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Super Champ 1983 - Optimizing

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

  1. Jaketone

    Jaketone Tele-Meister

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    I’ll start there but I do wonder if something happened to the mixing bridge during soldering..?

    I’ve ordered a few caps and a replacement 3.3M resistor to try there myself.
     
  2. Wally

    Wally Telefied Ad Free Member

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    Jake, from what I find that 291ACX is less than ideal for the Super Champ. The heater filament circuit is not designed to support the tube compliment in the Super Champ. If my early morning mental functions are correct, the tube compliment of the Auper Champ would want to work with a PT that has a capability of supporting a current draw of 1.95ma. That 291ACX is rated for 1.5....which would be fine for the single 12AX7 and 2 x 6V6’s in the Super Champ X whatever amps...but not the 12AX7, 12AT7, 6C10 and 2 x 6V6’s in the Super Champ.

    Reverb....the 12AT7 is the driver. One triode in the 6C10 is the recovery. And....personal thing...but I don’t have any problem at all with brightness. These amps work. I have found that my Rivera era 2 x 10 cab loaded with OEM 16 ohm EVI’s in parallel for an 8 ohm load give a Super Champ’s output a bit more ‘mass’...body...than does a single EVI in the cab. I ran ALK’s in my SC’s for over 20 years, and I think you will find they will be a better match than the 1058. I may be putting the ALK’s back in as I have a new application for 2 EVI’s.....a 1964 Dual Showman that fits right in a Pro Sonic combo cab!!!!

    Good luck with the Reverb....and that PT. IMHO, your tech should have made a better choice for the transformer.
     
  3. Jaketone

    Jaketone Tele-Meister

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    Thanks Wally - yes the SCXD PT felt like an odd choice to me. With all the research I’ve done on the amp and this excellent thread I actually feel quite qualified to have done the work myself as I am handy with a soldering iron. Although I am only now beginning to understand the circuit beyond its values etc.

    Anyway - let’s see how I go with a new mixing bridge, new AT7, one of my backup 610Cs and 1028ks! This might be it!
     
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  4. Jaketone

    Jaketone Tele-Meister

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    Well just to follow up -

    @Wally I can see why you like the 1028K - made a HUGE difference. Not dissimilar to the 1058 but a little less spike in the upper mids and still plenty of bass.

    Also, I replaced the 3.3M resistor and changed the cap to a 10pf value in the mixing bridge and suddenly I have the most luscious reverb back! AND It sounds so much warmer and rounder but still has plenty of presence with volume and tone dimed on guitars if need be. Finally I can use more of the range of the treble pot which is great.

    Still not the most amazing sound with pedal overdrive but I think a little bit of that is the blackface thing. Cleans are beautiful.

    I might still look at a few more mods but I think I am 90% there..!
     
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  5. ScottJPatrick

    ScottJPatrick Friend of Leo's

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    Jaketone, if it interests you I have just had a Classictone output transformer fitted to my Super Champ which gives me an extra 4ohm tap and output. Bendyha has been helping a lot with this and I am going to start a new thread about it once I get the chance.
     
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  6. Dacious

    Dacious Poster Extraordinaire

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    An update: finally got around to fitting my 240volt transformer. David Brown, of Brown Vintage Radio in Geelong wound it for me with laminations and bits he had lying around - he uses proper formvar wire. Cost me $50us approx! It's identical footprint to the stock US, a bit taller and bolted straight in. He previously wound me a DR output trans with 4 ohm and 8 ohm secondary and I may fit that later

    IMG_20190421_132343.jpg

    Looks a bit zebra-ish with alternating lams. Works well. Seems to run cool compared to stock US voltage original..

    IMG_20190426_140745.jpg
    Lets me use Australian domestic plug - amp weighs 28 pounds with Alessandro SC64 speaker!


    Unloaded, the stock transformer through a 110 volt stepdown gave 420 volts B+.

    The new one produced 390 when first fired up, went down to 385 with tubes. 48 volts on bias, 6.1 at the lamp in heater circuit. As the new caps have been working, B+ crept back up.

    Checking bias with the trans resistance method I got 9.08w @ 351 plate volts and 9.2w at 351v on the two tubes, what look like original Fender-branded greyplate RCAs in smoked glass. I should fit some screen resistors too I guess.

    For the moment I'm leaving that. It's highish but there's no redplating and they seem to be OK .

    I also changed all the electros except the 4uf - I only got a 150v version - d'oh! Cap can - CE, a little physically smaller with 80-30-20-20. Two 100/100 caps for the bias network.

    Here's why I say changing out the small electros is worthwhile. This wasn't apparent until I desoldered it. Note it's bubbled and splashed around the side . One of the 100/100 Mallory caps was bubbling under its plastic end cap too.

    IMG_20190426_135728.jpg

    I took the opportunity to fit Bendy's bigger resistors to the drive channel Vactrol to fix the volume drop for the foot switch but haven't wired the footswitch yet. I can confirm if it has any effect unplugged it's only positive. I replaced the 470k with ones measuring 820 and 1.18 meg.

    Considering all the other mods, I clipped the .003 ceramic disc on the lead level pot. I may go to a smaller silver mica for the reverb/drive return later. I want to fit mid boost wiring and of course replace the 4/450 cap off the input end of the board.

    How does it sound - Wow. With nothing plugged in it's dead silent. The previous nice clean clear is even more so. It's got a bit more bass, a bit more top sparkle. It's really full-sounding.

    You need less treble and bass and gain/volume but it will take more without over-harshness or farting - it sounds way bigger than a single 10" speaker.

    My Gretsch sounds fabulous - thunky with an edge, pluck harder and it's getting that nice F'tron grind . My Melody Maker with Seymour P-rails is growly and grungy. Both of them sing even at less than cranked.

    The big news is - the combination of clipping the .003 in the drive level and a 12AU7 in the second slot has improved the lead channel immensely.

    I want to gig with it first before deciding - but ithe lead channel has gone from uninspired, unflavourful and unmusical mud to organic, chimy, crunchy, singing! I may have found my sound.

    It's a bit cranked Marshall crossed with early Boogie - but not tinny or harsh. It's almost like a stacked tube driver, through a TS9, through a SD1! Sonic mayhem at high settings, but I can still hear all the strings and there's no nasally honk or buzziness or farting.

    It sounds like a balanced bandwidth distortion. Pinch harmonics and hammerons are childsplay. Turning the level down tames it without it going thin.

    The essentials of the amp haven't changed. Light weight, small size, big BF Fender sound especially through the SC64 speaker. Super touch responsive. The speaker is a great match for the amp.

    Really, really impressed. It's even closer to a lifetime only gigging amp. I can get better tone at lower volume.

    Thanks to Ben and this thread for the suggestions! Can't stress enough how useful I've found them.
     
    Last edited: Apr 26, 2019
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  7. Dacious

    Dacious Poster Extraordinaire

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    Gig report - I used it at our regular country pub gig. Took my Rivera Pubster as a spare just in case, but it ran 3 hours flat out. Drums, bass, HRDx 40 competition.

    With my Gretsch, great clear cleans. Just cranking the volume I could do clean solos.

    Back off - cleaned straight up. We've had volume issues in this space before, I could get it singing on 8 channel/8 master. Treble 6, bass 4.

    The drive channel is now awesome. I flubbed the footswitch I was making so had to do without, but I pulled the gain for the last song - Highway to Hell. With my Melody Maker with P-rails in humbucker mode - pure Angus.

    All that's left for me to do is screen-grid stoppers and the footswitch and mid-boost.

    I can heartily recommend going to 12AU7, and clipping the .003 ceramic cap on the lead level pot.

    The Alessandro SC-64 sounds great now it's broken in. The whole rig takes pedals a treat - I was using a Sola Tonebender, SD1 and tube driver models on my M13. No farts, no flub.

    Good caps, a good speaker - this might be a keep-forever amp. My Marshall is feeling unloved.


    FB_IMG_1556413140600.jpg
     
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  8. Frenster

    Frenster TDPRI Member

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    This thread gets better and better!
     
  9. try1256

    try1256 TDPRI Member

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    Just completed the first two mods on my SC. First was easy. I replaced the 12AT7 with an AU7. I replaced the 12AX7 while I was at it. I used Tung Sol reissues. Probably not the last word in tone but not bad and reasonably priced. The reverb is a lot better now. Before, anything past 3 was way to wet. I can use more of the pot now. I also put in a pair of Brimar 6V6’s I had from my stereo preamp. It uses them to supply voltage to the 6922’s. When I bought it extra tubes came with it. The Brimars are tone monsters! I had Groove tubes before and they weren’t bad but these kill it.

    Next up, the foot switch mod. The resistors came in the mail today and I couldn’t wait to get them in. It wasn’t difficult and didn’t take long. All I can say is WOW!!!! The Footswitch works now. The clean tone with the Footswitch plugged in and the lead pulled out sounds just like no FS. Thank You Bendyha!!
    The tone seems to be more balanced as well. I am almost hesitant to do the voicing mods I intended to do.

    Monday, I have a Ted Weber Signature 10S arriving. Got it for a real reasonable price and thought it would be a good way to try a better speaker. I have heard that the Signature series can be bright so the voicing mods may come back into play.

    Anyway, so far, so good. I am really glad I found this thread. I will report back on Monday.
     
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  10. Wally

    Wally Telefied Ad Free Member

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    Try1256, if I were going to run those precious Brimars in the SC, I would have to known the bias numbers. Ime, these SC’s run hot biasing. That righteous sound may have a lot to do with a lot of current draw.
     
  11. try1256

    try1256 TDPRI Member

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    I think the Brimars had been used quite a bit when I got them. I have 4 sets of 6v6 tubes, the Groove tubes, Bimars, Tungsol Re-issues and JAN Sylvanias. The Brimars and Sylvanias came with my BAT stereo preamp and I had purchased the Tungsols for it as well. The funny thing is all three sets were microphonic in the preamp. I have another set of JAN Sylvanias in there now and they are fine. None of the 6V6's are showing any sign of being microphonic in the SC. Kind of puzzling to me. I rolled in the JAN Sylvania's and they are quite sweet sounding as well. A bit more relaxed than the Brimars or the Tungsols. I think some NOS preamp tubes are going to be on tap for the near future. Thinking about some JAN Sylvania's or RCA black plates. Any other ideas?
     
  12. Wally

    Wally Telefied Ad Free Member

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    The only...or first...idea I have is as stated above....I that one would do well to know the biasing numbers, ime. What is the plate dissipation of every tube you put in there? Imho, comparing or just observing Sonics is not complete until the biasing numbers are known. Ommv...but it is very interesting to adjust bias while taking note of the vast difference between various bias points....from too cold to just before redplate hot.
     
  13. try1256

    try1256 TDPRI Member

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    Thanks Wally. I am not sure how to check or set bias on the SC. Is there a link to any instruction on that?
     
  14. Wally

    Wally Telefied Ad Free Member

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    I like to suggest that people check out Aiken amps before falling off into tech work...as well as many other sources. Rob Robinette...robrob here on the TDPRI...has an extensive site that would be a good place. A search for ‘vacuum tube history’ is a really good beginning so that one gets an idea what goes on in these tubes...what each element does.
    The Super .champ does not have an adjustment potentiometer for the bias voltage. I am going to install them in mine when I retube.
    Until a pot is installed, one has to change a resistor to change the bias. Or....use power tubes with operation specs that lean to the cool side of operation. Every SC I have measured has been dissipating well over 70%.
     
  15. try1256

    try1256 TDPRI Member

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    The Ted Weber Signature 10s arrived today. I was a bit surprised the original speaker was stuck pretty tight to the baffle. I finally coaxed it off and got the Weber installed. I know these need some break in but it sounds pretty darn good right out of the box. It is bright but the tone is so much better than the oem speaker, it isn't a problem. The one big thing I noticed is it sounds much better at low volume. I put the Tung Sol's back in for a while. They are pretty good sounding tubes and seem to have a bit more volume than the other tubes I have.

    tedweber.jpg
     
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  16. hepular

    hepular Tele-Meister

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    Bump.

    I never got the lead level pot to work (posted last year about that), but I'll check the footswitch jacks. (it doesn't bother me since I rarely use the channel & can tame it with guitar volume anyway . . .)

    Can confirm that 12au7s make the lead channel worthwhile . . .

    Just got brave enough to pull the chassis & discovered a cooking 70/100 neg bias cap--so I'm working on my soldering skills since Lubbock's too far away, & there doesn't seem to be anyone trustworthy in Abilene . . .
     
  17. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    Check out the photos in #post 162 and try to put the cap in like on the lower photos to keep it from the heat of the resistors.
     
  18. hepular

    hepular Tele-Meister

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    that's what i was looking at, thanks. this thread is an absolute marvel.

    i've got a few hours of practicing on desoldering & resoldering some old circuit boards before i trust myself inside the SC. (why didn't i start with a nice 5f1 or something with space in the chassis?)


    think i'll start with that (& replacing that 470 .5w resistor) before checking the 25/25s and the cap can.
     
  19. schmee

    schmee Doctor of Teleocity Silver Supporter

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    Wow, resurrected from the dead!
    Speaking of SC's, I have 3 EV Force 10's I just haven't used for a while. I can't decide whether to sell them or not. I think they are about $150 each usually on the market, but man shipping could be hell. But it's like $450 laying around...
    [​IMG]
     
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  20. ScottJPatrick

    ScottJPatrick Friend of Leo's

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    I also have a spare EV10L/Force 10 which I'm afraid to sell in case I ever find another Super Champ I can use it in. I just know I would regret selling it and would probably never find another one.
     
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