Hughes & Kettner Red Box Mk. II

Here's a nice utility box for home recording or even live application (if you've run into a sound guy who hates guitar amps 😠). It's a direct box but also a cab sim (4x12). It won't run off phantom power, so just power it with a 9v wall wart or a battery. Also, I added a ground lift switch that's absent in the original. If you don't want to include it, omit the 100n cap and 10Ω resistor coming off of pin 1 of the XLR and just connect pin 1 to ground. Also, connected to the Speaker In pad should be another jack for "speaker through" (so you don't blow up your amp). Here's the schematic and original user manual for reference.

Bajaman AC30 Normal Channel

Here's Baja's AC30 Normal Channel emulator. Throw a treble booster in front of this and you're pretty darn close to nailing some Brian May tones. Schematic and discussion here on FSB.

DAM Buzzotron

For Fuzz Friday, here's the D*A*M Buzzotron with a few modifications (based on H.A.'s suggestions).The Buzzotron is a tweaked Burns Buzzaround, which can also be built on this layout. What I've added is a master volume control and a ICL7660-based voltage inverter. This allows you to power the effect with a standard +9v supply and use PNP germanium transistors like the originals. Here's the Buzzotron and Buzzaround schematics for reference.

And if you're interested in building the original Buzzaround populate the board like this:

Baja AC30TB Emulator

Another one of Bajaman's many amp emulator circuits. It emulates the frequency response of the classic Vox AC30 top boost channel, including power amplifier emulation. It's designed to fit in a 125B with top mounted jacks. Schematic and discussion on FSB here.

The input buffer stage uses a 2SK117 JFET with DGS pinout, but I've throw in an extra pad to use JFETs with GSD pinout (J201, 2N5457, etc). If you're using the 2SK117 you won't need to populate the jumper by Q1, but if you're using a GSD pinout transistor, you will need that jumper.

Budda Om Overdrive

Stumbled across this one and it seems pretty cool. It's like an Escobedo Punch-in-the-Face sandwiched between two opamp gain stages, and is very similar to the Carl Martin Crush Zone. Wide range of gain and tones on tap as well. Pots are board mounted and it'll fit in a 1590B.

Catalinbread WIIO

The Catalinbread WIIO is a Hiwatt amp emulator specifically going for the sound of Pete Townsend's Hiwatts on the Live at Leeds album. (Throwing this and a Univox SuperFuzz in the same box would be a must if you're a big fan of the Who...) The topology of the circuit (cascaded MOSFETs) is similar to the zVex Box of Rock and Catalinbread's other Hiwatt emulator, the Rah. Here's the schematic for reference. Should fit in a 1590B just fine.

Basic Audio Spooky Tooth

Found a trace of this over on the Tagboard Forum. It appears to be a highly modified Fuzzrite with an added gain recovery stage and a lot of value changes. The Saturation pot increases the output cap of the first stage, and the Fuzz pot is a pregain control. Originals use PN2222 transistors for Q1-2, which is a TO-92 packaged 2N2222A, so either will work just fine. Here's the schematic for reference and I will have fabricated boards for this in the store soon.