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Cmoy Help

post #1 of 18
4/6/10 at 6:27pm
Thread Starter 
Hi,
i am going to make a CMOY just for fun as i am doing electronics at school so i think it would help.
I am going to use the amp for UE MetroFI 220.
I know they are low impedance as I said this just for fun but if there any tweaks I can do to make the sound better with the amp please tell.
i am using the parts list i found on tangents site. this is what i am going to buy.
IMAGE REMOVED NO NEED NOW
am i missing anything?
oh and does anyone know where to but a metal mint box in Australia?
and i was reading up that u can put a bass booster on it.
All i can find about it the cmoybb but i don't want to w8 for the pcb to come in the mail so anyone know how to mod the normal cmoy with bass boost?
Thanks,
Chris
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post #2 of 18
4/6/10 at 8:24pm
The resistors are in packets of 8 so you are buying 24 10K resistors not 3

cheers
FRED
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post #3 of 18
4/6/10 at 8:38pm
Thread Starter 
thanks for that will save me a few bucks

I have been reading on low impudence headphones for the cmoy and my understanding is to just put a resistor before it goes to the output jack right?
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post #4 of 18
4/6/10 at 8:50pm
Which part of Australia are you in? I've only been able to find 1 store in melbourne which stocks altoids.

If there's a Chinese grocery store around you, there's a type of cough lolly that comes in a dark green metal case. The case is similar shape, but has slightly different dimensions. I've built 2 cmoys into these cases without any problems.

Make sure to line the bottom of the case with something though.
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post #5 of 18
4/6/10 at 9:02pm
Quote:
Originally Posted by chriswolf View Post
thanks for that will save me a few bucks

I have been reading on low impudence headphones for the cmoy and my understanding is to just put a resistor before it goes to the output jack right?
if you follow Tangent's guide the resistor is R5, on the proto board it's replaced by a link

cheers
FRED
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post #6 of 18
4/6/10 at 9:17pm
Thread Starter 

i found this and it shows the r5 is shorted but the resister goes on after the r4 goes to the ic does it make a difference in the order?
what would be good gain for metrofi 220 (Impedance: 18 ohms at 1 kHz)
Thanks
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post #7 of 18
4/6/10 at 9:22pm
I would skip the output resistor but set gain to 2x.
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post #8 of 18
4/6/10 at 9:29pm
Thread Starter 
so i would change the r4 from a 10k to 1k and leave the r3 at 1k?
Thanks
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post #9 of 18
4/6/10 at 9:47pm
Quote:
Originally Posted by chriswolf View Post
so i would change the r4 from a 10k to 1k and leave the r3 at 1k?
Thanks
that's right

measure those gain resistors (R4 and R3) with digital multimeter, make sure that they are pretty close each other. then you get proper channel balance.
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post #10 of 18
4/6/10 at 9:56pm
Thread Starter 
i am copying this design
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post #11 of 18
4/6/10 at 10:17pm
These are the changes I would recommend:
1) Replace C1/C2 with 1K resistors
2) Change R7/R8 to 1K resistors

Interesting layout, but I would recommend moving R5/R6 closer to the opamp (moving C1/C2 one position farther), moving R2 one spot left so that R4 and R8 to line up. It is also an option to move R5/R6 to be UNDER your opamp.
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post #12 of 18
4/6/10 at 10:32pm
Thread Starter 
so I want all the resistors that are part of the amp as close as possible to the ic.
C1/2 are capacitors are you sure u can swap them with resistors? sorry don't know much about this.

oh on the picture there is yellow wire going to the pot and output can i just do two different wires from the pot and output going to ground then one going to both?

and what Gauge wires do i need to connect the jacks and pots?

is it ready to build after this?

Thanks.
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post #13 of 18
4/7/10 at 12:28am
This is where I did the rest of the stripboard cmoy
http://www.head-fi.org/forums/f6/str...isited-460669/
the pictures might help.

I left the spacing resistors etc wide so it was easy to see the layout

cheers
FRED
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post #14 of 18
4/7/10 at 7:40am
Thread Starter 
I am getting 470 and 0.22 caps for better bass
r3 and r4 are 1k to make a gain of 2
i'm not sure on what resistor to use for the led
I am going to pick parts up tomorrow
DescriptionQtyID
CAPACITOR ELECTROLYTIC 470UF 10V 105C L/ESR2C1
0.22UF/220NF 100V MKT CAPACITOR2C2
Resistor to match led (input 9v) (270 ohm resistor? not sure)1RLED
4K7OHM 1/2 WATT 1% METAL FILM RESISTORS - PK.81*(2)R1
100KOHM 1/2 WATT 1% METAL FILM RESISTORS - PK.81*(2)R2
1K0OHM 1/2 WATT 1% METAL FILM RESISTORS - PK.81*(2)R3
1K0OHM 1/2 WATT 1% METAL FILM RESISTORS - PK.80*(2)R4
IC OPA2134PA OPAMP AUDIO HI PERF DIP81OPA
LED 3MM DIF GRN 40MCD1D1
3.5mm Stereo SWITCHED PCB Socket2IN/OUT
PC BOARDS VERO TYPE STRIP - 95MM X 76MM1BOARD
8 Pin Gold Insert Machined Pin IC Socket1SOCKET
SPDT Miniature Toggle Switch - Solder Tag1SWITCH
15MM METRIC KNOB - BLACK1KNOB
SAFETY 9V BATTERY CLIP - HIGHEST QUALITY1CLIP
10K 9MM SQUARE POTENTIOMETER LOG DOUBLE GANG (A)1POTENTIOMETER
3mm LED Clips Black - Pack of 201LED CLIP
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post #15 of 18
4/7/10 at 7:44am
Use the 4k7 you'll have spares and the led will be plenty bright enough

cheers
FRED
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