ELKA Solist 505

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"The ELKA Solist 505 is a little, affordable, italian, late seventies, monophonic preset synth. It provided a nice alternative to the Moog Satellite ARP Pro Soloist. It had 11 presets, all which could be changed with freq/res, attack/release, vibrato and portamento. Notably, it contained the famous Moog ladder filter. Although basic in function – no CV, no MIDI – it could produce some lovely tones, and the keyboard action was very nice indeed – something you’d expect from a renowned Italian organ manufacturer!
The preset sounds are of the same quality as on other preset synths from this time and in this price tag range. It only features a very few user editable parameters in the 'Variation' mode. But when you use the filter and change its frequency and "Wow" amount, you will notice its nice sound.

The plastic top and its metal front and bottom plate are made well enough to be used live. The two slots on the top are for a note paper support that came with the unit then (lost on mine).
The buttons on the front tell you that it was market as an organ set-atop keyboard like most monophonic preset synths. Maybe because those players did not like the knob loaded synths and preferred the easy and quick to set presets sounds more then other buyers of synths. And ELKA was mainly an organ manufacture.
The 11 presets are:

Trombone
Trumpet
Sax
Clarinet
Oboe
Guitar
Hawaiian Guitar
Violin
Flute
Cosmic
Telstar
The available parameters to change the preset's sounds are:
Slow Attack
Decay
WOW (bandpass plus resonance)
Cut-Off Filter (filter's cut-off frequency)
Vibrato Depth (the speed is stored in the preset)
Bend (auto bending at note start from low to played pitch)
The highest key doubles the note c key one octave below. This saved them one octave sensing stage of the keyboard logic. So this is a kind of hardware bug by design. This is something you have to get used too while playing. But there is one little special thing hidden under the keyboard (while all other electronic are behind the keyboard) inside:

Do you spot those two Moog transistor ladder filters?
The 10 transistors needed are left and right those 4 capacitors with the bright orange colour. At that time these filters were still under a patented. So this was most likely not 100% legal. Or did they pay for it???

Anyway, one ladders output is inverted and then mixed with the output of the other parallel ladder to team up as a bandpass filter. But most presets use lowpass filters.

The other boards inside are producing the keyboard logic, the oscillator (not a VC one, but an organ like styled), the preset waveforms, the envelopes, the VCA and the two filters.

All in all well done an solid build."