Building the 6L6 Champ

[Ten Over]

Not using a switch right now. A jack is in the socket and it is shorted to ground. I've tried it with and without the jack.

I guess Switchcraft calls it "Shunt". It's the middle tab on the jack. Move the ground wire to the ground tab and disconnect the middle tab. Or insert an open phone plug into the jack. The plug is the male equivalent and the jack is the female equivalent.

 

[Ten Over]

Like this:

 

[Phrygian77]

 

[schmee]

Like this:
View attachment 981387

View attachment 981395

SUCCESS!
Sweet jaysus that was STOOPID.
I installed a shunt jack for the damn pedal! DUH.... I think originally I was going to put the speaker jack there.
It's always something simple....
Working fine now. The 25k Audio pot seems to work fine also...
Thanks all.
It's the pits getting ancient....

 

[schmee]

UPDATE: The amp plays fine, I have the new PT in it. But it seems to hum too much now that the chassis is back in the cabinet.
The weird thing is it hums with the guitar volume in the middle of the sweep. It stops humming at 0 and it stops humming at 10!
So I'm thinking this cheap Tele type I'm testing with is the issue. NOPE, I plug into one of my other amps and they are quiet with the same guitar.
So I have some things to figure out.

One thing is the power tube is very close to the speaker magnet. Probably 1/2" away from it. This was not an issue when this (experimental) amp was wired as a BF Princeton. I wonder if Cathode Bias makes a difference in some way regarding that?

But maybe it's not the speaker proximity at all. I'll have to remove the chassis again to test it. I can certainly go with a 10" speaker if it is the speaker.

 

[Phrygian77]

What effect does the amp volume have on it, with and without a guitar plugged in? Also, try testing with a different V1 tube.

 

[schmee]

UPDATE on the Champ hot rod clone:

So today I went out with the same guitar and tested the Champ+ again. No hum now.
I realized that during the first test, I was sitting right next to the amp on top of another amp.
It's weird how that guitar did hum the other day but my Strat didn't, but still, once I'm sitting 3 feet in front of the Champ+ there is no hum now.
So.... problem solved!

This champ+ clone has some tasty tone to it and seems much louder and meatier than the SF Champ I sold not long ago. Better tone... probably due to the bigger deeper cab and 12" speaker to some extent, but I did try different speaker setups with the old SF Champ.
The bigger 14 watt multitap Output Tranny seems to do a lot for a Champ circuit. Right now I'm not running the 6L6WGB I planned on running in there. But it's cleaner and louder with just that tranny and the 6V6.
Cool!
To relabel the panel I covered it with thin clear vinyl maybe .040" and just put the labeling between the chrome and the vinyl.

 

[schmee]

Next I need to try the 6L6 version and decide. Right now I have it wired with the 5K primary for 6L6, even though I'm running a 6V6. So I need to test the 6L6 version and see if I want that or to rewire the primary to 7K. I might try the KT66 for giggles and wee if the tranny warms up much....

 

[Phrygian77]

I can tell you, switching the primary to 7k with the 6V6 will just reduce the clean headroom. If that's what you want, go for it.

 

[schmee]

I can tell you, switching the primary to 7k with the 6V6 will just reduce the clean headroom. If that's what you want, go for it.

Really? well that's good to know. I wonder why that is? The 7k is closer to the recommended.....

With the 5k setup, I'm running the output multi tap at 16 ohms (with 6V6)
SPEAKER LOAD: Using the 5K (Brown) primary winding:

6V6 POWER TUBE: use the 16 ohm setting for 8 ohms cabs

6L6 POWER TUBE: use the 8 ohm setting for 8 ohm cabs.

 

[Phrygian77]

Well, in that case if you're running 10k reflected, no. What I noticed when I built my last Vibro Champ is that switching the primary to 5k seemed to increase the headroom, or at least, it reduced the amplification factor.

 

[schmee]

Well, in that case if you're running 10k reflected, no. What I noticed when I built my last Vibro Champ is that switching the primary to 5k seemed to increase the headroom, or at least, it reduced the amplification factor.

makes me wonder if instead of switching the multitap OT 8 or 16 ohms, I should just connect the 8 ohm tap and switch the primary 5k or 7k instead....

 

[schmee]

UPDATE on the Champ hot rod clone:

So today I went out with the same guitar and tested the Champ+ again. No hum now.
I realized that during the first test, I was sitting right next to the amp on top of another amp.
It's weird how that guitar did hum the other day but my Strat didn't, but still, once I'm sitting 3 feet in front of the Champ+ there is no hum now.
So.... problem solved!

This champ+ clone has some tasty tone to it and seems much louder and meatier than the SF Champ I sold not long ago. Better tone... probably due to the bigger deeper cab and 12" speaker to some extent, but I did try different speaker setups with the old SF Champ.
The bigger 14 watt multitap Output Tranny seems to do a lot for a Champ circuit. Right now I'm not running the 6L6WGB I planned on running in there. But it's cleaner and louder with just that tranny and the 6V6.
Cool!
To relabel the panel I covered it with thin clear vinyl maybe .040" and just put the labeling between the chrome and the vinyl.

View attachment 984649

UPDATE #2:
Played a little Duo gig last night using the Champ+. It was dead quiet and worked great all night! I have a 10" Rajun Cajun speaker in it and it seems to fit that amp well. Really surprised at the clarity and headroom of this little amp with that output tranny..

 

[jsnwhite619]

I scanned through and didn't see, but what value bias resistor did you end up with?

 

[schmee]

I scanned through and didn't see, but what value bias resistor did you end up with?

It has the stock 470 ohm in there , at 2 watt. I have thought about upping that a bit, but it does sound good. Not sure what I should do if I go to the 6L6, but haven't done that yet.
Sometimes the tremelo works, sometimes it doesn't......

 

[jsnwhite619]

It has the stock 470 ohm in there , at 2 watt. I have thought about upping that a bit, but it does sound good. Not sure what I should do if I go to the 6L6, but haven't done that yet.
Sometimes the tremelo works, sometimes it doesn't......

I searched a lot online and asked here, and the consensus was a 10W resistor for 6L6/5881 tubes.

 

[jsnwhite619]

Well, here' a little extra info for this thread. I have been putting together another of my big bottle 5f2a amps, but had to use a different PT b/c availability - Hammond 290CAX instead of AX, so no 5u4 this time. But I have a gz34 and 5y3 on hand. I used the 10W 125DSE (5k primary) this time because the ESE was just ridiculously big before. Anyway, started with a 300R bias resistor to get it hot on the 5881. Using the 275v taps the B+ was right at 350v (the 315v taps with the gz34 put it at 417v B+). I've been messing with it and tweaking it the past week but never REALLY happy yet. After reading this thread, I swapped in a 470R 10W bias resistor instead and tried it. To my ears & not a mic, it sounded better. Still very close, but a little tighter and less ratty. Then, with the new bias resistor, I swapped in a new JJ 6v6 instead of the 5881. I honestly can not tell enough of a difference to reliably pick one in a blind test. I went back & forth and had to use a rag to handle the tubes, and I wouldn't be able to pick the difference in a JJ 5881 or 6v6 for $1 million.

Then I got my dB meter and set it on the ground approx. 15-16" in front of the cabinet. Through the Cannabis Rex, the 6v6 reach 116dB and the 5881 hit 117dB. It was "one more louder". So, take of that what you will. I'm a bit surprised and disappointed...haha. I'm wondering how much difference the 10W OT is limiting things vs the 15W last time?

 

[schmee]

Well, here' a little extra info for this thread. I have been putting together another of my big bottle 5f2a amps, but had to use a different PT b/c availability - Hammond 290CAX instead of AX, so no 5u4 this time. But I have a gz34 and 5y3 on hand. I used the 10W 125DSE (5k primary) this time because the ESE was just ridiculously big before. Anyway, started with a 300R bias resistor to get it hot on the 5881. Using the 275v taps the B+ was right at 350v (the 315v taps with the gz34 put it at 417v B+). I've been messing with it and tweaking it the past week but never REALLY happy yet. After reading this thread, I swapped in a 470R 10W bias resistor instead and tried it. To my ears & not a mic, it sounded better. Still very close, but a little tighter and less ratty. Then, with the new bias resistor, I swapped in a new JJ 6v6 instead of the 5881. I honestly can not tell enough of a difference to reliably pick one in a blind test. I went back & forth and had to use a rag to handle the tubes, and I wouldn't be able to pick the difference in a JJ 5881 or 6v6 for $1 million.

Then I got my dB meter and set it on the ground approx. 15-16" in front of the cabinet. Through the Cannabis Rex, the 6v6 reach 116dB and the 5881 hit 117dB. It was "one more louder". So, take of that what you will. I'm a bit surprised and disappointed...haha. I'm wondering how much difference the 10W OT is limiting things vs the 15W last time?

Good info. I've been disappointed in real Champs and have had 3 different ones in the last 12 years. This build with the bigger OT is what I've been looking for in the past. Tighter and less ratty than a 5 watt Champ, yet a hint of grit at lower volumes and has that "on the edge of screaming at you" voicing like CL A should. It sounds a lot more like my little Champ 12/6L6 did. (That amp would hold up in rehearsal etc.)
With the 6V6 it sounds about right for what I wanted. Thus I haven't messed with the 6L6/5881's yet. So it sounds like we are on the same page, at least a bit there.
I am tempted to put a switch on the 5k and 7k primary to see what difference there is by switching hot.... right now running with the 5k primary at 16 ohms output tap to an 8 ohm speaker.

 

[jsnwhite619]

Good info. I've been disappointed in real Champs and have had 3 different ones in the last 12 years. This build with the bigger OT is what I've been looking for in the past. Tighter and less ratty than a 5 watt Champ, yet a hint of grit at lower volumes and has that "on the edge of screaming at you" voicing like CL A should. It sounds a lot more like my little Champ 12/6L6 did. (That amp would hold up in rehearsal etc.)
With the 6V6 it sounds about right for what I wanted. Thus I haven't messed with the 6L6/5881's yet. So it sounds like we are on the same page, at least a bit there.
I am tempted to put a switch on the 5k and 7k primary to see what difference there is by switching hot.... right now running with the 5k primary at 16 ohms output tap to an 8 ohm speaker.

The ohms/switching/speaker combos can get a bit confusing sometimes, but I think you're only reflecting a 2.5k primary on your 6v6 right now, but somebody please check my math.

5k -> 16R tap with a 16R speaker = 5k reflected
5k -> 16R tap with 8R speaker = 2.5k reflected, half the speaker load, half the primary load
5k -> 4R tap with 8R speaker = 10k reflected

 

[schmee]

Next I need to try the 6L6 version and decide. Right now I have it wired with the 5K primary for 6L6, even though I'm running a 6V6. So I need to test the 6L6 version and see if I want that or to rewire the primary to 7K. I might try the KT66 for giggles and wee if the tranny warms up much....

Well, in that case if you're running 10k reflected, no. What I noticed when I built my last Vibro Champ is that switching the primary to 5k seemed to increase the headroom, or at least, it reduced the amplification factor.

The ohms/switching/speaker combos can get a bit confusing sometimes, but I think you're only reflecting a 2.5k primary on your 6v6 right now, but somebody please check my math.

5k -> 16R tap with a 16R speaker = 5k reflected
5k -> 16R tap with 8R speaker = 2.5k reflected, half the speaker load, half the primary load
5k -> 4R tap with 8R speaker = 10k reflected

Well, you guys decide and let me know!