reeeeeeeeeally dumb cmoy question

[onionblaster]

Yeah, this one's a groaner.

Okay, well I am not a DIY-er by any means. But my friend and I (my friend is really the one in charge of the construction, he built a computer when he was in 6th grade) are trying to build ourselves a cmoy and I'm in charge of buying the parts. I know it's irritating to have to busy yourself with newbs, but I'm just asking someone to look over my parts list and make sure I'm not missing anything. So far I have:

1 H-67 AC BLACK BOX 4.94X2.75X1.275" AC BLK
2 CAP 220UF 35V ELECT NHG RADIAL
2 .1 UFD POLYPROPYLENE CAP
5 RES 10.0K OHM 1/4W 1% METAL FILM
5 RES 4.75K OHM 1/4W 1% METAL FILM
5 RES 1.00K OHM 1/4W 1% METAL FILM
1 IC DUAL FET HI SP OP-AMP 8-DIP
1 LED SS GRN DIFF LO CURR PCB 3MM
2 CONN AUDIO JACK 3.5MM STEREO
1 SWITCH TOGGLE SPDT 6A
1 KNOB INSTRUM SGL BAR RND .7"DIA
1 IC SOCKET .300 8 DIP GOLD
1 POT 10K OHM 12MM HORZ MET BUSHIN
1 POT 10K OHM 12MM HORZ MET BUSHIN
1 POT 10K OHM 12MM HORZ MET BUSHIN

Sorry if you can't intepret what the parts are. I really feel like an idiot here, mainly because I am, but that's mostly copy/pasted from my digi-key order.

Sorry to be a waste of time, but want to avoid if possible getting partway in and realizing I have to make another order...thanks a whole lot.

P.S. I know I'm missing the protoboard, I'm ordering that from Radioshack.

 

[__redruM]

See http://tangentsoft.net/audio/cmoy-tutorial/ for complete parts list with numbers.

 

[jerb]

http://tangentsoft.net/audio/mint/cklist.html

its a check list of all the parts that your supposed to have. you should try printing it out and filling it in, it will both awnser your question and give you a handy refference sheet while building your amp

redrum! you beat me by like a second!

 

[n_maher]

Also, it'd be my advice to step up to modified caps as recommended in Tanget's "Tweaks " section at the end of the article. Might as well do it right the first time. The cost impact is negligible and I found that it made a nice difference.

And while you're ordering parts from Radioshack take a look at their Green LED's I found them to be much easier to get to look good than just hot-gluing a 3mm led to the case. See my sig for pics of them installed. I've used them on all of my amps so far and think they look pretty slick.

As far as comments go that looks to be a pretty big volume knob at .7", I've used .5" on all my altoids amps (again check the pics for reference).

And feel no shame in your newbness, we all started somewhere.

Nate

 

[bg4533]

Why 3 potentiometers? You only need 1.

Does the case you are using have a battery holder? If it doesnt you need battery leads.

You can only fit 1 9V in that case normally. Maybe 2 if it isnt the battery holder one. With 1 9V battery 16V caps are plenty. Pick up 470uF or larger 16V caps.

 

[miketriple]

-2 CAP 220UF 35V ELECT NHG RADIAL
--try 330 or 470 UF electrolytic caps, like it says in the "tweaks" part. also, read what he says about the polyprop capacitors. .1uf is on the small side, .22 or .47 would be better. just make sure that the voltage rating is fairly low.. 25-35v should be good. caps that are rated for higher voltages tend to be much bigger, and they won't fit in your case.

-you only want 1 potentiometer, get rid of the other 2 unless you have other projects in mind for them.

-you need 2 100kohm resistors, also (R2 in the amp section).

-get some battery clips. 1 or 2, depending on how many batteries you want to use. putting 2 9v batteries in series will definitely improve your sound, so i'd recommend using 2. but go back up and read about the caps. make sure they're rated for at least 25v to be safe. larger than 25v won't help, but sometimes you can only find 35v.

-those dimensions are larger than an altoids tin. it should be able to hold 2 9v batteries. BUT, that case is set up for AC. are you sure that you wanted that? most people build a cmoy to use batteries. i'd recommend the standard case, digikey # SRH67B-ND. it should have plenty of room for 2 9v batteries.

 

[@sia@home]

Ummm,

heres something different.

But It will be easy as pie to fit 6 AAA batteries inside a H67 with the empty box case, ie no AC or battery spot in the back.

That way you get ~7.2-8.4V, and your *battery will last a very long time compared to one 9V battery/cell.

For caps, I'd look at Panasonic FC or FMs, in the 10v 1200uF range or even 6.3v

P12348-ND, theres a part, 6.3v 560uF, panasonic FM series, its instock and costs 30cents. its still the 8mm diameter, 11.5 high caps, but sacrificing that wasted voltage tolerance for extra capasitance and better quality of capasitance.

Everything else looks fairly good to me. But do do the checklist stuff

What opamp are you using? OPA2134?

/edit.

You don't need dual 9V batteries

I've done my own testing, a single 9V battery is still heaps. In my mint, dual batteries means while one is discharged the other is still going hard and negatively charging the dead one.

This is bad, choose either single 9V or around 6 AAAs

If you read tangents opamp voltage guide it gives you some numbers. Oh and FYI I've managed to get a pimeta to work 100% fine with 7.2V

(with 627s of course, which also need more voltage then the rather generic opamps you will be using in your cmoy)

 

[jerb]

if you dont wanna use the radioshack green leds you could always buy led clips and put whatever color led you wanted. i know frozencpu.com has them (http://www.frozencpu.com/scan/se=Ele...nu_search.html)

do a google search if you like tose led clips, im sure you can find them cheaper if you look hard enough

good luck with your amp

 

[@sia@home]

Oh, I forgot to add.

Just short out the position of the input caps, they only protect you from bad sources, which is very unlikely to happen, compared to an error in your work, which isn't even protected by these caps.

If there is a problem with your side of the amp it will still be dangerous for your headphones.

Those *protection* capasitors do nothing but make the bass sound muddy. The way around is spending more money and using larger caps here.

 

[__redruM]

Quote:

Originally Posted by @sia@home Just short out the position of the input caps, they only protect you from bad sources, which is very unlikely to happen, compared to an error in your work, which isn't even protected by these caps. If there is a problem with your side of the amp it will still be dangerous for your headphones.

If you do this, take the time to learn how to check for DC Offset.The alternative is a blown set of headphones.

 

[onionblaster]

okay, my modified order is as follows:
1 H-67 AC BLACK BOX 4.94X2.75X1.275" AC BLK
2 .1 UFD POLYPROPYLENE CAP
5 RES 10.0K OHM 1/4W 1% METAL FILM
5 RES 4.75K OHM 1/4W 1% METAL FILM
5 RES 1.00K OHM 1/4W 1% METAL FILM
1 IC DUAL FET HI SP OP-AMP 8-DIP
1 LED SS GRN DIFF LO CURR PCB 3MM
2 CONN AUDIO JACK 3.5MM STEREO
1 SWITCH TOGGLE SPDT 6A
1 KNOB INSTRUM SGL BAR RND .7"DIA
1 IC SOCKET .300 8 DIP GOLD
1 POT 10K OHM 12MM HORZ MET BUSHIN
2 CAP 330UF 25V ELECT NHG RADIAL

I think the caps are still messed up...I got a little confused there

 

[@sia@home]

Quote:

Originally Posted by __redruM If you do this, take the time to learn how to check for DC Offset.The alternative is a blown set of headphones.

You don't seem to understand tho.

Those caps aren't gonna save you from a dodgey amp. Which is what its gonna be. Leaving out that part isn't gonna make a difference.

Has anyone even seen a source that puts out DC offset?

I mean more than like 1mV?

 

[bg4533]

Quote:

Originally Posted by @sia@home You don't seem to understand tho. Those caps aren't gonna save you from a dodgey amp. Which is what its gonna be. Leaving out that part isn't gonna make a difference. Has anyone even seen a source that puts out DC offset? I mean more than like 1mV?

My Ipod Mini puts out a few mV. My modded Emu 0404 without ouput caps put out 70mV but that is a bit different.

 

[aeriyn]

Quote:

Originally Posted by bg4533 My Ipod Mini puts out a few mV. My modded Emu 0404 without ouput caps put out 70mV but that is a bit different.

Really? The iPod Mini is supposed to have output coupling caps. I've never tested mine myself...

My Cambridge Audio CDP puts off so little DC offset that my meter cannot measure it.

 

[__redruM]

Quote:

Originally Posted by @sia@home Has anyone even seen a source that puts out DC offset?

http://www6.head-fi.org/forums/showthread.php?t=100375

Amps amplify DC Offset. So a source with an "in-spec" offset of 10mv gets amplified to 100mv with a stock cMoy gain.

Those caps save you from a dodgy source being multiplied by gain. If you use a source with caps, like an ipod, your OK, but not all sources are perfect. They can be in-spec yet made dangerous by gain. I spent hundreds on my headphones, and this is a risk I won't take, without great care.