Split audio signal - Multiple vs distributor

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Split audio signal - Multiple vs distributor

Post by Firechild » Sun Nov 25, 2018 7:49 am

I want to split an audio signal to 3 or 4 different modules. However just using a multiple will maybe not be perfectly correct? I guess I will loose signal level when using a passive multiple meaning worse noise to sound ratio?

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Post by Synthbuilder » Sun Nov 25, 2018 10:36 am

There may well be some loss in signal level but it should be relatively small. The loss is due to the inevitable 1000 ohm output impedance of the driving module which means that the voltage will fall the more module inputs you attach to it.

However, the input impedance of most modules will not be below 50,000 ohm. So even with four such modules connected via a passive mult the input impedance will fall to no less than 12,500 ohms. This gives a maximum of a 0.7dB loss which is negligible in most cases and certainly won't make an appreciable loss in S/N ratio.

Some modules have a higher input impedance than 50K so will have even less of an effect. Also some modules use a different output arrangement and are quite capable of driving multiple modules with no loss of signal at all.

The one problem where even the smallest of loss is perceptible will be when the signal in question is controlling the pitch of an oscillator. This loss in signal level will inevitably mean that the controlled VCO will not track properly and will be flatter than they should be. In this case it is wise to use a buffered multiple or a module that has a near zero ohm output resistance (eg. the Oakley Multimix, Fourmix and others) to drive a passive multiple.


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Re: Split audio signal - Multiple vs distributor

Post by Rex Coil 7 » Sun Nov 25, 2018 9:04 pm

Firechild wrote:I want to split an audio signal to 3 or 4 different modules. However just using a multiple will maybe not be perfectly correct? I guess I will loose signal level when using a passive multiple meaning worse noise to sound ratio?
Active buffered distributor. No two ways about it. I use the Dot Com Q147 myself. They work for audio or modulation signals. When used with audio signals, they work just as well with either modular level or "line level" signals without adding noise ... in fact being opamp circuit designs (TL074) they're very quiet. I've even used that same distributor module to split up my bass guitar's signal into 4 parallel paths for doing parallel FX processing. I then use a Dot Com Q113 mixer (another TL074 opamp circuit) to bring all four processed paths back together into a single summed signal that I then send out to the bass amp. That mixer and that distributor are plenty useful and plenty quiet.

With the Q147 being an "Active buffered distributor" it keeps all of the signals isolated from one another, and prevents any oddball impedance or "loading" issues from happening.

Being bipolar, you can also use the Q147 to kill any phase cancellation issues that may arise (depending on what you're doing with your signals). The "volume" knobs can be adjusted so the signal coming out of any given channel is polarized either positive or negative. This has been a very helpful feature for me any number of times.

I only mentioned that to demonstrate that the Q147 Distributor is well suited for pretty much any audio signal, no matter it's level.

Q147 WEB PAGE LINK = https://synthesizers.com/q147.html

Q147 DATASHEET PDF FILE LINK = https://synthesizers.com/products/q147/q147data.pdf

Carry on ....

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Post by Firechild » Mon Nov 26, 2018 3:04 am

Thanks a lot for your informative replies even though they saying different things...
I have looked up the Q147 before and it is a handy module for different things so I may add it in my next dotcom order anyways even though I guess a passive will work for my needs as Synthbuilder says.

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Post by mutierend » Mon Nov 26, 2018 6:47 pm

I think the Q114 can be used as a distributor too. Roger says as much in the Q114 video.

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Post by BugBrand » Tue Nov 27, 2018 2:43 am

I agree with Tony.

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Post by ranix » Tue Nov 27, 2018 4:28 pm

technically a mult should operate as a voltage divider, since the metal in the mult doesn't actually have 0 ohms of resistance. But realistically the input impedance on the module(s) you're connecting to will be much higher than the resistance of the metal and connectors so the divider effect will be unnoticeable.

If you split your signal too much and the output impedance of the source module isn't low enough to drive the inputs of all of the modules you've multed to you'll start seeing negative effects. The solution here is to buffer the signals with a buffered mult instead. I'm not sure if you could actually notice any voltage dividing effects in that failure situation, maybe you can but they might still be too small to notice even then.

A distributor like the dotcom distributor will buffer the signal but it has a somewhat-inaccurate knob you have to turn perfectly to achieve unity gain. I have several dedicated unity gain buffers in my system, 2 for voltage signals (unity gain adder with 3 inputs and 1 output + inverted) and several more for gate signals (unity gain OR modules).

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Post by Faustgeist » Tue Nov 27, 2018 5:51 pm

If you work in MOTM, DSLman makes a great powered mult and 'Active audio splitter'


https://www.dsl-man.de/pages/viewpage.a ... d=30179412
Seeking the esoteric and funky in 5U/COTK/MOTM and MODCAN B, send me a message if you are selling gear and thanks!

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