i built a DIY Cmoy amp a couple of years ago, and it's still working today. i used Burr-Brown OPA2604 dual-channel opamp (which is overkill, as it sucks the juice from the batteries like crazy).

the performance on my Sennheiser HD590 headphones: heavenly!
did i say it sounded heavenly? yep. HEAVENLY!

i built it when i was in UK, but here i don't know which shop can supply an OPA1302 (or other similar singla channel opamps).

but now my headphones have gone kaput: only right side got sound.

here are the pics of my amp. looks f**kin ugly, sounds f**kin amazing.

the guts


naked


in the case


This post has been edited by modD: May 24 2005, 06:59 PM

i'm in the process of transferring my cmoy into a new enclosure. that also includes getting a new circuitboard and new wiring jobs etc...
because of this small amp, my whole room is in a mess!

but i'm worried about unsoldering the opamp from the old pcb... can excess heat damage it?

looks like an 8 pin socket from pasar road is due soon...

Alamak, is your amp gonna have equalization?

Alamak, just wanna ask. in case i need an opamp, can i get it through you?

right now i'm using Burr-Brown OPA2604AP dual opamp, and i'm in the process of transferring the whole amp onto a new circuit board and casing. i'm afraid i might have burnt the opamp while desoldering (i didnt use a socket). i can't test this yet coz my headphones have gone kaput.

i'm currently in the process of moving my CMOY amp into a new casing.

well, not new actually... being a cheapskate, i decided to reuse an old external modem case for the amp.



the top post is the volume post which i will attach a black brushed aluminium knob later.




this is the rear part of the casing. i plan to have 2 inputs, one for the normal 3/4" minijack, and one for seperate right and left RCA jacks. the RCA sockets will be placed on the empty area on the left. on the righ, you can see the tops of the power supply capacitors. i purposely make it visible like that to look like american hot rod cars where the engines protrude from the hood hehehe




this is the PCB. i suck at planning circuits, so this is what i ended up with. actually, it's only halfway finished. i paused this project a few months ago and right now i forgot a lot of things about the circuit. it seemed like i have to start over with a new board... sigh...

maybe it'll take a while till i have enough time to continue this... anyway, i plan to spraypaint the whole casing. the Aztech Modem wroting kinda seem lame

damn... i could use one...
but no money now, double damn...

arghhhh my Cmoy doesn't work anymore! only a deep hum left... and no way to test which components failed. i tink it's the Burr-Brown OPA2604AP dual opamp...

biatchhhhhhh!

if an opamp fails, will it produce any sound at all? because in my case, there is still sound from the source which is a cd player, but it's VERY faint and flat. on top of the faint music, there's a deep hum on one side.

i'm trying to be optimistic and hope that the opamp is still working, and the fault lies on the other components or just my horrible circuit design.

nice, doc!
a bit of labelling here n there and you can open a custom amp shop

btw can i just go to farnell/RS and pick up stuffs? or do i have to be a registered company to buy things from them?

i'm looking into rebuilding my CMOY amp from scratch and i wanna get a Burr-Brown opamp, which i'm not sure i can get from Jln Pasar.

the schematic:

http://www.headwize.com/projects/showproj....e=cmoy2_prj.htm

for the opamp chip, go to www.rsmalaysia.com and search for OPA134PA. the manufacturer is Texas Instruments. for the other components, not hard to find in normal electronic shops...

and also, you need to mass produce the pcb with custom circuit. if not, you'll have to do lots and lots of wiring and soldering.

guys, i got a question

i got a dual potentiometer here, Alpha 10K log, but i can't find references to which pins do what... anybody got tips to identify them? i have a multimeter to test the resistance.

This post has been edited by modD: Nov 23 2005, 08:23 PM

thanks!!!

but anyways, after connecting the pot, i have confirmed that my CMOY has gone FUBAR!

i've transferred all the components onto a new board, double and triple checked the wirings... but no go

the sound crackled horribly, i mean HORRIBLY like i just played the music through a Metal Zone distortion pedal and Mesa Boogie Triple Rectifier amp.

to top it off, anything from the center channel of a song like vocals are lost. but when i slide the soundcard mixer's panning to left or right, the vocals appear, but still with the horrible distortions.

and the deep hum is still there too.

so that's it, i'm gonna feed this amp to the dogs (assuming they like to eat dead pcbs) and get the OPA2134 opamp from RS, and all the other materials from Pasar Road. i think the potentiometer still works though.

cheers!

yeah_guyz: yup, the sifus here are friendly indeed

chernloon: the grounds are correct, the inputs are correct... shouldn't be a problem because i used the same schematic before. the problem began when i stooopidly decided to disassemble everything and transfer them to a new enclosure. after that poof! my 3 year old cmoy went kaput.

i think i must've somehow fried the opamp during desoldering. that'll teach me to use sockets!

anyway, thanks a lot for the offer to take a look at it but i think i wanna start again from scratch. if that one fries too then i might take up on the offer

the 2 buffers would double the $$$ needed compared to a cmoy. how does it sound compared to the cmoy anyway? i'm using a Sennheiser HD590 btw...

i just realized that in Tangentsoft, the part numbers for Farnell (Newark) and RS are listed, and it can be used on the Malaysian version of these sites. makes it easier

chernloon, does the Alps dual pot that you got from RS has the power off feature when you dial it to the far left? how much is it? thanks...

This post has been edited by modD: Nov 24 2005, 01:00 PM

nicely packed! doctor, what caps are you using?

i think my amp is going in the 'abandoned projects' dustbin... with my headphones rosak and all...