Boss Katana 50 MK II Speaker Out Mod

I love the BOSS Katana amps.  I started with a MK I 100 Watt head.  Recorded an album track with it direct into one of my Wolfboxes (which I have not blogged about apparently).  Jammed and rehearsed with it a lot.  MK II is vastly superior to MK I mainly due to the INDIVIDUAL KNOBS for each effect.  Those half and half knobs were a nightmare.  Extra amp modes are also welcome.  The "variations" are all just a little brighter sounding than the MK I amps.  Useful.

The Katana 100 needs a global -2 or -3 dB EQ at about 4 kHz.  It's really sharp sounding stock.  This is an easy tweak with the Boss Tone Studio software.

The Katana 50 combo needs this on the clean amps mainly, dirty sounds are fine "stock."

Katana 100 feels a little more powerful in the hands, likely due to the beefier power section.  Katana 50 feels a little more midrangey and softer in some ways, which you could expect from a less powerful amp.  A little less bass authority, a little less top end push.

I wanted a speaker out on my Katana 50 so it can be my ultimate "any scenario" swiss army amp.  Combo it up, direct out, or launch it to Pluto with a bigger speaker cabinet.

The 100 Watt amps are just simply too loud.  People were constantly complaining at me to turn down, no matter where I took it.  I am talking about some loud cats too.  Katana 50 is more reasonable, and has the benefit of lower price, as well as a 25 watt mode for medium temperature porridge.  It feels a lot finer in terms of small volume control changes.  I never was able to use the 100W mode on the Katana head.  The 50 is also painfully loud through a 2x12 in 50 W mode.  Which brings me to my speaker out mod!

Got some hardware from Lowes.  A junction box, some M4 bolts and nuts and washers.  Drilled some holes.  Mounted the box to the cabinet.  Punched out the top hole in the junction box, fed wires through.  Clipped off the spade connectors.  Soldered a plastic 1/4" jack from Mouser for isolation (might not be needed).  Made a new short speaker cable to connect to the combo speaker.

FOR CLARITY: Red wire goes to tip of jack, black wire to sleeve.  Use heavy gauge wire for your short speaker cable.  Probably 18 gauge would be enough for this six inch run.

There is no room inside the chassis for a speaker jack, I checked.  PCBs are in the way.  I would have done it that way if it were possible.

Took a little longer than I expected for some reason.  The mod ended up working solidly.  Now I can use any speaker I want.  Here's the pictures to prove it.

These amps are fantastic once you get your sounds dialed in.  The FX are noteworthy also.  No brainers for $200-300.

Emerson Em Drive - DIY build - Old Turkey Head - Layout and Schematic

I started with IvIark's layout, it "worked"

The problem is crackly decay on the distortion, and too much distortion.

I have seen at least 3 different value resistors for the collector resistor in various internal pictures of original Emerson pedals posted around the web.  The 2Megaohm resistor seems to be constant.

The obvious answer and solution is that they are selecting resistors for each transistor that they test.

The easiest way to do this in a DIY build like this one is to simply remove the bias resistor and replace it with a 10K trim pot.

When I biased my 2N5088 to approximately 4.6 VDC on the collector, I was given a smooth, pretty gain sound with a gradual transition to heavy clipping with the Pico pot on full rotation.

This is a wonderful sounding pedal, and I recommend it.  I've had the privilege to play a "real" one and the DIY version is every bit as satisfying.  I'm currently using it in front of a Vox AC30HW but I'm sure it would work with almost any amp.

This is a very easy build.  There is some mojo in the caps, in my opinion.  I really like the way Paper in Oil caps sound and I use them at almost any chance that I get.  Just really smooth and clean with the tiniest hint of warmth.  I'm sure some nice film caps would do well too.

You can play around with transistor selection, and bias voltages, if you want to get tweaky with it or explore the range of this circuit.  I just quickly arrived at a working version and left it there.

I did a version with a 220 uF filter capacitor too, because I hate noise and hiss and hum.  My pedal build with the big cap is very quiet even at very high gains, just a small bit of hiss is left.  The stock version from Emerson does not use this cap.  I will include both layouts below.