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Adding L-Pad to Combo Amp 
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Joined: Tue Oct 02, 2018 10:04 am
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Hi im new to this forum and really happy to begin posting.

I just acquired a Jet City JCA2212C combo amp used for an excellent price, given the amps great internals and all the modding forums online I thought it would be a great place to begin my mod journey.

I have quite a few mods lined up for this amp but the first I want to do is add in an L-pad attenuator between the amp and the internal 1x12 speaker. Essentially I am trying to do this mod https://www.instructables.com/id/Guitar-Amp-power-soak/. The amp is just too damn loud and I want to tame it a bit.

However, I want to add in this lpad with true bypass as well as a single bright switch as seen here https://www.theguitarmagazine.com/diy/diy-workshop-build-your-own-attenuator/.

While not the best at schematics Ive been teaching myself and was hoping someone who has experience with l-pad could confirm my diagram.

Schematic: https://postimg.cc/XBXrfqBh

Thanks!!!


Tue Oct 02, 2018 10:16 am
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how is a 22 watt amp with a dirt channel and a master volume too damn loud?

not intentionally being a smartass, in all seriousness. if you can't get that low enough- you may do better with solid staters, potentially with smaller speakers. you may just be fighting physics too much if its gotta be speaking volume or lower.


Tue Oct 02, 2018 11:48 am
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newholland wrote:
how is a 22 watt amp with a dirt channel and a master volume too damn loud?

not intentionally being a smartass, in all seriousness. if you can't get that low enough- you may do better with solid staters, potentially with smaller speakers. you may just be fighting physics too much if its gotta be speaking volume or lower.


But I love the tube tone and the volume pots are very sensitive wherein im playing with mm in terms of adjusting volume. I have a DSL50 half stack and in all honesty was shocked just how loud this 20watt 1x12 amp was. I also want to do this for some nice powertube breakup.


Tue Oct 02, 2018 12:02 pm
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I'm not sure anyone here has worked with L-pad. But there's definitely some techy hommies around these parts. Hopefully someone can let you know if you've planned that schematic correctly.


But I have to agree that it doesn't make much sense to me. However, don't let that stop you. If you know what you're going for and can achieve it reasonably then fucking why not? These are good amps to tinker around in. I say go for it.

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Loop wrote:
Also, I hate to bring this to light considering there are some feelings in this thread, but you misspelled "disappointed".


Tue Oct 02, 2018 12:14 pm
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i know generally why youd go with an attenuator, and i get ya- but a high gain amp like that is kind of not really designed to be run into power amp distortion.


hm.. what are you not getting out of the amp, other than too much volume?


Tue Oct 02, 2018 12:15 pm
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ALSO.. try running your amp hotter and controlling volume with your guitar volume!


Tue Oct 02, 2018 12:17 pm
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If you don't mind modding the amp a better solution is to increase the size of the phase inverter bias resistor as this will get the amp to the sweet spot at lower volumes. By default it's almost certainly 470 ohms. What you can do is pop the resistor out, then add a 470r resistor in series with a 10 to 47k pot and then add that all back in on flying leads to where the resistor was on the board. Some Mojave amps use this trick. The only down side is that there is DC on the pot so it's scratchy when it's turned. Some people prefer to just hard set it or use a switch to select one or two values. At extreme levels it'll sound a bit sucky but if you just want to tame the MV a little it's a good thing to try.


Tue Oct 02, 2018 11:49 pm
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