HELP ME!!!
Oct 22, 2003 at 7:05 AM Post #61 of 82
Ok, for some reason it decided to work....like magic or something....I've been listening to it for a few hours now...crazy.

So I sealed it back up.

Now, this might be my imagination, but I think there is a little bit of a clipping-like noise when certain stuff is played....I'm not SURE it's there, but I think it is...

And is it going to cause problems having my R3 where it is right now? It's got the original 402ohm resistor with 2x 220ohm risistors in parallel with it....that brings the total R3 value to 86ohms....that's a LOT less than the original 402....and I thought it was 402 for a good reason. Opinions?
 
Oct 22, 2003 at 11:16 AM Post #62 of 82
Quote:

I think there is a little bit of a clipping-like noise when certain stuff is played....I'm not SURE it's there, but I think it is...


Put your meter on the DC millivolts scale and measure from output ground to left and right. What do you get?

Quote:

It's got the original 402ohm resistor with 2x 220ohm risistors in parallel with it....that brings the total R3 value to 86ohms.


What is your R4?
 
Oct 23, 2003 at 7:36 PM Post #63 of 82
Quote:

Put your meter on the DC millivolts scale and measure from output ground to left and right. What do you get?


I get 1mV from base to sleeve, and 2.5mV from base to tip....that's bad, isn't it?

Quote:

What is your R4?


3.3 kOhms
 
Oct 23, 2003 at 8:24 PM Post #65 of 82
Quote:

3.3 kOhms


No wonder it's clipping. Your gain is nearly 40x now! That's enough gain for some microphones. If you're not half deaf now, you soon will be.

I can't remember whether you have a 2x9V supply or 1x9V, or what chip your amp is using, and I can't be bothered to dig back through this thread to find it. But at the very best (2x9V and rail-to-rail chip) the amp will start clipping on low batteries when the source voltage is under 0.1Vrms. Since even the weakest sources will put out a few tenths of a volt on peaks, it'll definitely clip in that setup. With 1x9V, it starts clipping much earlier, and with practical op-amps it clips still earlier.

Bottom line, I don't see why you need 40x gain for a headphone amp.
 
Oct 24, 2003 at 12:27 AM Post #66 of 82
Why is my gain that high? Well, because Without it being that high, I can crank my volume knob to the max and still want more. With the gain where it is, I can get a good volume level (not unreasonably loud, mind you) without cranking it....it's about 2/3 max volume right now.

I'm using 2x9v and the AD8620 op-amp.

40x gain does seem like a lot....does that mean 40x louder than the input? That is definetly not what is happening...is it possible that something else is attenuating the signal?
 
Oct 24, 2003 at 12:40 AM Post #69 of 82
id just like to chime in and say i think everyone who is helping zemo with his meta42 is really really awesome. you guys are really good for helping out someone on the forums and im sure he appreciates it a lot.

i learned a lot from reading this thread as well. i currently have the same problem on not acheiving high enough sound volume for my ety er4s through my new meta42. im going to try to figure out how to adjust the gain higher (havent figured it out yet) soon. but in the meantime, i think you guys are really cool for helping zemo out.
 
Oct 24, 2003 at 1:13 PM Post #70 of 82
a 3rd PP3 will blow your amp, seeing as you have the AD8620 and its max voltage 26V; 3x9V = 27V, therefore a bad idea

a gain of 40 is ridiculous, as tangent said, that's into microphone territory.. also, with R3 that low, a lot of current is being dumped to ground. My suggestion is to return it to the person who sold it to you, as he said he would sort out the gain. With crossfeed and your cans, a gain of say 10-12x would do fine for me, but I do listen very low (my battery META without crossfeed for HD600s is only about 4.7 and I'm never over 12 o'clock on the volume).

So, my final suggestion is to return it to Shutakagi and get him to sort it!

btw, is there a resistor in R9 (on the bank of feedback resistors, the ones nearest the middle) or is it jumpered?? If there is a resistor, what value is it??

g
 
Oct 24, 2003 at 6:42 PM Post #72 of 82
Ruturn it? Well, this is what shu said

Quote:

Since you have the resources to do it yourself, I have no intention of refunding or reparing it.


is it possible that there is something else attenuatung the signal? It sounds like that with a gain of 40x, I should be bleeding from the ears, but again, normal listening is at 2/3rds full volume.

no, R9 is jumpered.
 
Oct 24, 2003 at 7:06 PM Post #73 of 82
no offence meant, but it seems that you don't have the resources to repair it; and if you received it in the current state (which I believe is the case, correct me if I'm wrong!), it is the sellers responsibility to repair it.

g
 
Oct 24, 2003 at 9:03 PM Post #74 of 82
That's what I'm saying! I PMed him, telling him I need to send it back. We'll see what happens.

Oh, and no offense taken. I'm a Bio/Music major, not an EE major!
 
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