Orchestra Manoeuvres

I did do most of them in the hours of darkness, yes.

I’ve been thinking about and planning the power supply a good deal this week, but it’s turning into a mini project of its own and I wanted to keep the momentum up on the rest of the SS-30M.

As the weather is good and I now have an electric heater for when the evening temperature starts to drop, I was out in the garage again tonight with the aim of trying out the redesign of the Orchestra section.

You may recall that the SS-30 Orchestra effect section has four controls.

Depth - Which is actually a form of dry/wet mixer knob which goes from mostly dry to mostly wet
Speed - A switch with a fast or slow setting for one of the LFOs
Cello - A switch to route the  Cello voice to the Orchestra, or bypass it.
Violin - A switch to route the  Violin voice to the Orchestra, or bypass it.

When I wrote the Orchestration blog post I came up with a more versatile scheme with three controls.

Speed - A knob which controls the speed of one of the LFOs
Cello Depth - A knob which controls a wet/dry mix for the Cello voice
Violin Depth - A knob which controls a wet/dry mix for the Violin voice

The advantages of this scheme are that with fewer controls I get greater control. Yamaha’s designers would probably argue that the benefits of controlling the speed are minimal but for such a small cost I simply say ‘why not?’. As for having a depth control for each voice, again it’s questionable when you consider that it’s mostly an on/off choice, but I think having the greater freedom allows for more possibilities - even if you don’t always want to take advantage them.

This evening I got the new scheme working with some linear rotary potentiometers. The old controls are gone.
This was the rough sketch I did before and it’s what I ended up doing.

It leaves the dry mix of Violin and Cello from ‘Mixing Amp’ unused. Previously, some of this would have made it into the mix even when the Depth setting was full on. The depth pot was 50K so not much would have got in, but some would. Now the balance of wet/dry is done before the mixing of the voices, but a little of each will get through even when the setting is at the extremes.
I used 100K for the Violin voice but I only had a 47K left so used that for the Cello.
I’m not sure how much difference this makes, if any. I could eliminate this slight bleed through at one end if I use a pot with a switch. Perhaps so the dry mix is totally dry.

The other thing, which I didn’t consider before, is that even when little or no signal is going into the Orchestra effect there is still some noise coming out. In the original design the switches ensured that this would never reach the output. I need to do some listeing tests and think about this.  The effect is not totally clean but I didn’t hear anything untoward this evening.