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The Super Champ XD club

Discussion in 'Amp Owners Clubs' started by Kid Klash, Jun 26, 2009.

  1. JohnS

    JohnS Friend of Leo's

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    Output transformer
     
  2. Shardik

    Shardik Tele-Meister

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    Ah..!
     
  3. brewwagon

    brewwagon Poster Extraordinaire

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    (zapped again!)




    priceless wt!
     
  4. JohnS

    JohnS Friend of Leo's

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    Anyone tried a Fender (Emi) V1030m speaker? I just bought one for $25 and
    I am curious if it is good or landfill. My Weber Sig alnico 10 S is wonderful but I still need to fix it until it is broke.
     
  5. Hiker

    Hiker Poster Extraordinaire

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    Output Transformer. Here's an earlier thread discussing the Princeton OT.
     
  6. Gnobuddy

    Gnobuddy Friend of Leo's

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    Thanks for those search terms, wabashslim! Tubes being over a century old technology, I'm quite sure I won't be thinking up anything that hasn't already been thought of long before I was born - it may be new to me, but I'm sure someone thought of it long ago! But it would be fun to re-discover something that has perhaps been forgotten over the decades.

    Back to the supposed Princeton PI imbalance, I think the flap over the additonal 1k cathode resistor is nonsense. The 56k cathode and anode resistors are 5% types in the SCXD, which means they can vary by up to plus or minus 2.8 kilo ohms just because of random manufacturing variations. The additional 1k cathode resistor is considerably smaller than this - less than 2% of the 56k's value - so any imbalance it may cause is very tiny, and much less than the imbalance caused by normal manufacturing tolerances of those two 56k resistors!

    I wouldn't be at all surprised if the tiny mismatch between supposedly "matched" output tubes is also much bigger than the 2% effect of that 1k resistor. So I think we can probably entirely dismiss that 1k resistor as a factor in the sound - the normal manufacturing tolerances elsewhere in the amp completely swamp any effect it might have.

    Going back to the idea of intentionally upsetting the balance in the output stage, my guess is that it's going to take a much bigger imbalance than 5% to let those 2nd harmonics leak through the push-pull circuit. (And presumably output power and clean headroom will go way down in the process, as the circuit moves away from Super Champ and towards plain old Champ. So this won't be a mod favoured by those who want maximum output power, but it might suit us living-room players).

    I've been too busy to experiment these last few days, but when I get the chance I might put a variable resistor across the PI anode resistor and see what happens. Heck, I might just put a good sized electrolytic cap across the anode resistor and entirely remove that signal, so the output stage effectively goes back to a very low power Champ (only 20 mA bias current per tube).
    I wonder if the bad overdrive sound you heard might have had another cause? I've been reading Merlin Blencowe's book "Designing Tube Preamps for Guitar and Bass", and there is a section where he discusses the failings during heavy overdrive of the cathodyne / split-load phase inverter design used in the Princeton and SCXD. He agrees with you that it can make some really unpleasant overdrive sounds.

    Long story short, he says the fix is to use really large grid stopper resistors on the output tubes as well as the PI stage. By large he means 100 kilo ohm or so grid stoppers for the output pentodes, and up to a 1 megohm grid stopper for the cathodyne stage itself. Way huge compared to "normal" design practice.

    The stock SCXD has no grid stoppers at all in any of those three locations. :eek: As for the PRRI, the official schematic shows tiny 1.5 k grid stoppers for the output tubes, way too small a value to stop the nasty noises from the cathodyne PI. Also there is no grid stopper at all for the cathodyne stage.
    That's the one that raises the B+ voltage to the PI stage, right?

    I'm really starting to wonder if one output stage can ever give you both really beautiful cleans and really great sounding overdrive. Right now it seems as though my favourite clean sound is a single 6V6 output stage preceded by a Fender tone stack, while my favourite overdrive sound may be the 18W Marshall sound: one-knob tone stack, EL84 output tubes in push-pull. Chalk and cheese, as far as differences go!

    I'm still not really a fan of any of the channel 2 sounds I can manage to get out of my SCXD, but I'm a bit happier with the amp models in a Zoom G3 feeding into channel 1 on the SCXD (or into my modified all-tube SCXD). The Zoom can have up to 3 effects or amp models in its internal chain, and at the moment I'm enjoying using just two - a Two-Rock amp sim feeding into the Zoom's "HD Reverb", then into the SCXD.
    I was rather disappointed to find the Blues Jr. also suffers from a too-small output transformer, just like the SCXD.

    -Gnobuddy
     
    Last edited: Sep 18, 2012
  7. JohnS

    JohnS Friend of Leo's

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    Anyone? Or have we now gone to minute?
     
  8. Dauntless

    Dauntless Tele-Meister

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    I personally, have not. :eek:
    At least that I know of.
    Let us know how it sounds! :cool:
     
  9. Manolian

    Manolian Tele-Meister

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    Oh yeah Markley makes great amps , Bill Connors used them in the 80's.;)
     
  10. JohnS

    JohnS Friend of Leo's

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    Found out the Fender V1030 was designed by Ted Weber and built by Eminence for Fender. Much more interested in its next Tuesday arrival now.
     
  11. oldwhatshisname

    oldwhatshisname TDPRI Member

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    speaker

    I have a Weber Sig 10F smooth cone 25 watter in mine, I had the Lil Buddy, which im selling on TGP, it sounded really big, like a 12, and the tone was wooly but still had some chime with the treble dimed, though the treble had to come down when i cranked out voice 9, 13, and 14.
    the Weber lets my treble knob be more effective.
    BTW, I just found out my VHT Special 6 Ultra foot switch changes channels on my SCXD....
     
  12. Dauntless

    Dauntless Tele-Meister

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    :cool:
     
  13. william tele

    william tele Doctor of Teleocity Ad Free Member

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    I took my SCXD in last weekend for repair/exchange. Before taking it in I had to replace the chassis into the standard cabinet from the 12" cabinet it had been residing in. I went ahead and plugged in the factory speaker and re-checked...no sound. (previously I'd plugged the line-out into another amp and had sound so suspected the digital stuff was still good)

    Anyway, the man called me yesterday and said it was a problem with the speaker wire and that it had been playing fine for hours. ??????? Oh well! I sure would rather have that one than the replacement...(I think?) I'll pick it up this weekend and give a shout back.

    A question just came to mind...could he have meant the wiring to the speaker jack? Isn't that jack soldered straight to the board? thanks guys!
     
  14. Dauntless

    Dauntless Tele-Meister

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    Could have been a cold joint at the speaker end.
     
  15. JohnS

    JohnS Friend of Leo's

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    Well, I got the V1030 speaker today instead of Tuesday. I like the Weber Sig 10S alnico better. Weight is the same, but the fender speaker blurred the notes a bit. You could not hear the individual notes in a cord like you can with the Weber on channel 1. The Fender sounded pretty good on the high gain models, but I pretty much live in channel 1. Worth the $25 to find out.
     
  16. JohnS

    JohnS Friend of Leo's

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    Well. I tried it again. I must have mounted it poorly the first time. More efficient (louder) than the Sig 10. Has the typical Ceramic punch and good clarity. Interesting that the cones of the Weber and the Fender look identical. Appears that the only diff is the magnet (to a non-tech guy.) I'm going to use it for a month before I make any decisions.
     
  17. Mr Perch

    Mr Perch Tele-Afflicted

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    I promised this a while back -- my band playing "I Need Your Love So Bad."
    SCXD on voice 10, gain at 8, phasors on "stun", neck pickup:

    http://www.bandmix.com/out478414/
     
  18. JohnS

    JohnS Friend of Leo's

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    Sorry. The Fender V1030 did not last a month. All hail the Weber sig 10S alnico. :D
     
  19. oldwhatshisname

    oldwhatshisname TDPRI Member

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    scxd

    selling mine w/ a weber sig ceramic speaker
     
  20. davidchagrin

    davidchagrin Tele-Afflicted

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    I'll be gigging my SCXD at a bar for the first time on Saturday. Wish me luck!
     
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