JMP 2204 3-way bright switch

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psychic fuzz

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Hey all :victoire:

Newbie here. Found a couple relevant threads doing research and figured I'd join in the fun and see if anyone could help me on my tone quest.

I'm thinking of adding a 3 way "on on on" bright cap switch on my JMP 2204. I chose a DPDT to make it easier to swap different values.

I'm going to use the "Low" input hole so I'll have to do a little rewiring. Here's a drawing of what I think I'm doing. I got the switch wiring idea somewhere deep on the interweb so not sure if it'll work. Any insight greatly appreciated, thanks!

bright switch.jpg
 
psychic fuzz said:
Hey all :victoire:

Newbie here. Found a couple relevant threads doing research and figured I'd join in the fun and see if anyone could help me on my tone quest.

I'm thinking of adding a 3 way "on on on" bright cap switch on my JMP 2204. I chose a DPDT to make it easier to swap different values.

I'm going to use the "Low" input hole so I'll have to do a little rewiring. Here's a drawing of what I think I'm doing. I got the switch wiring idea somewhere deep on the interweb so not sure if it'll work. Any insight greatly appreciated, thanks!

View attachment 104349
Click to expand...

The amp filaments should be de-buzzed before installing modifications.
These amps are known for hum and buzz, which can be tweaked out.
(there are several tweaks to lower the filament noise)

First, The LOW jack should be replaced with a new jack, because the switch contacts fail from age.
When this LOW jack fails, the HIGH input will stop working.
Be careful that you use a REAL UK Cliff jack. The jack will have "UK" stamped on the plastic.
Beware of fake Cliff jack counterfeits.

1. The green wire between the pot and the next preamp tube stage should be a shielded wire. (add)
2. The bright caps and related switch / wiring will pick up buzz noise from the magnetic field of the filament wires. I advise using shielded wire for the interconnection, and use some type shielding tape around the switch and capacitors. The capacitors will be very sensitive to oscillations without some added shielding around the circuit.

Inside the amp, the filament wires run left to right. -------------------------------
the audio path and components runs front to back I I I
This 90 degree difference in layout should be maintained to minimize added filament buzzing. (or add shielding)

3. The resistors add hiss, but you can use bulk metal foil audio resistors or wire wound to keep the noise lower.

4. The switch may add a loud POP when you operate it....
You may have to come up with some tweak to De-POP the switch.
 
Amp Mad Scientist said:
Are you planning on drilling a hole in the faceplate for the switch?
If I were you I would use a push/pull pot DPDT switch on the volume pot instead of drilling any holes.

View attachment 104352
Click to expand...
nope doing my best to avoid drilling that’s why I’ll be using the low input jack hole. Maybe my post wasn’t clear enough. I apologize. I’m removing the low input Jack and putting a switch there, in theory
 
psychic fuzz said:
Hey all :victoire:

Newbie here.
Click to expand...
First of all…
Welcome to TTR… :cheers:

I’ve got two 2204 amps, and with each one, I have modded them with bright cap switches. On the following pic of amp-1, the first position is a stock 1000 pF. Second position is NO CAP. Third position is a 4700 pF. Using a SPDT On-Off-On switch:
IMG_1507.jpeg
No popping switch noises either! I might end up replacing the 4700 cap with a much smaller value like a 250 pF.

Amp-2 bright cap switch is set up a little different, but I need to fire up the PC to confirm the details.

I’m very interested in your approach of a 3-way bright cap switching circuit. I can’t wrap my head around how yours is supposed to work. What value for each cap, and what total effective value for each position are you considering?
 
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syscokid said:
First of all…
Welcome to TTR… :cheers:

I’ve got two 2204 amps, and with each one, I have modded them with bright cap switches. On the following pic of amp-1, the first position is a stock 1000 pF. Second position is NO CAP. Third position is a 4700 pF. Using a SPDT On-Off-On switch:
View attachment 104355
No popping switch noises either! I might end up replacing the 4700 cap with a much smaller value like a 250 pF.

Amp-2 bright cap switch is set up a little different, but I need to fire up the PC to confirm the details.

I’m very interested in your approach of a 3-way bright cap switching circuit. I can’t wrap my head around how yours is supposed to work. What value for each cap, and what total effective value for each position are you considering?
Click to expand...
Thanks for including the pic! Suprisingly hard to find a diagram or pic of a Marshall bright switch.
I may just make it easy on myself and go on off on, but I don’t like how the amp sounds without the cap. So was hoping to do 3 options including the stock.

Honestly I have no idea if that switch wiring will work, like I said I just saw it on a forum lol I’ll try and find the link.
 
psychic fuzz said:
Im a dumba$$ because I can't seem to wrap my head around that diagram :unsure:
Click to expand...
I forgot to mention that in that Ceriatone diagram, that is a On-Off-On DPDT switch that is only using one pole. Just like a SPDT switch.

But I think I got the On-On-ON DPDT switch figured out! I can see the advantage this switch has because you can arrange the resistors in any order to correspond to the position of the toggle. Tada...:
3 Way Brite Cap Switching.png
 
syscokid said:
I forgot to mention that in that Ceriatone diagram, that is a On-Off-On DPDT switch that is only using one pole. Just like a SPDT switch.

But I think I got the On-On-ON DPDT switch figured out! I can see the advantage this switch has because you can arrange the resistors in any order to correspond to the position of the toggle. Tada...:
View attachment 104377
Click to expand...
Awesome! I think that’s they way I originally drew it out, but yours looks much prettier
(y)
 
So went to get this project started and unfortunately the input jack hole is 1mm too small. Measures about 10.6 mm

The switch jack is 11.7mm

I could open it up easily with a drill but I’m sticking to my vow of not drilling anything. Gonna have to rethink this. Maybe a push-pull. Oh well!
 
psychic fuzz said:
So went to get this project started and unfortunately the input jack hole is 1mm too small. Measures about 10.6 mm

The switch jack is 11.7mm

I could open it up easily with a drill but I’m sticking to my vow of not drilling anything. Gonna have to rethink this. Maybe a push-pull. Oh well!
Click to expand...
Bummer. I was rooting for you. I hope you get something figured out.
 
psychic fuzz said:
The switch jack is 11.7mm
Click to expand...
What kind of brand and type of switch are you trying to use?

You must be using a full size toggle switch that requires a 1/2” opening. Those are way overkill for what you need. A mini toggle needs a 1/4” or 6.35 mm opening… and maybe one washer between the faceplate and securing nut.

A push pull 1 Meg audio pot for the Pre Amp control would be perfect if you want just two options for the bright cap switching.
 
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syscokid said:
What kind of brand and type of switch are you trying to use?

You must be using a full size toggle switch that requires a 1/2” opening. Those are way overkill for what you need. A mini toggle needs a 1/4” or 6.35 mm opening… and maybe one washer between the faceplate and securing nut.

A push pull 1 Meg audio pot for the Pre Amp control would be perfect if you want just two options for the bright cap switching.
Click to expand...

Well I was hoping to the use the existing input jack hole on the amp but you're right I wasn't thinking.

For some reason I was thinking a switch and input jack were the same size, I spaced out. Although it was only a 1mm difference.


There were only 2 options, this size (11.7mm/.46") or mini (5.3mm/.21")
 

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