mox confusion

[cowanrg]

so im finally getting around to putting the mox boards together and i have many many questions...

ive read all the documentation, all the threads, etc, but i always find conflicting or incomplete information regarding what part is what. a lot of the part numbers in the shopping list are discontinued and there dont seem to be any substitutions and im just having a hard time figuring out what is what... is there a list that says, R001 = 3k, R002 = 4k, etc... the one on jens site seems to be incomplete.

also, on the discrete opamps, im confused by C2 and C3 (not to mention the VERY tight layout, and extra component pads that arent even used). in the pictures for assmebly on tyler's site, it seems like the caps are reversed. in the third picture on the first page it looks like they are placing the wrong caps in the wrong places. plus, i couldnt find any caps that actually fit those tiny spacings.

its just a bit frustrating because the boards dont seem like they were ready for a group buy. the information for this project is just so scattered. even with the shopping list, i was missing several parts and now have to re-order and pay a second shipping fee that will equal the parts cost.

[moamps]

Hi,

C2 is a 47 to 100pF silver-mica or styroflex type capacitor.
C3 is a 33 to 100nF MKT capacitor.

The MOX is not all that complicated at all and I'm sure all your questions are answerable.

Regards,
Milan

[cowanrg]

thanks moamps.

after reading more of the construction threads about the mox, i plan on making a beginner's guide. well, not so much beginner's, just a non-engineer's guide. its a VERY simple circuit but has been made VERY complex with all the jumpers, infinite settings, etc...

i just find it wierd that there are many places on the board that by default are left open (why have them there at all), etc.

its a simple project that 5 pages worth of info could completely cover. i would also revise the shopping list to include all the parts needed, and parts that actually fit right. i went to my local surplus today and spent about 2 hours rebuying tons of parts that fit correctly.

thankfully i havent wasted that much money yet on rebuying parts. however, i hate paying multiple shipping charges when the parts only cost a few bucks.

if anyone wants to contribute to a manual/guide for this project, email me, i could use the help. this could be an awesome project if it was organized a bit better.

[roddyama]

Originally posted by cowanrg
i just find it wierd that there are many places on the board that by default are left open (why have them there at all), etc.

The fault lays with a lot of us guys asking for more flexibility from the design. Milan, Jens, and Tyler did a super job in granting most of our wishes at the expense of design simplicity.

[fcel]

Hi Roddy ... didn't see you here for a while now. Where have you been? How is everything?

[roddyama]

:-)
I've been in forced hibernation,... well, kinda :-)

Suffice it to say I'm slowly working my way back into the grove of things here.

[fcel]

Sounds good. Cowanrg probably have other questions. So, I'll leave it at that.

[cowanrg]

i always have questions

im still (and may always) be a novice at this stuff. im being too hard on those guys though, i know i am. they did a great thing and created a great product. but its a very complex task to make something so flexible and meet the demands of many.

i might be looking at the mox lite when i get this one up and running just to make a simplified version that will have permanent settings. that will simplify things a bit. just trying to get your head around all the settings and what you need and dont need can be confusing at first.

at this point, im just going to stuff the whole board and use what i need. its a shame, considering its only to be used for one set of speakers and wont be used for prototyping, but its easier that way. and once i get it working and setup, im sure someone else could have a use for it.

fcel:

i dont know if you saw my other post, but i think that velleman kit solved my issue with the bosoz. it seems to work just great. its a neat little kit and only took about 45 minutes to an hour to build, test, and install. i just wished i had planned for it, i dont completely like where it had to go, it looks like an afterthought. oh well, as long as it sounds good.

[cowanrg]

ya know, i did come up with a question...

C200 and C500, what are they for? why would someone need them, and what value would they be?

as a side note, im sorry to everyone that i seem to ask a TON of questions and not really get anywhere my education is psychology, its not technical at ALL. but i do try and search and i try and share as much info as i can and help people out. i get a lot of emails from my website and i answer many questions (all of them very easy of course, i cant answer anything too hard!). diyaudio is a great place and i dont want to give any other impression.

[moamps]

Originally posted by cowanrg
C200 and C500, what are they for?

They are part of the ultrasonic LP filter (with R200 and R500)
(lowering gain at high frequency).

why would someone need them

You don't need them if you are using the discrete opamp.
They are needed sometimes if a fast opamps are used to
avoid the HF oscillation or partial instability.

and what value would they be?

Usually 10-100pF (silvermica, styroflex) depending of
the parallel resistor's value.

(for example:
R=22kohm
f(LPF)=200kHz
C=1/(2*pi*f*R)= 36pF)

Regards,
Milan