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AM 8005 Module - Roland SH-5 Filter Cube
You Tube Video of SH-5
Overview This is the centre section from the unusual and rare Roland SH-5 analog mono synthesizer from 1976. The AM 8005 Filter Cube has:
- A 4-input audio mixer with filter selection
- Ring Modulation
- Voltage Controlled Filter with 3 modes: BP, LP and HP
- Dedicated Band Pass Filter
- LED indication of output signal level
The first two features are contained on the AM8002 module, whilst the 2 filters form the AM8005. The SH-5 synthesizer has been used by many famous
musicians including the Ozric Tentacles. Technically its a tour de force with 4 filter modes (hence me calling the clone a Filter Cube), and 3 separate filters:
- 1-pole HPF based on OTA (CA3080)
- 4-pole resonant diode ladder LPF with voltage control
- 1-pole resonant BPF filter
The SH-5 filters create a very interesting sound, based around the diode LPF which is not unlike the EMS VCS3 diode filter.
Original Circuit
The original design by Roland is based around a 4-pole low pass diode filter, very similar to the one used in the System 100, and using diodes rather than transistors. But that is just a starting point, there is a 1-pole High Pass Filter which can be used in conjunction with the diode LPF to create Band Pass filter responses. Then there is a dedicated Band Pass filter with resonance, AND a ring modulator based on the MC1496 chip. That is a lot of power, coupled with an audio mixer which has both level and filter selection.
AM8005 Module I have simplified the SH-5 design just a little, by having four audio input sliders rather than five - but the rest of the design has been replicated completely, with just a few improvements. I have
changed a few of the resistor values in the BPF to give a better response, and feed the HPF filter straight out rather than via the LPF, I have managed to get the inversion working through the LPF yet. The LPF filter does not break into
oscillation,
The original TA7136 SIP Op Amps have been replaced with modern FET Op Amps, such as the TL071 and LT1012 for CV signals. The original Japanese transistors
have been used, such as the 2SC945 BJT and 2SK30 JFET. The hard to find ITS1276 Japanese dual transistor and the base BJT pair of the ladder have been replaced with LM394's matched pairs - although even these are obsolete now!
There are four PCB's
- Pot PCB: holds the 4 sliders and 4 switches
- RM PCB: the Ring Modulator, and active input mixer
- VCF PCB: the low and high pass filters
- BPF PCB: the Band Pass filter and final audio mixer and LED driver
The AM8002 module has the following front panel controls:
Signal Input Levels (x4) - fourth is pre-wired to Ring Modulator output Four 3-way switches to route these signals to VCF, BP or both
The AM8005 module has the following front panel controls:
3-way switch for VCF filter mode - HP, LP, BP Frequency Cutoff and Resonance for the VCF Keyboard CV level and (x2) VCF Modulation CV levels for the VCF Frequency, Level and Resonance for the BPF
The Pot PCB is mounted to the left hand side of the panel with the Ring Modulator PCB attached behind it. On the right hand panel there the main VCF
and the BPF PCB's are attached via Pots. There are five 3.5 mm jack sockets mounted at the base of the left hand panel, and one on the right hand panel these are:
Signal Inputs (x3) CV Inputs (x2) Signal Output
Front Panel
The front panel has two sections; the first module is the AM8002 Audio Mixer and Ring Modulator with 4x slide pots and 4x three way slide switches. The pots control the level from 3 audio sources plus the ring modulation from a mix of Signal A and B. The slide switches route the signals to either or both of the filters.
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