[Troy81]

My very first build, ever. i was suprised at how smooth it went, it took me about 3 hours total. everything seems perfect except i burnt out the light since i didnt order diodes, i knew it was coming so its all good.

Question, when i turn my sandisk player all the way up, the sound cuts and restarts, the battery is completely dead on the sansa so im trying to charge it then find out. but if it doesnt fix the problem, or if this is a common problem what is it? i dont think there are any shorts anywhere

 

[Troy81]

i charged the battery on my sansa and it didnt fix it at all... im thinking the problem is coming from the power section, seeing as no matter how high the volume on the potentiometer it doesnt cut out. im only using 1 9v battery but i dont see that making it cut out at higher volumes from the sansa. is it possible that there isnt enough impedence on the output? im using a 1k resistor and cheapo earbuds(wating on headphones). any input would be appretiated


and thank you to everyone that chimed in on my other thread. appreciate it alot.

 

[Troy81]

does anybody know if it would be a bad idea to try to let my CMOY run computer speakers? just to see if the increased load kept it from cutting out

 

[Troy81]

ok, so i decided to try it and it didnt seem to hurt the amp at all, of course the speakers were hooked to a USB port so that may have takin some strain away, i doubt it though. butt the problem still persists with the amp. if i turn the sansa up past about 5/8 power it cuts in and out.
just to clarify, the potentimeter can be all the way up, or almost all the way down and it still does this cutting.
also i noticed, if i put my hand over the sansa the music gets louder and more clear.

 

[Tomo]

You should use your multimeter and check the circuit again. The power supply rail should be +4.5V and -4.5V to ground. Often this gets screwed up for one thing or another.

You should also check the headphone output to ground. This should be nearly Zero.

I think you are getting clipping problem because you are using cheap earbuds. Probably those earbuds are running 8 ohms and that is too small. Note I think CMoy is designed for anything above 30 ohms. (probably 120 or more)

This also means driving computer speakers is out of question. It can, but you can't expect much.

 

[Troy81]

if the power circuit is off just a little will it run fine at low volumes? it runs for a long time at low volumes just fine(i dont know the limits)

head phone output/ground was good

If i put a larger resistor in the output would it have a significant enough change?

i guess ill be waiting to get my Headphones. what kind do you reccomend? nothing too expensive, gotta keep the wife happy, im still under like 30$ right now

 

[DKJones96]

Your speakers probably worked fine because the input impedance of the amp for the powered speakers is high. The more load you put on an amp, either by volume or lower Z, the more likely you are to find a flaw in the amp. Almost any amp will run great at low volumes no matter the load. However, stick a low resistance set of cans on an amp, crank it all the way up and few amps will keep up gracefully. Especially solid state amps.

What opamp did you use? A lot of the amps recommended here don't run great at 9 volts. The dual from radioshack hardly runs at all.

 

[Tomo]

Quote:

if the power circuit is off just a little will it run fine at low volumes? it runs for a long time at low volumes just fine(i dont know the limits)

When you turn off your amp, your amp stops drawing electricity from your batteries. However, there is some power left in the capacitors in the power supply. So the amp will keep running for some time. ... If the sound is coming through considerably long time, your amp circuit may have leakage from input to output.

Quote:

head phone output/ground was good

Good. Now check the rails. You gotta do it because it's important.

Quote:

If i put a larger resistor in the output would it have a significant enough change?

I would not do anything with resistors. It is an (old) conventional practice to add 120 ohms at output, but it doesn't really do something you want. I would wait for a good pair of headphones (30 ohms at least).

Quote:

i guess ill be waiting to get my Headphones. what kind do you reccomend? nothing too expensive, gotta keep the wife happy, im still under like 30$ right now

You don't have to tell your wife everything. But if you are yapping about 30 bucks, you might want to stick with your earbuds. There is nothing that good in that range. You might try Sony StreetStyle headphones, you can use it later for work or sport if you get a better pair.

 

[Ashkii21]

I remember when I built my first Cmoy, I accidentally put one of the power caps in the wrong orientation. Luckily when I turned it on, the cap didn't pop open, the top just kind of popped up. I would recheck your circuit with a multimeter. Also it is a good idea to let us know which opamp you are using. I started with an OPA2132 then used an OPA2227. I now use the TLE2072. (I like this one the best) These work fine with a single 9V battery. Recommendations for headphones would be the Koss KSC75 (sportsclip/clipon), it is about $15 and I think they are around 60ohms. I feel they are the best headphones for a low price.

 

[Troy81]

im using opa2134pa

the music stops intantly when switched off

rails?

it also distorts when i turn up the potentiometer.

the sansa by itself is louder than through the amp

circuit seems fine

 

[DKJones96]

It's unity gain stable, running at 4 volts above minimum spec, and offers plenty of current.

I'm with Tomo, check your rails. Where did you get your build instructions?

My cMoy I only use for testing anymore but running off a single 9v battery and I believe a gain of 9 will be blasting your ears before my M240, E260, or my Clip get above half volume.

Rails, that's what the positive and negative become with the virtual ground. They should be equal, or at least damn close, from the virtual ground you made with the resistors and caps.

 

[Troy81]

http://tangentsoft.net/audio/cmoy-tu...angent-sch.pdf - schematic i used

i didnt really use instructions, i looked at some pictures if i got stuck somewhere, i cant remember where i got them, i printed them out.

i had excess soldier, no noticable bridges, so i decided it may be time to lessen the piles. i got some braid, cleaned it all up to the best i could do. now there are definately no bridges.
im not sure if the problem persists because now when i turn the amp on and it starts playing music i slowly turns off. im not sure what would make this do this. i thought maybe capacitors? no shorts or bridges anywhere, i need to get a real mulitmeter to check numbers not just shorts. i just dont really want to spend money right now so im hoping for an answer that doesnt cost me anymore for now.s amp is pushing 50 bucks.

 

[Tomo]

Well 50 bucks? Did you know Grado RA-1 cost about 300-500 dollars? You are saving money like a demon, man. Get a multimeter. Without it, it is like trying to golf without any clubs.

A multimeter is absolutely important to have and to know how to use. You don't need to be a master of it, but you ought to be able to use:

1. DC volt-o-meter
2. AC volt-o-meter
3. Ohm meter (Resistance)
4. Conductivity Checker

You only need these features most of the time. You might want capacitance meter, but this feature pull up the price ... doubles it? Any cheap one would do. I really like a RadioShack Auto-ranging multimeter. I can operate with one arm and have it dangling.