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| | |-+  A Champ is born...		 « previous next »
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Author Topic: A Champ is born...  (Read 25059 times)
mcinku
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« on: February 16, 2009, 10:22:01 PM »
A friend of mine wanted a Champ bad, so I volunteered to help. I ordered a kit from Nik and he made a chassis.
The one from Ceriatone was not good enough for what we had in mind.

This how we started...
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« Reply #1 on: February 16, 2009, 10:23:33 PM »
This Champ will use 6L6, will have a Tweed mod, Middle control and a Standby switch.


PT done... Wink
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« Reply #2 on: February 16, 2009, 10:24:36 PM »
Board in and tube sockets with OT done...
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« Reply #3 on: February 16, 2009, 10:27:58 PM »
After 10 hours of wiring the amp is done...




Currently I'm still using 6V6. I'm waiting for one resistor which needs to be replaced for 6L6 tube.
 Wink
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« Reply #4 on: February 16, 2009, 10:30:42 PM »
I forgot to say...the board is for VibroChamp but my friend didn't wanted the vibro part, so I didn't wire that up.
Maybe he will change his mind someday.
  Cheesy
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wyatt
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« Reply #5 on: February 17, 2009, 01:55:56 AM »
Is that the basic Gerald Weber Tweed mod?

If you are switching out the Tone stack, make sure to lift the 2uF cap off the pin 8 cathode, or have it be able to switch out.  otherwise you end up with a massive amount of extra gain  from the loss of the tone stack.
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« Reply #6 on: February 17, 2009, 07:14:20 AM »
Well, I don't know what Gerald Weber Tweed mod is  Embarrassed
I found this schematic on the web somewhere, so I wired it that way and it works.  Cheesy
I know a lot of people just lift the ground of that 15K resistor but that's not exactly it. With that you still have treble pot working. This way tone stack is completely out, just like with real Tweed Champ.


Quote from: wyatt on February 17, 2009, 01:55:56 AM
Is that the basic Gerald Weber Tweed mod?

If you are switching out the Tone stack, make sure to lift the 2uF cap off the pin 8 cathode, or have it be able to switch out.  otherwise you end up with a massive amount of extra gain  from the loss of the tone stack.

* Tweed_mod.JPG (18.56 KB, 387x282 - viewed 1386 times.)
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« Reply #7 on: February 17, 2009, 08:18:07 AM »
If you just do the mod you have posted, you are getting soemthing a little different just Tweed 5F1 tone.

Fender had to introduce more gain in the preamp of the BF Champs to compensate for the higher resistance of the BF tone stack.  Remove the tone stack and you end up with a ton of additional gain that Tweed Champs didn't have.  It creates a hot-rodded, fire-breathing monster of an amp. It's a fun little crunch machine, but much, much hotter than a real Tweed Champ, and sometimes it would be nice to dial it back to get some tweed cleans.

So, to balance it out, we switch out the 2uF electrolytic coming off V1B's cathode.  This creates a much more dead-on 5F1 sound out of the AA764 circuit. 
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« Reply #8 on: February 17, 2009, 08:42:15 AM »
Quote from: wyatt on February 17, 2009, 08:18:07 AM
If you just do the mod you have posted, you are getting soemthing a little different just Tweed 5F1 tone.

Fender had to introduce more gain in the preamp of the BF Champs to compensate for the higher resistance of the BF tone stack.  Remove the tone stack and you end up with a ton of additional gain that Tweed Champs didn't have.  It creates a hot-rodded, fire-breathing monster of an amp. It's a fun little crunch machine, but much, much hotter than a real Tweed Champ, and sometimes it would be nice to dial it back to get some tweed cleans.

So, to balance it out, we switch out the 2uF electrolytic coming off V1B's cathode.  This creates a much more dead-on 5F1 sound out of the AA764 circuit. 

Actually, I like that extra gain... it's like having an extra OD ch. The volume jump is huge but the sound is cool and I like how interactive the amp is with a guitar volume pot.
Thanks for your hint... if my friend doesn't like that volume jump... I can always do what you said.

 Wink
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wyatt
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« Reply #9 on: February 17, 2009, 03:30:58 PM »
Quote from: mcinku on February 17, 2009, 08:42:15 AM
Quote from: wyatt on February 17, 2009, 08:18:07 AM
If you just do the mod you have posted, you are getting soemthing a little different just Tweed 5F1 tone.

Fender had to introduce more gain in the preamp of the BF Champs to compensate for the higher resistance of the BF tone stack.  Remove the tone stack and you end up with a ton of additional gain that Tweed Champs didn't have.  It creates a hot-rodded, fire-breathing monster of an amp. It's a fun little crunch machine, but much, much hotter than a real Tweed Champ, and sometimes it would be nice to dial it back to get some tweed cleans.

So, to balance it out, we switch out the 2uF electrolytic coming off V1B's cathode.  This creates a much more dead-on 5F1 sound out of the AA764 circuit. 

Actually, I like that extra gain... it's like having an extra OD ch. The volume jump is huge but the sound is cool and I like how interactive the amp is with a guitar volume pot.
Thanks for your hint... if my friend doesn't like that volume jump... I can always do what you said.

 Wink

On mine, I have the cap switchable.
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« Reply #10 on: February 17, 2009, 05:32:21 PM »
Quote from: wyatt on February 17, 2009, 03:30:58 PM
On mine, I have the cap switchable.

Do you by any chance have a gut picture... so I could see how you did it?
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« Reply #11 on: February 17, 2009, 07:38:55 PM »
It's been maybe a decade since I've had this chassis open.  Yeah, I did this to a '68 drip edge.  Still have the leftover blue molded caps somewhere, I guess they go for $20 a piece on eBay.  I did have a jackass tech work on this amp once since then, I just noticed he added a f*ckin' death cap back on the power switch; the SOB Conrad Johnson designer cut the chassis to fit the new switch. 



You can see the switch up top, all it does is lift the ground of of the 2uF so that is is disconnected to the 1.5K resistor.

RCA 6V6GT, CA 5Y3GT, GE 12AX7, Weber P8R (8A100) very much a neil Young tone, more so than my Tweed Deluxe.
« Last Edit: February 17, 2009, 07:40:34 PM by wyatt » Logged
mcinku
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« Reply #12 on: February 17, 2009, 08:00:26 PM »
I just played the amp for the first time today (at higher volumes) and I noticed how much quieter the VibroChamp is compared to plain Champ. Not only quieter but also warmer, almost Twin like in a way. I think I like it.  Shocked
...and the only difference is that cathode bypass cap. Vibro has 10uF and Champ has 2uF.

Damn now you got me thinking...I could put a on-off-on switch, so I could select between 2uF - 10uF or nothing, now that would be cool.
 Cool

Thanks man.

Back to drawing board.
 Grin
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« Reply #13 on: February 17, 2009, 08:26:36 PM »
I think even thought the extra gain is fun, the stock Tweed circuit offers more than enough gain and is more versatile and musical in the long run.

That Champ Vibrochamp difference may not be cap, it may be extra resistance in the signal path introduce by the trem circuit.  In the larger Blackface Fenders, the "vibrato" circuit adds about 56K of resistance; obvious the VC uses a complete different circuit but I don't have a VC to poke around in. 
« Last Edit: February 17, 2009, 08:32:19 PM by wyatt » Logged
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« Reply #14 on: February 17, 2009, 08:47:02 PM »
Quote from: wyatt on February 17, 2009, 08:26:36 PM
I think even thought the extra gain is fun, the stock Tweed circuit offers more than enough gain and is more versatile and musical in the long run.

That Champ Vibrochamp difference may not be cap, it may be extra resistance in the signal path introduce by the trem circuit.  In the larger Blackface Fenders, the "vibrato" circuit adds about 56K of resistance; obvious the VC uses a complete different circuit but I don't have a VC to poke around in. 

Hmmm, but my vibro part is not wired, so it should not affect anything, right?
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