A great 16 channel summing mixer design from NewYorkDave!

I'm finally getting around to building a summing box. I'll be using a pair of Neve 3415s.

I'd like to base it on NY Dave's LCR design with 16 inputs.

I'll be taking the outputs from an Apogee DA16X into various compressors and EQs and running it into this box for summing.

Could anyone offer advice as to what resistor values would suit this application?

Any other advice?

If your 3415's have 10468's try values between 4.7k and 15K.

dave

Use 1K between pin 1 and 5.

Use two 15K for each 0dBm input, up to around 15. For 16 inputs, all permanently connected to sources, you could omit the 1K load on pins 1+5.

Ytrehalf called me last night, and we discussed his requirements in some detail. After mulling it over, I came up with this:
Schematic, 39kB GIF

The outputs would connect between pins 1 and 5 of the Neve line amps. The 600-ohm (nominal) output impedance would allow it to work well with a variety of line amps--basically, anything capable of 30dB or more of gain and designed to be driven from a 600-ohm source. When driving a 1.2K input, as found on many mic preamps and on the low-level input of the Neve, there's an additional 3.5dB of loss from mismatching. Big deal :green:

A switchable termination is provided on each channel for devices that want to see 600-ohm loads. With the termination off, the input impedance varies between 4k and 9k depending on the setting of the controls. This is somewhat short of the ideal for a "bridging" input, but it's still well within the range of what professional gear can drive with good performance. Even most prosumer gear can handle this without serious consequences.

I don't claim that this is a one-size-fits-all solution, but it should do the trick for Ytrehalf's application and probably those of other folks as well.

You're a good man, Dave!

Thanks!

:thumb:

Funny... I had trouble finding this thread again because the subject line was changed. You'd think I would have noticed my name up there in lights and all that...

Anyway, here's a wiring diagram to go along with the schematic:
20kB GIF

give that man a :guinness:

:thumb: :green:

Well, like I told Ytrehalf in PM, this design works out well on paper, but is untested in the real world. So, he's acting as a guinea pig of sorts. I hope he'll report his results--good or bad--to the Lab.

By the way, nobody should expect a perfect "kill" from the level control when it's turned down all the way. It's theoretically possible, but it's not going to happen with real-world components and amplifiers. Up to -60dB should be possible in the real world; this is low enough that you probably won't notice the tiny leakage in the context of a mix. I included the mute switch for when you require a true "channel off", as well as for reasons of operational convenience.

That is very interesting NYD, thanks.
Stephen

Speaking of summing mixers, I've only used the DAW versions but have been interested as of lately in building the real thing 'cause I keep hearing about how much better they sound.

My question is this: How do you know when you need an active mixer or if a passive one will do? Also, are individual line amps necessary when you already have line-level signals (like from my Aardvark Q10)? Wouldn't just a couple of output line amps do for make-up gain?

What's everyone's thoughts on this?

I need something that is a significant step-up from the "Mackie" solution.

Broken link on NYD website?

Info about connecting the 3415 can be found at www.danalexanderaudio.com

Normaly the input transformer is wired as 1200ohm if so you'll shall have 4k7 bus resistors for 8 channels ( 8 stereo pairs ) or 8k2 for 16 channels!
buss loss is 22,22dB for 8ch and 27,54dB for 16 channels

You can also make the buss balanced and use halv the values for each resistor!

Make-up gain for the 3415 is normaly +30dB so to lower the level at the input Neve used to put an extra resistor over the inputtransformer to lower the buss signal to -30dB, that way the headroom will remain at +26dB!

If you feed the input with higher signal than -30dB and trim down the level between the stages instead, you'll loosing headroom through the first amp stage!

Hope this helps!

both work fine for me! :green: :thumb:
chef

:guinness: :guinness: :guinness: to NYDave! :grin:
d.

it looks great and simple but 1 question.
anyone an idea for a line amp for te left and right outputs for gain makeup.
btw sorry for my bad english.
btw i like to do it with triodes (12ax7 or something???). and just simple.
i like to use this passive mixer (with reduced inputs) for having several inputs that i can mix before an fm transmitter. everythinh with tubes. but to drive the transmitter i need to have enough gain.

Has anyone built this passive mixer, or a similar one?

cheers,
t

is it possible to put this passive volume

before this balanced mixer ?
http://www.twin-x.com/groupdiy/albums/userpics/balancedmxr.pdf

snif....  :'(

does anyone have a copy of the schematic that dave posted.. links dont seem to be working.

I expect it's probably this one:

http://www.twin-x.com/groupdiy/albums/userpics/balancedmixnetwork.pdf