PLAN B analog blog

Clipping at all inputs at balls out:

This is a tough one.  I can say without any doubt that unless signals
come from the Model 25 Attenuator with those intentionally set at +6dB
amplification, then no mixture of Plan B signals will clip at unity
gain.  But all bet's are off for the umpty-ump modules made for
Eurorack which who knows what their output levels are.

Mixers are summers - adders if you will. They are btw one of the most
common circuits in electronics, they are used whenever CV signals are
combined with manual controls.  For instance, the M15 has a 5 input
summer for it's freq pot, fine freq pot, two bipolar VC inputs and the
1V/oct input.  The FM in comes in at a different place in the circuit.

Anyway they add the voltages together.  It's not linear, but the
overall level of the output is greater than the high levels of the
input.  You can actually amplify a single signal by bringing it into
multiple inputs of a single mixer.  However, the outputs of all of my
audio signals are set for the quoted Doepfer standard of  +/- 5 volts
(10 volts RMS).  Given my output buffers can pass signals up to +/-12
(24 volts RMS), with a range of about +/- 11 before weirdness starts,
I think there is plenty of headroom for mixing.  Running signals
within a volt or so of the supply voltage of a TLO op amp can cause
some funky things to start happening, among other things clipping.

hope this helps-

- P





--- In PLAN_B_analog_blog@yahoogroups.com, "NoRMaN PHaY"
<vietgrove@...> wrote:
>
> I think the unity gain input is much more useful than an output level
> pot, personally.  I'd definitely go for that.  I have a couple of
> serge MIX2 modules which have this feature, and it's very useful to
> have & adds versatility.
> 
> As the m12 filter has an input level pot, as long as the mixer isn't
> going to overload internally when all of the ins are cranked up full,
> I don't think the output pot would be missed at all in use.
> 
> A simple dual attenuator (passive) or dual reversing
> attenuator(active) might be a useful future utility module.
> 
> --- In PLAN_B_analog_blog@yahoogroups.com, "(i think you can figure
> that out)" <peter@> wrote:
> >
> > Got a question for the group, please give me input.  
> > 
> > One thing that's pestered me about most Eurorack line mixers is they
> > have this overall output level pot which I feel is at best an option,
> > at most a redundancy, if nothing else another pot you need to deal
> > with along with the level pots - and they all omit something tey could
> > slap in the same space as the output level pot that I feel would be
> > much more useful:  a fifth buss input to stack mixers together so you
> > don't have to take one of the input channels to do it? 
> > 
> > Do you guys see a need for a mixer that is stackable at the risk of
> > removing the output level pot?
> >
>