Jump to content
Sign in to follow this  
Notes_Norton

Looking for a passive way to combine the outputs of 4 synth modules.

Recommended Posts

Looking for a passive way to combine the outputs of 4 synth modules.

 

My old Samson MPL1204 Mixers are getting old and cranky (http://www.samsontech.com/samson/products/mixers/mpl-mixers/mpl1204/).

 

I have spares, and repairing them is a bother. I pull one out, send it to the repair shop, put a spare in. It doesn't happen that often, but it's getting more frequent, and I don't want it to fail on the gig. I lost one channel, and I have one unused channel. That was a close call.

 

So something new is in order.

 

There is no small 12 compact mixer that I can find that has 12 true channels. Both the "Alesis MultiMix 12R Rackmount Mixer" and the "Behringer Eurorack Pro RX1202FX Rackmount Mixer with Effects" are really 10 channel mixers with the last two channels stereo. The Behringer looks better because it has balanced outs, but I'll be short one channel with no spare.

 

So I thought of this solution. I have 4 synth modules that take up 4 channels in my mixer.

 

I'd like a passive way to mix the outputs of 4 mono synths (1/4" phone jacks/plugs) to one channel. I don't need volume, eq or anything like that. Just a way to mix them together without creating an impedance mismatch or anything else I may not know about.

 

Someone must make one. I'm searching sites but am having any luck. Perhaps I don't know what it's called.

 

Thanks.

Notes

 

Share this post


Link to post
Share on other sites

You can never find exactly what you want, but the Rolls MX42 will do the trick (twice, because it has stereo inputs and output) and it's less than $50. All of its connections are on RCA jacks, so you'll need some new cables to integrate it with your present system. If you want balanced outputs, you'll be in for $100 or so more because it'll need power, more components, and more expensive connectors.

 

Or, if you're handy with a soldering iron you can build once with just the layout you need from a handful of jacks, resistors, and a box.

  • Like 2

Share this post


Link to post
Share on other sites

For a while when I was running two keyboards and a rack synth I used the Behringer RX1602. there are 16 channels and if you don't need pre's (and it doesn't sound like you do) it's a great option, line level mixer. I'd read in Keyboard magazine that the E Street band was using them and I figured if they were good enough for that group, it's probably good enough for me!

 

Another option to consider is to buy an old Presonus FP10 from ebay. Although it's a firewire interface it can also be used as an 8 channel mixer with pre's.

  • Like 1

Share this post


Link to post
Share on other sites

Thanks y'all.

 

I took Mike Rivers' advice.

 

I found a schematic involving 4.7k resisters, jacks and a project box, so I built one myself.

 

Much to my surprise, it works!!!

 

Notes

Share this post


Link to post
Share on other sites

like I always say...okay, maybe not 'always', but I have said it....problems are the parents of invention and ingenuity.

Edited by daddymack

Share this post


Link to post
Share on other sites
Thanks y'all.

 

I took Mike Rivers' advice.

I found a schematic involving 4.7k resisters, jacks and a project box, so I built one myself.

Much to my surprise, it works!!!

 

Great!

 

Learning how to build solutions to your connection problems is a useful skill. Modern designs with low impedance outputs and moderately high impedance inputs makes splitting and combining audio signals relatively painless.

 

  • Like 1

Share this post


Link to post
Share on other sites

In the days before I got my first mixer, I used a simple "Y" connector to combine 2 signals. I did this often when I had 2 turntables crossfading to my cassette recorder. The output was higher when combined but this could be adjusted by turning volume down on each source or going through a few resistors.

 

Oh to those days of long ago !

 

Dan

Share this post


Link to post
Share on other sites

With a Y connection, I would think there would be an impedance mismatch and possible distortion. But it's been so long since I had an electronics class, and since I don't use what I learned long ago, I could be combining two memories.

 

Notes

Share this post


Link to post
Share on other sites
With a Y connection' date=' I would think there would be an impedance mismatch and possible distortion. But it's been so long since I had an electronics class, and since I don't use what I learned long ago, I could be combining two memories.[/quote']

 

Today's solid state line level audio gear has a very low output impedance and substantially higher input impedance. You can directly connect as many inputs (within reason of course) as you want to a single output without problems. The rule of thumb is that the load impedance should be at least ten times the source impedance, so a 50 ohm output can happily drive a 500 ohm load. So you can split the output to up to 20 typical 10,000 ohm inputs.

 

Combining outputs, though, is different. Connect two 50 ohm outputs together and you're hanging a 50 ohm load on each one, violating our 10x load impedance rule. This is where the "passive mixer" comes in. If you want to connect two outputs to a single input, put a 1000 ohm resistor in series with each output. You'll have some voltage drop, but generally things work out OK.

 

  • Like 2

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...