Another Neve 1272 summing mixer.

[Rocinante]

I need recall and automation and want to simplify at the same time so am seriously considering loosing the console in trade for a summing mixer.  I bought a couple of Martin's ezln72 and want to use them as the gain make up for this summing mixer.  My thoughts are 16 passive in > 8 bus >  vtb 9046 > EZLN72 > VTB 1148 or Ed Anderson 1148 to stereo out.  AT the stereo out I would like two inserts so I can incorperate hardware during mixdown.  I am also going to incorporate either Forth Monkey's buss selector or a series of the illuminated push-buttons similar to other members builds (Holger, Majestic 12,) for the bus selection switches.
Below is a very ROUGH draft of my idea.  It shows only 8 of the 16 channels going in.




I have been reading Geoff Tanners invaluable explanations of Neve console bus summing.  From what I gather I believe I will need 2 x 5.1k per xlr  for 16 channels (I need to recheck my math) and/plus incorporating the 8 busses.  I have several questions regarding inserts and the busses.
For one; do i need to put resistors on the busses?
I think I want inserts on every channel but I definitely want two inserts (so two sets) on the stereo master outs so I can use various buss comps and EQ's in the final mixdown.  Everything  will be coming from patchbays so it isn't crucial to have inserts on every channel but it might be nice.
Can someone point me in the right direction on how I can do the inserts?  Will I need 'slug' resistors for them and do I add those resistors to the total impedance of the summing mixer?
Does anyone know of a thread where this is talked about?
I've looked tirelessly for this. 
And finally I am debating leaving a header connection on every channel for usb/midi.  Is this a ridiculous idea?  I know with several members working on automation it could be invaluable to have a direct usb connection to every channel.
Thoughts?
Thank you.

 

[ruffrecords]

For inserts anywhere on a balanced line levele signal all you need is half-normalled insert. Check out this SOS article:

http://www.soundonsound.com/sos/dec99/articles/patchbay.htm

Check out my DB25 configuration document for details of how to determine bus slugging resistors:

https://drive.google.com/file/d/0B_n67A1hN3qtZGtMdjNybnF6XzQ/view?usp=sharing

Cheers

ian

 

[Rocinante]

Ahh Ian thank you.
Back to reading.

 

[Rocinante]

I have finally resurfaced for air. 
Yes along with the 100 + other projects I have going on, work, studio-work, and family I have been researching a good deal into building a Neve 1272 ended summing mixer.  And apparently I am certainly not alone, although most threads regarding Neve-ish summing mixers go nowhere. 
Often the 'member' comes up with their idea and throws it out there.  A few of the senior gurus add some suggestions and point out problems.  The person thanks them for their coveted advice, and then we never hear from them regarding their "Neve" summing mixer again. 
Luckily a few report back with a post.  But rarely is it anything Neve based.

I have been playing with groups inside the daw (which I have been using for years since I use a console) and trying to lower the channel count from 16 to 8  (but with the option to add up to 16 later).  But for now 8 will have to do.
I have decided I definitely want inserts and direct outs on each channel and two auxes.  I also still want two stereo master inserts but that's not a problem as far as I can tell. 

So it is becoming more of a passive line mixer?
More like the 8816  now.
I understand (now) that once I start introducing active parts the topology changes and I start adding potential problems.
I just don't know how much I would like my workflow without inserts or auxes.  Right now I am dependent on them. Obviously a LR switch or mono-stereo switch is essential
Applying parallel compression and reverb to several track seems integral to my workflow but maybe not.
So please bear with me and I thank you in advance.

Okay so a few questions;
I want to use Forth Monkeys channel cards http://groupdiy.com/index.php?topic=60430.0
I guess I would use Pier's app-992 for the DOA's since they are 24v but I am open to suggestions.
So it would be 8 channels.  Each channel the signal path would go:

XLR or DB25 in > Forth Money API-esque channel boards > to possibly  Forth Monkey board (or bus bar) >VTB 9046 line input xfmr (along with the other 3 of 8 channels) > EZLN 72 > VTB 1148 output xfmr > stereo insert switchers > stereo out.

What do I need to keep in mind?

Forth Monkeys boards take care of inserts,  panning etc...  Seems pretty nice if I can get them to work.  The direct outs on every channel would be easy i would think.

Doable?

Suggestions?

 

[ruffrecords]

I think it has become a line mixer which uses (unbalanced) passive mixing. If you want AUXes then you really have little choice but to do it that way. The per channel active unbalancer provides the low Z drive you need to feed pan pots and AUX sends. However, if you add in a channel fader after  the unbalancer (as in Forth Monkey's schemo), then you need to think carefully about crosstalk or change to a virtual earth mixing system.

Cheers

Ian

 

[Rocinante]

Thanks a ton Ian.  Super helpful as always.  So I could  skip the fader using the DAW?
What other options are there?
That's to general of a question, so let me be specific;
What can I do to prevent crosstalk and does that mean I'd have to integrate a balancing line amp?
If so how much would that effect the 'sound'?
I see that the 8816 uses NE5532 and tl074s going into the input transformers.

Cheers

 

[Joechris]

I can only speak for myself, but it seems like you make this a little more complicated than it is.  I have made myself a 12 channel summing box with 3 stereo and two mono inputs, and some aux inputs. And thats it!  My insert points is between the audio interface and the summer. Insted of aux sends on the summing mixer, I send my aux sends from the computer to some analog rev/echo and return that on my summer aux inputs. Final analog eq/ compression is done after the summer and back to the computer. You could of cause add more inputs, but I just submix everything down to three stereo busses in the computer...drums, guitars and the rest....and use the two mono inputs for vocal or anything mono that need some analog treatment.
No master volume on the summing box, just a stepped gain control to push the output level a bit, if needed. Neve makeup amps...all you ever want Just the last stage of a BA283.

 

[Rocinante]

I hear you man, I really do. I've been staring at the 'summ-thing' (NY Daves summer in pushbutton form)  pcb layout for a few days and coming from a console it just seems so sparse which i also understand was its intended design.  I really like having inserts as it feels like it ties the whole studio together. Bypassing an eq with the flip of a switch seems pretty elegant and i dont think its tooo much work. The way i look at it; if im gonna ditch the console i want it to be for something that's more suited to my workflow.  Something I like to use. I also plan on building a 10 channel meter bridge that can attach to it via Ian's Db25 pcbs. Nothing is set in stone yet. 

 

[ruffrecords]

I think you first need to decide exactly what you want this box to do. Then we can worry about the technology. It is easy to argue that the most important thing is that you are comfortable using it because if you are not then you will soon want the change it or get rid of it.

A straight forward passive summing mixer can only do so much. If what you want the box to do is more than a summing box can be expected to do then change the technology. If you want a line mixer with pan, AUX sends , a P&G fader, inserts and direct outs that's fine, it can be done.

PS, if you have AUX sends then will you also need AUX returns?

Cheers

Ian

 

[Rocinante]

I guess i want the kit and kaboodle. Within reason of course. I want to use forth monkeys boards as they seem to summ (no pun intended ) what i want into one but am willing to sacrifice (i.e. do i Need faders?)  Ive been reading about neve busses and line amplifiers for weeks and think i can pull it off within reason. and of course with help. I'm not going to go nuts though.
More specifically i think it would be interesting to use ba 440s or ba226s for the pans and auxes. I dont need auxes as Joechris pointed out but i do need inserts. Id like to have single jack inserts but im fine with using a send and return via dsub or trs. I also have two 2u cases with 4 trs hole cut outs per channel ready to go but im willing to do the dsub route if it makes everything easier.
I played around with the dangerous 2bus and the spl mixdream recently and the insert and channel switching made them incredibly desirable. I use panning via a console often as i record a lot of acoustic instruments and feel its an important feature.  Plus its easy enough to recall.
I don't want to battle crosstalk and Id like to keep it somewhat simple but not as simple as the average passive switchbox i guess.
I hope that makes sense.
Oh and ne5532 for the monitor outs.

 

[ruffrecords]

OK, draw up a block diagram showing all the functions you want and how they connect together and post it here.

Cheers

ian

 

[Rocinante]

OK, draw up a block diagram showing all the functions you want and how they connect together and post it here.bug
Cheers

ian

Ha. I've been working on it since the last post albeit slowly since im at work.
And thanks again Ian

 

[Rocinante]

Thomas from Vintage Designs or TK has been very helpful and was very kind enough to help me out with how he implemented inserts and auxes using the ba226 op amps in his SU2 summing mixer.  I am guessing I can make up some of those or maybe (as fate would have it via the BM)  pick up  some ba340 and ba 338 op amps which I believe should work just as well but i have to look more into it. From what I gathrr they were the b340 was the output amplifier in the monitor section as well as used as op amps in the 1081.  *edit: I corrected the ba340 information. *

Thoughts anyone?

As far as master inserts I think Majestic12's is very elegant.

http://groupdiy.com/index.php?topic=56613.0

I obviously would need to get 24v relays in order to use it in this build.  I am also not completely opposed to dsubs as much anymore as I'm looking for the 'cleanest' way to go about this.  Which might actually be trs 1/4 inch and xlrs I am not sure.

At any rate here is the block diagram.  I have only done one channels 'wiring' as doing all 8 seemed like it would be too much on the eyes.  I placed Forth Monkeys summing channel cards near the xlrs as I didn't want to run wires across the diagram but they naturally would connect to the front panel.  It actually helped me out looking at it like this. 

For now I am drawing it without auxes but I have not decided if they are worth the work. 

*I had to edit the drawing as there were errors but they are now repaired



http://postimage.org/app.php

 

[Rocinante]

Upon my research for my Neve ended summing line amp/box thingy I came across this schematic at Dan Alexander Audio:


http://postimage.org/

I noticed that the 3415 line amp is used throughout the mixer for various tasks.
The b440 and b438 are the make up amps for the 3415 line amp
The ba338 and ba340 are used in the 3405 line amp.
So I am considering using  some ba338's and ba340's (with the thumbs up from several trusted sources)  for my summing mixer's  master inserts, monitor outs,  and possibly auxes, while using the ezln72s as make up for the stereo out but am finding it nearly impossible to get the pin outs  for the ba338 and ba340 amps and I am not sure which circuit to actually choose from.  I debated reverse engineering this schematic for the 3401 distribution amplifier

http://postimage.org/

or using the schematic for the 3405 which uses the ba338 and ba340


http://postimage.org/

and finally here is the 3415 schematic which uses the ba438 and ba440 which are nearly the same thing as the ba338 and 340 but with a few additions and from what i read you can use either or but the ba4xx are considered upgrades.


http://postimage.org/


So my question is; has anyone made a 3415 pcb or at least drawn a design for it?



And finally the 1081 uses both the b338 and b340, do you think I could use the circuit in the 1081?


I am not planning on using them together as I am not trying to make a mic preamp but as two different circuits laid out on the same pcb?  The pin out is really the most difficult part although I guess I could try to reverse engineer the 1081 since their is an actual pcb document for it which leaves me with which circuit to choose from.  Fwiw I already have and am beginning to populate the ba338s and ba340s.  Also I am no Neve guru or audio equipment designer and am not nearly as experienced as many many others.  I've built a decent amount of gear but I am still pretty damn green.  But I am willing to learn and from the feedback I have received from some respectable sources I am apparently on the right track.  I have also found in my research that I am not the only one who has decided to go this route within a Neve-ish summing line mixer.

And thanks in advance.  I always am appreciative to any wisdom you guys lay down. 
I've been actually working on this quite regularly and the parts are beginning to come in albeit slowly.

 

[Joechris]

Its hard to follow you in this last post. What do you ask for? The pin outs is on every schematic.  The 3415 is a exelent sounding unit,
But Im not shure you could get the output transformer...mabye. If you just want to use the amps like the BA340 for a unbal output you should be ok. But i would not care to build them for aux outpts, The BA640 with an opamp would do just as well.
I migth repeat myself and say you overthink this summing box...you are on the way to make a console...
By the time you are finished, everybody is mixing in the box..
Best Jo

 

[Rocinante]

I guess thats what i want; a neve-ish mini console.  Jk.  I suppose I am taking the term 'summing mixer' literally.


Yeah I might've had a bit too much coffee right before that last post so allow me to rephrase:

What I'd  like to know is what surrounding circuit do i need to use the ba340s for monitor outs as well as use the ba338s for my inserts and possible aux send and returns?    I will/can do it on vero board but id like a somewhat pro looking build and the footprint for the ba340 and ba338 boards are hard to come by.    So I'd like to design a pcb or use someone else's for the ba338s and ba340s.  I am guessing I can just use the circuit in the 1081?   
Eisen Audio, Aurora Audio,  Pheonix, and BAE have all done very similar summing/mixers and from what I've read they are mostly exceptional pieces with the worst being still pretty damn good.
I've seen a bunch of them in varying degrees of complexity.
I am trying to keep the parts of a console that I feel are somewhat integral to me but stripped down.
And thanks for the feedback and insight joechris.  I really do appreciate it.  I very well might fail and look back and think: "well you were warned you jack ass."  My fingers are crossed.
And yes, in the end it all gets run through the box but I actually use mostly outboard and use the daw more as a fancy tape machine that has a few really great effects.  Who knows maybe that will change?  I doubt it will be  anytime soon though.
 

 

[ruffrecords]

There is no reason in principle why you cannot use any of the BA440 and friends like DOAs in a mixer design.  How many of which type you will need depends on exactly what you decide this mixer must do. So I would again suggest you draw a block diagram showing what this mixer does - forget implementation details like  PCBs, DOAs and transformer numbers and just draw a diagram showing where you want the signals to go and do. Everything else follows from that.

Cheers

Ian

 

[Rocinante]

Will do, thanks Ian

 

[Rocinante]

Okay so here is the redrawn block diagram.  As you can see there is no aux as I'd like to make this a little less complex right now't feel it's Needed but I am not ruling it out altogether. 


http://postimage.org/

 

[ruffrecords]

That's more like it. A couple of point you could clarify for me if you would:

1. Insert and Direct out - are they pre the gain pot or post?

2. I think on your first diagram the insert was unbalanced on a single TRS. Is that what you want or would you prefer a balanced insert?

Cheers

Ian