24 channel mixer the "Stereotype"

[galapagoose]

looking forward to the boards arriving out here (though not expecting them before xmas).

can you lend any insight as to why you would use the DC coupling caps or not on the inputs for all the channels?

thanks and sorry if this is really newbie question!

 

[hakanai]

It's actually a really good question. And the only answer I know is that DC blocking is only necessary when there may be DC on the input. If you know that there isn't then simplify the circuit and get another cap out of the audio path. They are a precautionary thing, not a requisite one. I am sure there are a lot people around here who could talk more extensively on the subject, and I would love to hear more myself.


Don

 

[funkmuffin]

Don -- For those of us using simple toggle switches for "pan", how should they be wired to the board?

 

[hakanai]

It's pretty easy to wire up a DPDT toggle for this. If you look at the attached page from the C&K manual for the 7211 style, you would wire it as follows: you jump points 2 and 4. put 5k resistors between points 1 and 3, and again between 4 and 6. Then 1 and 6 are your L and R, and 5 is goes to ground. I made a bunch of these a while back and it's pretty easy once you do one. You need to use at least 1% resistors to maintain any sort of center consistency, I think I used .5% and it worked out well.

don

 

[baadc0de]

Yay, I received my PCBs They're looking very very good. Some of the best PCBs I've had yet. Thanks and be prepared for my torrent of questions..

 

[funkmuffin]

Has anyone finished their Stereotype?  I'm nearing completion -- 3 Stereotype boards built, 2-aca-bo almost done, and 28 GAR2520's built and tested (WOO!).  My power supply, 2 rails of a 51x PSU, is also almost complete.

I'm starting to look at the "ins and outs" and a case...  Currently, my studio has everything flying around on 3 XLR-to-TRS snakes, so my initial plan was to have all 24 channels arrive on TRS, then on to the Stereotype boards.  Now I'm debating using DB25's at the mixer inputs to simplify having 24 TRS connectors on the back of the case and all those wires everywhere.

I'm interested in what others are doing and how well their choices are working for them.

Also, for hakanai -- a couple pan questions.  Two posts up, you gave me the rundown on wiring DPDT switches for LCR pan.  I think I get it, but if I indeed caught it correctly, the idea is to short the unwanted side of a channel to ground (i.e., if the channel is to be hard left, short the right signal from that channel to ground).  Is that right?

If I wanted to hardwire these -- I could just use a jumper to short the unwanted side at the pan terminals, right?




Thanks!
 

 

[mylesgm]

Is another run of these boards going to be organised?  I'd love to grab at least a pair of the mixer pcbs.  If not does anybody have some they wish to sell?

M

 

[Citrus Hill]

I would also be interested in purchasing a few of the boards.  Please let me know if any more become available.
Thanks,
Rob Mc.

 

[zmgwg]

also interested

 

[Marcocet]

hey Don

So I'm getting ready to build the prototype for my headphone cue mixers and I'm having a lot of trouble sourcing 1k faders (especially log!). I know that changing the fader to 10k shouldn't pose any problem to the 2520 but will require some changes in the pan circuit. I'm planning to just use a dual gang pot instead of the pan switch. My question is: if I follow the 10:1 rule and change the pot to 100k linear do I also need to change the surrounding resistors? And if so how were they calculated?

Thanks so much for your help! PS my studio's just around the corner on Broadway and Hewes and I've love to check out those 200 series filters you built if you've got a loaner rack available.

 

[hakanai]

Ok, so here's the deal. I'm currently on a very long trip out of the country so communication will be spotty from me. It is looking like there is enough interest for me to do a second run and have it be fairly easy. I will try to organize something with my assistant who is still in NYC to handle distributing the boards, but this may take a bit of time to set up. I'll do my best.

As for the pan questions; I have definitely had a few thoughts on how I would do it if I were to build another mixer. I would probably do 8 fixed LR pairs, 8 LCR switches, and 8 of the 7 position pans. As for hard wiring L or R I would probably leave the unwanted side of the channel unstuffed and put a 10K to ground in place of the unused pan. That should preserve levels to other channels using pans. You could also potentially use the pan space for a pad. This is again pure speculation and untested but I have always intended to do a version with switchable 12db pads on all channels. But in simplest terms, to answer your question directly yes the unwanted side gets shorted to  ground. The only thing to remember (and I'm not sure how much bearing this has on the circuit) is that the side you are hearing is still connected to ground through the 10k of the pan. That coming right before a 47k resistor must surely have an impact on the level hitting the bus.

Now as for recalculating the resistors around the pan for different value pots. Haha, at this point I must admit I am usually lucky enough to be surrounded by some very smart people and I am only mildly capable in the EE end of things. If you read the earlier posts you'll see the story behind this project and how it was simply my stumbling upon a few different circuits that looked like they would be compatible. So this is again a long way of saying I'm not sure what you would want to change the surrounding resistors too. The one thing I would watch is the final bus resistors. Their value is what the summing ACA wants to see. My personal thoughts on tackling this problem would be 2 things. I would try simple putting a 1K or 1.25K resistor in parallel with my 100K pots or (<-bad advice, sorry) I would use my pan boards to make a stepped switch.

Ok the gelato shop in Mexico is not very impressed with my internet usage to gelato buying ratio, so I better go. I will keep you guys posted on another run of boards and email anyone who has emailed me. Also, keep me posted on your progress, I am excited to see some projects in progress. And what options are you guys using/not using? faders? blocking caps? other changes?

thanks for al the interest
Don

 

[hakanai]

Oh and as for the 200 series filter/EQ module. There should be a rack of twelve arriving in NYC any day now and if anyone wanted to try them out I could arrange something. They are comin together nicely and the first dozen will be floating around NYC until I am back. You get some more preliminary info at the link in my signature

Thanks again
Don

 

[Marcocet]

Awesome. Thanks Don. Let me know who to get in contact with to try out those filters! And have a great time in Mexico.

I'm just gonna build one of these damn things and see how it works out. Since each one is looking like it's going to cost close to $1k in parts it's gonna have to be damn good for me to build any more.

 

[mylesgm]

Definitely in for boards for a 16 channel 'no pan' mixer.  Thanks Don...

 

[mylesgm]

Just wondering whats happening with this...

M

 

[madreza]

interested too if something happens

 

[baadc0de]

I didn't start yet. I'm still debating with myself if I would be better served with a full featured DIY mixing desk. You know, with busses and auxes. As it is, I might let my 24 channels (with pan pots) go for a fair price..

 

[madreza]

just a question :
can something like that be done with BA283 ? ( and of course it'll need an input tranny per channel ..... )

 

[baadc0de]

just a question :
can something like that be done with BA283 ? ( and of course it'll need an input tranny per channel ..... )

http://www.groupdiy.com/index.php?topic=41599.0

 

[gar381]

hey Don

So I'm getting ready to build the prototype for my headphone cue mixers and I'm having a lot of trouble sourcing 1k faders (especially log!). 

Jeff will soon be stocking 1k P&G faders.

Check it out... http://www.groupdiy.com/index.php?topic=31736.msg547709#msg547709

Hope this will help you out.

GARY