DIY Big Knob Router Advice

[drumminhands]

Hi all,

I've been using a Mackie Big Knob for a while in my home studio. I like it.

I'm looking to make something similar for my work, but with less features. I have a few high level ideas to ask you all. But first, the basic idea:
Two inputs, each with a stereo mini plug, each with a mute button, each with a potentiometer. Probably will have one from my computer and one from my iPhone. Then, I'll combine the signals into a big knob potentiometer and a mute button. Then have two outputs, each with a button to choose to use it or not. One output will be for my headphones (stereo mini plug) and one output will be for my KRK Rokit 8 powered speakers (TS balanced or unbalanced?).

Here are the questions:

1) Should I include a headphone pre-amp or anything in the system? Any recommendations for something that will sound good but not color the signal too much? I want good sound but don't want to destroy the signal. I don't expect to be doing a lot of mixing on this system, but if I were to mix something quick, I don't want to shoot myself in the foot.

2) Should this be a powered system or just passive? That will depend on the answers to the first question I suppose.

3) The two outputs behave a bit differently--line level for speakers but headphones for the other. The speakers don't totally want line level output, but I assume they are slightly different than the headphones. Thoughts?

4) Any other snags I should look out for when designing the circuit?

Thanks for the feedback.

[Mick Bailey]

Just to make sure I'm thinking straight on this;

2 x stereo input channels with individual level controls. Then mixed down to a single stereo signal controlled off one pot. Signal then split into stereo headphone out + balanced line out. Mutes on both inputs and outputs.

Too many losses for a passive system. Is the output to the speakers stereo?

[drumminhands]

Yes, I'd like to keep stereo channels throughout.

How about this? Start with 2x stereo input channels (each with their own level control and mute button), then mix down to a single stereo track, then run through a headphone amp, then give a big knob master volume control, then use a toggle switch to choose one of two outputs (headphones or speakers), and then route to the output jacks.

This might simplify things a bit. I'm worried about the toggle switch causing a pop in the speakers or headphones when switched. Any advice on mitigating that pop? And any other advice in general before prototyping?

[Enzo]

I don't see this as difficult. Something like a Behringer Xenyx502, Mackie MIX5, and other brand similar units are on the market everywhere. They have two stereo inputs plus a pannable mic input, they have built in headphones amps, plus the main out to send to an amplifier. Phones and main out levels are independent. Under $50. Similar products incrementally can be had with more channels or more features at pretty much any level you like.

[drumminhands]

Thank you. These both do much of what I want, but not all. Neither have a mute button or large main control knob. I can probably get used to knowing which knob is the mains if it's small. But the mute button is needed. When I'm listening to music and get a phone call, I need to instantly mute the music and pick up the phone.

So, I may work on building a mute button only and using these devices. Or building my own as listed above. I'll have to think about which I want more.

[Enzo]

Those are basic, you can get a small mixer with a few more channels and it will have mutes. Your mixer will have to feed into an amplifier for the speaker, you can easily put a mute switch on that line. I think once you have turned it a couple times, you will have no trouble finding the main volume control. Or dab some sparkly hot pink nail polish on the knob top.

I am not married to those choices, I was just using them as examples of inexpensive commercial products that do what you want, or at least come close. There are a zillion more products at every level of complexity you could want.