[genclaymore]

I have used 2x LME49710NA, 1x LME49720HA and 1xLME 49860 in the amp without any issues but I not using 0 gain.

 

[Chris J]

Quote:

Question about op amps...
Someone, I assume you Chis said somewhere that 4562 may not be stable on 0 gain setting..... (cant seem to find where now)
What specs do I need to look at to understand why? 
I have a dual 49990 and a 49860 i am wanting to try and wondering if they can be used on 0 gain or not?
 
Cheers

 
You won't find this in spec sheets.
I use to design analog signal processing systems for a living.
I've seen this happen in a few designs, you layout a printed circuit board, select an Op Amp that should work, then you test the circuit out and find oscillations where you shouldn't.
I've even seen this happen after we have carefully performed some computer aided analysis, taking into account parasitic capacitance, etc.
Everything looks OK in the computer model, and first time you test the system, you get some unforeseen oscillations somewhere.
 
There is an old saying (or designer's joke) "Amplifiers always oscillate, Oscillators never oscillate".
This really refers to building prototypes.
 
Unless you can verify that you are no oscillating with an oscilloscope, I would just try to be safe and set gain to 10 dB instead of slowly frying the amp or a headphone.

 

[the search never ends]

My TF.10's don't hum or anything, nor any of my iem's i tried a half dozen, none of them had any artifacts in the sound.  If your triples have the mic in them, that's probably the problem, I have a few iem's with mic's and none of them like to play well with a powerful desktop amp, no idea why, but have seen many posts saying the same thing from other members. Otherwise, I have no idea.  You could try the 75 ohm resistor trick, since the triples are very low impedance, it's cheap and worth a try.

 

[Mad Max]

When there is hum, it could be from a ground loop.  TF10's excessive sensitivity would make it obvious.

 

[tolame4aname]

Cheers Chris and Mad Max, 
I will keep the gain at 10db.
 
I am liking 49860 so far, but still only a few hours on it. Haven't had much time with it but an instant impression is it seems to have made the K702's sound even more like speakers.
Before the change I used to put on moonlight sonata when I was showing them to friends and they would take off the cans thinking that the speakers where still on.
 
Now I can do this with most songs. . Good start.

 

[GamerOne]

Thinking about getting an OPA Moon for my M-stage, but does it even fit in an M-stage? Also, if I'm buying one I'll order it from ampcity.co.uk and they have an "Optional extra" which is "Extension cables for dual OPA (100mm)", what exactly is this for and do I need it?

 

[Mad Max]

Yes, you need the extension cable.  OPA Moon/Sun/Earth are far too big to sit upright inside the M-Stage.

 

[wilky61]

Those of you with the LM4562, have you added the resistors to class-A bias your opamp, or is this not necessary for the LM4562?

 

[chicolom]

Quote:

Thinking about getting an OPA Moon for my M-stage, but does it even fit in an M-stage? Also, if I'm buying one I'll order it from ampcity.co.uk and they have an "Optional extra" which is "Extension cables for dual OPA (100mm)", what exactly is this for and do I need it?

 
BTW, If you have the M-Stage with the built in USB DAC I don't think there is enough room inside for the AudioGD opamps.

 

[GamerOne]

Quote:

Yes, you need the extension cable.  OPA Moon/Sun/Earth are far too big to sit upright inside the M-Stage.

 
Ah, I suspected as much Thanks for the reply!
 
Quote:

 
BTW, If you have the M-Stage with the built in USB DAC I don't think there is enough room inside for the AudioGD opamps.

 
I don't, but thanks for the heads up

 

[creal]

Quote:

My TF.10's don't hum or anything, nor any of my iem's i tried a half dozen, none of them had any artifacts in the sound.  If your triples have the mic in them, that's probably the problem...

 
My TF10 are equipped with the UE Custom-Cable and still hum quite noticeably at the lowest gain setting. I already tried a different power cord, a different plug (wall plug) and tightened up the screw at the bottom of the amp.
 
By the way, I noticed something interesting: if I set the volume knob around 3/4 or more volume the hum increases a fair amount just by touching the metal knob of the potentiometer. At lower volume settings nothing audible changes. What could it be (maybe the alps itself)

?
 
Edit: I took the dac module out and noticed it wasn't the reason for all this hum with my IEMs. The noise created by touching the volume knob increases with the volume setting itself. It sounds different than the hum which is always there.

 

[Mad Max]

Quote:

Those of you with the LM4562, have you added the resistors to class-A bias your opamp, or is this not necessary for the LM4562?

 
It's already biased to class-A internally, or so one guy says.
purrin says that it gets warmer in sound on headphonia.
I would suggest a 0.1uF C0G/NP0 ceramic cap across pins 4 and 8 (power supplies) instead to get the best sound out of it.  A Russian K42-Y2 PIO film capacitor would be worth a try, too, if you have one.

 

[the search never ends]

Sounds like an internal problem with the amp, ask if you can return it for the amp sans dac, make sure he knows you're a member at headfi, he knows all too well that the majority of his sales are headfi related. It could be be the potentiometer, but you'd have to replce it to find out, and he may claim you voided the warranty. Whatever it is, I'm pretty darn sure something is wrong internally with the amp. And I don't feel the usb version is worth buying. TF10's aren't especially prone to problems with amps, in fact I think they improve more than most iem's amped. What you are describing eliminates an impedance problem being the sole cause. I saw where one member had a tough time getting responses from him, that is not my experience though. Good luck getting it resolved, and give the amp another shot, it really is great value.
Quote:

 
My TF10 are equipped with the UE Custom-Cable and still hum quite noticeably at the lowest gain setting. I already tried a different power cord, a different plug (wall plug) and tightened up the screw at the bottom of the amp.
 
By the way, I noticed something interesting: if I set the volume knob around 3/4 or more volume the hum increases a fair amount just by touching the metal knob of the potentiometer. At lower volume settings nothing audible changes. What could it be (maybe the alps itself)

?
 
Edit: I took the dac module out and noticed it wasn't the reason for all this hum with my IEMs. The noise created by touching the volume knob increases with the volume setting itself. It sounds different than the hum which is always there.

 

[creal]

Quote:

Sounds like an internal problem with the amp...

This might be the case, at least the background noise isn't introduced by the source (no RCA or USB connected at the time of testing).
 
 
Quote:

Originally Posted by the search never ends /img/forum/go_quote.gif
 
And I don't feel the usb version is worth buying.

The DAC module is nothing special, but for the additional price asked it isn't a bad deal by any means. SQ wise it shouldn't make a difference anyway, they just stripped the 2nd RCA input and added 3 mounting holes for the DAC board itself (otherwise everthing is the same).
 
 
Quote:

Originally Posted by the search never ends /img/forum/go_quote.gif
 
TF10's aren't especially prone to problems with amps, in fact I think they improve more than most iem's amped.

To be fair I don't wanna use the TF10 with this amp. The 5ohm output impedance wracks the frequency response of the drivers and in comparison with my portable setup, they just sound quite odd. But most people said there is no audible hiss/hum with their IEMs below 3/4 volume at min. gain and it's just not the case for myself. Really seems like hit and miss with the M-Stage, at least I'am not the only one with this problem

. With my full-size headphones there are no problems at all, not at full and especially not at min. gain - it just sounds great.
 
 
Quote:

Originally Posted by the search never ends /img/forum/go_quote.gif
 
I saw where one member had a tough time getting responses from him, that is not my experience though.

I don't know if we both mean the same reseller, since i bought my one from a british shop. It would kind of suck to ship the amp back to them because I'am located at the main land and therefore shipping gets somewhat expensive and I'am just a student on a small budget. But sure enough I would like to get all issues resolved, so let's see what's gonna happen.
 
Thanks

 

[Chris J]

Quote:

Those of you with the LM4562, have you added the resistors to class-A bias your opamp, or is this not necessary for the LM4562?

 
I have never bothered to do a Class A mod on an LM4562.
 
Please keep in mind that the Op Amp does NOT directly power your headphone, there is a discrete transistor Class A driver between the Op Amp and your headphones.  
In ten words or less, this Class A driver is what actually provides all the current to your headphone.