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PostPosted: Tue Mar 29, 2005 2:01 pm 
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A couple of months ago, I gutted an old Guild 1x12 combo and turned it into a Lightning. I ended up using the BBQ Deluxe/18Watt PT (has low and high B+ taps), a spare Deluxe Reverb OT, a 4x20 cap can, a couple of spare 20uF Sprague Atoms, and a BBQ 12" ceramic Blue Dog. Even though it's kind of a mongrel. This amp absolutely rocks.

Three other things: 1) I changed the 10K resister coming off Bass pot and replaced it with a 50k audio taper pot for a Midrange control (like a "raw" control in a Fender amp). 2) I added a bright switch. I left a 47pF cap (like a Deluxe Reverb) in the fixed position and added a switchable 150pF cap (which, when it's "on," brings the total value close to the stock 180pF...very useful since you still get some bright when it's "off"). and 3) I added a second parallel output jack in case I wanted to run a second cabinet. This amp sounds huge with two 12s in separate cabs.

This is one of my favorite circuits so far. I'm looking forward to building one that's a bit more stock.


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PostPosted: Tue Mar 29, 2005 11:31 pm 
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Holy Ghost
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What ohmage speaker did you use? Did you match the impedances or not? i.e. did you 'simulate' a 4K load on the EL84s?

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PostPosted: Wed Mar 30, 2005 10:46 am 
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I used a regular 8 ohm load for the on board speaker (the BBQ Blue Dog). The extra cab I have is a small, ported monitor shaped speaker with a ceramic 8 ohm BBQ California in it. Both loads (8 ohm or 4 ohm) happen to sound great with this amp.


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PostPosted: Wed Mar 30, 2005 11:00 am 
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I ordered a spare 500k (or was it 1M... i don't have the schematics in front of me) pot, basically just one more of what all the other pots are.. I was just gonna hold on to it as a spare in case I somehow ruined one of the others, but if I can use it for something then that would be cool.

what would happen if I used this pot as a mid control rather than a 50k one like you used? Would the fact that the resistance is 10 or 20x more basically just butcher the tone? Could I put another cap or resistor across it to 'change' it? Any ideas or suggestions would be great...

I had already planned on adding a bright switch to mine, which would completely bypass the 180p cap or not.

I haven't started laying out the chassis yet so I'm still looking at all the options :)


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PostPosted: Wed Mar 30, 2005 12:33 pm 
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Joined: Fri Mar 25, 2005 9:47 am
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My only experience with a midrange/raw control with a value that high is in the Allen V18 project amp I built. The V18 is the same thing as David's Sweet Spot amp which, in turn, is his take on a blackface Princeton Reverb. David modified the tone section by adding a 500K pot as a midrange (either 500K or 100K...I think it was 500K). Now, I love Princeton Reverbs. They're my favorite amp by far. To me, the extra grit and grunge went too far for my tastes. So, I backed the value down to 50K and I'm much happier. In my Lightining clone, the 50K (audio taper) is plenty.

David's V18/Sweet Spot had some other mods too which tightens up the phase inverter and power section and seemed to compensate for the extra grind of the preamp. However, I changed most of that back to stock BFPR values as well. So, I basically de-evolutionized the amp back to its roots.


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