Mods for my 2204 build - switchable JEL and #34?

ledvedder

ledvedder

Well-known member
Now that I've got my 2204 build complete, it's time to start modding! I can't leave well enough alone.

I'm thinking about a switchable Jake E Lee / SIR 34 type of thing with a few 3 way switches.

Switch 1 - 3k3/0.68 parallel with 10k cathode, 220k from gain wiper to ground on one side.
0.01 cap in parallel with 10k, 150k from gain wiper to ground on the other side.

I'll probably put a 22uF bypass cap permanently on the 820r at v2a. But I'm thinking another switch to add a 0.68 in series.

And maybe another switch to choose either 0.022 or 0.0022.

There are a few other changes with the JEL and 34 mods, such as plate resistor bypass caps, but I haven't figured those out yet.

I'm curious to hear everyone's thoughts about these ideas.
 
I’ve tried both and wasn’t a big fan of either, but my goal was tons of gain. I prefer something like a #39. If your not going to add an additional tube a 2.7k with a .68 on v1 A and B,(220k plate) followed by a 0.0022 (or something in between a .022 and 0.0022) and switchable diodes works great for my taste. And a 2200pf to 4700pf bright cap. That combos bright and punchy yet thick.
 
Chubbs said:
I’ve tried both and wasn’t a big fan of either, but my goal was tons of gain. I prefer something like a #39. If your not going to add an additional tube a 2.7k with a .68 on v1 A and B,(220k plate) followed by a 0.0022 (or something in between a .022 and 0.0022) and switchable diodes works great for my taste. And a 2200pf to 4700pf bright cap. That combos bright and punchy yet thick.
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Pretty much this. I like the 36/39 mod more but you’ll need to add another tube.

Why not just do an Aldrich mod by turning the cathode follower into a gain stage and plate feed the tonestack?

I’d also still permanently add a cap across the 820 but play with the value. Somewhere around 2.2uF will be more than enough. I don’t see a need for the 0.68 with such a low value cathode resistor.
 
glpg80 said:
Pretty much this. I like the 36/39 mod more but you’ll need to add another tube.

Why not just do an Aldrich mod by turning the cathode follower into a gain stage and plate feed the tonestack?

I’d also still permanently add a cap across the 820 but play with the value. Somewhere around 2.2uF will be more than enough. I don’t see a need for the 0.68 with such a low value cathode resistor.
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I'm not familiar with the Aldrich mod.
 
ledvedder said:
I'm not familiar with the Aldrich mod.
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You are now.

Of course you’ll need to tune values but start with what works. 220k plate, 1.5k cathode, no caps across the cathode.

Use a good quality 0.047uF cap as the blocking cap to the 33k slope resistor.

Don’t change anything else in the amp. Try that and see what you think. Easily reversible if you don’t like it (which I doubt you won’t)

This isn’t the exact Aldrich but is closer to the gain level you’re looking for and it won’t botch the tone with all of these switches and mods that annoyingly thin amps out really bad.
 
glpg80 said:
You are now.

Of course you’ll need to tune values but start with what works. 220k plate, 1.5k cathode, no caps across the cathode.

Use a good quality 0.047uF cap as the blocking cap to the 33k slope resistor.

Don’t change anything else in the amp. Try that and see what you think. Easily reversible if you don’t like it (which I doubt you won’t)

This isn’t the exact Aldrich but is closer to the gain level you’re looking for and it won’t botch the tone with all of these switches and mods that annoyingly thin amps out really bad.
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This is on v2b?
 
ledvedder said:
This is on v2b?
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Yes V2b

Tap the voltage for the plate from the same node as the 820 ohm stage.

For the voltage divider into the grid of V2B, try 330k/1M. This is a starting point but try this setup first. Then you can try various resistors in parallel with the 1M to ground and see what final value you like.
 
glpg80 said:
Yes V2b

Tap the voltage for the plate from the same node as the 820 ohm stage.

For the voltage divider into the grid of V2B, try 330k/1M. This is a starting point but try this setup first. Then you can try various resistors in parallel with the 1M to ground and see what final value you like.
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Are there any schematics or layouts for this?
 
ledvedder said:
Are there any schematics or layouts for this?
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it’s no different setup wise than the other 3 stages of your amp. You’ve built quite a few other amplifiers, it’s a very basic starting point that’s all.

If you need a schematic I can draw one up.

Layout wise that’s why it’s called modifications. It’s not stock at that point so you’ll need to be creative. I like to mount strips to the tube socket screws but everyone is different.
 
Similar to this?
rocco mod.jpg
 
Tweak the 1M, stock it won’t sound 100% IMO. You can parallel values with it until you find what you like. Connect a 1M pot in parallel to it and turn the knob until it sounds good. Solder that value resistor across it and you’re good.
 
glpg80 said:
Tweak the 1M, stock it won’t sound 100% IMO. You can parallel values with it until you find what you like. Connect a 1M pot in parallel to it and turn the knob until it sounds good. Solder that value resistor across it and you’re good.
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Just so I'm sure, the 1M/330k divider replaces the 470k-470pF/470k divider?
 
ledvedder said:
Just so I'm sure, the 1M/330k divider replaces the 470k-470pF/470k divider?
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Nosir, it’s new. Remember you’re replacing the cathode follower stage. Currently the grid of the cathode follower is attached to one side of the 100k plate resistor of the 820 ohm stage and has about 150V DC on it.

You’re going to disconnect the cathode follower stage/wiring and begin with a 0.02uF cap to the left and build up the stage drawn.

Let me know if you need more guidance! You got this and you’ll love the result :rock:
 
glpg80 said:
Nosir, it’s new. Remember you’re replacing the cathode follower stage. Currently the grid of the cathode follower is attached to one side of the 100k plate resistor of the 820 ohm stage and has about 150V DC on it.

You’re going to disconnect the cathode follower stage/wiring and begin with a 0.02uF cap to the left and build up the stage drawn.

Let me know if you need more guidance! You got this and you’ll love the result :rock:
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Thanks! Yeah, I'm walking through the schematic and just realized it's net new. I'm still learning this stuff, so I really appreciate all of your guidance! 🤘
 
Last night, I quickly hooked up a switch to switch in some of the changes for the JEL mode, just because I was curious how it sounded and felt. It seems to work, except the sustained notes sort of begin to putter out as they fade while in that mode. Like a static-y kind of effect while they fade out.
20220901_220732.jpg
 
I've been doing a lot of searching, trying to find some thoughts and opinions about this method. I'm not finding many good things about it.
 
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