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I was hoping Stephen or someone could chime in and recommend the best way to do it and where. I want to add the resonance/depth and presence controls. Any help would be appreciated.

Thanks,

Brian

For feedback, try this:

Disconnect the 56K PI tail resistor from ground. Connect a 1.5K resistor from ground to the 56K resistor. Also connect a 100K resistor to the 56K PI tail resistor and then connect a wire from 8 ohm output to the 100K. The 100K & 1.5K resistors form a voltage divider for the feedback. You can adjust the amount of feedback by changing the values so YMMV.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Well I still haven't had much luck. I'm attaching a picture to help. I'm not using both channels anymore which might make a difference. I'm using the right side cap (.022) as my master volume tap. WHen I have it hooked up like this it squeals like crazy. From what I have read on 18watt.com that may be solved by reversing the OT wires to the plates, but mine are wired correctly per the instructions. Hope someone can help me out.



Thanks,

Brian

Feedback is not correct. Connect a 1.5K resistor from ground turret to the 56K resistor. Also connect a 100K resistor to the 56K PI tail resistor. Then connect a wire from 8 ohm output to the 100K. Dont connect it to the coupling cap of the other channel (even though it's not used.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

email sent for 18wTRex that might help you out.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I got it to work and work very well. I may decide to tweak some values to my taste. From my pic above I added a 1.5K resistor from the IN of the pot to ground for the voltage divider. I also had to swap the OT Primaries which got rid of the squeal. The amp is still nice and quiet. I'm going hook up my other pot later for the resonance control which should be easy now since everything is working. Thanks for the help Stephen.

-Brian

Good news. What did you notice in the tone?

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

It seems to have tightened up the amp just a bit (which is OK), and when turned up it adds some sparkle to the top end. When your say chugging on the low E string it sounds a bit more percussive, which was what I was hoping for. I still have lots more tweaks to do, but this one was one of the bigger ones to this already proven design. When I get a little bit further I will post some clips so you will be able to decide what you think.

I also just added in the depth control and it worked as planned too. It adds some nice subtle lows that are more noticeable at lower volumes but still sound sweet as the volume increases. Overall the mods were simple after figuring out the NFB piece and the add some flexibility since I'm only using one channel now. Now I will just be tweaking things to suit.