[Build] Stereotype Mark V Mixer (photo heavy)

Ok So the other thread has become long and convoluted and there has been a lot of requests for a new thread showing where this project is at. So here it is in pictures:

This is an input board for channels 9-12 and I have another identical for 13-16. 9-14 will all get a fader, LCR toggle, and a 3 position toggle for mute/solo/on. I have some screw terminals coming to stuff the fader and pan terminals. I'll post pics when the toggles are done.

This is the input board stuffed for channels 1-4 (and another for 5-8). You can see the difference in how the two are stuffed pretty easily. I have some screw terminals on order to replace those 9 pin headers.

The channel board ready and waiting

This is one of the little headers used for connecting the channel board to the input board. All signals get 2 pins. The little 4 pin set pictured here is for power, ground, and the unbalanced signal.

Since the frame on the male pins doesn't actually stand off enough to allow the shrouded female sockets over the board, I have to solder the first joint using the socket as a spacer.

Here you can see the headers and DOA sockets are in. On the left you can also see the little jumper I just put in to wire the direct out to be fed pre fade signal. You can also see where I will make another little jump to decide if aux 1/2 are pre or post fade.

All resistors, headers, and sockets in. The feedback cap (C3) for the amp needs to be stuffed with the resistor because the pads are so close it can easily get filled if you are a bit overzealous when soldering the resistor.

Originally I was going to put the small decoupling caps on the under side of the board, but half way through I decided to start putting them under the amp.

I bent the further cap up just a touch so it wasn't laying directly on the feedback path. May just be paranoia.

Originally the bigger cap was meant to be on the top of the board but then I realized that it would get in the way of the trimmer so I stuffed underneath.

All pots in.....except the fader. With all the revisions I did on this board before ordering I managed to swap the pins on the fader so clockwise is attenuate. No problem if you are wiring off for linear faders, but now I have to wire off the pots. What a dummy.

All pots and switches in. That little toggle has to be stuffed first! Well I had stuffed a few boards, with just switches, to show a mockup in the other thread and when I went to finish them I had some fun getting to all of the resistors and pots. My own worst enemy.

The "assembled" backplane. I am going to have super short hard wire tails on one board and the screw terminals on the other for all bussing. The attentive will notice one set of ceramic and one set of mica caps. I'll let you know how those compare.

From the front! It looks a bit dense, and it is. I did have some knobs laying around and tried them out to see how clearance was. I think it good. The auxes are tight but fine and the fader and pan have a lot of space. All of the switches are set to be very flush with the panel so as to keep the knobs clear.

Now some glamour shots

You can see the connections really well there.

My brooding little monster

Thanks!
Don

looks great! Can't wait the overall system to see and hear in action

Wow,that's a serious piece of work Don,congrats!
All the pots,are they sfernice plastic conductive types (they look so at least)?
Also it would be useful to have a block diagram and/or schematics in this new thread to get some ideas,same as you did for your 8-ch. Stereotype over in the old thread.
So to start with it we need  summing/make-up stages like ACA/BO,right?
Or have you done a ic based summing stage for things like aux bus etc?
Did you leave the place for slugging resistors in to use linear pors or faders?

Very very nice project,

best,

Udo.

Looks GREAT Don

GARY

Very cool, Thanks for your work on this. Can you post rough schematic when you get a chance. Also, what are the pots and switches in order? Top down.

Cheers,
Dave

Ok here are some long awaited schematics. I tried using digikey's free schematic software, it's a bit clunky so these are a bit clunky, but they do the job.



Kante,
The pots are these P260S-S1AF3CB10K. Conductive plastic. Slugging resistors for all auxes and faders. I am thinking summing will be through Jeff's big ACA for the main bus and his transformer free ACA for the secondary bus and another of the same for the auxes. Balanced out with my little That output board. I am going to put together a center section board with everything for the solo section (summing, level, routing), an assign switch for the secondary bus to feed the primary or it's own independent outs, and 2 footprints for dual deck blue velvets for the 2 stereo busses. Toying with a third Blue velvet footprint for monitor level and maybe a headphone amp, but one thing at a time.

Thanks for all the kind words!
Don

Very impressive - the feature set is spot on and the modular mechanicals appears to be very well thought out and executed for a robust package well up to the job.

I think this could be a real winner - with some big faders it would be the ideal minimum signal path with doa monitoring-mixer for a great big stack of diy channels of all persuasions



Awesome!

Thanks Alex! this project has been an adventure. And of course things are always changing so I have to adapt this thing to keep it going. I just saw that Jeff has changed hi smaller summing board from "stocked" to "special order". I really don't know what special order in the DIY world means (isn't it all kind of special order?) So I am inclined to design my own solution. I have been laying out the center section and after seeing the need for this summing I have expanded it to include all summing except the primary 2 buss (which will still be Jeff's larger transformer loaded ACA/booster board). The auxes will be IC amps and the secondary stereo buss will be 4 DOA's for summing and buffering/boosting. The way I have it laid out right now from left to right on a 14x3 inch board is:

Aux 1 Master
Aux 1 solo
Aux 2 Master
Aux 2 solo
Aux 3 Master
Aux 3 solo
Aux 4 Master
Aux 4 solo
Buss B master
Buss B Solo
Buss B send to Buss A
Buss A Master
Solo Level trim
Solo listen pushbutton
Buss A / 2 track return monitor toggle
Monitor Level
Headphone Level
Wired off panel mount headphone jack

Thoughts? Feedback?

thanks
Don

That's fairly comprehensive.

Something that might be nice is one pair (or more!) of fx returns onto the summing amp for one of the main bus.

Might make things a bit busy on the centre-section though.

Perhaps just a switched+gain adjustable stereo bus A, B expansion capability so as to pipe in more channel buckets.

One thing I like also like is having a switched insert on the stereo bus A, B. It's nice to have some outboard patched in or not on these.

I can see how one might want the modular option to work up a more elaborate center section.

Interesting to see how you go.

Anyhow - I'm sure it will all be good.

Hi Don,

What is the spacing between the modules? Is it similar to the 500 module standard?
Amazing work btw!

Regards,

Pierre

alexc said:

That's fairly comprehensive.

Something that might be nice is one pair (or more!) of fx returns onto the summing amp for one of the main bus.

Might make things a bit busy on the centre-section though.

Click to expand...

FX returns are essentially just a line input and this is a line mixer. Simply adding another input board will give you this feature. If I were to add it to the center board it would have to be IC based or the board would need to grow considerably.

alexc said:

Perhaps just a switched+gain adjustable stereo bus A, B expansion capability so as to pipe in more channel buckets.

Click to expand...

I don't entirely understand what you mean by this, but if you are asking about adding additional buckets to build something like a 48 channel mixer (please do, I want to see one built!) then the current summing amp can handle something in the range of 40 channels (check in Jeff's summing build thread) and you can always go to bucket summing with the addition of a small summing amp in each bucket (that special order board from classic api is exactly for this purpose).

alexc said:

One thing I like also like is having a switched insert on the stereo bus A, B. It's nice to have some outboard patched in or not on these.

Click to expand...

This always a nice feature. It would make the board either bigger or more dense. It will also be relatively easy to accomplish with a 4PDT panel mount toggle. Simply toggle between the send and return signal feeding the main fader. This would be a good use of the second output of the first stage on the summing board. For bus 3/4 (or "B" as I occasionally call it) I could add a switch that would insert a IC based balanced IO loop, probably a THAT 1646 output and a 1206 or 1200 input. Switch or no switch I suppose I need resolve both of these insert issues. I suppose both buses really should have the switch on the front panel. I was trying to limit the board size to 14" so there would be 3" or so for some small meters, other wired off controls, or front panel labeling. Now I am thinking  I will need to do a slightly bigger board. Would the inclusion of 2 tricolor led's as basic stereo metering be of interest? I would have them follow the monitor selector (pre monitor level of course).

Not sure about this LED meter thing but it's something to think about I suppose.

anjing said:

What is the spacing between the modules? Is it similar to the 500 module standard?
Amazing work btw!

Click to expand...

The channel spacing is 1.3" as opposed to the 1.5" of the 500 series. I did this so I could get 12 channels across a standard 19" rack. Thanks for the kind words!

So either way I would like to include some sort of metering considerations. Whether that means including vu buffers or simply having the taps for metering. We'll see what fits.

Don

There's a lot of scope here for some different size 'center section' module arrangements.

The nice thing is, it is all very modular and quite tidy to build up - I'm thinking a couple of 8-ch racks to tie up all my diy, another one to take some computer feeds and a final one on the desktop with big faders, to tie up all the others.

Mind you, in my case, its in my head only, having already a bunch of mixing capabilities on hand!

But sure is easy to imagine some very interesting ways to put together some groovy, custom, distributed stuff.

So I have been kicking around the idea of making the center section have all the summing necessary for the mixer. Meaning it would have the primary summing bus amps and transformers all in one place. I like this because it would mean less wiring (therefore less room for easy errors) and it would allow me to do a few little things that would let me add a "character" switch to the bus' (loading the transformers and amps in various ways). I am debating whether it should all be transformer balanced (8 transformers!) or if only the primary bus needs that kind of treatment. My current working plan is to have the first stage of both buses get a pcb mounted transformer and the second and final stage of both would use a chassis mount transformer or a small IC based solution. I think this gives the best flexibility and organization. What do you guys think of this? So just to be clear, for a summing box or basic line mixer, like the original Stereotype I built, Jeff summing board would still be used, but for mixers using the channel cards or other the new center section board would take care of all summing. It could be stuffed exactly the same as the original API board, but I would probably monkey with mine.

I am also pretty sure I want to add a 2 4 segment led arrays for metering. This should give a decent, and very cost effective solution. Something like 7$ in parts will get us a decent little stereo meter that is green (-20) green (0) yellow (+10) red (+20). And if you want analog meters you will be able to simply leave out the LED circuitry and only stuff the buffer to feed your meters.

Of course this is all operating with the idea of using the systems as designed, which was never my intention. I have always tried to add features I won't use, or leave options for things I can only imagine. Realistically any one of these boards could be used without any of the others. So maybe I am over thinking things.

AHHH! The gear are spinning!

Don

I wont be able to jump in right away because all my energy(and$) is focused on the eztube mixer but i really hope to eventually built either an 8 channel line mixer and i was also considering some artist monitoring mixers...Anyhow i'm following with great interest, more as a voyeur for now.
The four led segment array should do the job, the analogue meter is more eye candy. Do you plan on having the led driver integrated on the main pcb or a seperate one? A seperate one i guess would interest many people who could use them in all sorts of other projects as well....

The reason i was asking for the width is because i was thinking of putting 500 preamps before each line input, Jeff has some nice 500 buckets, but thats just daydreaming...the eztube project gave me the mixer bug!

Regards,

Pierre

hakanai said:

....I just saw that Jeff has changed hi smaller summing board from "stocked" to "special order". I really don't know what special order in the DIY world means (isn't it all kind of special order?)....

Click to expand...

This is just boilerplate text that shows up when a product is out of stock with no delivery date for restock. I made a few tweaks to the large 2-ACA-Bo board and would like to do the same for the small inverting ACA before I reorder. Nothing serious.

jsteiger said:

This is just boilerplate text that shows up when a product is out of stock with no delivery date for restock. I made a few tweaks to the large 2-ACA-Bo board and would like to do the same for the small inverting ACA before I reorder. Nothing serious.

Click to expand...

That makes sense, thanks for clearing that up.

I have been working on the layout of the center section quite a lot. It's a monster. I just got these meter sample parts. They are small but I think they could be quite cool for this purpose. Would people be into these with the support circuitry as an independent board? I currently have them laid out on the main board and you can simply skip a few components to drive some bigger VU's if you want.

Don

note - that's a nickel, not a quarter

Last year I've spent about a week intensively searching for these, substituting one burned LED on my Lavry converters. These spare parts are hard to get I can tell for sure. LEDs inside are not interchangeable. If one lamp is broken, the whole part must be replaced.

Please make sure there're valid partnumbers inside your BOM.

I try and only design around readily available parts. This little guy is not hard to come by as near as I can tell. And they are cheap (about $1.50 each).

don

edit: also if they are impossible to find all it really is, is 4 rectangular led's in a little housing. You could just get any led's and bend them to the shape you want.

hakanai said:

I have been working on the layout of the center section quite a lot. It's a monster.

Don

Click to expand...

Awesome - some monsterism is a good thing

These pics are really just to illustrate the amount of stuff on this board. Don't get too hung up on anything technically, these are my "work in progress" (drawn on the train) schematics. The meter section and relay support circuitry are not there yet, some multipole switches are shown with the wrong relative positions, and a lot of values are place holders. That being said, if you see something that looks impressively dumb or wonderfully good, let me know so I can change/keep it. The 1646's and the final pair of transformers (T3,T4) are not board mounted, everything else is.

Right now I have all the big components laid out on a 16.5"x5" board. I am just trying to plan power and ground and then I will start adding all the resistors and running traces. This board may end up costing a little more, but it will be a pretty damn comprehensive center section and will yield a very cool 12x4x4 mixer in 4ru. Although I would love to see someone do a 30x4x4. That would be 24 channels across 2 4ru racks with the center section across the top of one and some stereo return faders across the top of the other. Hot damn, who's doing it?! hahaha

Don