[john57]

If DC offset is going to be a problem it will show up at the output since I think that the Little Dot 1+ is directly coupled and does not use a cap at the output to block the DC.

 

[Aynjell]

I am not sure if I am testing this right but I believe I am. I have connected a cable with a 1/4 end to my headphone jack and I come up with 0.

My DMM is kind of crappy albeit, but I have it set to DCV 200M, and the black is plugged into COM, and the red is plugged into 10ADC and it comes out to 00.0

if I use V(ohm)mA it's 12-14ish. (This number doesn't change when moving to the stock OPA, or at least not by much.)

So either I'm doing it wrong or I can't find any dc offset issues. :\

 

[markkr]

forgive my ignorance here, but I looked up DC offset on the web and I have NO idea what it is.. or how its harmful to headphones. Would someone mind putting it into plain (stupid English) for me?

Thanks... (I think I'm going back to the stock opamp ASAP... I killed my wallet for these RS2's and if I ruin them... my Wife will kill me!

 

[Aynjell]

Quote:

Originally Posted by markkr /img/forum/go_quote.gif forgive my ignorance here, but I looked up DC offset on the web and I have NO idea what it is.. or how its harmful to headphones. Would someone mind putting it into plain (stupid English) for me? Thanks... (I think I'm going back to the stock opamp ASAP... I killed my wallet for these RS2's and if I ruin them... my Wife will kill me!

DC offset can apparently reposition the drivers causing them to sound terrible. I am not sure how much DC offset is out of bounds, but I am not sure even how to measure it or if my DMM can measure it accurately.

 

[markkr]

Quote:

Originally Posted by Aynjell /img/forum/go_quote.gif DC offset can apparently reposition the drivers causing them to sound terrible. I am not sure how much DC offset is out of bounds, but I am not sure even how to measure it or if my DMM can measure it accurately.

ahhhh, ok... thanks, that makes sense.

 

[theryaner]

So what's the final verdict? is the LT1364 harmful? Ive been using it for 2 weeks w/o any issues.

 

[markkr]

I've been communicating with David at LD about this issue, he says they have not tested other opamps, and therefore cannot recommend any others. He did not discourage opamp rolling, but recommends being careful if you dont know what your doing (as I do not).

Hopefully someone here is an EE, and can chime in???

 

[Aynjell]

I would have to measure it, but will need instructions on how to do so properly.

 

[theryaner]

Ah alright. I think if people were having issues with the op-amp, would have said something here by now.

 

[john57]

I do know that the standard op-amp MC33078 used in the Little Dot 1+ has lower noise 4.5 nV/√Hz vs the LT1364 9nV/√Hz Input Noise Voltage and a max Input offset current of 150nA on the standard op-amp vs the LT1364 350nA Maximum Input Offset Current as shown on the spec sheets. There is a thread that talks about the offset at http://www.head-fi.org/forums/f6/def...-offset-98680/

I personally like the OPA2107 for its smooth and detailed sound.

 

[Aynjell]

Anybody think this amp can drive the AKG K701/702? Based on it's impedance and maximum input it looks like our amps can more than handle it's load. Also, I'm considering the following op-amps (Yeah never got around to ordering):

OPA2107
LM4562
LME49720

Anything I should add to this list? The more I order, the better so I save on shipping. Wanting to basically order up the definitive list of op amps. I already have:

LT1364
LM4562 (doesn't work)
OPA2227
OPA2134
MCC33078 (stock opa)

My tube range is:

Sylvania GB408A
Mullard EF91
Mullard EF92

Any tubes I should hunt down? I'm also seriously considering a little dot DAC, and also a hardware based crossfeed if I can find something that offers such functionality, that or DIY a linkwitz and do the full blown version with configurability. If I can get a K701, the dac, and a crossfeed, plus get this little amp fully configured the way I like it, I can then move on to something higher end for some HD600's or something, who knows.

 

[Trapper32]

Quote:

Originally Posted by john57 /img/forum/go_quote.gif I personally like the OPA2107 for its smooth and detailed sound.

After many different opamps I've finally settled on this one too. Nice all rounder and seems to be very stable as well.

 

[markkr]

How do you think the LME49720 compares to the 1364? and does it present the same DC Offset problems as the 1364?

How would you compare both of the above with the OPA2107?

 

[john57]

I would say that according to the spec sheets the LME49720 is electrically better than the stock or the 1364. It has a wide range of operating voltage of 2.5 to 17 volts, low noise and low drift over temperature. How does it sounds sonically is another mater. I did try the LM4562NA which had good specs but did not like the sound.

 

[Trapper32]

Supposedly the LME 49720 is identical to the LM4562 and is just renamed as a part of marketing strategy?? In either case I found their sound too abrasive and unmusical for me. I enjoyed the 1364 but finally settled on the 2107. The 2107 had the bass and mids that I enjoy.. a more laid back sound. This is with the Grado 225. With other cans I may prefer different opamps.