MixBuzz

The MixBuzz 500 is a modern recreation of the classic SSL bus compressor. The Ramshackle Audio build prescribes some specific options and components to make the build as easy as possible.

The MixBuzz 500 has a few options for choosing different components. To make things easy, our BOM sticks to the following options:

1. The sidechain VCA is used

2. The threshold points are fixed (this means we used fixed resistor values in some places, rather than trimpots)

3. We use a single THAT2181C for the VCA. This reportedly gives a more characterful sound. The other option is to use 4x THAT2181A for each VCA board.

Notes

• R4, R39 and all resistors marked fb are ferrite beads

• A 5K1 resistor is used in place of RV1 (it is for setting the threshold point)

• TR_TRM should be omitted. (It is for setting the threshold 'zero')

• Do not install SC_SYM and R33 (only 1 50k trimpot needed for SYM)

• Ignore the pads marked SJ1, SJ2 and SJ3

• R87 and R98 are 1/6 of the relay (RREL) coil resistance. This has been calculated for the relay given on the BOM

• Do not link JP1 on each audio board; this will enable sidechain filters

VCA Board

• In our parts kit, we supply 1 THAT2181C for the VCA board. This configuration gives a slightly more gritty, big sound. With a single VCA, we use the following component values: R3=20k, R6=0 (install a jumper), R100=909R. C1 can be lowered to 22pF

Installation Order

Audio Board

1. Starting with the audio boards, install the jumpers, ferrite beads, diodes and resistors

2. The small capacitors (non electrolytic)

3. Install the IC's and the trimpot

4. Headers/connectors and electrolytic capacitors

5. Relays

Large Control Board

1. Install all resistors and capacitors and the LED

2. Add the Lorlin switches

3. Install the potentiomenters (MAKE-UP and THRESHOLD), making sure they come to the same height as the Lorlins

4. Switch

5. Headers/Connectors on the reverse of the board

Small Control Board

1. Resistors

2. Small capacitors

3. Transistors/IC

4. Electrolytics