100 watt Guitar Amp Pedal

Continuing on my Stomp Amp theme; I have created a 100 watt (24V supply, 4 ohm load) guitar amplifier with FV-1 based DSP reverb and optional treble boost. It fits in a 1590b stomp box. Yes it really is a 100 watt amp!

red_scare

It has Gain, a single tone control, and reverb level control. The reverb room size is set by a resistive divider(R21 , R22) and can also be made adjustable. It utilizes a TPA3116D2 class D amplifier IC which can be configured for mono or stereo output.

Click Here for Large Schematic Image:

Stomp Amp 100_mini

The amplifier sounds delightful. The class D topology provides greater than 90% efficiency. This  eliminates the need for substantial heat sinking. The only penalty is that for guitar applications, pushing the amplifier to distortion does not sound so great. I use an overdrive pedal so I don’t care about this.

Update: I added a LED clipping circuit to make sure the input into the class D final amplifier is level limited(clips/distorts) before the final amplifier starts distorting

Link to Revised Schematic

 

pop_pcbred pcbHome brew laser printer resist circuit board

Completed Circuit Board 

Link To CAD FILES: https://www.adrive.com/public/QpRQMX/RED%20SCARE.zip

The single tone control is surprisingly versatile. It alters the level and center of a MID scoop. You can get really FAT all the way to bright twang all with one control. The circuit  can easily be modified to employ a more sophisticated tone stack if desired. The amplifier requires a 12-24V power supply with at least 4 amp sourcing capability. You can purchase a small lightweight switch-mode supply from Amazon for less than $20.00 that will work nicely. It is ridiculously small, lightweight, loud as hell, and sounds superb through a couple of 10″s or a single 12″  cabinet.

 

Quick Demo of built in Blue LED clipper limiter added to original prototype(you can see the LEDs flash as the input is clipped)

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3 thoughts on “100 watt Guitar Amp Pedal

  1. Hi Ray,

    First of all, I wanted to say I am a huge fan of this blog. I got into guitar pedals and related electronics while studying RF engineering so I think it is obvious why I love it.

    I want to give a try to this design in order to use it with a Tech 21 Fly Rig I got for small gigs and flying, so I don’t need the FV-1 reverb at all (maybe at some point I will try and add an fx loop, but not for the 1st iteration).

    Would it be necessary to do any other modifications further to just removing the FV-1 circuit, pre and post filtering and the voltage regulator? I think that’s all, but double checking is always good.

    Thanks in advance!

    Best,
    Adan

    • cool! yeah you can just remove everything at node connecting R9 and at the node at R12, the regulator and the FV1 stuff. Note: You may want a more sophisticated tone stack which easily will drop in(could use the extra room obtained by removing FV-1 in the layout), for what I do what I have is fine. Also the cap C3 has a lot of bass roll off you may prefer a 2.2 uF there or not..so be aware. Q1 is a T0-252 DPAK and needs to be any PMOS FET that is rated for 6 or more amps and 40 volts or more. You can remove this to if your not afraid of polarity issues.

      • Thank you very much for the notes!

        I quite like the jazz tones you get out of it and my Fly Rig already has a Fender-like tone stack for further sculpting so I think I will try it like this (plus I also love simple circuits that just work well).

        If I like the way the way it sounds I may work on a more advanced version that could work for both my semi-hollow and my acoustic Weissenborn with more complex features, but for now this version without the reverb looks just right for me.

        I plan to work on my own layout and will of course share it here once its done (it may take a while, I am a little bit rusty on circuit design atm, it’s been a while)

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