Small mixer build using Green Pre & Calrec circuits?

So my old Souncraft Ghost (which I got super-cheap after being trashed in a shipping accident and fixed up to the best of my ability) started smoking, and I got that sickening feeling... knowing I'd have to crack this beast open once again and start f'ckin around. A tough thing to do for someone with no scope, not much electronics experience outside of what I've learned here, no schematics, and alot of doubt as to whether I'd know how to test it even if I had documentation. I've gotten lucky in the past, but at some point my lack of knowledge will prevent me from going much farther.

This happens right after I've completed my first DIY build -- a GSSL. I got all excited and confident, and started thinkin I don't even need a board this big anymore, maybe I could DIY a small board using proven and very well documented circuits like the Green Pre, and maybe a Calrec (or simpler/more cost efficient?) as the channel eq -- maybe 8 of these. Bussing isn't a big deal, direct outs would be fine as I'm just feeding an AD converter and can reroute channels if need be in my DAW. Then 8 simple line level inputs with volume and panning, clean and transparent, for tape returns and line level sources. I'd think there are plenty of circuits for these and think I could build 'em easily enough.

I'd need a good summing circuit, but again I think this would readily available. I'm guessing the biggest challenge would be tying it all together -- feeding the summing circuit, building the power supply to run it all at once, the solo/mute functionality (lots of relays?), and implimenting separate monitors chains, since application-specific info on this stuff seems less readily available. Realistically, I know there are a million other issues I'm missing which will make this a big undertaking. And I haven't looked into the cost yet... But if I build up the pre's, eq's, line amps separately... do you guys honestly think a motivated newbie could find the info (honesty, more like bother you guys for info!) to complete it? Or am I being an overconfident and presumptuous idiot?

If it seems feasible, any input on where to start would be great. Again, to make it easily, I'd love to approach it in a modular fashion using some pretty common circuits, so I have plenty of info to sort through when problems come up. Thanks for reading!

Oh yeah -- I have access to a machine shop for the metal work!!! Score!

would you be ok using the ghost for spares, why not build it using the ghosts frame psu etc? if you made a channel pcb that fit the ghosts facia i think it would be a large, but not imposiible task.




it will still be much easier to fix the ghost tho,

toby

I did think about using the power supply from the Ghost... Unfortunately the frame isn't modular though -- not drop in channels or anything, so in the end I'd wind up having to make boards with the same number of knobs, button sizes, etc to fit through the mixer top without having a bunch of holes left over. I dunno, I guess I'm gonna try to get it working again, I was just pretty frustrated with it when I posted and didn't even wanna look at it. All in all it's served me well despite it's condition, and it sounds good enough...

In a perfect world I'd still like to DIY some kinda small mixer. But I think for now I have alot to learn before I attempt it. I was thinking I could take these individual pre, eq, and summing circuits and bootstrap them together to make a little mixer. But the more I read, the more obvious it becomes that it isn't quite so simple!

Fitting the calrec eq into a channel module is a bit difficult...
You have two boards of Eurocard size and they are meant to have the pots attached to them...
I have managed to fit a Calrec Eq into a 1.75 inch wide 8.25 inch tall module - depth is about 220mm - but it is a tight fit..
I soldered wires from the front panel pots to the boards.. and made my life more miserable by using relays for the switches (I wanted illuminated 19mm Highland EAO latching switches instead of the 2 and 4 pole Alps).. thus I had to have a couple of small PCBs for the relays...
The only way I could get all of it to fit properly was to fit the 2 pcbs at right angles to one another and stacked...
I couldn't stack them on top of each other as the top of the molex connectors is too tall.. however if you put them at 90 degrees then you can put the top PCB lower as the centre of the PCB doesn't contain any tall components...
If I had my way again I would make the depth of the "cassette module" about 280mm

seems that your difficulty will be the same if you re-layout boards or try to cram the exisiting ones into small areas. I would go for a new layout that includes both your green pre and calrec circuits.

but that may be a lot of work too!

I'm sure many here would love to have boards for this too...

Yeah, looks like space would be an issue... Really, my main motive for using it was because its such an accessible design, and there's alot of info on it. I don't think I could redesign the PCB layout to utilize both - maybe I'll grab some software and give it a shot as a learning venture... But I know off the bat grounding and merging the power supplies would be big stumbling blocks for me. Any ideas on other circuits that would useful as tracking eqs, that would require a smaller footprint?

BTW - I am doing EXACTLY what you are doing... and learning along the way...

I have had some half width rack units built in 1,2 and 3 RU heights
Turn them vertically and hey presto the beginning of a cassette system
Use 19inch rack strip bolted hortizontally 8.5 inches apart ot fix them into a desk..

Problems and ideas so far...

Build a modular PSU to feed the cassettes (do you go for unregulated DC which is then regulated in each of the modules or do you build loads of regulated DC outs..)
- I went for the second option... because I could use existing PCB layouts - one big PSU box with loads of individual PSUs inside them - each with their own regulators..
15-0-15, 48-0, 18-0-18, 24-0 etc...

I then use XLR 5 and six pin connectors to send the DC out the cassettes..
e.g. to feed the Calrec cassette I use a 5 pin XLR..
18,0,-18,24,0 (the 24-0 is for relays)

To be quite honest I should have built the biggest 50-0 (I chose 50 out of the air cos you can get 48v from it) I could and then regulate it inside each cassette down

If you are using your own sized cassettes (liek I am) - then the Mic pres are going to have a problem...
You have a Gain knob a few buttons for phase, phantom etc.. and maybe a line input knob then ... there is an awful lot of spare space (I am thinking lots of bar graph LEDs to fill up the space)

Grounding grounding grounding.... I still haven't got to the bottom of this - I think it will bite me much later and then I will be well and truly f***d

Manual Routing via a patchbay or clever stuff using a million relays... (Patchbay for me!!!) - will be using a patchbay to connect the various modules together..

Non channel related stuff - compressors etc... - I am going to be using the 2 and 3RU half width rack cassettes - have a look at how a SSL bus compressor sits in a SSL desk - that is how I will be mounting them...

Hope this gives you a few more pointers....
Why am I mounting everything vertically where everybody else in DIY is doing it horizontally..
...Because it makes it harder for me and I can't crib from anyone and it makes me HAVE to learn...
This month I have been learning about metalwork!!

well this is interesting and almost on the way to making a *groupDIY* console.. :green:

just a few more wires and amps and we could have inserts and busses too..

this may indeed be easier than we expected. a few rack rails and a wood box could indeed make this cheap and easy..


*IF* i get some time i might just try a layout of a simple preamp and EQ.. I'd like to see a 1272 mated to the calrec(i just wish it had FULLY adjustable bandwidth adjustments :roll: ) but maybe without the output trafo on the pre and some kind of servo in it's place.. add a simple opto compressor like the Tommytones/FredForssell one and we might really be on to something here... :thumb:

Yeah, pretty cool! I'm sold on the rack/module mounting idea for sure. I'm thinking maybe I could eat up some extra space on the pre modules with some post preamp linear faders... Maybe keep the eq module above it, with the mic pre/fader directly below. Out of curiousity -- how are you going about channel summing? Patching channel outs directly into summing bus inputs somehow?

there are numberous ways of doing so. patching with cables is one, routing via relays or switches is another and so on. summing buss amp designs are plentiful so it really just boils down to personal preference..

maybe we should move on this idea? i think it would be a lot more simple than most think...

To make this simpler my idea was to do a split console...
This is my big idea....

So I was planning to add HPF and LPF filters to the Group DIY preamps (if they don't have them available) add a few DI boxes and this goes to a patchbay which a HDR or Tape is patched into...
Since I am only recording me - I am doing compression Post tape (BTW group DIY mics)

The mixing section for the desk starts with a patchbay out from the Tape/HDR into the EQ sections...
Also in there may be DI boxes for synth feeds from Midi (I don;t really want to do this -- see later) then into EQ modules
Inserts on the patchbay deal with compression from the Group DIY compressors.

Now this is where I have stopped thinking...
Ideas for the next stages are Daves Summing Box and how to do the post fader auxillaries for DIY plate or spring reverbs.
And how to do monitoring back from Stereo and to headphones so I can hear the backing track...

In addition I want to put a little midi box so I don't have to use a PC.. (one of those ucapps boaxes migth do this) - then I can put tape transport buttons on the "desk" to control the HDR recorder!

Long long term project - one step at a time.... 10 years might do it they way I am going