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WIGGLING 'LITE' IN GUEST MODE

Dot Com Mixer Mods?
MUFF WIGGLER Forum Index -> 5U Format Modules  
Author Dot Com Mixer Mods?
Bryan B
I just got my Variable State Filter along with a Filter Mixer from DotCom last night. I started wondering why there were so many unused connectors. Then it struck me, it is because the PCB is fully built to be an 8 channel mixer!

So I went back to the data sheets for the 8 channel mixer and found that my suspicions seemed correct, the layout is identical for the Q112, Q113, Q161 and Q162.

Has anyone ever brought this up here before?

I have an Oscillator mixer coming tonight and was eventually planning on buying the 8 channel mixer next, but now I am thinking I will buy a couple blank panels and mount some jacks and pots in it instead. It might be nice to add switches for AC and DC outs as well.

This seems like a killer mod if someone has one of these 4 channel mixer modules and is trying to save money (to buy more modules)!
doctorvague
A standard way to build a mixer is with opamps wired as inverting amplifiers.

http://www.doepfer.de/DIY/a100_diy.htm

If you scroll down to 'Inverting amplifier', there's a schematic and an explanation. The inverting input is a 'summing node' where you can add more inputs. Scroll just below to '3. Circuit examples' for a schematic adding more inputs with attenuators. Just like Arrick's 8 channel mixer, some inputs can be wired just as a jack and some with attenuators in any combination you like.

I would check the gain on the filter mixer to make sure it is unity. There's a chance it might be wired for less than unity (same circuit board with different resistors). I'm not saying that's the case but it's something I would check if I was doing this.

STG's 'imagine panel' would allow for 6 more input jacks, 3 of which could have attenuators, if that interests you. I wired one as a passive 3 channel attenuator.


I'm no EE so if I've got any misinformation here - anyone, please post.

Cheers
Phil
Bryan B
I am a bit familiar with the workings of a mixer, but it is nice to get a different perspective as well.

According to the data sheets, the PCB and component values are all identical.

The imagine panel looks awesome and a great suggestion! I may need to work some custom magic for what I really want to do though.

It would be nice to have 4 input jacks, 4 attenuating pots for the inputs, Inverted out (or switch), combined out, AC out and DC out (or a switch).
Henfield
You could use STG's panel to make the 4 channel mixer into an 8 channel mixer, but I am not sure about the cost effectiveness.
bwhittington
Bryan, I was tickled when I first figured this out, too. I didn't know about the Q161/162, but the Q112 pcb is wired for use as a Q113. I've experimented with using the jacks and pots with the other set of connectors, and it works perfectly well. That's the reason I've never bought a Q113. It seems like a horrible waste if you can buy the same board less a few pots for so much less.

When I get around to it, I intend to wire up a single-width expansion panel with two sets of jacks and pots (using .5" MOTM-style knobs) to put between two Q112's. It's a great little project for a DIY rookie like me.

Cheers,
Brian
Bryan B
Am I late to the DIY DotCom mixer expansion party? Sorry to rehash old information.

Brian: I will post some pics of my new cabinet soon. I can't stop staring at it!
bwhittington
Bryan B wrote:
Am I late to the DIY DotCom mixer expansion party? Sorry to rehash old information.

Brian: I will post some pics of my new cabinet soon. I can't stop staring at it!


I don't think this has been discussed here before, and it hardly matters if it has. I think it's a cool idea, and discovering a few little things like this was what really made me fall in love with the Dotcom format.

I can't wait to see pics of your cabinet--hopefully from lots of angles. It sounds awesome.

Cheers,
Brian
kindredlost
Bryan,

Post this to the Yahoo group if you are a member. If you are not, do you mind me posting it? This is a killer DIY project.

-David
Bryan B
Go ahead and post it there, no worries.

I just posted it here to get the info out to other people who could use it.

I am a noob to the DotCom modules, so I am not any modular groups or forums (except this one of course).
Bryan B
I now have a few panels, now I am just looking for the Dotcom style jacks. They are plastic in the back, but have metal threads (where they come through the panel). Does anyone know a mouser part number for them?

I would also like to get some pots and knobs, if they are cheaper than the $4 each (on the DotCom website). I have some cheap pots and knobs that are very close, but I would rather they look spot on identical. $50 for 6 pots and 6 knobs seems slightly steep, but maybe I am wrong and that is the cost of quality.
bwhittington
Bryan B wrote:
I now have a few panels, now I am just looking for the Dotcom style jacks. They are plastic in the back, but have metal threads (where they come through the panel). Does anyone know a mouser part number for them?

I would also like to get some pots and knobs, if they are cheaper than the $4 each (on the DotCom website). I have some cheap pots and knobs that are very close, but I would rather they look spot on identical. $50 for 6 pots and 6 knobs seems slightly steep, but maybe I am wrong and that is the cost of quality.


Knobs

(Spot on, to my eyes, though maybe don't order a million on my word alone.)

Jacks, Nuts, Washers

(Though Modcan uses Switchcraft 112A jacks, which feel a lot better.)

Pots

(I believe the 24mm 100k linear pot is what Dotcom stocks. Wait for someone else to pipe up on that before ordering, though.)

Cheers,
Brian
Bryan B
Wow, thank you Brian! Those parts look great to me and the price is even more fantastic. This project is really shaping up better than I ever hoped.
chromium
I have those knobs from Smallbear, and they match just fine IMO.

I still have a bunch of the Switchcraft 111 jacks from when they had them at tedss.com for cheap. Every now and then I need TRS for something, though.

That prompted me to look at the Neutrik NYS234 - which are TRS with "normaling" contacts for the tip and ring (which could also be put to good use). I still haven't ordered any to try out, but I've had good experiences with other Neutrik connectors... and these cost quite a bit less than the Switchcrafts. Anyway- FWIW:

http://mouser.com/ProductDetail/Neutrik/NYS234/?qs=sGAEpiMZZMv0W4pxf2H iVy2l1tTxTkO1ijALz%2f8mp%2fo%3d

There's also a TRS version without normaling for even less, but those are out of stock (NYS234-3)

Note that they are intended for PCB mounting, but I figured I could deal with that.
essex sound lab
Wow, excellent work Brian!
Henfield
Bryan B wrote:
I now have a few panels, now I am just looking for the Dotcom style jacks. They are plastic in the back, but have metal threads (where they come through the panel). Does anyone know a mouser part number for them?

I would also like to get some pots and knobs, if they are cheaper than the $4 each (on the DotCom website). I have some cheap pots and knobs that are very close, but I would rather they look spot on identical. $50 for 6 pots and 6 knobs seems slightly steep, but maybe I am wrong and that is the cost of quality.


I don't know if you realize it, but the pots and jacks that are available through the Dotcom website aare already wired with the header connectors. That way they are "plug and play" with the Dotcom modules. Although you will find the jacks and pots for less money elsewhere on the web, you will have to source the wire and connectors, as well as solder them up.

To Turn your 4 channel mixer into an 8 channel mixer, you would need 3 pots from dotcom ($12), 6 jacks from dotcom ($15), an Imagine Panel from STG ($35), and 3 knobs from Small Bear ($3.60) for a total of $65.60 (plus s&h) and about 10 to 20 minutes of your time to plug in the parts and screw them into the faceplate (very simple DIY).

You would then have a mixer that can be configured as 2x4 or 1x8, and does not take up any more power than the existing 4 chanel mixer.
Bryan B
I already bought connectors and the proper gauge wire. I bought it all when I saw that power cables were really expensive and decide to make all of my own internal cables. I bought the 2, 3 and 6 pin connectors and a 100 foot spool of wire and it already paid itself off when I ran the power.

I will be saving over $100 on this 8 channel AC/DC mixer easily, so a little time investment to make it happen is no big deal to me.
bwhittington
Henfield wrote:

To Turn your 4 channel mixer into an 8 channel mixer, you would need 3 pots from dotcom ($12), 6 jacks from dotcom ($15), an Imagine Panel from STG ($35), and 3 knobs from Small Bear ($3.60) for a total of $65.60 (plus s&h) and about 10 to 20 minutes of your time to plug in the parts and screw them into the faceplate (very simple DIY).


I suppose you could do that, but the price difference between the Q112 and Q113 is $68. Spending more (with shipping) to DIY an 8-channel mixer makes little sense. Slopping your own together behind a blank panel (my intended approach), runs about $19 for parts + a single or double panel, about $30 or less per mixer depending on how you do it. When you start counting your time, the Q113 starts to look like a pretty reasonable deal, though I have my own design in mind for my panel . . . and like pretending I know what I'm doing with this stuff.

Cheers,
Brian
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