eric g's synth DIY
DIY synths:
EHS-30 modular synth
Synthi mu, Synthi A clone
EHS-33 Fatfoot pedal synth
MS-911 semi modular synth
EHS-26 voltage controlled sampler
Modifications:
1. Hard sync and sync sweep by filter contour generator. Rotary switch for Off/Sync/Sync sweep.
2. Left hand performance pot. Cut-off frequency in normal mode, sync freq in sync mode, sync contour amount in sync sweep mode.
Rotary switch and pot are placed at the left hand panel, instead of the Release and Glide jacks; i.e. no drilling.
1. MG2 output level increased. Great for extended PWM and resonator sweeps.
2. MG2 rate decreased. I want the resonator to be swept more slowly.
3. Ensemble speed decreased. I don't want that vibrato effect. Now it sounds more like a Roland chorus.
1. Extra LFO for PWM added.
2. VCO ext CV trimmable to 1V/oct.
3. Vibrato switch added.
4. Sub osc added.
5. Cut-off slider added.
6. Filter overdrive added.
7. VCF keyboard track.
8. VCF extra CV input.
9. Audio bandwidth, bass and treble, increased.
10. VCF sustain level not locked to 0 Volts.
1. Input jack for PWM added.
2. VCO ext CV trimmable to 1V/oct.
3. Vibrato switch added.
4. Cut-off slider added.
5. Filter overdrive added.
6. VCF keyboard track.
7. Audio bandwidth, bass and treble, increased.
8. VCF sustain level not locked to 0 Volts.
1. VCO ext CV trimmable to 1V/oct.
2. VCF extra CV input.
3. MG max freq increased to audio.
4. Audio bandwidth, bass and treble, increased.
5. EG1 sustain level not locked to 0 Volts.
1. Channel A and B +/-5 V outputs are changed to +/-2.5 V.
2. Channel C 0-5 V output is changed to +/- 2.5 V.
3. 1k resistor on all outputs (for trimming) are removed to decrease output impedance. This is to enable connecting multiple synths without loss of scale.
4. 470 ohm resistor on all outputs are removed to decrease output impedance.
5. Reset switch added.
6. Reset step rotary switch added.
1. Two separate LFOs for chorus (i.e. PWM) are added. Fixed rate, different rates for upper and lower voice. No panel tampering.
2. Upper VCO is routed to lower saw-mixer, replacing 2', for a two-VCO lower voice possibility.
1. KCV output jack added.
2. S-trig output jack added.
3. Ext input jack added.
4. Some presets are changed, i.e. noise added and attack and decay time increased on some brass and woodwind instruments.
1. Filter Q decreased.
2. Power LED added.
3. Keyboard port added for bass pedal connection.
1. The Q value of the filters is increased by changing all Ra & Rb from 4.7k to 2.2k and all Rc & Rd from 2.2M to 4.7M. Also, a buffer OP-amp is inserted after the level pot on input 1 and input 2 respectively.
2. The 4.9kHz filter is changed to the same filter response as the other filters by changing C2, C3, C21 & C34 to 330p.
These mods provide a much better speech recognition than the original design.
3. C75 in the mic direct path is decreased to 3.3n to provide a sibilance bypass.
1. DIN sync input added.
1. Trig outputs for analog sequencers and synths added. 1/1, 1/2, 1/4, 1/8 and 1/16 note, positive or negative pulse.
DISCLAIMER: I will not take any responsibility for any damages from performing the mods above