Active vs passive mixer

[Joniverse]

What is the difference sound wise anyway? I'm looking to sum a few keyboards to a stereo output (live) and the passive mixers seems just perfect, is there any downsides to a passive mixer vs an active one?

[psycho_monkey]

Originally Posted by Joniverse

What is the difference sound wise anyway? I'm looking to sum a few keyboards to a stereo output (live) and the passive mixers seems just perfect, is there any downsides to a passive mixer vs an active one?

Well, post passive mixer you need make up gain. Ie it needs to run into a mic pre, not a line pre.

Probably not the biggest disaster in a live setup assuming you're playing a reasonably sized venue....

[Joniverse]

Originally Posted by psycho_monkey

Well, post passive mixer you need make up gain.

I was actually thinking of adding a nice stereo DI after the passive mixer. Maybe a Radial JDI Duplex. Would that take care of it?

[Mgr]

Originally Posted by Joniverse

I was actually thinking of adding a nice stereo DI after the passive mixer. Maybe a Radial JDI Duplex. Would that take care of it?

A D.I. will not give you gain, you'll need a preamp or a line amp after the mixer.

[Joniverse]

Yes, but there is always a front of house mixer at the venue. There shouldn't be any difference plugging my keyboard directly into a DI rather than plugging it to a passive mixer and then DI, right?

Keyboard -> DI -> Front of huse

or

Keyboard -> Passive mixer -> DI -> Front of house

Should give the same result, right?

[psycho_monkey]

Originally Posted by Joniverse

I was actually thinking of adding a nice stereo DI after the passive mixer. Maybe a Radial JDI Duplex. Would that take care of it?

Any di, nice, stereo, or not, doesn't add gain.

Originally Posted by Joniverse

Yes, but there is always a front of house mixer at the venue. There shouldn't be any difference plugging my keyboard directly into a DI rather than plugging it to a passive mixer and then DI, right?

Keyboard -> DI -> Front of huse

or

Keyboard -> Passive mixer -> DI -> Front of house

Should give the same result, right?

No it doesn't.

The output from a keyboard is (more or less) line level. You use a DI to enable you to run it over long distances without noise, by converting it to a balanced, mic level signal that can then easily be amplified by a standard mic preamp.

the output of a passive mixer is closer to mic level, hence needing a mic preamp for makeup gain (to bring it to line level).

Your "end result" is actually simpler than you think - you just don't need the DI box in the way. Treat the output of your passive mixer as the output of a DI box, and run it down mic lines to the front of house mixer (where the mic amps provide the make up gain).

It IS dependent on the quality of the mic pres in the mixing console at FOH of course. Most quality venues won't have a problem, but if it's the sort of place where they struggle to mic a kit, 2 guitars and bass and have enough working mic pres left over for 3 vocals, you're going to be in trouble.

[Matt Syson]

Hi
You only need a bunch of resistors such as Folcrom unit. Then use the desk mic input to bring it back up in level.
There are minor differences between 'passive' and 'active' mixing but in reality they are BOTH active as BOTH need an amplifier.
Matt S

[psycho_monkey]

Originally Posted by Matt Syson

Hi
There are minor differences between 'passive' and 'active' mixing but in reality they are BOTH active as BOTH need an amplifier.

...the difference being that things market as "passive mixers" require the user to add the amplification, right? (I know it's possible to have passive EQ with inbuilt makeup amplification...)

[Matt Syson]

Hi
The action of 'mixing' and 'EQ' is ALWAYS a passive process. You ALWAYS get less 'out' than you put in. As a result an amplifier is needed to recover this 'loss'. There are various ways of achieving this and it can be done in the same 'box' as the process, or externally.
Marketing has added a layer of BS to this to try and 'dress it up' which confuses matters slightly. Depending on exactly what you want to achieve, 'current' (virtual earth) summing can have advantages over 'plain resistive' summing, in that if you switch off unused 'channels' the noise contribution can be reduced compared to the simple resistive summing where you need the same 'gain' regardless of the numbers of channels actually in use.
Distortion and frequency response are simply matters of design of the amplifier stage which can be done well, or badly in either case.
Matt S

[Joniverse]

Wow, this is complicated. I just want to so sum 4 sources (two keyboards, one sampler and one iPod) and send a stereo signal to front of house. It has to be compact and sound good without ruining me. I thought this was going to be simple. The ART Splitmix4 seemed to be the perfect solution but now I don't know...

[Matt Syson]

Hi
If you are running ling cables from your little 'mixer' to the FOH desk then whatever it is should be 'active' so that it can send at balanced line level to FOH position. A purely resistive mix would bring it down to almost mic level and would be unbalanced.
You COULD go 'passive' with a transformer to balance it but it is still 'low level'.
If it is made into a balanced feed you then have a possibility of 'ground lifting' which may be necessary as some of the gear is presumably mains fed.
Matt S