Guide to fix up a Cmoy 2

[RancidM 0]

Cheers again Heady.

 

i will keep it all simple and just use a 12Vdc power supply and mount a dc socket on the box.

 

maybe when all the parts come i will take some pictures..

 

[Guest strumluff]

Heya, thanks for the advice

 

Can i just confirm then, that a 220R 0.6W metal film resistor is okay for an RLED that has a resistance of 183.3 Ohms?

 

As for the stereo sockets, are PCB mountable ones preferred over the narrow tube type sockets?

 

Thanks again!

[heady 0]

Heya, thanks for the advice

 

Can i just confirm then, that a 220R 0.6W metal film resistor is okay for an RLED that has a resistance of 183.3 Ohms?

 

As for the stereo sockets, are PCB mountable ones preferred over the narrow tube type sockets?

 

Thanks again!

 

I must emphasize that I studied physics like 30 years ago. So I am no expert. But I do know that to make sense out of the RLED values, we also need to know what voltage are you planning to run the amp at.

 

I copied this from Tangent's site (sorry Tangent):

RLED

This is the LED current limiting resistor. Use Ohm's law to figure current given the LED's voltage drop and the power supply voltage. For example, consider a 1.8V LED with a 15V power supply and a 4.7 KΩ RLED:

 

I = V/R

I = (15 - 1.8) / 4700

I = 13.2 / 4700

I = 0.0028

I = 2.8mA

Most LEDs require 1mA to get minimum useful brightness. More current gets you more brightness, but of course uses more power, which mainly matters with battery power supplies. You don't want the LED to be too bright, because that's annoying.

 

Typical values are 1 KΩ to 10 KΩ. I personally use 2.2 KΩ and 4.7 KΩ most often.

 

 

 

Hope that will help you with your decision on what value to use. Most LEDs are 3V and current can be up to 20mA. So take your pick of how bright you want it to go.

 

As for the 3.5mm sockets, I guess it all depends on how you are going to case it. The CMOY2 has no provision for the sockets on the pcb, so you will have to find some way to secure them. So, that's why we normally use the type with the screws, so we can fasten them to the casing.

 

Anyway, I prefer not to use the pcb mounted ones as casing them is a real pain. Make a tiny mistake in the drilling the holes and the stupid pcb won't fit because of the sockets. And kiss goodbye to another botched-up case.

 

 

Edited August 30, 2006 by heady

[Guest strumluff]

Thanks for the help Heady, thats some interesting info that I didn't know about before .

 

Can I ask why carbon resistors are preffered for RLED over metal film? Will using metal film hurt at all? At the moment 0.6W metal film is all i can use

Edited August 30, 2006 by strumluff

[heady 0]

strumluff, reason for specifying carbon instead of metal film, is to lower cost. A carbon resistor 5% is more than sufficient quality for this purpose, as it is not in the audio chain. And it can be easily obtain and cheaper to boot.

Edited August 31, 2006 by heady

[jasonhanjk 0]

Hi ya. I am back after 2 days on the Battle Field (2).

 

For the LED, giving it 5mA will be sufficient. Designing it to go higher would also means that your battery will go flat very fast. My recommendations is to use resistor between 1.2k to 1.5k, 1/6W carbon.

 

As for removing the LM6171. I don't recommend for newcomers as one false step could burn the other ICs easily. My bad on the dual voltage, seems like I was greedy back then. Cmoy2 was design for beginners so I wouldn't count on it to be as great (sound) and expensive as other amp.

 

RancidM,

The default gain would be sufficient as onboard sound gives at least 1Vrms. I would also suggest to get a soundcard if you intend to do serious listening. In my experience, most onboard are noisy.

 

Heady,

Thanks for standing in in my absent. Hopefully I will be having some "prototype" next year and let you havefun wif 'em.

Edited August 31, 2006 by jasonhanjk

[Guest strumluff]

Thanks guys, now I been to Maplin today and I can really go on a rant about the poor service and lack of stock but I'll spare you all

 

I bought these stereo sockets, it has 2 pins, I'm guessing for left channel and right channel...but where's the ground?!

 

Linky: http://www.maplin.co.uk/Module.aspx?Module...rce=14&doy=31m8

 

Ta!

Edited August 31, 2006 by strumluff

[heady 0]

strumluff - I see 3 tabs. According to the link, the copper coloured tab is tip (left), the silver is ring (right) and last tab must be ground. You can test it easily by using a mini phono to phono cable, plug it in and test with multimeter.

[RancidM 0]

Jason mate...

 

would you have an issue if started a new thread follwing my building of the Cmoy2 ?

think of it as the most basic instructions for the very very amature electronics chap. (ie me)

[ClieOS 0]

Here is my first try, fitted in a poker box.

The modification i make: set gain to 3, interchange opa2227 with a pair of op270. The only downside is op270 eatup a lot of battery and die in less than 10hrs, but than i can continue to use the same battery with opa2227 . Most of the part are from farnell, the best i can find anyway.

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[heady 0]

Nicely done. Good show. How do you like the sound?

[ClieOS 0]

With opa2227, sound not as good as my mint with opa2227 (close actually), but does have a wider sound. With op270, i think it sound better than mint, mid and low range stand out much clear but not overpowering, a warm sound in general. Personally like it better than mint.

[jasonhanjk 0]

Jason mate...

 

would you have an issue if started a new thread follwing my building of the Cmoy2 ?

think of it as the most basic instructions for the very very amature electronics chap. (ie me)

 

Sure thing..

[pegasus21 0]

Ok, just finished one with an AC to DC regulator... Plugged in AD8620. Sounds nice. Just need to figure out how to mount it in the casing.

 

Oh and a better IC.

Edited September 4, 2006 by pegasus21

[loop_ 0]

that's a very nice casing..did you secure the board with a glue gun?

 

what are those black resistors? Holco? from farnell?