configuration as the Super Champ, but instead of the 100k resistor that is inline from the tap above the reverb transformer going to the boost, he uses a 1M5 ohm, (shunted by a 22 pF cap, which adds a treble boost). I suspect Rivera left the 1M ohm shunt to ground high so as to not affect the boost pedal switching. I might try replacing the 100K with 470k, with no cap shunt.


    A great little amp, and small package, but if you're wishing you had one, IMO, what with collector's prices and the lack of 6C10's, definitely an amp to build from scratch. (This guy has 2 spare 6C10's ).

    Rivera's Princeton.

    Dan
     
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