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Gain switch (JCA100H) vid


Duesentrieb

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Ok, I have went ahead and soldered the 66k (two 33k's) to the top left.. I have soldered what will be the ground wire to the middle left, and the 100k to the bottom left.. Does that look right to you? I realize the soldering is a bit much, but I will be more delicate on the board..

switch-solder.jpg

And to recap.....

2112Detail1.jpg

I will solder the other end of 66k (top left of switch) and 100k (bottom left of switch) to the right side of R52 (closest to the input) in the pic above..

I will test both sides of R29 (grey) or R26 (by input) for a suitable ground for the other end of the ground wire (middle left of switch) to run to..

So what I have left to do is drill a 1/4" hold for the switch.. Test R29 or R26 for ground, and make the appropriate soldering (delicately) to the board...

Am I missing anything?

2112Detail3side.jpg

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So, I've changed some parts to SLO specs and raised the voltages to its specs as well (preamp). Sounds cool(er) IMO.


Btw. Drew: since you're using a BiasRite - how many volts do you read off the plates in your amp?

I'm asking because my guess is that in the US you will get voltages closer to the "originals" (480V) - I'm on 230V prim and the PT is wired for 240V (which means some volts less, about 20V in the B+).

Thanks.

 

 

I'll take a look at tomorrow.

 

 

Amp sounds good! I dig the 3 way switch for the normal channel! It'd be cool to have it foot switcable to one or the other value as an on/off. To be able to go from a clean to a semi dirty sound without having to use an external boost pedal.

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Thanks Drew.


Its an Edwards JS, Shiny. Merci
:)



Steve: No - pots facing you, solder it to the right side !!!!

Where the "VR7" label is.


Ground probably R26 (at the side which is closer to the frontplate)

Make sure with a beep that this is the ground.



Ok, sorry.. So it is the side farthest from the input of R52 with the VR7.. I thought by pots facing me you meant the back side of them (like in the pic) facing me.. I am glad I clarified that..

I will test for ground to be sure.. Can I still use R29 if one side is ground? There is a metal lip about an inch hanging over the front of the board making soldering there a pain in the ass.. I can use R26 if I have to, but it will be awkward soldering there..

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Thanks. My guesses (sp?) were correct about the resistors . . .

 

 

Thanks for confirming.. It never hurts.. I was sure your guesses were correct anyway on R52, and which side of it to use (the side with "VR7")..

 

I intend to use R29 for ground.. My guess is that it is the side closest to the edge of the board (away from V1), but I will beep to make sure...

 

Thanks for all of your help Olaf.. Others with JCA2112RC's will be able to use this thread to do the mod as well..

 

I will keep you informed and let you know if I have any more questions..

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The problem I see here Steve, is that the volume drop between the two sounds is too big to use it live without further modifications of the amp (doubling the "master", installing a second - then you need a relay and some kind of extra power supply internally (a 6V transformer with supply (rectification, filtering and such)), so thats a lot of mods.

Not for me, but for you guys playing around with 120V and such . . .

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The problem I see here Steve, is that the volume drop between the two sounds is too big to use it live without further modifications of the amp (doubling the "master", installing a second - then you need a relay and some kind of extra power supply internally (a 6V transformer with supply (rectification, filtering and such)), so thats a lot of mods.

Not for me, but for you guys playing around with 120V and such . . .

 

 

I understand.. It's more of a recording (non-live) mod..

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Actually if you put the gain on 1.5 or so and crank the volume, you get a cleanish sound that can be boosted with pedals for a live application.. I am thinking about getting a 50H later on, and will probably do this same mod to make the clean channel more manageable..

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The problem I see here Steve, is that the volume drop between the two sounds is too big to use it live without further modifications of the amp (doubling the "master", installing a second - then you need a relay and some kind of extra power supply internally (a 6V transformer with supply (rectification, filtering and such)), so thats a lot of mods.

Not for me, but for you guys playing around with 120V and such . . .

 

 

This is the same sort of problem that zach has with the titan. It has the clean/crunch switch for the rhythm channel of the amp but there's a huge volume increase going from clean to crunch setting.

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Well, he should be able to solve that, add another volume (and also a gain pot) and switch from VTL-switching (if he should use them) to relays . . .

. . . and then make it at least double eq-ed or three eq-ed and then add a better loop and then add midi (or at least a more sophisticated switching matrix) and so on . . .

 

Thats pretty much "my evolution" of building amps, I've started with SLO-clones and did exactly that.

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