[mminutel]

I want to start off by saying that other that my Nano, a horrible cd player and my pc with onboard are the only sources i have access to. I just built my CMOY and had fun doing it for the most part but now it is becoming annoying.

there is a slight hiss which is said to be corrected with resistance on the outputs (R5 in tangents guide), when i put 1 ohm in i didnt notice much but when I put in 10 ohms my 2132 seems to get very hot and gives very low output sound. any suggestions on that would be appreciated.

NOTE: There is significantly more hiss when I have it in my CD player rather than my nano but when i turn either of them off it goes away. so would this be my source causing it and nothing to do with the amp.

for my next problem, it just sounds horrible:bloated bass mainly. did i do something wrong with putting it together or do these just not sound that good.

Also, my nano does NOT have a TURBOdock. I should be getting that Monday or Tuesday at the latest. Could this cause that problem? it is plugged directly into phone out so maybe that is causing some of it?

If there is anything I have done wrong wiring it has anyone done the same thing and found a way to correct it? I am open to any suggestions. The hiss, I assume, is my source and hopefully the line out will cure it but as for the bloated bass and such, i have no idea.

Thanks guys.

I have done about everything Tangent has suggested.

 

[Filburt]

Have you checked to make sure all of your connections are correct? Is the output VERY LOUD when you get music at all, or is it still fairly normal volume?

If it is not just outrageously loud and giving only a small portion of the audio band, you probably have feedback, although check to make sure you have the right value resistors and that they're connected correctly as, for example, you may have switched them by accident. The noise and warmth issues make me think your op-amp could be oscillating. The remedy for that could be to place something like 2.2uF ceramic capacitors at each rail (power) by connecting the capacitor between pins 8 and 4 on the op-amp and ground.

 

[tomb]

As constructed by Tangent's tutorial, the CMoy should have a nice, well-rounded and sweet sound with the 2132. It should also be dead quiet - without the output resistors. The usual response in cases like these is, "photos, please!" We may be able to spot something.

 

[Slaughter]

The 2132 should never get warm in a cmoy, so pics will be needed.

 

[mminutel]

unfortunately I am limited to dial-up at my moms house so pics will probably have to wait. ill toy with it some more and see what happens. If is helps, I am still at the stage where he used gator clips to check to see if it was working so should i try to hook up the other stuff and try it? maybe im just not getting good connections.

 

[Pars]

If the opamp is getting hot, I'd wait unless you want to toast it.

 

[mminutel]

Follow Up: I have gotten both sides to sound really good SQ wise but there is still the slight "hum" that comes out even when the source is at extremely low volume. The hum goes away when I turn off the source so does this mean that the source is the culprit? Someone said that lowering the gain would keep the amp from amping the sound of a bad source. Anyone confirm or deny this? I am a little afraid to mess with it anymore.

Anyways, I am getting a TURBOdock V for my iPod very soon so could that possibly take out the hum?

 

[threepointone]

if it changes when you change the volume on the amp, it's the source that's noisy. It might be fine if the iPod/turbodock isn't very noisy. lowering the gain or reducing the volume on the amp shoudl work.

 

[Seaside]

Good to hear that you got good sound quality outta your Cmoy.
And that is what the amp supposed to do. Cmoy can do this.

The OPamp could get warm, but It will never get hot when it is working at right condition. If it gets hot, the OP is osciliating. Which means there could be some shorts on the circuit or something is not wired correctly.

Noisy sound is sound too. What amp is doing is to amplify whatever sound gets in from the source. So, Noisy source will make sound more noisy after the amp. That akso means more gain = bigger sound = more noise. That is why you shouldn't need higher gain. What you need is adequate gain. I think default gain of 11 on Cmoy is way too much. But your idea may be differ from mine.

 

[arspy87]

Also, the ideal way to set up your volume when using the CMoy (if your CMoy has a volume control, or even just a level switch) is to have your source volume maximized as much as possible (or at least close) and adjust the CMoy volume control to attenuate the output to the level you want. This should make any hissing from the source very difficult to notice, if not inaudible.

 

[mminutel]

I have one more question. This thread might be too far along to get anyone to answer it but I will give it a shot. I am using two batteries. I have the switch on the left channel where to negative lead goes to BAT- but the LED still glows a slight bit because it is getting power from the second battery. Is there a problem with my wiring? And I notice that turning the amp off still delivers 9V to the right channel. It does turn off the amp but there is a faint clicking noise in the headphones. Any idea where my wiring could be wrong?

-EDIT- I also got almost all of the noise out of the headphones. I am currently using a gain of 3 and it is still stable with the OPA2277 as well. i havent really listened to the difference but i might post about what I think of the 2277. I accidentally picked it up instead of the 2227 but i might like it more

.

 

[tomb]

It sounds like you have the batteries and switch wired up wrong. The batteries should be in series, meaning one battery's positive terminal is connected to the other battery's negative terminal - with nothing inbetween but the connecting wire! That gives you a negative lead on one end and a positive lead on the other. With the switch at either end (positive is usually preferred, however) - not in the middle - that will cut off all power, period. The LED may glow for a few seconds (or several), but that's the caps draining, not power from the batteries.

 

[mminutel]

DO I have to use higher resistors on the virtual ground then? If i have 1 battery hooked up then i get +4 and -4 like I should but when i hook up the batteries in sequence, i get +16 on one side and nothing on the other side. The VGround works for 1 battery but not two.

 

[Pars]

That is a wiring problem... vground doesn't care how much voltage it is being fed, it will split into 1/2 as a function of a voltage divider (which is what it is). The resistor sizing is a balance between current draw and stability: the lower the resistor value(s) in the splitter, more current it will draw, but be "stiffer". The downside to this is you will drain your battery faster. The 4.7K chosen is a balance.

Make sure that you have things hooked up as in the attachment below (from Tangent's Cmoy schematic).

 

[mminutel]

Thanks. I got it figured out after I signed off but forgot to edit my post. I will have to wait a while because I cant get it to fit into the mint tin. I drilled the holes too low and the board wont slide under. This is getting rediculous, i had no idea it was going to be this hard. also, do you have to put something under the board because my amp will work outside but when i try to use it inside it wont work.