freestompboxes.org

Anyone know what the circuit is for the CJ11?

I have read that it is Deluxe based, and the circuit uses 2 12AX7's and 2 6V6's to give 11 Watts and has a Volume, Treble, Bass and Master Volume configuration.

I am guessing then , that it is cathode biased with a cathodyne PI and the first 12AX7 is cascaded and uses a VOX Top Boost tone stack probably between the first pre amps.

Anyone know any more about this?

conger wrote:Anyone know what the circuit is for the CJ-11?

In a nutshell, it is all Fender deluxe...but a clever blend of two classic era's.

The CJ-11 uses a AB763 blackface deluxe front end.
.1/.047/100k slope-250pF tonestack, 100k plates, and uses 3.3k cathode resistors, bypassed by 10uF caps on both.

The pull boost switches in a 100k resistor in series with the fixed 6.8k mid resistor on the bass pot and switches in a 250pF with the exisiting fixed 100pf bright cap to enhance the sparkle factor when pulled.

The afore mentioned switchable 100k resistor functions basically as a switchable tonestack bypass, ie RAW control. A simpler, and infinitely more adjustable implementation would be to just use a 100k mid pot, and just put the bright cap values on a separate 3 way switch. 100pf-none-250pF.


Then on into a basically stock 5e3 tweed deluxe cathodyne PI and cathode biased power section.

It uses a version of the Ken Fisher type 2 master volume (google LarMar MV).

That basically...is it.
PM me for more pics.

topbrent wrote:In a nutshell, it is all Fender deluxe...but a clever blend of two classic era's.

The CJ-11 uses a AB763 blackface deluxe front end.
.1/.047/100k slope-250pF tonestack, 100k plates, and uses 3.3k cathode resistors, bypassed by 10uF caps on both.

Many thanks. Very interesting. Are you sure they are 3k3 resistors. They look like 330R in the photo? Either value is unusual. Also looks like the gain stage on V2 uses a 470R cathode resistor instead of the 5E3's 1K5.

topbrent wrote:The pull boost switches in a 100k resistor in series with the fixed 6.8k mid resistor on the bass pot and switches in a 250pF with the exisiting fixed 100pf bright cap to enhance the sparkle factor when pulled.

The afore mentioned switchable 100k resistor functions basically as a switchable tonestack bypass, ie RAW control. A simpler, and infinitely more adjustable implementation would be to just use a 100k mid pot, and just put the bright cap values on a separate 3 way switch. 100pf-none-250pF.

Yes, the 100k pot would make more sense although maybe the average user will find it difficult to understand. A switch labeled Boost is easy for everyone.

Also, the coupling cap from the Pre to the PI is a .022 with a 470k load dump to ground. (Signal reduction)

This is a quickie schematic I mashed together, but it basically gets the point across.

Caveats:
- I decided to just include the 100k mid pot as opposed to the 100k resistor on a switch. More adjustibility.
- Also, I put the two bright caps on a switch, this way the player can have 100pF, 250pF or none.

This looks a lot like the fender deluxe 5E3 I built. Swapped the newer tone stack in place of the old and voila, a simply gorgeous sounding amplifier that breaks up into incredible overdrive. Highly recommend a build like this.

topbrent wrote:This is a quickie schematic I mashed together, but it basically gets the point across.

Caveats:
- I decided to just include the 100k mid pot as opposed to the 100k resistor on a switch. More adjustibility.
- Also, I put the two bright caps on a switch, this way the player can have 100pF, 250pF or none.

Cool. Thanks for doing that.

Those pre amp cathode just look all wrong. I know that's what the resistor values look like, but 3k3, 3k3 and the 470R! Also I would have thought there would be too much gain in this amp without some extra attenuation.

It's interesting that it is not too far from the Vox Night Train but with no NFB and 6v6's instead of EL84's.

That's a 4.7k on V2A cathode, not 470 ohms...

TT

ALso, it's a Blackface TB tone circuit with a 6.8k resistor replacing the mid control and not a TMB as shown in the schematic.

TT

tictac wrote:ALso, it's a Blackface TB tone circuit with a 6.8k resistor replacing the mid control and not a TMB as shown in the schematic.

TT

Read my caveats.

Here is the updated schem with the 4.7k cathode resistor on v2a. Thanks for the catch.

Shouldn't you midpot read 10 K instead of 100K ?

fosnal1950 wrote:Shouldn't you midpot read 10 K instead of 100K ?

No. Not necessarily.

The stock CJ-11 has a fixed 6.8k mid resistor (like a stock vol-treb-bass AB763 front end,) and a 100k resistor in series on a push-pull boost switch.

That is quite a big jump. By using a 100k pot it allows the player to have control over the level of boost.

topbrent wrote:By using a 100k pot it allows the player to have control over the level of boost.

Absolutely. A better way to do it.

By using a 100k pot it allows the player to have control over the level of boost.

You're right there ! But when you go past ,let's say 25 K , can you still a difference when changing the value towards 100 K ?

fosnal1950 wrote:

By using a 100k pot it allows the player to have control over the level of boost.

You're right there ! But when you go past ,let's say 25 K , can you still a difference when changing the value towards 100 K ?

It affects the amount of boost to the signal. See the attached picture of what is happening to the overall level when you increase the mid resistor/pot value. It boosts everything.

In my opinion, the reason the CJ-11 has that extra 250pF bright cap that gets switched in as you pull the boost is so your ear still perceives the sparkle of the AB763 circuit. Otherwise, the big 100k boost can swamp out the sparkle.

any information about the voltages. At least B+ or PT voltage could be usefull.I think voltage must be slightly lower compared to fender 5e3 ...

topbrent wrote:Also, the coupling cap from the Pre to the PI is a .022 with a 470k load dump to ground. (Signal reduction)

Hello,
I might be wrong but to me it looks like 47k load dump resistor not 470k. I just finished building this
and got huge blocking distortion with 470k. I haven't tested it yet with 47k but tomorrow i will.

47k would load down V1b more than I think would make sense in this circuit.

If you look at the picture with the big blue electrolytics you can see some series resistance and voltage divider action going on after the 22n coupling cap from V1b.

This would remove blocking distortion, give suitable signal levels at V2a and prevent heavy loading of V1b.

dread pierat wrote:
If you look at the picture with the big blue electrolytics you can see some series resistance and voltage divider action going on after the 22n coupling cap from V1b.

This would remove blocking distortion, give suitable signal levels at V2a and prevent heavy loading of V1b.

sorry, but could describe the hidden resistor in sereis with 22n cap? i had a close look at both pics and couldnt find the specific resistor between the 22n coupling cap and 470k. Though there could be some sort of arrangement of a voltagedivider hidden somewhere (kometamps use 100n-220k-330k to ground).

snyder80 wrote:

dread pierat wrote:
If you look at the picture with the big blue electrolytics you can see some series resistance and voltage divider action going on after the 22n coupling cap from V1b.

This would remove blocking distortion, give suitable signal levels at V2a and prevent heavy loading of V1b.

sorry, but could describe the hidden resistor in sereis with 22n cap? i had a close look at both pics and couldnt find the specific resistor between the 22n coupling cap and 470k. Though there could be some sort of arrangement of a voltagedivider hidden somewhere (kometamps use 100n-220k-330k to ground).

Hello,
I can't see any series resistance there between 22n and v2a...
After 22n there is 47k resistor to ground(other end is connected to ground bus under input jack I think),
V2a's cathode resistor and cap is connected to ground same turret(ground).
Then there is shielded wire going from junction of 22n and 47k to grid of v2a. Shielded wire's metallic shield is connected to "ground side" of cathode resistor and cap of v2a I think...
Basically I see it is connected just like in the schematic but 470k replaced with 47k.

I will try that in practise soon and post here how it works.