I set up the Aural Exciter/insert cable trick using an insert cable from the Voyager’s MIX OUT/FILT IN to the mult on my VX-351 and then to a BBE signal processor and back into the Voyager’s EXT AUDIO INPUT. It works great!
I was reading over the trick of running the Voyager’s Left Audio Out into the EXT AUDIO INPUT and I wanted to know if both the Left Audio Out of the Voyager and the return from the BBE can be run simultaneously into the EXT AUDIO INPUT of the Voyager using a dual mono to single mono Y adapter? If not, would the mixer on the C-251 work? Or is it just one or the other?
It’s never a good idea to tie two output signals together with a ‘Y’ cable (or adapter). The safe way is to use a simple mixer to mix the two signals together. The mixer can be passive or active - it doesn’t matter which - although passive mixers will tend to attenuate the signal. Alternatively, you can use the mixer on the CP-251 as it can handle audio frequencies with ease. But watch out for the Mixer’s OFFSET control, which will add a DC component to the signal (suggestion: zero out the OFFSET control by plugging the Mixer Out (+) into the Voyager’s Pitch Input. Set the Mixer Master control fully CW, then adjust the OFFSET control until no change in pitch is discernable. Be careful not to bump the OFFSET control after adjustment).
Basically you’re right, especially if you’re using the Mixer for some audio signals like Lengai. But realize when using the CP’s Mixer this way that even a little DC offset can cause audible popping when audio connections are made. The OFFSET control 12:00 position is pretty close to zero volts, but every CP-251 is just a little bit different, so I wouldn’t assume that the ‘straight-up’ knob position is exactly zero. Mine is off just a little bit.
I have a couple of questions. First, will DC offset damage anything or will it only make audible popping sounds? Secondly, I’ve never heard of an active vs. passive mixer. I use Behringer line mixers. I’m assuming they are passive. Who makes an active mixer that would work for this type of application?
A small DC offset shouldn’t damage anything. The only popping you would get from a DC offset is when the initial connection is made (think of what would happen if you connected a 1.5V battery across the terminals of a 1/4" jack and then plugged that into an amp - pop!). But I wouldn’t worry about it. Take a common sense approach and keep the audio turned off while making connections.
A passive mixer is nothing but a few resistors or potentiometers (one per channel) that sum together into a common output. I occassionally use this simple passive mixer made by ART:
The downside to using a passive mixer in any application is that it attenuates the signal slightly (it’s less than unity gain from input to output). This means that passive mixers are best used for line-level signals only, or for combining CVs. Also, passive mixers generally only mix signals - they do not provide any equalization or effects sends/returns.
On the other hand, an active mixer uses powered (i.e. active) circuitry to sum the inputs. The circuitry is generally designed to provide at least unity gain, and often a bit more. Active mixers can also have extensive EQ, panning and send/return features, in addition to supporting many, many channels. AFAIK, all Behringer mixers are active (if it has a power cord or power source, it’s active).
The mixer in the CP-251 is active. It is a unity gain mixer with two variable inputs (channels 1 & 2) and two fixed inputs (channels 3 & 4), giving you four channels total. Although it’s intended for mixing CVs, the frequency response of the mixer is sufficient to handle audio signals too (kinda handy!).
