Flight Of Harmony V'Amp VCA Barebones Pack

via this auction

"What is it?
The V’Amp is a combined voltage-controlled amplifier (VCA) and ring modulator (A.K.A. ring “mod”), with a little bit extra. The effect of a VCA is known as amplitude modulation (AM), while a ring mod is a frequency mixer, an effect known as heterodyning.
Heterodyning takes two frequencies –– traditionally known as the “carrier” and the “modulator” –– and mixes them, producing the frequencies that are sum and difference of these two at the output, i.e., if the carrier is 220Hz and the input is 400Hz, the sum frequency will be 620Hz and the difference frequency will be 180Hz. Ring modulation is used to generate non-harmonic (not an integer multiple of the base frequency –– 2x, 3s, etc.) frequencies, which are necessary for, say, metallic sounds like cymbals. A perfect heterodyning will have neither the carrier nor the modulator present in the output. While achievable on paper, this is extremely difficult to accomplish in reality, so some bleedthrough of one or the other (or both) is often present to some small degree.
While typical ring mod devices are designed specifically for frequency mixing, the V’Amp allows you to not only change the degree of the mixing and the level of the bleedthrough, but can also be used as a VCA at the same time. The mixing can be varied from VCA (carrier only), into ring mod, then out of ring mod into inverting VCA (inverted carrier).
Mod1 is the modulator. Envelope and Mod2 should be thought of as VCA (AM) inputs, but separate. Envelope is a straight VCA control voltage (CV) input, while Mod2 is an attenuated/variable CV input.
The morphing of the Mod1 function is not fully controllable by CV and must be varied using the knob to access the full range of variation. However, experimentation has shown that a DC offset voltage applied to the Mod1 input can be used to voltage-control a small range of the function morphing.
As with all f(h) products, the V’Amp was engineered towards maximizing functionality while keeping cost as low as possible. If some aspects of the unit seem awkward, it is most likely due to this. The goal is to make unique, useful, enjoyable, and affordable instruments, not just hoover1 out your bank account, so each module requires a little patience and experimentation before their secrets become apparent.

Controls
Mod1: This is the magic knob, controlling the frequency mixing as described in the introduction. Mod1 varies the amount that the Mod1 signal modulates the input signal, as well as controlling the polarity of the output: positive from 7:00 to 12:00, negative from 12:00 to 5:00.
Mod2: This is the Mod2 input attenuator control.
Offset: Think of this as an internal gain control. The Offset can be used to raise or lower the general level of the output signal, but it also can be used to fine-tune the interaction of the various CV inputs. Try it, you’ll understand.
Input: This is the input level control. Just like a volume knob – clockwise increases level, counter-clockwise attenuates the signal level.

Output: Output level control. Acts the same as the Input control. Jacks
Env in: Unattenuated VCA CV input. Mod1: Modulator signal and/or CV input. Mod2: Attenuated VCA CV input. Input: Signal (or carrier) input.
Output: The output jack."