Small mixer features

[NewYorkDave]

Some of you know about my mixer design project that's been going on mostly in my head and on paper for the past year now. This is a small ten-input line mixer for mixing down from an 8-track recorder. It's a passive mixing network followed by tube gain. There are no preamps or EQs.

I'm finally at a point where I'm about ready to heat up the iron and build this thing. Before I do, I'd love to hear some comments on the feature set I've decided upon. Although I'm designing this mixer for myself, it would be nice to know whether or not the features are useful to others, in case I ever decide to build more mixers using the same circuit.

So, here's the rundown:

8 mono channels with level controls, mute and PFL pushbuttons, pan, and two aux sends, switchable pre/post.

1 stereo channel with level and balance, mute and PFL, but no aux sends. This channel can also be used as a ninth mono input channel with the balance control acting as a pan.

1 Aux send expansion input to allow a small external mixer to act as a "sidecar" of sorts when more input channels are needed. The external mixer's program outputs would go to the stereo input of the main mixer, and the aux sends would connect to the aux send expansion inputs.

2 stereo aux returns with PFL buttons.

Switchable monitor output with level control. The available sources are stereo program, split (mono program on left speaker, PFL on right speaker), PFL only, mono only, and stereo tape return.

Note that the PFLs in this mixer do not override the setting of the monitor selector. Pressing a channel's PFL only assigns its prefader signal to the PFL buss; you must manually select "split" or "PFL" on the monitor selector in order to hear it. Really, I'm not sure if I should call this function "PFL" or "Cue" or something else altogether...

And, of course, there are send level controls for the auxes and a master program fader, and two program VU meters.

Some of the seemingly arbitrary choices, like the number of input channels and the lack of aux sends on the stereo input channel, were dictated by the fact that I want this to fit on a 19" wide panel.

So, for those of you who record on 8 tracks or fewer, and who don't need onboard preamps and EQ, is this something you could use?

 

[radiance]

I vote for inserts on the master buss and maybe you can give the PFL bus his own outputs, so it can also act as a separate buss.

 

[NewYorkDave]

Here's a block diagram of what I have in mind:
http://electronicdave.myhosting.net/pdf/mxrblockdiag.PDF

 

[NewYorkDave]

[quote author="radiance"]I vote for inserts on the master buss[/quote]

Pre- or post-master?

I almost never use program buss inserts since I'm not a practitioner of "2-buss compression."

 

[neilium]

Dave,

This is awesome. My band records to 1/2" 8-track, and I would love to build a mixer. I'll be watching this thread. Between us we have two old 8-4-2- mixers; I'm trying to convince them to let me gut one and rebuild it.

thanks
neil

 

[radiance]

[quote author="NewYorkDave"][quote author="radiance"]I vote for inserts on the master buss[/quote]

Pre- or post-master?

I almost never use program buss inserts since I'm not a practitioner of "2-buss compression."[/quote]

Pre master I suppose. You can use it to insert a pre amp for gain make up. This way you can choose between different fravors.

 

[Guest]

Let me ask a question about the stereo input (9 and 10). If the PFL is only on 10, do you loose this feature in mono? or is it also on 9?

 

[NewYorkDave]

Thomas,

Inputs 9 and 10 both have PFL.

Radiance,

There's already make-up gain there; inserting a preamp would be redundant and would add noise and distortion. This is a complete line mixer with the necessary gain built in, not an all-passive "Folcrom" type box to use with external mic preamps.

 

[NewYorkDave]

DUH... I just noticed that I left the aux send expansion inputs off the block diagram.

These are simply two jacks on the back of the mixer that go to 6dB pads, then to Net3 and Net4, respectively. These signals are summed with the aux sends from the various mixer channels.

 

[Samuel Groner]

Is there a headphone amp? Just a pot and a cheap IC, but very handy IMO...
Samuel

 

[CJ]

build it on a big chassis in case you want to do add ons.
cool project. might save me from doing a lot more work, ala Neve 1073 type 8 into 2.
Track direct, mixdown thru the box, sounds low noise-hi-fi to me!
P and G faders?

 

[daArry]

wow, turnin out nice again :thumb:

 

[NewYorkDave]

[quote author="cjenrick"]build it on a big chassis in case you want to do add ons...
P and G faders?[/quote]

No and no, at least for my mixer. The whole point of this thing is to be fairly small in size and to use no exotic parts.

 

[CJ]

OK, I'm with ya so far...
(dang, these NY guys hate my freakin guts!)
:?

 

[peter purpose]

They're only human Chris.. :green:

 

[hitchhiker]

hey Dave,

Looking good. I asume this is point to point wiring.

Are you using 600 - 600 ohm faders? If so and you are still looking I am
still able to sell you some . Drop me a PM.

If you are doing point to point I'm wondering if you would consider a
kind of tutorial for the Lab ? Like how to make it work and look good too.
That old style of wrapping the wires with string is so cool.

Lance

 

[Samuel Groner]

You can send to headphone amps via aux sends.

Was not thinking about headphone mixes for the musicians. A headphone amp would be handy for the engineer as well - some things I just don't hear on my monitors (yes, they are good!).

I would want to PFL the aux sends, so that I can hear what I'm mixing here.

Samuel

 

[hollywood_steve]

Greetings,

You asked for comments from 8 track users so......

I record on location to a Genex GX9000. I prefer to record to DSD format, then come back to my studio, convert to analog, mix to stereo and then convert the 2 track mix to whatever format the client requires. so I am looking for a high quality, line level 8x2 mixer.

Personally, Aux Sends are of no use to me. What I need are a high quality rotary fader and a pan pot on each input channel, and a mute switch to kill any unused channels. That's it for the input side.

On the output side, I want a top quality stepped fader for the master output. That's the only master section control I need. But I would like three sets of balanced outputs, all on XLRs: one for the two track record output, one for monitor output and one for metering. (the monitor ouput could be pre-fade).

As far as circuitry goes, passive summing is my preference and transformer coupled I/O is a requirement for location use (IMHO). A great make-up gain amp will be required to offset the 30dB or so of loss through the mixer. My only other request concerns packaging: there are a couple of very high end mini mixers available that I wouldn't take if they were free, strictly due to the absurdly small scale of construction. I want to be able to turn knobs without skinning my knuckles on adjacent controls. And I'd like to be able to read any control markings without a magnifying glass. IN a 19" chassis, you could use 2" wide modules and fit the required 8 inputs and single master module.

I thought that I was the only one who had any interest in this type of product until this was posted to another forum today:
http://recforums.prosoundweb.com/index.php/fa/267/1359/?SQ=b91b777b50d9ad3314faf433b71b74a6

 

[NewYorkDave]

That Chandler mixer is adorable. How many thousands of dollars do they get for that thing?

Using bigger knobs for the pans rather than for the faders seems backward to me, though. If I owned one, I'd probably swap the knobs around.

So Steve, do you have a preference for tube or solid-state in this 8x2 of yours? And you want to do your metering outside of the box?

 

[hollywood_steve]

That Chandler mixer is adorable. How many thousands of dollars do they get for that thing?

Using bigger knobs for the pans rather than for the faders seems backward to me, though. If I owned one, I'd probably swap the knobs around.

So Steve, do you have a preference for tube or solid-state in this 8x2 of yours? And you want to do your metering outside of the box?

1. I think that the initial info says the Chandler is supposed to run about $6k for the base unit, but I'm sure you could option it out and spend closer to $10k
2. pan pot knobs - If you read the Chandler post that accompanied that photo, he stated that those were temporary knobs, he has special EMI style knobs being fabricated.
3. solid state or tube? (I'm guessing that you mean for the make-up gain amps? either, as long as it sounds good.
4. meters - I already have a pair of Dorrough meters. It would cost nearly $1k to add meters that good to the mixer; I'd rather just have a good quality send to feed my existing meters. Same with monitor controls. Outboard monitor controllers (with and without meters) were the *hot* new product of 2004. So if we have all purchased these things already, why would we want to duplicate these expensive pots and switches (and meteres) on the master section of our mixer?
5. I am SO pleased that both Chandler and Tonelux are building modular line mixers. (when I asked for such a thing two years ago, I got bombarded with replies stating that modular construction for a line level mixer makes no sense as their is "nothing" in the module. Glad to see that somebody else agreed that there is value to modular construction.