MOX builder’s thread

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#4
#5
MOX builders thread is about the construction of an adjustable cross over module, partially based on moamps original design – hence the name has been reused.

Thanks to moamps for his efforts in both the descrete opamp and the original filter design found here : http://www.diyaudio.com/forums/showthread.php?s=&threadid=27651&highlight=

Also many thanks to Tyler who has made it all happen, for managing the group order and for his excellent page here:
http://www.anidian.com/audio/home.shtml

The board is a module that can form the following signalpath:

An externally hosted image should be here but it was not working when we last tested it.


My prototype board looks like this:

An externally hosted image should be here but it was not working when we last tested it.


More info can be found here on my homepage

Active filter two - mox

Please post pictures and other relevant material here

\Jens
 
#6
Tiroth,

I have noticed two different resistor values listed for collector resistor R3 on the discrete opamp. One is 392 ohms and the other is 360 ohms. Which value would be more optimum? You had posted your findings on a very low DC output offset, with which resistor value? Was this one of the follower buffers, HP, LP filter or was it with gain?

Putting together my order of parts. It always adds up to more than you think. A couple hundred dollars just to populate six boards. Still deciding on a power supply. What is everyone else going to use?

BDP
 
#8
Batteries are great, but 33AH? Pretty stiff supply! 😉

BDP, I used 392. The offset is going to vary slightly depending on the supply voltage. You can trim it to zero by using a pot or a selected resistor in R4. I did not need to trim it for my use--the offset was so small that it did not affect the operating point in the MOX circuit.

I measured the offset both in-circuit with one sample and on the bench (Gain=1 buffer). The results were similar.
 
#10
Probably a stupid question...


Can two active xovers be hooked in parallel to one set of output jacks, ie one rolling off at say 200 hz and one going out to 2000?
Will it do what I want, reinforcing the lower bass, or will it screw something up?
A simple equalizer circuit built on the experiment hole portion of the board is probably a better idea. Thanks. I hope I can comprehend the answer. We'll see...
 
#16
All of the parts seem relatively easy to find, except the 1uf cap in the 5mm size in polypro. I can find the other three values, but I am only finding PE in the 1uf. Any mfgs or part numbers would be appreciated.

The 15.2K resistor looks like it can be arrived at by a 28K and a 33.2K in parallel. Gets ya' to 15.19K by my calculations.
 
#18
marsupialx said:
All of the parts seem relatively easy to find, except the 1uf cap in the 5mm size in polypro. I can find the other three values, but I am only finding PE in the 1uf. Any mfgs or part numbers would be appreciated.

The 15.2K resistor looks like it can be arrived at by a 28K and a 33.2K in parallel. Gets ya' to 15.19K by my calculations.
Click to expand...

as Jens said, PE is just fine. as for the resistors, i use vishays in my stuff, and mouser has vishays in 15K range, just get a few extra and since they are 1% tolerance, you should be good with 15.2K. i needed a 120ohm resistor before, so i just got a bunch of 121's and tested them out to 120 ohms.

btw, you still need to email me so i can send out some batteries 🙂
 
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