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Small mixer for home setup

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Re: Small mixer for home setup

Postby Hugh Robjohns » Tue Jul 14, 2020 12:11 pm

I fear we have a confusion of philosophical, practical, and technical thoughts here, which aren't helping anyone, least of all the OP.

1. As a general concept, I think (hope) we can all agree that using a mixer purely as a signal switcher for a small audio interface is not the greatest idea, philosophically, practically, or technically.

The idea solution will always be an interface with sufficient input channels, because it would be easier and faster to use with the DAW, take up much less space, and maximise reliability and sound quality.

But, if acquiring a larger interface is not an option, it's not an option... so other solutions must be considered.

2. A patchbay is often a very convenient way of re-plugging multiple sources into a limted number of input channels, but in this case we have the significant complication of needing to connect balanced mics, unbalanced instruments, and stereo line-level unbalanced headphone/line feeds...

While possible with some care and custom engineering, that combination really doesn't lend itself to a simple patch-bay like the Samson.

3. The OP's original complaint was:

manwilde wrote:My ... RME Babyface mk I ... has only two analog inputs that I want to feed from the mixer master outputs. Currently using an old Behringer desk which is noisy as hell, even going out from the fx send instead of the master (a bit less noisier, but still -65dB noise floor!)

To be honest, that's a lot more noise than I was expecting, even from a Behringer desk.

But it was due to this high noise floor that the OP was seeking a better mixer.

Just to pick up on Dave's comment in passing:

ef37a wrote:These small mixer have about the same amount of electronics as a decent active monitor controller and probably the same op amps.

In fact a small mixer will have at least twice as many gains stages in the signal path as a decent monitor controller, including the potentially noisy preamp and bus-mix amps.

Back to the plot... and why was this Behringer mixer producing so much noise? Well, we find out from the OP's comment here:

manwilde wrote:...the way I´m using the Behringer, no gain is applied from the desk: I just leave the gain pot at "zero" ... set channel and send faders at 0 = Unity, and add tipically +35db or so at the Babyface input channel for voice recording, +27dB for bass DI, and +30dB for guitar.

And that, gentlemen, is where the problem lies. Terrible gain-structuring! :shocked: :shocked: :shocked: :o :o :crazy: :crazy: :wtf:

Manwilde, by working this way what you're doing is running low level signals through the mixer, so you have a truly terrible signal-noise ratio there, and then amplifying that signal to a sensible level in the interface, which just drags up the mixer's inherent noise floor. Result, very noisy recorded signals.

Instead, what you should be doing, is running the interface inputs at line level, unity gain, never to be touched again. And then adjust the mixer's input preamps to optimise the gain for each of your various sources...

The reason the Effects output is quieter than the main output is because they use a slightly different output topology... But I'd go back to using the main outputs so you can switch channels with your faders, routed to the main outputs. Dedicate the different input channels to your different sources and optimise the gain structure through the mixer.

I suspect that if you do that, your noise problems will largely go away and you will probably no longer feel the need to spend money on a new mixer.

Try it, and let us know!
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Re: Small mixer for home setup

Postby ef37a » Tue Jul 14, 2020 12:19 pm

"In fact a small mixer will have at least twice as many gains stages in the signal path as a decent monitor controller, including the potentially noisy preamp and bus-mix amps."

But my ZED10 is pretty good don't you think Hugh?

You mention "gain structure". That is where I suspect the mixerphobes have come unstuck. I reckon the mixer idea is at 'Deuce' at the moment.

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Re: Small mixer for home setup

Postby Hugh Robjohns » Tue Jul 14, 2020 12:30 pm

ef37a wrote:But my ZED10 is pretty good don't you think Hugh?

Sure. I love those A&H desks. They are very well designed.

But I refer you back to my point 1 above. A mixer as an extra front end shouldn't cause a significant problem if used correctly, but it's not the ideal solution and it does place a lot of stuff in the signal path that really doesn't need to be there... If sound quality is the prime requirement, there are better solutions.... even if 'better' is only by a small margin... ;-)
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Re: Small mixer for home setup

Postby manwilde » Tue Jul 14, 2020 12:32 pm

Thanks, Hugh. I'm gonna be away most of the day, but first thing I'm doing back home is follow your advice. I was using RME's gain rather than the desk's because I remembered those preamps not being silent at all, but what you're saying makes perfect sense... :headbang:
I will report my findings ASAP.
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Re: Small mixer for home setup

Postby Hugh Robjohns » Tue Jul 14, 2020 12:35 pm

manwilde wrote:I was using RME's gain rather than the desk's because I remembered those preamps not being silent at all...

No, they won't be the greatest, but at least you won't be amplifying the whole mixer's noise floor by 30dB!

If the B mixer's noise floor is, say, -95dBu (i.e. not quite as good as Dave's beloved Zed10 :-) ), and you're running that into your RME adding 30dB of gain, guess where the noise level will now be?

*Answer... -65dBu... (and it would still be at -70dBu-ish even if you were using Dave's mixer that way!)
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Re: Small mixer for home setup

Postby ef37a » Tue Jul 14, 2020 12:55 pm

Hugh Robjohns wrote:
ef37a wrote:But my ZED10 is pretty good don't you think Hugh?

Sure. I love those A&H desks. They are very well designed.

But I refer you back to my point 1 above. A mixer as an extra front end shouldn't cause a significant problem if used correctly, but it's not the ideal solution and it does place a lot of stuff in the signal path that really doesn't need to be there... If sound quality is the prime requirement, there are better solutions.... even if 'better' is only by a small margin... ;-)

Yes, not "ideal" but maybe not detectable? My figures were for the line inputs of the KA6. Had I used my venerable 2496 there would have been nothing in it since its noise floor is only -93dBfs. I have already mentioned the things a mixer as a front end can do that few if any interfaces can. Then there is the source selection. Yes, can be done with a patch bay but as you say, mixing (oops!) various levels and bal/ubal? Nightmare!

I shall stick to my guns and say a GOOD small mixer, properly used will detract nothing from the OPs signal that HE can detect. N.B. The guy is recording guitar from the lowest budget model of a guitar amp's headphone socket FCS!

As I said before. Most of the time, most peeps that ask about a mixer are wrong. Not what they need but once in a bluey it is! And, used properly it will have minimal impact on the sound quality. Strange no one has suggested a Six!

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Re: Small mixer for home setup

Postby Hugh Robjohns » Tue Jul 14, 2020 1:05 pm

ef37a wrote:Strange no one has suggested a Six!

Not when it costs ten times the OP's proposed budget... :lol:
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Re: Small mixer for home setup

Postby manwilde » Tue Jul 14, 2020 6:12 pm

Ok, back from testing. I can´t even begin to explain how dumb I feel... ´cause it seems my brain just decided to ignore whatever little knowledge I had regarding gain staging. I mean it´s not that what Hugh advised was new to me, I just went with some very wrong assumptions that somehow crossed my mind when first setting up and never gave it a second thought. There I go... all wrong.

So, I tested voice and stereo ultra crappy guitar amp. Fiddled with gain levels on vox channel and amp volume to go into the Babyface at line level, peaking at -15dB, -13dB at most in every case. It is indeed more workable than what I had set up previously. Indeed. -93dB noise floor when idle and channel faders all down, -65dB at operating levels but obviously with a much better S/N ratio.
But I definitely can tell the difference on the voice recordings when compared to RME´s preamp with no mixer involved. Sound is grainier, for lack of a better word. It´s not just a matter of noise. But you know all that.

So, what to do?. I´ll probably go for some of the previously mentioned mixers. As ef37a says, it´s different levels, mono, stereo, balanced and unbalanced that I´m dealing with, and money is VERY tight now. Mostly because I´ve spent all my savings buying equipment for the project studio (RME UFX and Octamic, assorted mics, computer, cables, headphone amps... well, you know). Also because I´m probably gonna be unemployed in less than a year due to COVID.
What I take from all this is: a) Never buy the cheapest mixer/guitar amp/whatever again. :lol:
b) It´s really something wonderful to have knowledgeable, nice people to lend advice and give away their time for free just to help unknown people across the world. I truly, truly appreciate your replies and insight.

Thanks a lot, to everyone, and I´ll keep you updated just in case this posts might help somebody like me in the future.
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Re: Small mixer for home setup

Postby Hugh Robjohns » Tue Jul 14, 2020 7:27 pm

Glad that's brought something more usable -- and for free! :-)

manwilde wrote:... peaking at -15dB, -13dB at most in every case.

That's probably a little over-cautious for a situation where you can rehearse to set levels. I'd go a little hotter and allow peaks to between -8 and -6dBFS. That would improve your signal-noise ratio by another 6dB.

-93dB noise floor when idle and channel faders all down, -65dB at operating levels...

Sounds more reasonable. Most of the noise at operating levels will be source noise rather than the mixer.

The comparison between the quality direct into the RME and via the mixer is what I would expect, as discussed at length previously!
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Re: Small mixer for home setup

Postby ef37a » Wed Jul 15, 2020 6:07 pm

Last words on the mixer front?
Had a bit more time and set each of the 4 mic channels of the mixer for '0' ch gain and '0' mix out. Mic trim was set as before to get -20dBfs with a dynamic. Channels were panned L,RL.R
Results, L -93.8dB fs rms R -92.2dB fs. I would think those noise figures are well below any normal use by a home recordist but I have no data from any similar setups.

I do have a really cheap Wharfedale mixer somewhere about the place, not used it for years will see if I can find it and repeat the exercise!

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Re: Small mixer for home setup

Postby manwilde » Fri Jul 17, 2020 9:43 pm

Hello again. These past two days I´ve been testing my Behringer mixer with proper gain staging and I´ve come to the conclusion that a new, better but still budget mixer will surely make a difference in audio quality compared to what I have now, but probably not worth it for what this very humble home set up is meant to do: just simple demoing for further development at the project studio. So I´ll stick to what this is, knowing what it is, until I can afford good pres via ADAT. (And a better guitar amp :) )

On a side note, it really feels odd but very good thinking long and hard about whether to spend such a "huge" amount of money on equipment...

Thanks a lot for your help and patience!
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Re: Small mixer for home setup

Postby Hugh Robjohns » Fri Jul 17, 2020 9:53 pm

Sounds like a good decision, allowing you to save up for a decent ADAT expander preamp.
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Re: Small mixer for home setup

Postby manwilde » Wed Aug 26, 2020 9:52 am

Hi. Just to update this thread, last week I eventually bought a brand new Focusrite Octopre. Works as expected, sound is much cleaner than with the previous setup, and along with a 4U rackcase, my Babyface and my laptop, makes for a capable mobile rig.

Thanks again everyone for your comments and help.
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