6L6SE guitar amp project...

knockbill

Lunatic Member
Here's a couple pics of the 6L6SE guitar amp I've been contemplating... Kinda like a Champ, on steroids... Ideas from from a few different schems, some PS changes and different input tubes... Basically I replaced the 12AX7 with a pair of 6SF5s,, and used a 5881 output tube cause I only have one! It will get very loud, but breaks up real early,,, maybe 1-2 on VC... I've only tried it with a CDP tho, so it probably has too much input voltage... Heaters, plate and cathode Voltage on the meters... If this mule works out, the plan is to build it in a chassis that will fit the 5F1 box,,, so a couple mounting screws, and I will have a new/different amp...
Considering a tube rectifier, and replacing OPT as this one is 3.5K and RCA manual calls for 4.2 - 4.5K
As sloppy as the board is, its quiet with a bus, bonded line cord, and jumpers connecting it together... Gotta love the metal preamp tubes, with the built in shield!!
 

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I think you are fine with the 3.5K.

Have you played your guitar through the amp? Try it with both humbuckers and single coils if you can.

Here’s what I noticed about mine (using a 6SL7 input tube)....... it does break up when it is hit hard but ease up on the attack and it cleans up. Touch sensitive amps can be quite nice in the right hands but can be bloody awful in the wrong ones. I stopped bringing the amp to the monthly coffeehouse jam for this reason but love playing it at home.
 
Haven't tried it with guitar yet,,, just got it sorted this morning... had to parallel a bunch of resistors to get values, as you can see it looks like a trash pick!!! I will try it with both PUPs, hoping it wont need too much to get a bit of clean sound before it gets dirty... may have to try it with Champ input impedance, at 68k-100k instead of the 1M....
These 6SF5s have more gain than 6SL7s,,, amp factor 100 vs 70, IIRC,,,
Here's the input ckt,, for now... Gotta go drop a tree for a buddy in Rose Valley this afternoon, so I'll get back to this!
Thanks for replying...
 

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Got a chance to revisit this amp,,, hooked up a guitar (HSS Strat),,, seems to be fine with all the PUPs, but really shines with the humbucker, clean twangy highs, not sure on bass yet, test speaker isn't up to it! So, I'll do some housecleaning, replace paralleled resistors with single, close tolerance and get the jumpers and long leads sorted to get rid of ambient noise, and see what we have here... Thinking about removing the tone control also,,, not many Champs have them, the git tone pot(s) will suffice there... Probably need a higher watt speaker than the one on the bench, almost blew it off the wall!!!
 
Sounds like you are on the right path; thanks for the report. Humbuckers twangy? It's a world gone mad.
 
OK,,, I got this far with it,,, its extremely stable, Pd is 23.6W,, and it sounds much better than I expected with my Strat, which works out well, cause I'm returning the HSS to its owner!!! Its very quiet, even the 1,3,5 switch positions don't hum, which is odd for single wound PUPs... Not quite sure how to post a schematic, as I took some ideas from a few different amp ckts, built my SS PS, and used 3 different tubes 2x 6SF5 + 5881)... I'm curious how this "Super Champ" circuit compares to Rwoods??!! Take note of the extensive cabinet work on this one (so far)!!!!!
 

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I built a SE KT66 amp around a custom Heyboer E-Linear opt. 2k load. Sounds pretty darn fine; I don't play but I had some issue getting it back from the folks I loaned it to for an audition. Nothing but a vc. Tubes are 6GU7>EF184>KT66. The next incarnation will trade a single pentode for the cascaded 6GU7 stages. That will get loaded with a CCS, and gain managed with a resistor from plate to ground. Gain up to 350 is available, along with a PSRR to die for...:)
cheers,
Douglas
 
Sounds cool,,, I never had any KT tubes,,What kind of Pd do you get with that amp? I had this one orphan 5881, it needed something to do!!! This circuit does better with this tube than any 6L6GC I tried, so its a good use for it!!! I'm using a vintage 3.5K OPT/350Vp, not sure if it would sound better/different with 4.2K Tx the RCA manual calls for...
I've been banging on the Strat for a few hours now, and the amp is dead quiet, and very responsive... Probably deserves a nicer chassis/box!!!!
Thanks for replying!
 
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I never measured it. I suspect about 4 Watts...:) The OPT has a 40% g2 tap and a 10% E-Linear tap. Gapped to deal with 90-100 mA.
cheers,
Douglas
 
Actually I'd like to eliminate the tone control, but I couldn't seem to find the right resistor to eliminate the pot, and set the tone where it should be...
 
Update...
Finally got back to this guy,,, bent a chassis,,, brazed the corners, and started to cut holes for components,,, plan was to mount PT thru the chassis, but decided to use brackets and stand it on the rear side next to the OPT... That will leave more room under it to mount the PS as far away from the turret board as possible... Still have to finish shaping and paint the chassis, fill the board and mount Txs, and wire it,,, but its coming along!
 

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Here's the schem I came up with,,, started with some designs I found on line, changed the PS, tubes and Txs to fit with parts I had on hand... Appreciate any improvements, mods, thoughts etc before I load the turret board... Its easier to "adjust" while its on the bread board...
Thanks
 

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Looking very good.
Just a couple observations - first, why such a high value grid resistor on the first triode? Seems like 15K would do fine. And I think the power tube is going to run pretty hot with only 200 ohms resistance on the cathode. But now, I could be mistaken!
 
The 150K? Champ 5C1 uses 75K,,, 5F1 68K,, Angela uses 27K, just took the specs off the schem... Output tube is designed to dissipate 23W, (schem calls for 6L6WXT,but I can't find a spec sheet for it).... Pd works out to a little over 23W which is max for 5881,,, I can back it off if you think its necessary...
I appreciate the input,,, now's the time to make changes!!!! What kind of power do you get out of your super champ?

First coat of paint,, not sure I like the finish,, probably wet sand it tomorrow, fill a couple flaws and try a second coat...
 

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Hey John? Can you snap a better picture of the power supply drawing? I've got an old 6v6 PP mono chassis with a power trany still on it. Around 320-0-320 secondary with 5v and 6.3v taps. It should work for that amp I think.
I've seen wanting to build one for my son. His tube guitar amp is 300 watts and needs a small practice amp. I've got plenty of 6L6's and 5881's. I do have a fist full of 6J5's, but they may not have enough gain.
 
Hey John? Can you snap a better picture of the power supply drawing? I've got an old 6v6 PP mono chassis with a power trany still on it. Around 320-0-320 secondary with 5v and 6.3v taps. It should work for that amp I think.
I've seen wanting to build one for my son. His tube guitar amp is 300 watts and needs a small practice amp. I've got plenty of 6L6's and 5881's. I do have a fist full of 6J5's, but they may not have enough gain.

Sure,,, 6J5 is about half a 6SN7/12AU7 type, medium gain,,, I used 6SF5s,, half a 12AX7,,, Like to use metal drivers, specially in high gain circuits they have a built in shield, and are dirt cheap!!!!
This PT is 370-0-370V,,, used the 5V winding for bucking... Intended to use a 5Y3 rectifier, but wanted the chassis to be small enough to swap out in the Champ cabinet, so went SS...
 

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Sure,,, 6J5 is about half a 6SN7/12AU7 type, medium gain,,, I used 6SF5s,, half a 12AX7,,, Like to use metal drivers, specially in high gain circuits they have a built in shield, and are dirt cheap!!!!
This PT is 370-0-370V,,, used the 5V winding for bucking... Intended to use a 5Y3 rectifier, but wanted the chassis to be small enough to swap out in the Champ cabinet, so went SS...
Thanks John. I'll have to check the trany to be sure. If it is 320-0-320 it may be to small then.
 
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