John Bowen Synth Design

Thanks for the clarifications.

One question came up: is it the case that at Mixer1 there will not be an input for Mixer1 and not be an input for Filter1? (I assume it would be that way to avoid any possibility of infinite loops...)

Other one, I'm assuming that will be: SPDIF-L and SPDIF-R inputs?

Thanks again for taking time to clarify all this stuff.

The Audio Source list includes all mixers, filters, insert FX, and VCAs. The inputs to the mixers and the filters are selected from this list. You can have infinite loops (recursive feedback) with no problem. If you select Filter 1's input as Filter 1, however, you will get no sound.

I think S/PDIF-L and -R is correct, although we only have 7 spaces for the name, so probably without the slash as you suggest.
-John B.

updated later posting.

I will make a Modular patch in Scope for this.
I'll check back in a few months when the patch is done..............
Thanks Brotha' Man ScofKid...
Glad to see 'round again.

Same here.

I'll probably do one more version, merging the PRE/POST FX blocks into the filter blocks, adding the 2nd AM source, and then numbering correctly.

For the "simple examples": seems like the obvious top 3 might be: Filters in Parallel, Filters in Series, Filters with Feedback.

Actually, I think it's better to show the Insert FX blocks as separate from the Filter blocks, because that's how they are presented in the synth. If you were to merge them into the filter blocks, it could be misleading....

The harder part might be to show that both the Mixers and the Filters can choose from the same Source List for inputs.
-John B.

I tried to show direct input in the latest diagram. That was what that extra line at the start above the Mixer was for.

But clearly even that might not suggest the full flexibility here.. I suspect you can have 4 inputs into Mixer-1, and still select a direct source at Filter-1, and then select Mixer-1 as the input at Filter-2, for example.... It has occurred to me to draw some rotary selector icons at the filter start and amp start locations.

I'm trying to come up with a "short-hand" way to remind myself of approximately how the signal path fits together.

updated later posting.

John,

I would like to ask:

1. How many modulations sources can modulate a filter? are their depths/offsets adjustable?

2. How many modulation sources can modulate an oscillator? are their depths/offsets adjustable?

3. Is there provision for HEADROOM either to accomodate resonance build-ups or modulation of levels? If not is there some gain compensation circuit for resonance?

4. Is it possible to route the output of the FX section back to the mixer? By looking at the signal flow, maybe it's possible to do physical modeling:

a. Short burst of white noise (either shaped from a AD) or directly from a small sample in order to provide the initial excitation -->
b. Input mixer that provides a z-1 function for feedback IF there's provision to route the signal back. The z-1 function can be a crude 6-pole lowpass filter which is used in a lot of Karplus strong models -->
c. Delay lines: there is a delay FX but I wonder if it can be stacked, i.e. used multiple times (maybe even at the expense of other effects) so as to provide the tuning.

Regards,
Yannis

I am STARVING for a manual in pdf form.

updated later posting.

For the Amps, just add another red dotted feedback line for all the Amp Outputs-same as with the filters & mixers.
-JB

ThreeFingersOfLove wrote:John,

I would like to ask:
1. How many modulations sources can modulate a filter? are their depths/offsets adjustable?

2. How many modulation sources can modulate an oscillator? are their depths/offsets adjustable?

All oscillators and filters have 4 independent modulation paths each. For each path you have the following structure:
Source - Amount - Control - Strength - Destination
The Mod Source list is quite extensive; it includes all audio sources and all control sources. The Amount is an initial amount; the Control and Strength act as a sidechain control of the initial amount. The list of Control Mod Sources for sidechain control do not include audio rate sources. Both the initial Amount and Strength parameters are bipolar.

The possible destinations depend on the section the mod paths are in - for oscillators, you have exponential and linear frequency mod, or shape mod. For the filters, you have cutoff & resonance for all, plus damping for the Comb Filter, and crossfade and frequency for the Vocal Filter.

3. Is there provision for HEADROOM either to accomodate resonance build-ups or modulation of levels? If not is there some gain compensation circuit for resonance?

The Multimode Filter has gain compensation, the SSM and Mini do not (probably also not in the Obie, but I don't recall right now). You also can control the post-filter signal level at the VCA Output level.

4. Is it possible to route the output of the FX section back to the mixer? By looking at the signal flow, maybe it's possible to do physical modeling:
a. Short burst of white noise (either shaped from a AD) or directly from a small sample in order to provide the initial excitation -->
b. Input mixer that provides a z-1 function for feedback IF there's provision to route the signal back. The z-1 function can be a crude 6-pole lowpass filter which is used in a lot of Karplus strong models -->
c. Delay lines: there is a delay FX but I wonder if it can be stacked, i.e. used multiple times (maybe even at the expense of other effects) so as to provide the tuning.

This is what the Comb Filter's Tube model is for. The Comb Filter is a delay line, and uses the onboard RAM. There is a lower limit to the frequency, based on the maximum amount of RAM allocated (I don't have the proto right now to check, but I can report what that frequency is later).
The Damping control is a 6 dB lowpass filter built into the feedback circuit of the Comb Filter. If you want to add additional filtering, at this point you will have to use 2 filters in series. The Main Effects are outside of the synth engine, and so are not integrated on a per-voice basis, as are the Comb Filters. The Main FX are not stackable, but in an 'FX Pool'. Once you use one of them in an FX Bus, it is no longer available to the other busses.

-John B.

updated later posting.

Nice work.