Dear Dieter,

I know that the production design of the A-110-6 quadrature trapezoid VCO has probably been finalised, but hopefully this is something you would consider implementing I was reading J. Donald Tillman's article on quadrature trapezoid VCO design:

http://www.till.com/articles/QuadTrapVCO/discussion.html

And discovered that it is possible to voltage control the phase shift Would this be possible on the A-110-6 In my opinion it could become one of the most powerful features of this VCO.

Voltage Controlled Phase Shift

The quadrature trapezoid core also enables the imple mentation of voltage controlled phase shift over a multiple cycle range.  I'll cover the details of this in a later article.

While the Yamaha DX7 synthesizer is well known for its use of FM Synthesis, it really works with phase modulation. (The phrase  FM Synthesis  is used as a generic term to describe both frequency and phase modulation.)  So analog versions of many DX-7 algorithms are good applications for voltage controlled phase shift.

Audio rate phase modulation can produce some amazing glassy FM-like sounds without pitch drift. In eurorack Malekko Richter Oscillator II and Schippmann CS-8 Omega-Phi have phase modulation capabilities but since adopting a 100% Doepfer A-100 system I feel we are missing out on these sounds. At LFO rate we can achieve chorus / supersaw like sounds.

It is possible to approximate similar s ounds via Lin FM on A-110-4, but the pitch drift makes it less suitable for pitch perfect musical applications. Here is an older demo of mine exploring audio rate phase modulation feature on the Richter Oscillator II:

https://soundcloud.com/sfx-lab/malekko-richter-oscillator-ii-phase-modulation-demo

Is this something you have considered or would consider implementing on the A-110-6 or as a follow up model

Thank you very much! Really looking forward to exploring your new designs.

Best wishes,

Vytis Puronas