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FS: Custom CMoy boards - Page 3

post #31 of 108
Quote:
Originally Posted by wquiles View Post
In the end, what were your changes to the original design? Can you please share a short summary of what parts you changed/added to Joshatdot's schematic/parts list.
Here's Joshatdot's original thread, including his parts list... It's probably better for discussion than this FS thread, so please move subsequent replies/questions/etc. to the following location.

My custom CMoy Boards Arrived! **Pics inside & Parts List**

----------

My parts list has different resistors, capacitors, and op-amp (though, again, I don't recommend the OPA2228 op-amp without decoupling capacitors). I examined each component and tried to find the highest-quality part that Digi-Key stocked. The values of the resistors are lower and the ratio between them results in a gain of ~5.51 instead of the usual 11. The gain is calculated with the following formula: (R4/R3) + 1. I chose these particular values because they worked well in the similar Mini^3 amplifier, and because my low-impedance headphones didn't need a lot of amplification. They didn't even need a gain of 5, but some op-amps require a certain amount of gain to be stable, so it's a good value for compatibility.

I chose to jumper the R5 pads, and I also jumpered the input capacitor pads (C2), so those parts are not included in my list. My prototype used R3-value resistors for C2, as seen in my list, but they didn't really make a difference.

So, all of the most important parts are different, and eventually I needed an extra pair of capacitors for bypassing/decoupling (better purchased from Digi-Key than Radio Shack)--these aren't in the list, since they require some custom work. You might also decide to go with a 1,000 uF power capacitor instead of the 470 uF, since the 470 is already so large that it needs to be bent over to fit inside a mint tin.

I think I'll re-do my list later this evening and post it in Joshatdot's CMoy thread.
post #32 of 108
PM sent
post #33 of 108
PM sent as well!

post #34 of 108
Got my two boards - thanks much

Will
post #35 of 108
Quote:
Originally Posted by infinitesymphony View Post
Here's Joshatdot's original thread, including his parts list... It's probably better for discussion than this FS thread, so please move subsequent replies/questions/etc. to the following location.

My custom CMoy Boards Arrived! **Pics inside & Parts List**

----------

My parts list has different resistors, capacitors, and op-amp (though, again, I don't recommend the OPA2228 op-amp without decoupling capacitors). I examined each component and tried to find the highest-quality part that Digi-Key stocked. The values of the resistors are lower and the ratio between them results in a gain of ~5.51 instead of the usual 11. The gain is calculated with the following formula: (R4/R3) + 1. I chose these particular values because they worked well in the similar Mini^3 amplifier, and because my low-impedance headphones didn't need a lot of amplification. They didn't even need a gain of 5, but some op-amps require a certain amount of gain to be stable, so it's a good value for compatibility.

I chose to jumper the R5 pads, and I also jumpered the input capacitor pads (C2), so those parts are not included in my list. My prototype used R3-value resistors for C2, as seen in my list, but they didn't really make a difference.

So, all of the most important parts are different, and eventually I needed an extra pair of capacitors for bypassing/decoupling (better purchased from Digi-Key than Radio Shack)--these aren't in the list, since they require some custom work. You might also decide to go with a 1,000 uF power capacitor instead of the 470 uF, since the 470 is already so large that it needs to be bent over to fit inside a mint tin.

I think I'll re-do my list later this evening and post it in Joshatdot's CMoy thread.
Cool - thanks. Yes, please do post an update on Jos' thread when you have some time - that would be very appretiated as I don't want to start building mine until I can review your changes

Will
post #36 of 108
Thread Starter 
I've been out of these boards since Xmass. I ordered another batch from OLIMEX, so it'll be afew weeks till they arrive.
post #37 of 108
What's the process for getting one or two of these? Witing list, first PM, first served? I'd like at least one, and have subscribed to this thread. Thanks Joshatdot.
post #38 of 108
Thread Starter 
I'll post here when I get the boards in. I'll try and make a waiting list, as there are many who wanted these in these last few weeks.
post #39 of 108
I would like to know when more are available. I've been planning to build a cMoy for a while but am still working on getting my soldering iron repaired. I initially thought the iron pen was fubar, but now I suspect the base or cable. Last time it was used it worked fine, but after pulling out of storage, no heat.

Is it possible to use closed caps instead on this board? If so, what would you recommend? Also, is this board small enough to fit into an Eclipse mints tin?
post #40 of 108
Thread Starter 
closed caps? i designed the board to use small input caps, it'll fit 5.0-5.08mm lead spacing caps, or you can fit whatever you can on it & in case.

board was designed to fit in mint tins, check the CMoy in my sig.
post #41 of 108
Quote:
Originally Posted by Joshatdot View Post
closed caps? i designed the board to use small input caps, it'll fit 5.0-5.08mm lead spacing caps, or you can fit whatever you can on it & in case.
I suspected the board might be too large (wide?) to sneak into an Eclipse tin. I was merely thinking of creating a smaller package if your board was small enough.

Sorry, by closed I meant sealed. The cap marked 22 is not sealed and those can potentially leak/ooze. I'm not an electronics expert, just the occasional tinkerer, but I have had caps on audio gear, motherboards, etc, leak and I was merely wondering about swapping that out for sealed to prevent that possibility. My new motherboard (gigabyte) has all sealed caps. So if I were to use sealed, I was wondering which would be best.
post #42 of 108
Thread Starter 
please use my DIY thread for asking about the board

http://www.head-fi.org/forums/f6/my-...s-list-251361/
post #43 of 108
I would like to purchase two if possible. Thanks. Len
post #44 of 108
Thread Starter 
Quote:
OLIMEX - Shipped as of 1/15/2008
Dear Josh,

we can't offer re-order discount anymore, the archive is so huge that employee spend between 20 and 30 minutes to find phototools in the archive which makes the whole operation non-sense, so we decided to discontinue this option, instead of this we now give discounts if more panels are ordered.

I'm afraid that with the continuous USD/EUR falling rate the price will become higher and higher for US orders, I'm sorry for this, but we are in Europe and all our expenses now are in Euro so selling in USD with this 7 year in the row falling value is not possible anymore.

Best regards
Tsvetan / Olimex
post #45 of 108
Too bad, that was a good gig. Not surprising about the $. With luck, a new president and other electeds, maybe it'll start to rise again. Keep your fingers crossed.

At any rate, I wanted one, but I'd gladly take another one or two (depending on price) to help boost an order. I've been looking forward to my first amp build.
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