Summit’s architecture essentially comprises two complete, identical, but entirely separate synthesisers with a single set of controls. Depending on the type of Patch in use – Single or Multi – the two synths either work in an identical manner, with each control affecting the same parameter in both synths simultaneously (Single Patches), or they work differently, to generate Parts A and B of a Multi Patch, with each control affecting its parameter in only one of the two synths at a time.
Each of Summit’s two Parts uses eight separate voices, which are treated independently throughout the remaining signal chain. The voices are synthesised digitally in a Field Programmable Gate Array (FPGA) using Numerically Controlled Oscillators running at an extremely high clock rate, resulting in waveforms which are indistinguishable from those using traditional analogue synthesis.
Each voice is a mix of the outputs of the three oscillators; when you adjust one of the oscillator level controls ,
or
you are effectively adjusting the level of eight voices simultaneously. The subsequent elements in the signal processing chain are entirely in the analogue domain. Note that distortion can be added in several places – before the filter (Overdrive
), after the filter (FltPostDrv in the Voice Menu) and after final voice summation (Distortion Level
). The sonic effect can be quite different in each case.
Note that the time-domain effects (FX) – chorus, delay and reverb – are digitally generated within the FPGA as well. The stereo effects send into the FX processing section is taken from post the main VCA, so all distortions added to the signals are processed by the FX. The FX return signal is added back to the same point in the signal path.
Summit also has a pair of audio inputs (see at Rear panel): these allow you to connect external audio sources – e.g., from other synth modules - and then use Summit’s extensive processing capabilities to treat their sounds. The two ¼” jack sockets are intended for the left and right signals of a stereo pair, but you can connect a mono source to the LEFT input only if you wish.
Page 3 of the Voice menu enables these inputs and lets you choose whether the external signals connected are to be mixed with each of the 16 voices at the input of the analogue filter section, or to be added to the synth sound “post-VCA” at the output of the filter section. The first option – PreFilt in the menu – effectively adds the external signals to Summit’s own internally generated sounds, and they will therefore undergo the same signal processing as the native synth sounds, including analogue Pre Filter Overdrive and Pre-VCA Distortion.
The second option – PostFilt in the menu – lets you route the external signals directly to Summit’s FX section, where they can either be added to the native synth sounds, or have one of the FX sections allocated to them exclusively: this selection is made on Page C of the Settings menu. Because the outputs of the FX sections may be routed to either the main or auxiliary outputs, this allows you to add FX to external signals entirely independently of any synthesiser functions.