DIY Analog Mixing Console

RICK FITZPATRICK said:
got the time, or patience or frankly, the financial resources to take this on. But I have to say....this is VERY COOL frederic!

It's a completely modular design, and once I get the input channel finished (EQ needs to be finished, then pan/fade/solo logic and so on), I'll post a page with all the parts, and we can price it out together from digikey, allied electronics, or mouser, or all three. Then we know what the input channel will cost.

We'll do the same for the master busses, aux submixers, and so on.

Then you can weld together (or screw together aluminum extrusions like you enjoy :D), and you can decide what you can afford now. Maybe that's 8 input channels, two aux sends, and four master busses. Then next year, you could double that, and simply "plug them in".

RICK FITZPATRICK said:
You are a gentleman to take the time to do this. But for me...well, reality is only a visit to the shop away.

I enjoy self-inflicted punishment. I've wanted to do this for a while, however I too a buried in projects, and with my new son free time is even more precious. Come spring, I'll probably not have time to read forums... I have a 500cid stroker for my crewcab to finish... preferably before all the go-fast goodies start to rust while sitting in the garage waiting for me to "get to it".
 
I'll post a page with all the parts, and we can price it out together from digikey, allied electronics, or mouser, or all three. Then we know what the input channel will cost.
Wow, very cool frederic. :eek: :) :) :cool: I'd like that a lot. What bothers me is the circuit boards. More on that later. Hey buddy, if theres something I can do with the format conversion thing just give me a holla. I have Paintshop Pro 8, which will convert anything to anything...I think. :D Maybe send me a file, and I'll convert and post it for you. Just let me know.
]
hen you can weld together (or screw together aluminum extrusions like you enjoy
Funny you should mention that. I've already thought about it. I've got the perfect extrusions too. :D I'm using some of it for my iso box, which I just finished routing the door frame for smoked plex covers. I'll post the pics tomorrow. Too tired tonight. That stuff takes time, as you well know.
I enjoy self-inflicted punishment.
You too huh? :D If my console is indication, I'll enjoy another 8 years building the mixer. Hahahahahaha! Shit, I might even get around to recording with it before I fucking die. :D

preferably before all the go-fast goodies start to rust while sitting in the garage waiting for me to "get to it".
God do I know what you mean exactly. I've had stuff waiting to install in my console and studio for 5 years. Hell, some of it is brand new, but obsolete by todays standards. :rolleyes: Geeeeeeeezus...if I knew then what I know now....I'd probably have taken up golf or something...ha! But like you said...self inflicted punishment is fun sometimes. :p BTW....DAD! Don't let those moments with your son slip by. Hell, he'll be starting college before you know it ;)
 
RICK FITZPATRICK said:
What bothers me is the circuit boards. More on that later.

There are several ways of doing this. A more expensive way, whereas each input channel, master buss and aux send/return is on it's own board, thus 100% modular, or you can put the modules in logical groups, say, four or eight. So to add an input channel, soldering all the parts on the board will give you four more channels. That cuts down on circuit boards, but makes them bigger of course.

Many ways to skin this cat. Obviously, the more stuff you cram onto a board, the less costs in making boards there will be, but then should you have to troubleshoot you have more parts to sift through.

RICK FITZPATRICK said:
anything...I think. :D Maybe send me a file, and I'll convert and post it for you. Just let me know.

The printscreen method is working believe it or not... and the gif files are fairly small amazingly enough. I was expecting 200k images... it's like 1/3 that.

RICK FITZPATRICK said:
Funny you should mention that. I've already thought about it. I've got the perfect extrusions too. :D

I figured you would :-D

RICK FITZPATRICK said:
I'll post the pics tomorrow. Too tired tonight. That stuff takes time, as you well know.

Yes it does, I have no time as it is. Looking forward to the pics.

RICK FITZPATRICK said:
You too huh? :D If my console is indication, I'll enjoy another 8 years building the mixer. Hahahahahaha! Shit, I might even get around to recording with it before I fucking die. :D

hear hear. My problem has always been I have too many, complicated, expensive, time consuming hobbies. One day I'll wake up and realize I barely have time for one hobby, and I'll decide between recording, and building 1000HP emissions compliant "sleepers". Recording will probably win. I think this twin-turbo crewcab is going to be my last project for a while.

RICK FITZPATRICK said:
said...self inflicted punishment is fun sometimes. :p BTW....DAD! Don't let those moments with your son slip by. Hell, he'll be starting college before you know it ;)

I know.... I generally only read forums and draw console schematics when he's sleeping... and I'm at least upright ;-)
 
Hello frederic. Thanks for the reply. Say, you might be interested in this little gem. I recieve an online "newsletter" every Monday from an audio engineering "institute", and this morning this article was among the usual little gems that fill the newsletter. It might help with this project, although I wouldn't know. Interesting though. Check it out.
http://www.record-producer.com/learn.cfm?a=3080
 
Hello frederic. Thanks for the reply. Say, you might be interested in this little gem. I recieve an online "newsletter" every Monday from an audio engineering "institute", and this morning this article was among the usual little gems that fill the newsletter. It might help with this project, although I wouldn't know. Interesting though. Check it out. Its about a $5 preamp beating out a $1500 pre in a listening test. Theres also one about a SM-58 beating out a Neuman also:eek: :D
http://www.record-producer.com/learn.cfm?a=3080
 
mshilarious said:
Very cool. I don't really understand timing circuits at all. I know that caps filter frequencies by imparting a phase shift; I assume that is a timing delay that can be exploited for other purposes. What's the formula for determining a time lag in msec? Got any good links?

Huh. I though caps filtered frequencies in relation to their size, with the cutoff frequency determined by one of two formulas, depending if the cap is being used in a HP or LP filter. Am I missing something?
 
easychair said:
Huh. I though caps filtered frequencies in relation to their size, with the cutoff frequency determined by one of two formulas, depending if the cap is being used in a HP or LP filter. Am I missing something?

That is the end result.

But capacitors technically store electricity. The larger they are, the lower frequencies they can smooth out.

Usually to ground ;-)
 
easychair said:
Huh. I though caps filtered frequencies in relation to their size, with the cutoff frequency determined by one of two formulas, depending if the cap is being used in a HP or LP filter. Am I missing something?

In terms of the cutoff frequency, I believe the two different formulas simplify into the same formula for either circuit:

1/2*pi*R*C

C being expressed in farads rather than microfarads, I always use:

1,000,000 / 2 * pi * ohms * uF
 
I had a question for you, Fredric. What is C4 doing in your mic pre? I'm looking at the reference design from TI (I'm looking at making a buffer amp for piezo pickups in my electric guitars), and I noticed that you have a cap in the Rg loop. What's it for?

I'm afraid I'm showing my ignorence here, but I'm curious, and I can always stand to learn from those with more experience. I'm guessing (tell me if I'm wrong) that it is there to protect the opamp in some way, but that's just a guess.


Light

"Cowards can never be moral."
M.K. Gandhi
 
Light said:
I had a question for you, Fredric. What is C4 doing in your mic pre? I'm looking at the reference design from TI (I'm looking at making a buffer amp for piezo pickups in my electric guitars), and I noticed that you have a cap in the Rg loop. What's it for?

The R6/C4/R8 combination is the gain setting. The op amp as nice as it is, isn't 100% linear - but darn close. What the large cap does is filter out the higher frequencies in this loop, thus in reality giving the trim control (R6) a little more linearity so it's the range is less "scrunched" at the end of the pot. The value (470uf) was determined through trial and error. I started with 10uf and went smaller, with weird results. Then I went up in value and 470uf seems about right. 220uf is darn close as well. I happened to have a 470uf cap on my workbench :D
 
frederic said:
The R6/C4/R8 combination is the gain setting. The op amp as nice as it is, isn't 100% linear - but darn close. What the large cap does is filter out the higher frequencies in this loop, thus in reality giving the trim control (R6) a little more linearity so it's the range is less "scrunched" at the end of the pot. The value (470uf) was determined through trial and error. I started with 10uf and went smaller, with weird results. Then I went up in value and 470uf seems about right. 220uf is darn close as well. I happened to have a 470uf cap on my workbench :D



Makes sense. I actually was looking, and they recomend a reverse log taper for that pot, but your way seems much easier to find, and probably cheaper as well. I also notice you are not using the negative feedback loop, right? (The sense input). Any particular reason?


Light

"Cowards can never be moral."
M.K. Gandhi
 
frederic said:
That is the end result.

But capacitors technically store electricity. The larger they are, the lower frequencies they can smooth out.

Right, but I was curious about the concept of them filtering by applying a phase shift. My understanding was the unwanted frequencies were shunted to ground, not phase-shifted out of the signal.
 
easychair said:
Right, but I was curious about the concept of them filtering by applying a phase shift. My understanding was the unwanted frequencies were shunted to ground, not phase-shifted out of the signal.



In effect, the cap passes frequencies above a certain point. If the cap goes to ground, then those frequencies go to ground. But that is only one use. For instance, in guitars we use a thing called a treble bypass cap. This goes from the pickup side of a volume pot to the output side (from the clockwise lug to the center lug on a volume pot). It passes the high frequencies from the pickup side, and makes up for the high frequency loss which happens with a volume pot as it gets turned down, and keeps the guitar from getting muddy as you turn down. Of course, it always passes those high frequencies, so you end up with a brighter sound to begin with, but some people don't mind that. (Myself, I don't like them, but that's just me). The bigger the cap, the lower the frequencies it passes.

Or at least, that is the way I've always understood guitar tone controls. I'm sure that the EQ section Fredric is gonna be putting up soon (hint hint) will be more complicated than that.


Light

"Cowards can never be moral."
M.K. Gandhi
 
Seriously thinking about making an 8 channel compressor. I'm just afraid it would turn into one of those money wasting projects that doesn't get finished. I have some electronics background from the military but I've never made my own PCBs. I do however have access to and can program a CNC laser and press brake. I could make a damn nice box to mount everything in.
 
frederic said:
Microphone preamplifier:


I'm looking at your schematic and see only the connection for + 48v for the phantom power. Maybe I'm having a brain fart, but what happens to the - 48v line from the power supply?

Also, what are L1 and L2?

Thanks,

Jason
 
its 48V between +48V and ground (the upside down triangles). When I put forth the power supply schematic it will make more sense.

L1 and L2 are inductors. They are two donut-shaped ferrule beads with three turns of 16 gauge insulated, stranded wire spaced about 1/16" or so apart. They help with hum rejection on long XLR mic cables. They aren't critical if they aren't there. Just don't expect a 200' mic cable not to have a minimal amount of hum.
 
circa 1999 (or so)

Here is a picture from my last analog home studio, when I lived in CT.

0603_001.jpg


Homemade furniture too (sorta). Sections of white formica countertops with bathroom vanities installed below for support. Very minimalistic.

I was going through an old, old laptop and found some neat pictures. Figured I'd shuffle the pics off before tossing it.
 
frederic said:
its 48V between +48V and ground (the upside down triangles).

Gotcha, that's what I figured, but I just wanted to be sure.

When I put forth the power supply schematic it will make more sense.

Hurryhurryhurry!!! :D Sorry, I'm getting excited about this project already, I know you've probably got a lot on your plate right now what with a new kid and all. :)

frederic said:
L1 and L2 are inductors. They are two donut-shaped ferrule beads with three turns of 16 gauge insulated, stranded wire spaced about 1/16" or so apart. They help with hum rejection on long XLR mic cables. They aren't critical if they aren't there. Just don't expect a 200' mic cable not to have a minimal amount of hum.

Good to know, I'm not going to be running anything that long at the moment, but I think I'll add them to mine when I build it, for future's sake.

Thanks,

Jason
 
Yep, nothing special about the inductors.

what I did on the final design was wrap one of the inductors (the 16 ga wire) around one half of the donut, and the other inductor around the other side.

Didn't seem to make much difference.

Excuse the old studio picture, I meant to put that on another thread.

Kinda of an "oops" thing :D
 
Not a problem for me, nice to see how things have progressed. One of these days I'll get around to posting pics of where I am now, and where I've started... Big changes since 1997.

Jason
 
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